Class 12 Medical Biology - Ecosystem

The pyramid of .......... is always upright.

The pyramid of energy is always upright because in an ecosystem when energy flows from one trophic level to next 10% is transferred and rest 90% lost by the life processes.

Ecological pyramids are usually upright. Meanwhile some, pyramid of biomass is inverted. Explain the reason.

In a pond ecosystem, phytoplanktons are the producers. The primary consumers are the zooplanktons and fishes are the following consumers. The biomass of the phytoplanktons is less than that of zooplanktons. Hence there is an increase in the number of organisms with increasing trophic level from primary producer to tertiary consumer resulting in an inverted pyramid of biomass.

What is succession? What are its type? Write any two stages.

Succession : The composition and structure of community constantly change in a response to the changing environmental conditions. This gradual change in the species composition of a given area that leads to the establishment of climax community in the end is called as ecological succession.

Types of succession : Succession has been classified as follows-

(i) Primary succession- This takes a long time to complete which can be thousand years or more.

(ii) Secondary succession- This takes less time for completion which is 50-200 years.

Explain energy pyramid.

The energy trapped per unit time and area in different levels of a food chain is shown as a graphical representation in the form of Energy Pyramid.

Since the flow of energy is always unidirectional, the pyramid of energy is always upright. The energy which is stored by the autotrophs in the form of food is available to the herbivores as food. Only 10% of this energy is stored by herbivores in their biomass and the remaining 90% is used by them in the metabolic activities. Similarly, only 10% of the energy of the lower trophic level is available for the organisms of next higher trophic level. Thus, the pyramid of energy depends only upon the energy in each trophic level.

Write the equation that helps in deriving net primary productivity of an ecosystem.

Net Primary Productivity (NPP) is given by Gross Primary Productivity minus Respiration loses (R).

Hence, the equation for deriving NPP is given by:-

NPP = GPP - R

What is succession? Discuss succession in ponds.

Ecological succession is a sequence of seres from baren land to the climax. In ecological terms, the developmental stages of a community are known as seral stages and the final stage as the climax community. The initial community of the area which is replaced in time by a sequence of succeeding communities until the climax is reached is called pioneer stage or pioneer community. The entire series of communities that is a characteristic of given site is called a sere.

Succession in ponds:

The hydrach succession or hydrosere succession is a succession in which a pond and its community are converted into a land community. Various stages of hydrosere are:

1. Plankton stage- It is the pioneer stage of hydrosere. Different spores reach the water body through wind or animals. The first organisms appear are minute autotrophs called phytoplanktons e.g. diatoms, green flagellates or filamentous green algae. Death and decomposition of these planktons produce organic matter. The latter mixed up with clay and silt at the bottom to form soft mud favourable for the growth of next seral stage.

2. Submerged stage- The bottom lined by soft mud having organic matter is favourable for the growth of submerged plants like Hydrilla, Vallisneria etc. They are rooted in the mud and form dense growth. As a result, sand and silt and humus get deposited around the plants. This enriches the newly built up bottom and makes it favourable for the growth of next stage.

3. Floating stage- Floating leave anchored plants appear when water is shallow. The plants make the water rich in mineral and organic matter. It becomes suitable for the growth of free-floating like Wolffia, Azolla etc. They cover the surface of water quickly.

4. Reed swamp stage- Amphibious plants grow where the water body becomes shallow. The plants of swamp stage transpire huge quantities of water. They also produce abundant organic matter. Their tangled growth accumulates silt.

5. Sedge or Marsh meadow stage- The shores built up by Reed swamp stage are invaded by grasses and herbs. The plants transpire rapidly and add abundant humus. Therefore soil is build up to invite the next stage.

6. Woodland stage- The periphery of sedge meadow stage is invaded by some rhizome which bears shrubby plants, which can tolerate bright sunlight as well as waterlogged conditions e.g. bogwood. The shrubs shade away from the plants of sedge meadow stage and they invite invasion by trees capable of bearing sunlight and waterlogging. The plants of woodland stage lower the water table by transpiration and built up more soil. Shade-loving plants grow below them.

Phosphorus cycle is an example of ........... cycle.

Phosphorus cycle is an example of biogeochemical cycle.

How much time is taken for a primary succession to complete?

It is often 1000 years or more for primary succession to complete

What is the ultimate source of energy for the ecosystems?

The ultimate source of energy is the Sun for the ecosystem.

Biogeochemical cycles describes the movement of water and other materials throughout the _ and _ environment.

A biogeochemical cycle is a pathway by which a chemical substance moves through both biotic (biosphere) and abiotic (lithosphere, atmosphere, and hydrosphere) compartments of Earth. For example - the circulation of chemical nutrients like carbon, oxygen, nitrogen, phosphorus, calcium, and water, etc.
A cycle is a series of change which comes back to the starting point and which can be repeated.

So, the correct answer is the abiotic and biotic environment.

The flow of energy is always _______ in food chains.

Characteristics of food chain:

1. A food chain is always straight and proceeds in a progressive straight line.

2. In a food chain, there is unidirectional flow of energy from sun to producers and subsequently to series of different types of consumers.

3. Usually there occur 4 or 5 trophic levels in the food chain.

4. Generally 80-90% of energy is lost as heat at each transfer in accordance with second law of thermodynamics.

5. Some organisms occupy different trophic positions in different food chains.

So, the correct answer is 'Unidirectional'.

Rewrite the given sentence, if it is a false statement:
'The flow of energy in an ecosystem is cyclic'.

The given statement is incorrect.

The correct statement is-

'The flow of energy in an ecosystem is unidirectional'.

The energy that is captured by the autotrophs does not revert back to the solar input and the energy which passes to the herbivores does not come back to autotrophs. As it moves progressively through the various trophic levels it is no longer available to the previous level.

Write the importance of phosphorus cycle in ecosystems.

Phosphorus is an essential element for all living organisms which is a structural component of ATP (adenosine triphosphate), a form of cellular energy as well as DNA and RNA, which are the important life-sustaining molecules. The human body has phosphorus in the form of bones and teeth that contribute 80% of the phosphorus requirement. Phosphorus limits plant and animal growth due to its low availability in soil and water bodies. It is found in phosphate ion form (PO₄^3-) in various compounds of soil, water, and rock sediments. Unlike other biogeochemical cycles, phosphorus circulation through atmospheric changes is very poor as the major reservoir of phosphorus is in sedimentary rocks. The phosphorus of these rocks is gradually eroding, releasing phosphates to the ecosystem or leaching into the sea where it is deposited in deep sediments.

The ratio of phosphorus to other elements in the organism is greater than the available and primary sources of phosphorus. It is an ecologically more important and limiting element that regulates productivity. Thus phosphorus cycle is known to be an important cycle of the ecosystem.

What does 'R' represent in the given equation for productivity in an ecosystem? GPP-R=NPP

The overall productivity of a system can be found in an equation, where the Net Primary Production, or NPP, is equal to the Gross Primary Production, or GPP, minus the Carbon respiration, or R.
The formula is the NPP = GPP - R.
The NPP is the overall efficiency of the plants in the ecosystem.Through having a constant efficiency in NPP, the ecosystem is then more sustainable. The GPP refers to the rate of energy stored by photosynthesis in plants. The R refers to the maintenance and reproduction of plants from the energy expended.

How much energy flows from one trophic level to next in a food chain ?

When green plants are eaten by primary consumers, a great deal of energy is lost as heat to the environment, some amount goes into digestion and in doing work and the rest goes towards growth and reproduction. An average of 10% of the food eaten is turned into its own body and made available for the next level of consumers.

Therefore, 10% can be taken as the average value for the amount of organic matter that is present at each step and reaches the next level of consumers.

What is the difference between biodegradable and non-biodegradable waste? Give example of each

Biodegradable waste: (1) Substances that are broken -down by biological processes are said to be biodegradable. (2) Example: Dead animals and plants , sewage, paper, etc.

Non-biodegradable waste: (1) Substances that are not broken- down by biological processes are said to be non- biodegradable. (2) Example: Plastic bags,glass,bottles,empty tin cans etc.

What are biogeochemical cycles?

Biogeochemical cycles are repeated circulation of biogeochemicals between abiotic and biotic components of the environment which result in their repeated withdrawal and replenishment of their pool.

What is the role of biogeochemical cycles in the environment?

In these cycles essential nutrients like nitrogen, carbon, oxygen and water are changed from one form to another.

Give the existence'of carbon.

Carbon exist in two different forms in nature free and combined form.
(i) Free form: It occurs in the elemental form as diamond and graphits.
(ii) Combined form: It occurs as carbon-dioxide, carbonates and hydrogen carbonatie salts in various minerals, it is also present in proteins, carbohydrates fats, nucleic acids and vitamins.

How is energy flux related to carbon oxidation and reduction reactions?

Most energy transformations in nature are associated with biochemical oxidation and reduction of carbon, oxygen, nitrogen, phosphorus, and sulpur. The oxidation of the carbon in carbohydrates in respiration releases energy whereas the reduction of carbon in photosynthesis requires the energy input from the sun. The gain of energy in photosynthesis and the subsequent use of that energy in respiration is the fundamental energy flux of nature.

Name the three types of biogeochemical cycles.

The three types of biogeochemical cycles are hydrological cycle, sedimentary cycle and gaseous cycle.

What are biogeochemicals?

Biogeochemicals are essential elements or nutrients required by living organisms which are obtained from earth.

All the living organisms are basically made up of C, N, S, P, Hand O. How do they enter the living forms? Discuss.

The substances like C, N, S, P, H and O enter the living body through biogeochemical cycles. The atmospheric carbon $$(CO_2)$$ is used by plants during photosynthesis to synthesize carbohydrate. When animals feed upon the plant products, carbon enters into animal's body.
Phosphorus and sulphur are absorbed by plants from soil. Animals obtain it through food and water.
Oxygen enters into plants and animals' body through the process of respiration.
Hydrogen enters into plant body through absorbed water and into animals body through food and water.
Plants absorb nitrogen from soil as nitrates and nitrites and convert them into proteins. When these plants are eaten by and animals, nitrogen enters into animals body.

What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?

Biological magnification is the phenomenon in which harmful chemicals enter in the food chain and its concentration increases at each tropic level. The levels of biological magnification is different at different levels of the ecosystem. It will be increases with each successive level. It is maximum at highest tropic levels and minimum at lowest tropic levels. For example, it is higest in humans and lowest in autrophs like plants.

State the function of a reservoir in a nutrient cycle. Explain the simplified model of carbon cycle in nature.

The function of a reservoir in a nutrient cycle: It meets the deficit which occurs due to the imbalances in the state of influx and efflux of nutrients.

Carbon cycle:

Carbon enters the atmosphere as carbon dioxide from respiration (breathing) and combustion (burning).
Carbon dioxide is absorbed by producers to make carbohydrates by the process of photosynthesis. These producers then give out oxygen.
Animals feed on the plants. Thus, they pass the carbon compounds along the food chain. Most of the carbon these animals consume however is exhaled as carbon dioxide. This is through the process of respiration. The animals and plants then eventually die.
The dead organisms are eaten by decomposers in the ground. The carbon that was in their bodies is then returned to the atmosphere as carbon dioxide. In some circumstances, the process of decomposition is prevented. The decomposed plants and animals may then be available as fossil fuel in the future for combustion.

In a food chain, if 10,000 joules of energy is available to the producer, how much energy will be available to the secondary consumer to transfer it to the tertiary consumer?

Answer:

According to the 10% law, only 10% of the energy is transported from the lower trophic level to the upper trophic level.
If the producer has 10,000 joules of energy, only 1000 joules will be available to the primary consumer, and only 100 joules will be available to the secondary consumer.
The energy available with the tertiary consumer will be 10 joules of energy.

Why the pyramid of energy is always upright? Explain.

The pyramid of energy is always upright because when the energy flows from one trophic level to another, some energy is always lost as heat in each step. This heat is lost to the atmosphere and never goes back to the sun.

Explain how does:
(a) A primary succession start on a bare rock and reach a climax community?
(b) The algal bloom eventually choke the water body in an industrial area?

a) A primary succession begins with the growth of lichens which dissolves the bare rock and cause weathering of rocks which results in soil formation. Then small plants like mosses can inhabit followed by herbs, shrubs and then trees. Finally, a stable climax community evolves.

b) Algal bloom causes increase in the number of algae in the water body. This might be due to the entry of industrial waste into the water bodies. Algal bloom increases BOD, resulting in the death of fish and aquatic life in the water bodies.

Differentiate between primary and secondary succession and provide one example of each.

Primary succession (PS) takes a long time for completion, 1000 years or more while secondary succession (SS) takes a less time for completion 50-200 years.
PS occurs in an area which is barren or lifeless while SS occurs in an area which has been denuded recently and was previously inhabited.
Soil is absent at the beginning of PS and the environment is not suitable for sustaining normal life forms, Soil is present at the beginning of SS with some organisms.
There is no humus in the beginning as soil is absent in PS. In SS, humus is present from the very beginning by the decomposition of previous occupants.
Intermediary seral communities are many in PS, while in SS, intermediary seral communities are a few.
Reproductive structures or propagules of any previous community are absent in PS. In SS, reproductive structures of the previous occupants are present in the area.

What amount of energy will be available to the organisms of the $$2^{nd}$$ trophic level of a food chain, if the energy available at the first trophic level is 10,000 joules?

According to Lindeman's 10% law, only 10% of energy is transferred to next level. If energy available at first trophic level is 10,000 Joules, then at second trophic level energy available will be 10% of 10,000 which equals to 1000 Joules.

(i) What is primary productivity? Why does it vary in different types of ecosystems?
(ii) State the relation between gross and net primary productivity.

(i) The amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis is called primary production.

The primary productivity depends on different plant species present in a given ecosystem and each of their photosynthetic efficiency. Also, the environmental factors, availability of various nutrients vary in different ecosystems, leading to variations in primary productivity.

(ii) Gross primary production of an ecosystem is the rate of production of organic matter during photosynthesis. A considerable amount of GPP is utilized by the plants in respiration.

Net primary productivity or NPP is the gross primary productivity minus the respiratory losses (R).
GPP - R = NPP

Write important features of a sedimentary cycle in an ecosystem.

Sedimantry cycle is the cycle of mineral found in the earth crust e.g., phosphorus, sulphur etc. Important features of a sedimentary in an ecosystem are:

1) It is the major reservoir for nutrients elements in the lithosphere and the elements are released by weathering.

2)E.g. phosphorous cycle, sulphur cycle, iodine cycle.

3)The sedimentary cycle is very slow than gaseous cycle and takes more time.

4)It is a less perfect cycle as elements get locked in earth crust for the longer time.

What is primary productivity? Give brief description of factors that affect primary productivity.

Primary productivity refers to the total organic matter produced by primary producers per unit area per unit time. It is affected by nutrient availability, types and number of primary producers present in an ecosystem, temperature, sunlight, water, precipitation etc.

Define decomposition and describe the processes and products of decomposition.

Explanation:

Decomposition refers to the breakdown of complex organic matters into simpler substances like carbon dioxide, water, and other nutrients,
The processes that take place during decomposition are as follows:

Fragmentation- It involves the breakdown of detritus matter by the activity of detritivores like earthworms.
Leaching- Leaching refers to the process by which dissolved materials are carried with water down to the soil layers.
Catabolism- In this mechanism detritus is further broken down by the action of bacteria and fungi.
Humification-Soil inhabiting microbes carry out the decomposition of organic matter and the resultant partly decayed organic portion of the soil is referred to as humus; the process of humus formation is called humification.
Mineralization-Nutrient present in the soil in biologically unavailable forms (for example-nitrogen) are converted into biologically useful forms by the process of mineralization

Define ecological pyramids and describe with examples, pyramids of number and biomass.

An ecological pyramid is a diagrammatic representation in the context of energy, biomass and number organisms showing the linkage between the various trophic levels of the ecosystem.

Pyramid of number- The pyramid that gives the number of organisms at each trophic level is called pyramid of number.

For example- oak → caterpillar → blue tit → sparrowhawk

The producer in the given food chain is the oak plant.

A caterpillar feeds on many oak leaves, the blue tit feeds on many caterpillars and finally, the sparrow hawk feeds on many the blue tits. Hence the number of organisms decreases at each trophic level.

Pyramid of biomass The pyramid that gives the total weight of the organisms at each trophic level is called pyramid of biomass.

For example- oak → caterpillar → blue tit → sparrowhawk

The total mass of organisms at each stage of a food chain decreases as the number of organisms decreases at each trophic level.

What is ecological succession. Mention its different steps. Explain Hydrach and Xerarch succession with diagramatic representation.

The process of change in ecological community of an area over time which in turn results in the formation of climax community is termed as succession. Ecological succession is the directional change in the flora and fauna of a given region over a period of time. It is the process of gradual change in the species structure of an ecological community over time.

There are three different steps as primary and secondary succession.

1) Primary (pioneer) succession is initiated when a new area that has never previously supported an ecological community is colonized by plants and animals. This could be on newly exposed rock surfaces from landslides or lava flows.

2) Secondary (intermediate) succession occurs when an area that has previously had an ecological community is so disturbed or changed that the original community was destroyed, and a new community moves in. This is more common than primary succession and is often the result of natural disasters such as fires, floods and winds, as well as human interference such as logging and clear cutting.

3) The last stage is considered as the climax stage when the population comes to a stable stage.

Hydrarch is a plant succession which starts in relatively shallow water, such as ponds and lakes and culminating in a mature forest, e.g. phytoplankton, Hydrilla, Vallisneria. Hydrarch succession takes place in wetter areas and the successional series progress from hydric to the mesic conditions. Xerarch is a plant succession starting on bare ground or rock and culminating in a mature climax forest. The pioneer species, such as lichens and mosses, result in the gradual accumulation of soil. Xerarch succession takes place in dry areas and the series progress from xeric to mesic conditions. In ecology, a mesic habitat is a type of habitat with a moderate or well-balanced supply of moisture.

What do you understand by ecological pyramid? Explain pyramid of biomass in a grassland with the help of a diagram.

An ecological pyramid is the graphic representation of an ecological parameter (number, biomass or energy). The rate of energy flow in an ecosystem will be considered in drawing the pyramid of energy, the dry weight will be considered in drawing the pyramid of biomass and number of individuals is considered for drawing the pyramid of a number. The terrestrial system consists of grassland and forests. Pyramid of biomass in a grassland is upright. The biomass decreases with each higher trophic level from plants to herbivores to carnivores. The least biomass is seen in highest trophic level, that is predators like foxes and eagles.

Observe the pyramid of number which is given below and answer the questions.
(i) As per the number of organisms in the tropic level, which group of organisms are more in number and which are less in number ?
(ii) What happens if Secondary consumers disappear ?

(i) As per the number of the organisms in each of the trophic level, there are more number of organisms in the producers level and less number of organisms in the trophic level of tertiary consumers.

(ii) If the secondary consumers disappear, then the number of primary consumers will be increased because there are no secondary consumers which will feed on the primary consumers. Thus, there will be a decrease in the number of tertiary consumers since there is no food available. The food chain will be disturbed.

What do you understand by energy flow in an ecosystem? Explain energy flow through different trophic levels. Draw line diagram of a food chain.

The ecosystem is an interaction between living beings and their physical environment. The most important characteristics of any ecosystem are energy flow and cycling of materials. Energy flow is always unidirectional. Energy flows progressively from one trophic level to another and cannot revert back. In most of the natural ecosystems, energy comes from the sun, it is trapped by producers and then pass on to successive trophic levels in the form of food.

The available energy decreases at higher trophic level. Out of the total energy available at a particular trophic level, only 10% is passed on to the next trophic level, making it impossible for energy to flow in the reverse direction. The flow of energy in an ecosystem occurs in the following sequence:

Sun ------> Producer ------> Herbivore -------> Carnivore -------> Decomposer

Observe the following biogeochemical cycle.
(i) Mention the nutrient in the given cycle.
(ii) Write the activities from 'A' to 'D'.

A= Photosynthesis: Carbon dioxide is absorbed by producers (life forms that make their own food e.g. plants) to make carbohydrates in photosynthesis.
B= Respiration: Carbon enters the atmosphere as carbon dioxide from respiration (breathing) and combustion (burning).
C= Combustion
D= Decomposition: The dead organisms (dead animals and plants) are eaten by decomposers in the ground. The carbon that was in their bodies is then returned to the atmosphere as carbon dioxide. In some circumstances, the process of decomposition is prevented. The decomposed plants and animals may then be available as fossil fuel in the future for combustion.
Nutrient in the given cycle is carbon dioxide.

Animals give out .......... through respiration.

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a) What is ecological secession?
b) Represent an ideal pyramid of number in a grassland ecosystem.
c) Name the two types of nutrient cycles with an example each.

a) Ecological succession is the process of gradual change in the species structure of an ecological community over the time. The pioneer species are the species which are first to colonise at an area and the begin with a chain of ecological succession that ultimately leads to a more biodiverse steady-state ecosystem.

b) The answer is represented in the image. The pyramid of number for grassland ecosystem is upright. The number of organisms decreases with increase in the trophic level.

c) The nutrient cycles are the biogeochemical cycles which involve the recycling of the nutrients. The two types of nutrient cycles are the gaseous cycle and sedimentation cycle. The example of the gaseous cycle is carbon and nitrogen cycle. The example of sedimentation cycle is the phosphorous cycle.

What is meant by ecological succession?

Describe the inter relationship between productivity, gross primary productivity and net productivity.

The rate of production of total biomass is called as productivity. Gross primary productivity is the rate of production of organic matter by photosynthesis and net primary productivity is the total available biomass for consumption for heterotroph. Thus, the productivity is the sum total of gross primary productivity and net primary productivity.

a) Distinguish between primary productivity and secondary productivity of an ecosystem.
b) Define food web.

Primary productivity	Secondary productivity
This is the production of the organic matter by the producers.	This is the production of the organic matter by the consumers.
The energy is obtained from the sunlight and food is produced.	The energy is obtained by the transfer of the energy through food chain.
The process of production is fast.	The process of production is quite slow.

b) The food web is the network of organisms which are connected to each other for food and energy. There are many food chains which are interconnected with each other for the transfer of food.

What is an ecological pyramid? Compare the pyramids of energy, biomass and numbers.

The ecological pyramid is the representation of the different organisms or trophic levels in a food chain in the form of a pyramid.

The pyramid of the number represents the number of organisms in a trophic level. The pyramid may be upright or inverted depending on the ecosystem.

The pyramid of biomass represents the biomass from all the members in the trophic level in a food chain. The pyramid is generally upright as there is decrease in te biomass with the increase in the trophic level.

The pyramid of energy represents the energy flow and the energy at every trophic level in a food chain. The pyramid of energy is always upright.

Write any two limitations of ecological pyramids.

The ecological pyramid is the representation of the different organisms or trophic levels in a food chain in the form of a pyramid. The limitations of ecological pyramids are:

The decomposers which are a major part of the food chain, are not given any place in any trophic level.
The organisms from the same species may be present in one or more trophic level but are considered in the same level.
The food web is not considered in the ecological pyramid but only the details of the food chain are shown.

Why is pyramid of energy never inverted in any ecosystem?

Pyramid of Energy: The pyramid which shows the energy accumulation by organisms of different trophic levels is called pyramid of energy. The consumers (primary, secondary and tertiary) of trophic levels, food chain, utilise 90% of energy obtained by food materials in respiration and store only remaining 10% energy. The primary producers in any ecosystem are characterised by maximum energy and the quantity of energy at each successive level of consumers goes on decreasing. So, the pyramid of energy is always upright.

Answer in 40 to 80 words:
With reference to ecological succession define the following terms:
i) Climax community
ii) Sere(s)
iii) Pioneer species.

1) Climax community is a stable, self-perpetuating and final community that appears in an area at the end of biotic succession. It is in perfect harmony with the climate of the area.

2) Sere is an intermediate developmental stage found in ecological succession in an ecosystem. This is a stage which is moving towards its climax.

3) Pioneer species are species which recolonize an area after there has been damage to the ecosystem. They are mostly hardy plants that can survive with little nutrition such as lichens.

Answer in 40 to 80 words:
What is ecological succession? Distinguish primary succession from secondary succession.

Ecological succession is the directional change in the flora and fauna of a given region over a period of time. It is of two types primary and secondary.

1) Primary succession is the sequence of changes that happens in an entirely new habitat which has never been colonized before. For example- newly formed sand dunes.

2) Secondary succession is the sequence of changes that happens on a previously colonized but damaged habitat. For example- plants are grown in an area after land clearance or a fire.

a) Draw an ideal pyramid of energy and mention the units.
b) What is an ecological succession?

a) The pyramid of energy is upright for any ecosystem. The producers are at the first level and possess high amount of energy. As per the 10% law, there is decrease in the amount of energy with the increase in the trophic level. The primary consumer will have energy less than the producer and go on decreasing with the higher trophic levels.

b) The process of change in ecological community of an area over time which in turn results in the formation of climax community is termed as succession. Ecological succession is the directional change in the flora and fauna of a given region over a period of time. It is the process of gradual change in the species structure of an ecological community over time.

The rate of biomass production in an ecosystem is called productivity. They are of two types, gross primary productivity and net primary productivity. How these two productivities are related?

Primary succession on rocks is known as xerosere. Answer the following related with xerosere.
(a) Name the pioneer community.
(b) Organic acids have important roles in this succession. Justify.

(a) Pioneer community is the first biotic community on a bare area. Plants that are first to invade the bare area are called pioneer species. Lichens are the pioneers in lithosere and phytoplanktons are the pioneers in hydrosere.

(b) The lichens are the organisms which produce the acids like the oxalic acids. These acids cause crevices in the rock where the organic matter gets collected and the rocks break and the soil particles are formed. This results in the succession process to start.

A list of different organisms in an ecosystem are given below
Arrange them in 1$$^{st}$$, 2$$^{nd}$$, 3$$^{rd}$$ and 4$$^{th}$$ trophic level.
(i) Phytoplankton
(ii) Man
(iii) Fish
(iv) Zooplankton

Many different organisms are included in an ecosystem. The correct sequence of the organisms in the ecosystem as per the increase in the trophic level are:

Phytoplankton- 1$$^{st}$$ level
Zooplankton- 2$$^{nd}$$ level
Fish- 3$$^{rd}$$ level
Man- 4$$^{th}$$ level

The species that invade a nude area are called ........... species. In a primary succession on rocks, the group that invade first are usually are known as

Pioneer community is the first biotic community on a bare area. Plants that are first to invade the bare area are called pioneer species. Lichens are the pioneers in lithosere and phytoplanktons are the pioneers in hydrosere.

a. Briefly explain ecological pyramids
b. Define primary productivity. Give two factors which affect primary productivity.

a. Ecological pyramids are graphical representation of various ecological parameters at the successive trophic levels of food chains with producers at the base, top carnivores at the apex and intermediate levels in between. Quantity at each level is indicated by length of bar in the graph. The common parameters used in preparing ecological pyramids are number of individual, biomass and energy at different trophic levels. The three ecological pyramids that are usually studies are:

Pyramid of numbers:

Upright: During transfer of food at any trophic level, only 10% of the food present in one trophic level becomes part of the next trophic level. 90% of the food is either lost in wastage or broken down during cellular respiration for providing energy for various life activities. With each successive trophic level, number of individual are decreasing. Therefore the pyramid of number is upright e.g., Grassland ecosystem and Pond ecosystem.
Inverted: In some case at each successive trophic level, number of the organisms as higher than in preceeding one and the size decrease gradually at successive level. Thus, shape of pyramid may be inverted. For example, a large-sized tree may support and provide nourishment to several frugivorous birds. The number thus increases at each trophic level.
Spindle: A tree supports a number of herbivores birds. The herbivores birds are eaten by one or two hawks of the area.

Pyramid of Biomass

Upright: biomass is the amount of living matter at any particular trophic level at a given time. Pyramid of biomass in terrestrial ecosystems is usually upright. For upright pyramid, total biomass of plants in a specific area is more than that of herbivores and it gradually decrease at each successive trophic level. It is least in top carnivores e.g., tree and grassland ecosystems.
Inverted: In aquatic ecosystem, the pyramid of biomass may be inverted. For example, biomass of zooplanktons in higher than that of phytoplanktons as life span of former is longer and the latter multiply much faster through having shortest life span. A number of generation of phytoplanktons may thus be consumed by single generation of zooplanktons. Biomass of fish may still be larger as fishes are larger in size with the longer life span and a number of generation of zooplanktons can be consumed by fishes.

Pyramid of energy: The pyramid of energy is always upright because the flow of energy is unidirectional from producer to consumer level. The energy content is maximum in producers. The energy decreases at each trophic level of food chain, as part of the energy is lost as heat and major part of energy is liberated during respiration for use in various activities. Only 10% of the energy of previous trophic level is received by next trophic level, as proposed by 10 percent law of Lindeman.

b. Primary productivity is the rate at which biomass or organic matter is produced by plants or producers during photosynthesis per unit area over a time period or it refers to rate at which sunlight is captured by producers for the synthesis of energy-rich organic compounds through photosynthesis. It is expressed in term of weight as ($$gmm^{-2}$$)$$yr^{-1}$$ or energy as ($$Kcalm^{-2})yr^{-1}$$ to compare the productivity of different ecosystems.

Several biotic and abiotic factors affects magnitude of primary productivity. Following are the two factors:

Photosynthetic capacity of producers which means the ability to utilize incident solar radiation to raise gross primary productivity.
Solar radiations available

What are ecological pyramids? Why is energy pyramid always erect? Explain.

An ecological pyramid is also called as trophic pyramid or energy pyramid. It is a graphical representation that indicates the biomass at each trophic level in a given ecosystem. It is the total amount of energy that is consumed at each trophic level in a given food chain. It is represented in three different ways, namely the number of organisms, the biomass in each level and the amount of energy in each level. The energy pyramid is always erect because the total amount of energy that is available in each layer is less than the energy available in the lower level. It is said that only 10% of the total energy is transferred from one trophic level to another trophic level.

Which of the following is correct with respect to the estuarine ecosystem?
A: Estuary constitutes one of the most productive ecosystems
B. It represents the transition zone between two populations of a species

Estuaries contain the most productive ecosystem because these are the area of the transition zone between two lakes or two ecosystems.

Estuaries maintain biodiversity as they provide a vast range of habitat for a variety of species to thrive and live.

Many mammals, fishes and birds live and thrive in estuaries. Many fishes and shellfish come toe estuaries to provide nourishment to their spawns and eggs.

So, both the statements are correct with respect to an estuarine ecosystem.

Give specific reasons for the following statements:
We cannot distinguish colours in moonlight.

Colours cannot be distinguished in moonlight because only the rods function in moonlight and not the cones.

How do you explain the following statement?
Energy used by a leaping frog is actually the energy obtained from the Sun.

Sun is the ultimate source of energy for all living organisms. Energy from the sun is trapped by photosynthetic producers. This energy is transferred in the food chain from producers to herbivores to carnivores and so on. A frog is a carnivore and it feeds on herbivorous organisms.

Hence, The energy utilized to leap is derived from sunlight.

Pyramid of energy is always..........

An ecological pyramid is a graphical representation designed to show the biomass or bio productivity at each trophic level in a given ecosystem. A pyramid of energy is a graphical representation of the amount of energy at each trophic level of a food chain. They are expressed in units of energy per area per time. Pyramids of energy will never appear inverted as some of the energy stored in one source is always lost upon transfer. Pyramid of energy is upright because when energy flows from a trophic level to next trophic level, some energy is always lost as heat at each step.

So the correct option is 'upright'.

Short / Long Answer Type Questions :
Construct an ideal pyramid of energy when 1,000,000 joules of sunlight is available.Label all its trophic levels

R.E.F image

$$1000000\,J$$ energy of sunlight

R.E.F image

Tertiary consumer $$10\,J $$

Secondary consumer $$100\,J $$

Primary consumer $$1000\,J $$

Producers $$ 10000\,J $$

Ideal pyramid of energy (3)

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The form of energy at the beginning of the food chain is ________.

Energy in the form of solar energy enters the food chain through photosynthesis performed by the producers.
By feeding on plants and on one-another, animals play an important role in the movement of matter and energy through the food chain. By breaking down dead organic matter, decomposers facilitate nutrient cycling by converting nutrients stored in dead biomass back to a form that can be readily used by plants and other microbes.

The form of energy at the beginning of the food chain is solar energy.

In an ecosystem dominated by trees, the pyramid of numbers is ..........type

Correct answer: Inverted type.

Explanation:
In an ecosystem dominated by trees, the pyramid (of numbers) is of Inverted type because it makes more biomass that leads to the large population of birds and insects as compared to the trees.

Short / Long Answer Type Questions :
It is stated that the pyramid of energy is always upright. Justify

An energy pyramid is always upright because the total amount of energy available for utilisation in the top levels is less than the energy available in the lower levels. This happens because according to the 10% law of energy flow, only 10% of the total energy is transferred from one trophic level to the next.

Differentiate between two different types of pyramids of biomass with the help of one example of each

The example includes pyramid od biomass in pond and pyramid of biomass on land.
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Write a difference between net primary productivity and gross productivity

Net primary productivity (NPP) is the rate at which all plants in an ecosystem produce net useful chemical energy. While gross primary productivity (GPP) is the rate at which primary producers save and collect biomass for energy conservation. NPP is the difference between GPP and cellular respiration.

Short / Long Answer Type Questions :
Carbon cycle in nature is a biogeochemical event. Explain

The carbon cycle is the biogeochemical cycle because in this cycle carbon is exchanged between the biosphere, geosphere, hydrosphere and atmosphere of the earth.

Short / Long Answer Type Questions :
(a) Why is pyramid of energy always upright? Explain. Mention the limitations of an ecological pyramid
(b) Construct a pyramid of biomass starting with phytoplanktons. Label three trophic levels. Is the pyramid upright or inverted ? Why?

a)Pyramid of energy is upright because when energy flows from a trophic level to the next trophic level, some energy is always lost as heat at each step.

Limitations of Ecological Pyramids:

(i) It never takes into account the same species belonging to two or more trophic levels.

(ii) It assumes a simple food chain, something that almost never exists in nature.

b)The pyramid of biomass of phytoplankton is inverted as the amount of biomass is lowest at the levels of phytoplankton.

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What is meant by ecological succession ? Differentiate between pioneer community and climax community.

Ecological succession is the gradual process by which ecosystems change and develop over time. Nothing remains the same and habitats are constantly changing. Succession takes place because through the processes of living, growing and reproducing, organisms interact with and affect the environment within an area, gradually changing it. There are two main types of succession, primary and secondary.

Pioneer community: It is the first biotic community which develops in bare area. It is established over a previously bare area. Pioneer community consists of a fewer small sized organisms. The area is hostile for pioneer community.
Climax community: It is final biotic community that develops in an area. It occurs over an area previously occupied by serai communities. It consists of numerous large and small sized organisms. The area is favourable for the climax community.

On what does the stability of a biological community depend ?

Community, also called biological community, in biology, an interacting group of various species in a common location. For example, a forest of trees and undergrowth plants, inhabited by animals and rooted in soil containing bacteria and fungi, constitutes a biological community. The resultant loss of species or other components in communities has potentially serious impacts on the provision of ecosystem services, including the future potential for those that are currently less concerned. Hence the stability of a biological community depends on the species present in that community.

Explain how xerarch succession progresses from xeric to mesic condition and forms a stable climax community.

Lichens that grow on the rocks secrete acids which help in weathering of rocks and thus forming soil. The gaps in the soil formed due to the acid activity create ways for the growth of small plants such as bryophytes, which have the capability to grow in a very small amount of soil. These small plants are succeeded by higher plants and after several stages lead to form a stable climax community.

Why is the rate of secondary succession faster than that of primary succession

In primary succession, there is no soil and it needs to form. This process takes time, as pioneer species must colonize the area, they must die, and as this happens over and over again, soil forms.
Secondary succession happens after some sort of disturbance. Vegetation has already been present in the area, but it no longer exists.

Trace the succession of plants on. a dry bare rock.

Succession on bare rock is called Xerosere.

The lichens are the pioneer species and invade the bare rocks. They secrete acids which dissolve the rocks, help in their weathering and formation of soil.
Mosses grow in with the lichens to form a mat over the substratum. Bryophytes or annual grasses succeed the lichens. They are able to hold small amount of soil.
Bigger trees appear in the later stages and are succeeded by other species untill a climax community forms an equilibrium with the environment. It leasds to the formation of forest ecosystem.

Explain how does a primary succession start on a bare rock and reach a climax community.

Lichens on the bare rocks produce acid which dissolves the rock leading to weathering of rocks into soil . This paves the way for small plants bryophyte which lead to bigger plants as well . This leads to the climax forest community when the conditions remain stable .

All successions proceed to a similar climax community-the mesic Explain.

1. Succession in plants occur as xerarch or hydrarch.

2. Xerarch succession takes place in dry areas and the series then progresses from xeric to mesic conditions. The hydrarch succession takes place in water bodies and the series then progress from hydric to mesic conditions.

3. Both these conditions lead to medium water conditions (mesic).

Define a climax community. How does a sere differ from a seral community?

The development of the vegetation for the process of the ecological succession for attaining the stable state called climax community , whereas seral community is an intermediate between the ecological and ecosystem advancing for the stable state i.e. climax community .

Starting from a bare rock or a site of volcanic eruption trace the organisms that participate in the process of succession.

Succession on a bare rock :

The lichens are the pioneer species and invade the bare rocks. They secrete acids which dissolve the rocks, help in their weathering and formation of soil.
Mosses grow in with the lichens to form a mat over the substratum. Bryophytes or annual grasses succeed the lichens. They are able to hold small amount of soil.
Bigger trees appear in the later stages and are succeeded by other species untill a climax community forms an equilibrium with the environment. It leads to the formation of forest ecosystem.

Write types of plant succession.

Plant succession is a process by which there is change in the species of plants in the given area over a period of time. It is of two types, namely Primary succession and secondary succession.

Primary succession begins in areas which have previously been unoccupied by plants. Secondary succession begins when the existing vegetation has been destroyed. It usually begins after forest fires, cutting of the trees, flood and erosions.

What is ecological succession?

Ecological succession is a process of gradual and predictable change in the species composition of an ecological community in a given area over a time.

Give an example for gaseous cycle.

$$\textbf{Solution:}$$

$$\bullet$$ The term biogeochemical is derived from the words "bio" (biosphere), "geo" (geographical segments), and "substance" (components that go through a cycle).

$$\bullet$$ Carbon, nitrogen, and oxygen can all be part of the gaseous cycle.

$$\bullet$$ The phosphorus cycle is a part of the sedimentary cycle.

$$\bullet$$ The nitrogen cycle is a biogeochemical cycle in which nitrogen is converted into a variety of structures, travelling from the atmosphere to the soil to creatures and back to the atmosphere.

Represent pyramid of number in a grassland ecosystem.

Pyramid of numbers in a grassland ecosystem. Only three top carnivores are supported in an ecosystem based on production of nearly 6 millions plants.

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What is ecological succession? How is hydrarch succession different from xerarch succession?

Ecological succession is a sequence of seres from barren land to the climax. In ecological terms, the developmental stages of a community are known as seral stages and the final stage as the climax. The initial community of the area, which is replaced in time by a sequence of succeeding communities until the climax is reached, is called pioneer stage or pioneer community. The entire series of communities that is a characteristic of given site is called a sere.

Xerosere or Xerarch succession and Hydrosere or Hydrarch succession are two main biological successions. These differ in following characteristics:

1. Xerosere originate on bare rock surfaces, where the original substratum is deficient of water and lacks any organic matter whereas Hydrosere is a succession in which a pond, and its community are converted into a land community.

2. In xerosere, pioneer stage is of lichens whereas in hydrosere, pioneer stage is of phytoplanktons.

Describe primary productivity and its types.

Primary productivity is the rate at which energy is converted by photosynthetic and chemosynthetic autotrophs into organic substances. In other words, it the energy produced per unit area in a time period by autotrophs. It depends upon several factors like plant species, environmental factors, availability of nutrients, etc. It is of 2 types, gross primary productivity and net primary productivity. Gross primary productivity (GPP) is the total amount of productivity in a particular region. Net primary productivity (NPP) is the difference between GPP and the respiration losses (R). Respiration loss incldues energy loss to metabolism and maintenance.

Hence, NPP = GPP - R.

Define biomass.

Biomass is the amount of living material or organic matter present in an organism, community or biome.

What is primary productivity? Why does it vary in different types of ecosystems?

Primary productivity is defined as the amount of energy accumulation in photosynthetic organisms, by the process of photosynthesis, as biomass or organic matter per unit area over a period of time. It varies in different types of ecosystems because of the different factors that influence it. For different ecosystems, plant species composition, and succession, their photosynthetic activity, availability of nutrients, availability of sunlight and precipitation, type of soil and a number of environmental factors, all differ and hence there's a variability seen in different ecosystems.

How are productivity, gross productivity, net primary productivity and secondary productivity interrelated.

Productivity is the rate of biomass production expressed in terms of g$$(-2)$$ yr$$(-1)$$ or kcal m$$(-2)$$. Primary production is defined as the amount of biomass or organic matter produced per unit area over a time period, all during photosynthesis.

Gross primary productivity (GPP) of an ecosystem is defined as the rate of production of organic matter or biomass during photosynthesis.

Net primary productivity (NPP) is GPP minus respiration loses (R), in the equation, written as NPP = GPP - R

Secondary productivity is given by the rate of formation of new organic matter by the consumers.

Hence, all are interrelated as mentioned above.

How does phosphorus cycle differ from carbon cycle?

The biogeochemical cycles are classified into two types namely the gaseous cycle and the sedimentary cycle. For gaseous cycles, the main source chemicals are atmosphere and oceans for example carbon cycle, nitrogen cycle.

In the sedimentary cycle made the sources are the soil and the rocks, for example, sulphur cycle and phosphorus cycle.

Why is the pyramid of energy always upright? Explain.

Of the enormous solar energy, plants are able to utilize and absorb only a fraction of energy. As per the 10% law of energy transfer, only 10% of energy passes from one trophic level to the successive trophic level. Energy is always dissipated in the process and therefore a comparatively less amount of energy is available for the successive trophic level. Hence, the pyramid of energy always remains upright with base showing large energy value while in successive levels it reduces considerably.

Define a sere.

The entire sequence of development stages of biotic succession from pioneer to a climax community is known as sere.

Write the importance of phosphorus in living organisms.

Phosphorous is a significant element of requirement in the living systems. It forms the inorganic component of nucleic acids, ATP, bones, teeth, and phospholipids. It takes part in performing various metabolic reactions involved in the release of energy and various other reactions.

Write one difference between net primary productivity and gross primary productivity.

The rate of production of total organic matter during photosynthesis is defined as Gross Primary Productivity (GPP). While a major amount of GPP is utilized by plants for respiration, Net Primary Productivity (NPP) is given by GPP minus Respiration loses (R).

GPP - R = NPP

GPP>NPP

"It is often said that the pyramid of energy is always upright. On the other hand, the pyramid of biomass can be both upright and inverted". Explain with the help of examples and sketches.

The number, biomass energy of organism gradually decreases and producer level to consumer level. This can be represented in the form of a pyramid which is known as the ecological pyramid. An ecological pyramid is the graphic representation of the number, biomass and the energy of the successive trophic level by ecosystem this helps in studying the ecosystem and identifying the energy transfer. For example, the pyramid of number is where the number of an individual at the trophic level decreases from the producer level to the consumer level. That is in an ecosystem the number of producers is for higher than the number of consumers. A number of producer per unit area is more in the pond ecosystem grassland ecosystem.

Energy flow in an ecosystem is from the producer level to the consumer level and this is shown by the pyramid of energy. Hence the amount of energy decreases from the producer level to the consumer level.

Explain the significance of ecological pyramids with the help of an example.

How does an age pyramid for human population at given point of time helps the policy makers in planning for future?

Age pyramid is the graphical illustration that shows the distribution of various age groups in the population.
It helps the policy makers to plan the healthcare programs, education policies, infrastructure, employment policies etc.

Fill in the blanks:
In an ecosystem dominated by trees, the pyramid of number is _______ type.

In an ecosystem dominated by trees, the pyramid (of numbers) is of Inverted type because it makes more biomass that leads to the large population of birds and insects as compared to the trees.

If you were to count the number of insects feeding on a big tree what kind of pyramid would you get? Now add an estimate of the number of small birds depending on the insects, as also the number of larger birds eating the smaller.

Draw the shape you would get from the above-mentioned data.

Depending upon the given data, a spindle-shaped pyramid could be observed. This indicates the pyramid of numbers. In this, the number of the tree will remain only one.
However, the number of insects will be in a large number. However, the number decreases from small birds to larger birds.
This indicates the number of primaries, secondary and tertiary consumers.

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Define with examples, pyramids of number and biomass.

Pyramid of Numbers

It is generally upright with producers population (e.g., grass plants, phytoplankton) being the largest. Producers support fewer herbivores (e.g., Grasshoppers, zooplankton). The number of primary carnivores (e.g., frogs, smaller fish) is still smaller. The number of higher order carnivores is very small. However, if the producer is large-sized like a tree, the pyramid of numbers can be inverted or spindle-shaped. A tree may support many herbivorous birds that may carry a large number of parasites or feed one or two hawks.

Pyramid of Biomass

Pyramid of biomass is generally upright with maximum biomass present in producers followed by lesser biomass in herbivores and still small biomass in carnivores. Only $$10-20\%$$ biomass is transferred from lower trophic to its higher trophic level. However, inverted or spindle-shaped pyramid of biomass is found in aquatic habitats due to smaller biomass of phytoplankton at any time because its members have a short life span but very high reproductive potential.

What would you do to help maintain the equilibrium in the various bio-geo-chemical cycles? Explain in brief.

Biogeochemical cycles refers to the movement of nutrients and other elements between biotic and abiotic factors in the ecosystem. Any disturbance in biogeochemical cycles will lead to climate change, increase the vulnerability of biodiversity, food security, human health, and water cycle.

To maintain the equilibrium in various biogeochemical cycles:

Avoid using phosphorus and nitrogen fertilizers to reduce their concentrations in soil. Increase of these nutrients in soil often lead to increase run off of landslides during wet weather conditions.
Reduce carbon pollution- by reducing usage of wood in cooking or any other domestic purposes.
Control vehicular and domestic pollution- It will reduce acid rains, droughts and wildfires affecting the ecosystem.
Conserve water and biodiversity- Limiting the usage of water and other resources would help in maintaining ecosystem. Water resources can be conserved through various techniques such as- Rain harvesting, metering and reducing valves pressure in taps and tanks.
Avoid deforestation- Forests play an important role in ecosystem, they control the weather, underground water levels and provide food and shelter to many organisms. Without them, the balance will disturbed.

The pyramid of biomass represents the relationships that exist between the quantity of living matter (biomass) at different trophic level. In the terrestrial ecosystem, the biomass progressively decreases from producers to top carnivores.
What does the biomass pyramid represents?

Pyramid of biomass represents the amount of living matter present in an ecosystem. In a terrestrial ecosystem, such as in case of a tree, the pyramid of biomass is upright as it supports a large number of birds and thus, biomass progressively decreases at each successive trophic level from producers to top carnivores.

The pyramid of biomass represents the relationships that exist between the quantity of living matter (biomass) at different trophic level. In the terrestrial ecosystem, the biomass progressively decreases from producers to top carnivores.
In which ecosystem the biomass progressively decreases form producers to top carnivores?

Fill in the blank:
In aquatic ecosystems, the limiting factor for productivity is ________.

In aquatic ecosystems, the limiting factor for productivity is light as plants and algae cannot grow in the absence of light.

Explain phosphorus cycle in nature.

Rocks undergo weathering and release free phosphorus into the soil.
It is taken up by the plants to synthesize energy in form of ATP.
Phosphorus is also added into the soil from manure and chemical fertilizers.
Animals take up this and synthesize energy in form of ATP.
Plants and animals after death get decayed by microorganisms of soil.
They release the phosphate in the soil by decomposing them.
The phosphate in the soil remains is deposited in mineral form in the soil.

Ecological succession begins with ........... species and end with ...........stage.

Ecological succession begins with pioneer species and end with climax stage.

Each trophic level has a certain mass of living material at a particular time called as the standing crop. The standing crop is measured as the mass of living organism (biomass) or the number in a unit area . The biomass of a species is expressed in terms of fresh or dry weight. Measurement of biomass in terms of dry weight is more accurate .Why?

The pyramidal representation of trophic levels of different organisms based on their ecological position [producer to final consumer] is called as an ecological pyramid.

Pyramid of biomass is usually determined by collecting all organisms occupying each trophic level separately and measuring their dry weight.

This overcomes the size difference problem because all kinds of organisms at a trophic level are weighed. Biomass is measured in g/m2.

Hence the biomass of a species is expressed in terms of fresh or dry weight. Measurement of biomass in terms of dry weight is more accurate.

Ecologist studied an area of wodland and estimated the biomass of each trophic level for one of the food chain in the woodland.
Some student wanted to use the data to draw a pyramid of biomass for the food chain table shown the students table.
The student added a column to calculate the width of the bars they would need to draw
Sr.No Tropic level Biomass/gm^{-2} width of bar/cm
1. producer 120 12.0
2. primary consumer 48 4.8
3. Secondary consumer 16 1.6
4. tertiary consumer 2
(i) Complete table 3.1 by calculating the missing value and writing it in the table

Sr.No	Tropic level	Biomass/gm^{-2}	width of bar/cm
1.	producer	120	12.0
2.	primary consumer	48	4.8
3.	Secondary consumer	16	1.6
4.	tertiary consumer	2	0.2

Above is the completed table of the biomass.

Early colonisers of bare and barren areas helps in _________ succession.

Colonisers of the bare and barren areas start the primary succession. These are lichens, arachnids, invertebrates. They make the soil inhabitable and also cause the weathering of rocks for more soil formation. When they die, their dead remains are decomposed that add up to the fertility of the soil and then advance life forms can start their growth.

Describe the energy pyramid.

The energy pyramid depicts the graphical representation of energy flow within the community. The different levels depict the different groups of organisms that constitute the food chain. The energy pyramid is always upright, it can never be inverted because the energy flow from one trophic level to another takes place and some amount of energy is lost as heat at each step. From the bottom to up different trophic levels are as such -

1) Producers: bring energy from the non-living sources into our food chain community.

2)Primary consumers: Herbivores in most of the communities thus eat the producers and derive energy.

3)Secondary consumers: Eat primary consumers, which make them carnivorous organisms.

4)Tertiary consumers: They feed on the secondary consumers.

What is energy pyramid? Correct the following diagram

The energy pyramid is a graphical representation of energy flow in a community. The energy pyramid is always upright it can never be inverted because at each trophic level loss of energy takes place in the form of heat. Thus, at every successive trophic level less amount of energy reaches as compared to the preceding trophic level giving an upright pyramid.

The following diagram has corrections as stated :

Maize $$\rightarrow$$ Producer

Grasshopper $$\rightarrow$$ 1st Trophic

Lizard $$\rightarrow$$ 2nd Trophic

Hawk $$\rightarrow$$ 3rd Trophic.

Draw a diagram of pyramid of energy.In the ecosystem, the energy flow is unidirectional. Explain.

In an ecosystem energy enters the food chain from the sun, when plants utilize sunlight to manufacture food. This energy than passes from one trophic level to the next. At each trophic level there is loss of energy. Only 10% of the energy of one trophic level passes to the subsequent trophic level. The rest of the energy is lost as heat. The energy lost as heat cannot be utilized by the plants again and do not return to the food chain. Hence, energy flow in an ecosystem is said to be unidirectional.
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"The pyramid of biomass of terrestrial ecosystem are always upright" said Jyothsna. Do you agree with this statement or not? Give reason.

Yes, I agree with the statement. In a terrestrial ecosystem such as a grassland ecosystem, the biomass decreases as we move from the lower towards each higher trophic level i.e from producers to primary consumers to secondary consumers. This happens because producers such as shrubs and herbs have the highest biomass and are higher than the animals which consume them. This decreases as we move towards higher trophic levels and is least in the highest predators in the food chain.

Explain productivity.

Productivity refers to the rate of generation of biomass in an ecosystem. It is usually expressed in units of mass per unit surface per unit time, for instance, grams per square metre per day.

There are three types of productivities – primary productivity, secondary productivity and community productivity.

1. Primary Productivity:

Primary productivity is the productivity at the producer level. It can be termed as the amount of organic matter produced by the plants from solar energy in a given area during a given period of time. Approximately 1-5% of solar energy that falls on the plant is converted to organic matter.

Primary productivity is of two types:

i. Gross Primary Productivity (GPP):

This refers to the total amount of organic matter produced. This also includes what is used by the producer in respiration. This can also be defined as total energy captured by the photosynthetic organism.

ii. Net Primary Productivity (NPP):

This productivity refers to the gross production minus the loss by respiration and decomposition. This is also called as apparent photosynthesis or net assimilation.

NPP = GPP – Respiration

2. Secondary Productivity:

This refers to the productivity at the consumer level. The secondary productivity reflects only the utilisation of food for production of consumer biomass.

3. Community Productivity:

This is the rate of net synthesis of organic matter by a community per unit time and area.

Explain primary productivity and the factors that influence it. Describe how do oxygen and chemical composition of detritus control decomposition.

a) Primary productivity is influenced by some physical options as

Light intensity light-weight length Temperature Soil pH convenience of nutrients carbonic acid gas levels

While different options influencing NPP is that the presence of biomass per unit space over a given period by plants throughout chemical change is outlined as primary productivity it's expressed in term of weight (g ) or energy (Kcal m ). Productivity will be categorized into gross primary productivity (GPP) and web primary productivity (NPP).

GPP is that the production rate of organic matter at the time of chemical change.

Primary productivity is directly proportional to the quantity of greenhouse emission, daylight, and water and is reciprocally proportional to metastasis losses. It will be expressed as NPP = GPP - metastasis losses (R)

b) Consumption of oxygen is the elementary step for decomposition that is directly associated with the quantity of oxygen within the atmosphere. Chemical nature of detritus and environmental condition regulates consumption of oxygen.

The rate of decomposition decreases if detritus is richly supported by polymer or polyose meantime its rate will increase if detritus is equipped nitrogen and sugar.

Draw the diagram of pyramid of number.

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(a)Why is Charcoal considered better fuel than wood?
(b)Write one disadvantage of converting wood into Charcoal.

(a) Charcoal is the pure form of carbon with high ignition value, it burns to give out high energy.
(b) The disadvantage of converting wood into charcoal is increasing pollution.

What do you mean by Nutrient cycle?

Nutrient cycle is the flow of organic and inorganic elements present in the ecosystem. The organic and inorganic elements flow in a cycle where they are exchanged back into production of matter. Unlike the flow of energy which is unidirectional flow of organic and inorganic matter is not unidirectional rather they are recycled again by passing through various components of an ecosystem. They are of two type- Gaseous and sedimentary. Examples are Carbon cycle, nitrogen cycle which are gaseous cycle. Whereas Sulphur and phosphorus are sedimentary cycles. Above is a picture provides for the carbon cycle. Where the organic carbon is released from the dead and decaying organisms, the air that is released by them while exhaling, the carbon that is emitted from the factories and vehicles, even that released from the water bodies which all goes in the atmosphere. This carbon dioxide released in the atmosphere is utilized by the producers ie the green plants via photosynthesis and is again introduced in the food cycle. In similar manner other cycles also takes place with just different sources where they are released and different sources of absorption.

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What are ecological pyramids? Explain with reference to pyramid of number in grassland ecosystem.

Ecological pyramids are also called as food pyramids or energy pyramids. They are graphical representations to show the biomass or bioproductivity at each tropical level in a given ecosysytem.

Pyramid of numbers is a graphical representation showing the population at each tropical level or each level of food chain. The producers are usually high in number in any ecosystem and hence it is upright pyramid.

In a grassland ecosystem, the producers which are mainly grass are high in number and followed by the decrease in population at each tropical level. The second tropical level is of herbivores, the third is of carnivores and the least number is of apex predators. Thus, a pyramid of numbers in a grassland is upright.

Define:
a) Stratification
b) Gross primary productivity
c) Leaching
d) Humification

a. Stratification: The vertical distribution of different species occupying different levels in an ecosystem is called stratification. Trees occupy the topmost vertical layer of a forest, shrubs occupy the second layer and herbs and grasses occupy the bottom-most or base layers.

b. Gross primary productivity: GPP is the net amount of energy that is produced by the main energy producers of the ecosystem in a particular area during the specific time. GPP tends to state the total productivity.

c. Leaching: Natural process by which water-soluble substances (such as calcium, fertilizers, pesticides) are washed out from soil or wastes is called leaching. These leached out chemicals cause pollution of surface and sub-surface water.

d. Humification: The process of the formation of humus is called humification.The creation of humus in the soil after interaction with bacteria which has broken down dead and dying biological matter into humus.

Identify the given pyramid and explain about it.

The given pyramid is of food chain pyramid where Hawk is the top of the food chain. Plants are eaten by aphids which are eaten by Ladybirds. These ladybirds are attacked by Insectivorous birds where they are hunted by Hawk. in the food chain

Write difference between pioneer community and climax community.

PIONEER COMMUNITY	CLIMAX COMMUNITY
1. It is the first biotic community which develops in bare area.	1. It is final biotic community that develops in an area.
2. Pioneer community is established over a previously bare area.	2. Climax community occurs over an area previously occupied by several communities.
3. Life span of organisms is short.	3. Life span of component organisms is generally long.
4. Pioneer community consists of a fewer small sized organisms.	4. Climax community consists of large and small sized organisms.
5. Growth is fast.	5. Growth is slow.

Is it true that there is more solar energy available in the tropics? Explain briefly.

It is absolutely true that more solar energy is available in the tropics. Sunlight falls directly at the tropics. Because of straight illumination, the duration of day is longer at the tropics than at higher latitudes. Due to this, plenty of sunlight is available in the tropics. Better availability of solar energy results in higher productivity which is evident from the rich biodiversity in this rogion.

What is the importance of different biogeochemical cycles in the nature? (ASI )

Biogeochemical cycles are important because they regulate the elements necessary for life on Earth by cycling them through the biological and physical aspects of the world. Biogeochemical cycles are a form of natural recycling that allows the continuous survival of ecosystems.

Biogeochemical cycles are named for the cycling of biological, geological and chemical elements through Earth and its atmosphere. The cycles move substances through the biosphere, lithosphere, atmosphere and hydrosphere. Cycles are gaseous and sedimentary. Gaseous cycles include nitrogen, oxygen, carbon and water. These elements cycle through evaporation, absorption by plants and dispersion by wind. Sedimentary cycles include the leeching of minerals and salts from the Earth's crust, which then settle as sediment or rock before the cycle repeats.

Repetition of the cycles is important. Plants absorb carbon dioxide and release oxygen, making the air breathable. Plants also acquire nutrients from sediment. Animals acquire nutrients from plants and other animals, and the death of plants and animals returns these nutrients to the sediment as they decay. The cycle then repeats and allows other living things to benefit.

The simplest example of biogeochemical cycles at work includes water. Water evaporates from the oceans, condenses as clouds and precipitates as rain, which returns the water back to the earth in a cycle.

Explain how diversity of living organisms helps in enriching any ecosystem.

The biological diversity of all the living organisms (flora and fauna) present in a region (ecosystem) is involved in the biological diversity of an ecosystem. This diversity of organisms help maintain the ecological balance by helping continue the food chains. They also help provide food and shelter to different organisms and help in the survival and sustenance of each other, thereby helping enrich the ecosystem.

Mesarch succession leads to which condition?

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Consider the following food chain which occurs in a forest $$:$$ $$Grass\dashrightarrow Deer\dashrightarrow Lion.$$ If $$10000 J$$ of solar energy is available to the grass, how much energy would be available to the deer to transfer it to the lion ?

Energy flows in an ecosystem in only one direction. The energy is only converted from one to another form. The sun is the energy provider. Flow of energy is through different trophic levels, first level includes primary producers which are known as autotrophs who perform photosynthesis. Herbivores, at second level take up the energy from grazing an autotrophs. At next trophic level, carnivores are present who hunt on herbivores and get energy from them. These all are interlinked and most of this energy is used upon carrying out regular bodily functions. When these die, decomposes like fungi, bacteria break down then and give it to the soil and hence the energy flows in an ecosystem.

According to the law of food chain, only $$10\%$$ of energy gets transferred to next level in food chain.

Gross (Energy) $$=10,000 J$$

Dear (Energy) $$=10\%$$ of $$10,000=\dfrac{10}{100}\times 10000=1000 J$$

Same way,

Lion (Energy) $$=\dfrac{10}{100}\times 1000=100 J$$

Explain ecological pyramids in detail

An ecological pyramid is the graphical representation of the biomass at each trophic level for a particular ecosystem. In the ecological pyramid, there are 3 levels of producers, consumers, and decomposers.

The ecological pyramid is of three types :

1. Pyramid of number - It shows the population of each chain graphically. These are the upright pyramid.

2. Pyramid of Biomass - It is the relation between the biomass at each trophic level. These are inverted pyramids.

3. Pyramid of energy - Its shows the productivity of the biomass at each trophic level.

Write down two special features of climax community.

Climax community is the final terminal community which can maintain its equilibrium itself and can

remain stable for long time until any external factors disturbs it.

Two main properties are -:

1) Stability $$\rightarrow$$ climax community is always stable with climate and can be replaced by competition.

2) Unitary $$\rightarrow$$ Climax is a unit, which acts as a guide of climate of an area.

The figure given below represents a food pyramid. Study it and answer the following questions.
i) Which trophic level has maximum energy ?
ii) Give one example for $$T_4$$ trophic level.

(i) The amount of energy at each trophic level decreases as it moves through an ecosystem. As little as 10 per cent of the energy at any trophic level is transferred to the next level; the rest is lost largely through metabolic processes as heat. Hence, T1 has maximum energy.

(ii) T4 includes second rank flesh-eaters such as Hawk.

What is primary production?

The primary productivity refers to the photosynthetic activity performed at the level of the producers at the first trophic level. When the producers convert solar energy into chemical energy to make the organic form of food, it is called the gross primary productivity. A portion of it is used in the respiratory activities of the plant and the remaining amount is called the net primary productivity, which is then available to the consumers.

Briefly explain the ecological pyramid which is always upright.

Ecological pyramids are of three general types namely:
(i) Pyramid of numbers, showing the number of individual organisms at each level
(ii) Pyramid of biomass, showing the total dry weight and other suitable measures of the total amount of living matter, and
(iii) Pyramid of energy, showing the rate of energy flow and/or productivity at successive trophic levels. (always upright)

Of the three types of ecological pyramids, the energy pyramids give the best picture of the overall nature of the ecosystem. Here number and weight of organisms at any level depend not on the amount of fixed energy present at any one time in the level just below but rather on the rate at which food is being produced. In contrast with the pyramids of numbers and biomass, which are pictures of the standing situations like organisms present at any moment the pyramid of energy is a picture of the rates of passage of food, mass through the food chain. In shape, it is always upright, as in most of the cases there is always a gradual decrease in the energy content at successive trophic levels from the producers to various consumers.

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How much energy from the sun can be converted into food energy by the green plants?

Energy flow in an ecosystem is unidirectional. Energy always flows from the sun to the producers and then to consumers. The green plants in a terrestrial ecosystem capture about 1% of the solar energy that falls on their leaves and converts it into food energy (chemical energy).

Under what conditions would a particular stage in the process of succession revert back to an earlier stage?

$$\textbf{Explanation:}$$

$$\bullet$$ During ecological succession there occurs gradual and fairly predictable change in the species composition of a given area.

$$\bullet$$ This change is orderly and sequential, parallel with the changes in the physical environment and leads to a community that is in near equilibrium with the environment.

$$\bullet$$ Such a community remains stable as long as the environment remains unchanged.

$$\bullet$$ Thus, only under natural or human-induced disturbances, a particular stage in the process of succession would revert back to an earlier stage.

Among bryophytes, lichens and fern which one is a pioneer species in a xeric succession?

Lichens are pioneer species in a xeric succession, crustose lichens are the first to inhabit rocks.

Give reason.

Energy flow through an ecosystem is 'one way'.

The producers convert solar energy into chemical energy in the form of organic compounds.
The primary consumers (herbivores) derive their nutrition from the producers.
According to the energy transfer law, only 10% of energy is transferred from one trophic level to the other.
So, the energy that is captured by the producers does not revert back to the sun and the energy transferred to the herbivores does not come back to the producers.
It just keeps on moving to the next trophic level in a unidirectional way.
That is why the flow of energy in the food chain is always unidirectional/one way.

Differentiate between "Pioneer-species"; 'Climax-community" and "Seres".

Pioneer Community

1. It is the first biotic community that develops in the bare area.

2. Pioneer community is established over a previously bare area.

3. The life span of organisms is short.

4. Pioneer community consists of fewer small-sized organisms.

5. Growth is fast.

Climax Community

1. It is the final biotic community that develops in an area.

2. Climax community occurs over an area previously occupied by several communities

3. The life span of component organisms is generally long.

4. The climax community consists of large and small-sized organisms.

5. Growth is slow.

Sere Community

1. Seres are classified primarily on the basis of the water content of the initial area in which they develop.

2. It is a transitional community that develops in an area during succession.

3. The life span is long.

4. The size of the individuals is small.

5. Growth is high.

Give reason.

Equilibrium is necessary in the various bio-geo-chemical cycles.

The cyclic flow of nutrients within an ecosystem is called the biogeochemical cycle. A continuous transfer of nutrients which are necessary for the growth of organisms occurs from abiotic to biotic factors and biotic to abiotic factors in an ecosystem. This nutrient cycle operates continuously through the biosphere formed by the lithosphere, atmosphere, and hydrosphere. The recycling of these biogeochemical depends upon the level of energy transfer in the ecosystem. Any type of disturbance at any level of these cycles affects the ecosystems and nature's balance. Hence, there should be equilibrium in the various biogeochemical cycles.

Name the following.
Inert gases in the air.

Oxygen and Nitrogen are the inert gases in the air.

Climax stage is achieved quickly in secondary succession as compared to primary succession. Why?

After primary succession, soil contains all the necessary nutrients, microbes and organic matter. Hence, the soil supports quicker growth of vegetation as compared to primary succession where all these factors are absent and and gradually become a part of the soil ecosystem during the process of succession.

In the North East region of India, during the process of Jhum cultivation, forests are cleared by burning and left for regrowth after a year of cultivation. How would you explain the regrowth of forest in ecological term?

$$\textbf{Explanation:}$$

$$\bullet$$ In Jhum cultivation or slash and burn method, the forest area or the agricultural field after harvesting or cutting is burnt with the remnants of the crops or the forest plants.

$$\bullet$$ After burning, the areas are left to recover for atleast a year for regrowth.

$$\bullet$$ The ash provides some fertilization that increases the potash content of the soil and supports better growth of crops or regrowth of the forest area.

$$\bullet$$ In ecological terms this is referred to as secondary succession.

Why are nutrient cycles in nature called biogeochemical cyles?

Nutrients are cycles through biotic components as well as through abiotic components. The term 'bio' shows biotic components while 'geo' shows abiotic components. Hence, nutrient cycles in nature are called biogeochemical cycles.

Primary productivity varies from ecosystem to ecosystem. Explain?

$$\textbf{Explanation:}$$

$$\bullet$$ Primary productivity is defined as the rate at which plants produce organic compounds from inorganic raw material during photosynthesis in an ecosystem.

$$\bullet$$ It depends on the plant species inhabiting a particular area, variety of environmental factors, availability of nutrients and photosynthetic capacity of plants.

$$\bullet$$ For example - Number of plants is higher in tropical rainforests as compared to deserts and hence, tropical rainforests have more primary productivity than deserts due to more photosynthetic activity.

$$\bullet$$ Since, the plant population and environmental factors vary from one ecosystem to another therefore, primary productivity varies from ecosystem to ecosystem.

Which of the following ecosystems will be more productive in terms of primary productivity: a young forest, a natural old forest, a shallow polluted lake, an alpine meadow? Justify your answer.

$$\textbf{Explanation:}$$

$$\bullet$$ Primary productivity depends on the plant species inhabiting a particular area and also on a variety of environmental factors, availability of nutrients and photosynthetic capacity of the plants.

$$\bullet$$ A young forest has not yet reached the climax and has low density of trees which accounts for its low primary productivity.

$$\bullet$$ A natural old forest is supposed to have reached its climax as it comprises of big trees with thick foliage which is responsible for its high primary productivity.

$$\bullet$$ A shallow polluted lake is devoid of producers as a consequence of pollution and accounts to a very low primary productivity.

$$\bullet$$ An alpine meadow is full of grasses with little or no tree which confers a low primary productivity.

$$\bullet$$ Thus, it can be concluded from the above discussion that a natural old forest ecosystem will be more productive in terms of primary productivity in comparison the above mentioned different ecosystems.

What is a biogeochemical cycle. What is the role of the reservoir in a biogeochemical cycle. Give an example of a sedimentary cycle with reservoir located in earth's crust.

The movement of nutrients through various elements of ecosystem is called nutrient cycling or biogeochemical cycle. Nutrient cycling ensures that nutrients are never lost from the ecosystem. They keep on getting replenished in the reservoirs in ecosystem.
Role of Reservoir: Whenever there is an imbalance between efflux and Influx of a particular nutrient, there can be deficit of that nutrient. The reservoir counters this deficit by supplying the required nutrient.
Phosphorus Cycle: The reservoir of Phosphorus is located in the earth's crust. Phosphorus cycle is one of the examples of sedimentary cycle. Rocks are the natural reservoirs of Phosphorus. It is present in rocks in the form of phosphates. During weathering of rocks, minute quantities of phosphates get dissolved in soil solution.
Phosphates in soil solution are absorbed by roots of plants. The primary and secondary consumers get phosphates from plants.
When dead organisms are decomposed by phosphates-solubilising bacteria, Phosphorus is released back to the environment.

Justify the following statement in terms of ecosystem dynamics. 'Nature tends to increase the gross primary productivity, while man tends to increase the net primary productivity".

Rate of production of organic matter in an ecosystem is called Gross Primary Productivity (GPP). When we subtract the respiratory losses (R) from GPP, we get Net Primary Productivity (NPP).
Nature provides various biotic and abiotic factors to enhance the rate of Gross Primary Productivity. Hence, it can be said that nature tends to increase the gross primary productivity.
But human beings need to make optimum utilization of the biomass produced. This is achieved in various ways; like harvesting the crop at the right time and plucking the fruits at the right time. If fruits will be left on the tree for a longer time, it will result in higher respiratory losses. A higher respiratory loss will reduce NPP. By plucking the fruits at the right time, man tries to increase the net primary productivity.

Write a short note on pyramid of numbers and pyramid of biomass.

Pyramid of Numbers: This pyramid shows the number of individuals at different trophic levels. Producers are kept at the bottom of the pyramid; followed by primary consumers, secondary consumers and so on. In most of the cases, the shape of the pyramid upright. In some cases, this pyramid can be inverted in shape.
Pyramid of Biomass: This pyramid shows the biomass (in terms of dry weight) at different trophic levels. Producers are kept at the bottom of the pyramid: followed by primary consumers, secondary consumers and so on. In most of the cases, the shape of the pyramid is upright. In some cases, this pyramid can be inverted in shape.

Why are oceans least productive?

Availability of solar radiation is least in oceans; especially in deep oceans. Due to this, oceans are least productive.

Why is the rate of assimilation of energy at the herbivore level called secondary productivity?

$$\textbf{Explanation:}$$

$$\bullet$$ Primary productivity is defined as the rate of biomass or organic matter produced by plants during photosynthesis.

$$\bullet$$ The herbivores get raw materials from producers or plants through assimilation for formation of new organic matter.

$$\bullet$$ Thus, the rate of assimilation of energy at the herbivore level is called secondary productivity.

Sometimes due to biotic/abiotic factor the climax remain in a particular seral stage (pre climax) without reaching climax. Do you agree with this statement. If yes give a suitable example.

This entire sequence of communities that successively change in a given area are called sere (s). All the biotic and abiotic factors play crucial role in this transition process and thus enable a community to reach the climax. If biotic and abiotic factors are not supportive enough for climax then the community may remain in a particular seral stage without reaching the climax. Presence of sparse vegetation at table top mountain can be one example of a community in seral stage. The community at the table top mountain may be in a stage in which only ferns and mosses may be present, in due course of time, it would pave way for higher plants.

The biodiversity increases when one moves from the pioneer to the climax stage. What could be the explanation?

Biodiversity of a community depends on the availability of food for consumers. If there is rich diversity in flora then more types of consumers can be supported in community.
When a community is at pioneer stage, lichens, bryophytes and pteridophytes are the main plants. These plants do not produce enough biomass which can sustain a diverse fauna. Hence, biodiversity would be limited at this stage.
When community reaches the climax; it is proliferated by gymnosperms and angiosperms. These plants produce enough biomass to sustain a diverse fauna. Hence, biodiversity increases at this stage.

What is common to the species shown in figures A and B?

Both are examples of Keystone species. A species which has a very high impact on its environment and the impact is disproportionate to its numerical strength; is called a keystone species.

What characteristics make a community stable?

Following characteristics make a community stable:
(a) Least variation in productivity from year to year
(b) Resistance to occasional disturbances
(c) Resistance to invasion by alien species

According to David Tilman, greater the diversity, greater is the primary productivity. Can you think of a very low diversity man-made ecosystem that has high productivity?

Crop field has high primary productivity but a low diversity. Crop field is a man-made ecosystem.

Difference between primary and secondary ecological succession.

Ecological succession is mainly of two types: Primary succession and secondary succession. The primary succession is a slow process that initiates in areas where there are no living organisms. Secondary succession begins in areas that were once inhabited but destroyed due to environmental disturbances.

Can you describe the efficiency of energy transfer between trophic levels?

Energy transfer between trophic levels typically follows the ten percentile rule. From each trophic level to the next, 90% of the starting energy is unavailable to the next trophic level because that energy is used for processes such as movement, growth, respiration, and reproduction. Some are lost through heat loss and waste. Thus, the remaining ten percent of the energy can be transferred to the next trophic level.

How do chlorofluorocarbons (CFSs) enter the atmosphere and how do they affect humans? Explain.

$$\textbf{Solution: }$$

$$\bullet$$The ozone layer is responsible for protecting the earth's atmosphere from the harmful Ultraviolet rays received from the sunlight.

$$\bullet$$The major constituents responsible for ozone layer depletion are chlorofluorocarbons (CFCs) such as freons, halons, and other compounds.

$$\bullet$$CFCs are widely used as coolants in refrigerators and airconditioners, in fire extinguishers, aerosol spray and as propellants.

$$\bullet$$Chlorofluorocarbons (CFCs) cause the depletion of the ozone shield by producing active chlorine which breaks ozone enzymatically.

$$\bullet$$Depletion of the ozone layer allows the UV radiations to enter the atmosphere

$$\bullet$$This can result in the incidence of cataracts, snow blindness, skin cancer and also reduces the functioning of the immune system of the human body.

Complete the world puzzle.
Down
1.Species on the verge of extinction.
2.A book carrying information about endangered species.
Consequence of deforestation.
Across
Species which have vanished.
Species found only in a particular habitat.
Variety of plants, animals and microorganisms found in an area.

Down
1.ENDANGERED
2.RED DATA BOOK
5. DROUGHT
Across
1.EXTINCT
3.ENDEMIC
4.BIODIVERSITY
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Define ecological pyramid

Ecological pyramid is a graphic representation of an ecological parameter (like biomass) sequence wise with producers at the base, herbivores above them followed by carnivores, secondary carnivores, etc. with the tip occupied by top carnivores.

Write the equation that helps in deriving the net primary productivity of an ecosystem.

Gross primary productivity (GPP) - Respiratory losses (R) = Net primary productivity (NPP)

(a) Draw a 'pyramid of numbers' of a situation where a large population of insects feed upon a very big tree. The insects in turn, are eaten by small birds which in turn are fed upon by big birds.
(b) Differentiate giving reason, between the pyramid of biomass of the above situation and the pyramid of numbers that you have drawn.

(a) Image has been attached.

(b) The difference in the shape of pyramids is because in the pyramid of energy, energy is lost at every step of the food chain. In pyramid of number, only the number is considered.

What are ecological pyramids? What precautions should be kept in mind in calculating its different aspects? Draw the diagrams of pyramids of grassland ecosystem and energy flow ecosystem.

Precautions should be kept in mind while calculating its different aspect:

Any calculations of energy, biomass, or numbers should include all organisms at each trophic level. Also, a given organism may occupy more than one trophic level simultaneously. Thus, one should know that the trophic level represents a functional level. For example, a sparrow is a primary consumer when it eats seeds, fruits and a secondary consumer when it eats insects and worms.

Differentiate between.
Primary and secondary succession

Succession always starts on bare area. When an area is colonised by organisms for the first time, the succession is called primary succession. If the succession starts on the area previously colonised but has been cleared off, it is called secondary succession.

Application based questions.
What would happen to all the energy fixed by autotrophic organisms if the community has no animals to eat the plants?

You can think of predation as natures way of transferring to higher trophic levels the energy fixed by plants.

In terms of energy, who is at an advantageous position, a vegetarian person or a non-vegetarian person?

In a food chain, the amount of energy transferred to the succeeding trophic level is only 10%. The remaining energy is wasted as heat to the environment. Let us consider the following food chain:

Producer (plants) $$\rightarrow$$ Primary consumer $$\rightarrow$$ Secondary consumer $$\rightarrow$$ Tertiary consumers

So, the producers (plants in this case) will have the maximum amount of energy. Of this, only 10% of energy gets transferred to the next trophic level i.e., a vegetarian person. Now, if a person is non-vegetarian, they obtain their energy from other animals that are either primary consumers or secondary consumers. Hence, the amount of energy received from them is even more reduced. Thus, a vegetarian person is at an advantageous position as they obtain energy directly from the producers, compared to the non-vegetarian person.

What is an Eltonian pyramid?

Eltonian pyramid or ecological pyramid is the graphic representation of an ecological parameter (like the number of individuals, biomass or energy) present in various trophic levels of a food chain with producers forming the base and carnivores the top.

What is primary productivity? Give brief description of factors that affect primary productivity.

Primary productivity refers to the total organic matter produced by primary producers per unit area per unit time.
Factors affecting primary productivity are-
1. Nutrient availability,
2. Temperature, sunlight, water and rainfall
3. Types and number of primary producers present in that ecosystem.

Construct an ideal pyramid of energy when 1,000,000 joules of sunlight is available. Label all its trophic levels.

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Why are the pyramids referred to as 'upright' or 'inverted'. Explain.

Pyramids are referred to as upright or inverted based on the number, biomass or any other factor that show gradation from producer to consumer level.

In an upright pyramid, producer occupies a broader base while successive trophic levels decrease in width or size due a decrease in the fact of under consideration. Like a pyramid of energy shows gradation with a broader base having a large amount of energy at producer level decreasing gradually towards successive levels.

Likewise, as in a pond ecosystem, the pyramid of biomass is inverted because biomass of fishes far exceeds the biomass of phytoplanktons. Producer this occupies a smaller base and consumers are more in biomass. The pyramid is inverted.

Explain primary productivity and the factors that influence it.

Primary productivity is used to describe the rate at which plants and other photosynthetic organisms produce organic compounds or organic matter or biomass in an ecosystem.

Primary productivity has two aspects :

• Gross productivity = the entire photosynthetic production of organic matter during photosynthesis in an ecosystem.

• Net productivity = the organic materials that remain after respiration loses incurred in photosynthetic organisms in the ecosystem or in simple words it is defined as gross primary productivity minus respiratory losses

NPP= GPP- R ( Respiration loss)

Since oxygen is one of the most easily measured products of both photosynthesis and respiration, a good way to measure primary productivity in an aquatic ecosystem is to measure dissolved oxygen.

Gross productivity cannot be directly measured because respiration is always occurring simultaneously with photosynthesis that involves use of oxygen and organic compounds.

Factors that influence primary productivity are:-

1. Light: The light field varies with depth in the ocean, with time of day, and with time of year.

Primary production in the ocean exhibits a strong depth dependence and a strong time dependence.

2. Temperature: Temperature controls the enzyme-mediated dark-reaction rates of photosynthesis.

3. Species composition also influence rates of primary production. For example, the size distribution of the cells and the pigment composition of the cells can both change with species composition, thus influencing nutrient uptake and light absorption for photosynthesis.

4. Availability of nutrients and photosynthetic capacity of plant also influence the primary productivity.

5. Species succession is also a determining factor.

Differentiate between primary and secondary succession. Provide one example of each.

Primary succession	Secondary succession
Ecological succession taking place in an uninhabited and barren land with no history of life support.	Ecological succession occurring in land previously occupied by organisms or communities.
Takes thousands of years to occur.	Occurs in about 50 to 400 years.
Eg. Newly formed bare rock pioneered by lichens.	Eg. Agricultural land left barren after use.

Construct a pyramid of number by taking suitable examples for each trophic level in an ecosystem.

The number of an individual at the trophic level decreases from the producer to consumer level. That is in an ecosystem is the number of producers is less. The number of herbivores are lesser than the producer. Similarly, the number of carnivores are lesser than the herbivores. The number of the producer per unit area is more in the pond ecosystem and grassland ecosystem. In the forest ecosystem, the pyramid of number is an intermediate point near the number of primary consumers is more than producer as well as that of the consumer.

Cite an example of an inverted ecological pyramid. What kind of pyramid of energy would it have?

Generally, in many aquatic ecosystems, the pyramid of biomass would be an inverted form. In this pyramid, the primary producer biomass is less when compared with consumer biomass. Hence, the pyramid assumes an inverted shape. Sun is the primary source of energy. Thus, the producers have the highest energy level. The energy always decreasing as go to higher trophic levels from producers. Hence, there is no inverted pyramid of energy.
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Represent a forest food chain with the help of flow chart. Also find out the amount of energy available at the third trophic level, if plants absorb $$1000$$ kilo joules of energy from the sun.

According to 10% law of tropic level, each trophic level will get 10% of energy from its previous trophic level. So, if a plant has a NET of 1000 KJ of energy then 100KJ of energy will transfer to the next level.
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Give a brief note on different bio-geochemical cycles

A biogeochemical cycle is a repeatable pathway by which either the chemical element or a molecule moves through both biotic and abiotic components. They include the following cycles -

Oxygen cycle- It is the exchange of oxygen in the atmosphere, biosphere, hydrosphere and lithosphere

Carbon cycle - It is the exchange of carbon dioxide with the biosphere, atmosphere, lithosphere etc.

Nitrogen cycle- It this cycle nitrogen is converted into many forms and circulates in the ecosystem.

Water cycle - This cycle describes the continuous flow of water above and below the earth. It is also known as the hydrologic cycle.

In the following food chain, 100 J of energy is available to the lion. How much energy was available to the producer?

There are three trophic levels the producer, the consumer and the secondary consumer according to 10% of energy transfer in trophic level.

If the lion has 100 J of energy then

let's take 10% of x = 100 J , then x = 1000J

Thus the producer had 1000 J of energy.

In the following pyramid of energy, label all the trophic levels and show the amount of energy available in each, if $$1,000,000 J$$ Of sunlight energy is available.

In a food chain of an ecosystem, 10% rule of energy transfer depicts that 10% energy of a particular a trophic level is passed on to the next trophic level. In this question, if 1000000 J of sunlight energy is available then first trophic level will have 10%X1,000,000= 100,000 J energy while the second trophic level will have 10%X100,000=10,000 J energy. The third trophic level will have 10%X10,000=1,000 J energy whereas the fourth trophic level will have 10%X1000=100 J available energy for tertiary consumers.

What are pioneer species? Give an example.

Pioneer species are hardy species which are the first to colonize previously biodiverse steady-state ecosystems. Some lichens grow on rocks without soil, so may be among the first form of life. The example includes bacteria, fungi, and lichens.

Calculate the amount of energy available to a lion in the following food chain, if plants have $$20,000$$ J of energy available from the sun.
Plants $$\rightarrow$$ Deer $$\rightarrow$$ Lion

If plants have 20,000 J of energy, a transfer of 10% will take place at next two levels.

Thus, the amount of energy available to the lion will be 200 J.

What is Nutrition Cycle

In our biogeochemical system, there is a flow of various forms of energy from one organism to another. The exchange of nutrients leads to the exchange of energy. The recycling of nutrients in the form of various components in the entire ecosystem is known as nutrient cycle or it is also called as biogeochemical cycle.

There are various types of nutrient cycles such as nitrogen cycle, oxygen cycle, carbon cycle, water cycle.

What is ecological succession? Explain the various stages involved in xeric succession hydric succession.

When a series of ecological communities are developed naturally in the same place till the formation of a climax community that doesn't develop further, it is called as ecological succession.

Xerarch succession: It is the succession that takes place in dry habitats like sand dunes, deserts etc, Plants growing in xerarch succession are called xerophytes.

Various stages by which xerarch succession develops are outlined below:

(1) Crustose lichen stage - Crustose lichens like Graphis, Rhizocarpon are thick and very resistant and grow on bare rocks as an external protective layer. They can tolerate extreme conditions and desiccation and can stick to the rock surface. The acidic substances produced by lichens results in the corrosion of rocks and formation of a thin layer of soil. The dead and decaying lichens then add humus to the soil making the habitat suitable for the growth of foliose(e.g. Parmelia) and fructose lichens.

(2) Foliose and fructose lichen stage: These lichens are leaf-like, soft and have a tender stem. They stick to the rock at one point only and increase shading due to their larger size. The dead organic matter forms humus, increases the moisture content of the soil and makes the soil suitable for the growth of mosses.

(3) Moss stage: Now that the habit is suitable, the mosses(e.g., Tortula, Grimmia) grow. They produce shade due to their larger size and replace the lichens. More soil accumulates as their roots penetrate deeper and the organic matter adds humus and moisture content to the soil.

(4) Herb stage: Small herbaceous plants now start to grow due to the presence of humus and moisture content of the cell. They pentrare their roots deeper secreting acids and weather the soil. Death of herbs adds more humus to the soil.

(5) Shrub stage: The habitat occupied by herbs soon become suitable for invasions of shrubs like Zizyphus and Rubus due to the presence of more humus. As shrubs are larger in size, their roots penetrate deeper, causing more fragmentation of rock and hence more soil accumulates.

(6) Tree Stage: Then woody trees begin to establish due to the increased moisture and humus content. The growth of tree species is supported by environmental change. The organic material like leaf litter and decaying roots add more humus to the soil.

(7) Forest stage/ Climax community: The succession stops in a forest which consists of many trees. It takes a very long time for the establishment of the climax community. The nature of the climax forest depends upon the climate of that area.

Hydrarch succession: It is the succession that takes place in wetter areas like freshly formed ponds. Plants growing in hydrarch succession are called hydrophytes.

Various stages by which hydrach succession develops are outlined below:

(1) Phytoplankton stage: It is the pioneer community of hydrarch succession when phytoplanktons grow in the pond as a result of the distribution of their spores by wind or animals. They multiply rapidly and zooplanktons feed upon them. The death and decaying plankton forms mix with clay and slit at the bottom of the pond to form soft mud. Then the next stage grows.

(2) Submerged stage: Here, the pond becomes shallower and nutrients are moderate in amount. These plants are submerged in water and their death adds organic matter to the bottom level which then rises and provide space for floating leaves hydrophytes.

(3) Floating stage: Here, the pond becomes more shallower and the leaves of the rooted plants in mud float in water.

(4) Reed swamp stage: More shallowing of plants occur due to continued siltation which paves the way for the growth of rooted emergent plants i.e., reeds(amphibious plants).

(5) Marsh-meadow stage: Reed swamp stage is invaded by marshy plants. With increased settling of silt and deposition of dead organic matter derived from floating and rooted species, the pond becomes shallower until it gets transformed into terrestrial habitat. E.g., Carex, Juncas.

(6) Scrub stage: Marsh-meadow stage is replaced by shrubs. E.g., Salix, Populus.

(7) Climax community: The scrub stage is replaced by trees which grows to greater heights. The nature of climax community depends on the climate of that area. E.g., Forest.

Give any two examples of xerarch succession.

$$\bullet$$ Xerarch succession takes place in dry areas and the series progresses from xeric to mesic conditions.

$$\bullet$$ Two examples of xerarch succession include -

1. Lithosere - Ecological succession on a bare rock.

2. Psammosere - Ecological succession on sand.

State the different types of bio-geochemical cycles and explain the importance of those cycles.

To maintain the concentrations of different naturally occurring substances in the environment, there are mechanisms that constantly recycle these substances. These recycling mechanisms are called biogeochemical cycles. So, biogeochemical cycles are the cyclic flow of nutrients between non-living environment and living organisms.
Types of Biogeochemical Cycles
There are two major types of biogeochemical cycles
1. Gaseous cycle: These are the biogeochemical cycles in which the reservoir pool is the atmosphere or hydrosphere. For example, Carbon cycle, Nitrogen cycle, Oxygen cycle and water cycle
2. Sedimentary cycles: These are the biogeochemical cycles in which the reservoir pool is generally lithosphere. For example, Phosphorous cycle, Sulphur cycle etc.

Importance of these cycles

All these cycle follow a common path of movement, they are part of the abiotic system, move into the biotic system, get assimilated in the biotic system, the death and decay by detritus organisms releases these nutrients back into the abiotic system.

Thus, these cycles maintain a constant flow of essential nutrients into biotic system.

They maintain a balance of substances or minerals between the abiotic and the biotic systems of the ecosystem.

Ecosystem - Class 12 Medical Biology - Extra Questions

The pyramid of .......... is always upright.

Ecological pyramids are usually upright. Meanwhile some, pyramid of biomass is inverted. Explain the reason.

What is succession? What are its type? Write any two stages.

Explain energy pyramid.

Write the equation that helps in deriving net primary productivity of an ecosystem.

What is succession? Discuss succession in ponds.

Phosphorus cycle is an example of ........... cycle.

How much time is taken for a primary succession to complete?

What is the ultimate source of energy for the ecosystems?

Biogeochemical cycles describes the movement of water and other materials throughout the _______ and _______ environment.

The flow of energy is always _______ in food chains.

Rewrite the given sentence, if it is a false statement:'The flow of energy in an ecosystem is cyclic'.

Write the importance of phosphorus cycle in ecosystems.

What does 'R' represent in the given equation for productivity in an ecosystem? GPP-R=NPP

How much energy flows from one trophic level to next in a food chain ?

What is the difference between biodegradable and non-biodegradable waste? Give example of each

What are biogeochemical cycles?

What is the role of biogeochemical cycles in the environment?

Give the existence'of carbon.

How is energy flux related to carbon oxidation and reduction reactions?

Name the three types of biogeochemical cycles.

What are biogeochemicals?

All the living organisms are basically made up of C, N, S, P, Hand O. How do they enter the living forms? Discuss.

What is biological magnification? Will the levels of this magnification be different at different levels of the ecosystem?

State the function of a reservoir in a nutrient cycle. Explain the simplified model of carbon cycle in nature.

In a food chain, if 10,000 joules of energy is available to the producer, how much energy will be available to the secondary consumer to transfer it to the tertiary consumer?

Why the pyramid of energy is always upright? Explain.

Explain how does:(a) A primary succession start on a bare rock and reach a climax community?(b) The algal bloom eventually choke the water body in an industrial area?

Differentiate between primary and secondary succession and provide one example of each.

What amount of energy will be available to the organisms of the $$2^{nd}$$ trophic level of a food chain, if the energy available at the first trophic level is 10,000 joules?

(i) What is primary productivity? Why does it vary in different types of ecosystems?(ii) State the relation between gross and net primary productivity.

Write important features of a sedimentary cycle in an ecosystem.

What is primary productivity? Give brief description of factors that affect primary productivity.

Define decomposition and describe the processes and products of decomposition.

Define ecological pyramids and describe with examples, pyramids of number and biomass.

What is ecological succession. Mention its different steps. Explain Hydrach and Xerarch succession with diagramatic representation.

What do you understand by ecological pyramid? Explain pyramid of biomass in a grassland with the help of a diagram.

Observe the pyramid of number which is given below and answer the questions. (i) As per the number of organisms in the tropic level, which group of organisms are more in number and which are less in number ? (ii) What happens if Secondary consumers disappear ?

What do you understand by energy flow in an ecosystem? Explain energy flow through different trophic levels. Draw line diagram of a food chain.

Observe the following biogeochemical cycle.(i) Mention the nutrient in the given cycle.(ii) Write the activities from 'A' to 'D'.

Animals give out .......... through respiration.

a) What is ecological secession?b) Represent an ideal pyramid of number in a grassland ecosystem.c) Name the two types of nutrient cycles with an example each.

What is meant by ecological succession?

Describe the inter relationship between productivity, gross primary productivity and net productivity.

a) Distinguish between primary productivity and secondary productivity of an ecosystem.b) Define food web.

What is an ecological pyramid? Compare the pyramids of energy, biomass and numbers.

Write any two limitations of ecological pyramids.

Why is pyramid of energy never inverted in any ecosystem?

Answer in 40 to 80 words:With reference to ecological succession define the following terms:i) Climax communityii) Sere(s)iii) Pioneer species.

Answer in 40 to 80 words:What is ecological succession? Distinguish primary succession from secondary succession.

a) Draw an ideal pyramid of energy and mention the units.b) What is an ecological succession?

The rate of biomass production in an ecosystem is called productivity. They are of two types, gross primary productivity and net primary productivity. How these two productivities are related?

Primary succession on rocks is known as xerosere. Answer the following related with xerosere.(a) Name the pioneer community.(b) Organic acids have important roles in this succession. Justify.

A list of different organisms in an ecosystem are given below Arrange them in 1$$^{st}$$, 2$$^{nd}$$, 3$$^{rd}$$ and 4$$^{th}$$ trophic level.(i) Phytoplankton(ii) Man(iii) Fish(iv) Zooplankton

The species that invade a nude area are called ........... species. In a primary succession on rocks, the group that invade first are usually are known as

a. Briefly explain ecological pyramidsb. Define primary productivity. Give two factors which affect primary productivity.

What are ecological pyramids? Why is energy pyramid always erect? Explain.

Which of the following is correct with respect to the estuarine ecosystem?A: Estuary constitutes one of the most productive ecosystemsB. It represents the transition zone between two populations of a species

Give specific reasons for the following statements:We cannot distinguish colours in moonlight.

How do you explain the following statement?Energy used by a leaping frog is actually the energy obtained from the Sun.

Pyramid of energy is always..........

Short / Long Answer Type Questions :Construct an ideal pyramid of energy when 1,000,000 joules of sunlight is available.Label all its trophic levels

The form of energy at the beginning of the food chain is ________.

In an ecosystem dominated by trees, the pyramid of numbers is ..........type

Short / Long Answer Type Questions :It is stated that the pyramid of energy is always upright. Justify

Differentiate between two different types of pyramids of biomass with the help of one example of each

Write a difference between net primary productivity and gross productivity

Short / Long Answer Type Questions :Carbon cycle in nature is a biogeochemical event. Explain

Short / Long Answer Type Questions :(a) Why is pyramid of energy always upright? Explain. Mention the limitations of an ecological pyramid(b) Construct a pyramid of biomass starting with phytoplanktons. Label three trophic levels. Is the pyramid upright or inverted ? Why?

What is meant by ecological succession ? Differentiate between pioneer community and climax community.

On what does the stability of a biological community depend ?

Explain how xerarch succession progresses from xeric to mesic condition and forms a stable climax community.

Why is the rate of secondary succession faster than that of primary succession

Trace the succession of plants on. a dry bare rock.

Explain how does a primary succession start on a bare rock and reach a climax community.

All successions proceed to a similar climax community-the mesic Explain.

Define a climax community. How does a sere differ from a seral community?

Starting from a bare rock or a site of volcanic eruption trace the organisms that participate in the process of succession.

Write types of plant succession.

Biogeochemical cycles describes the movement of water and other materials throughout the _ and _ environment.

Rewrite the given sentence, if it is a false statement:
'The flow of energy in an ecosystem is cyclic'.

Explain how does:
(a) A primary succession start on a bare rock and reach a climax community?
(b) The algal bloom eventually choke the water body in an industrial area?

(i) What is primary productivity? Why does it vary in different types of ecosystems?
(ii) State the relation between gross and net primary productivity.

Observe the pyramid of number which is given below and answer the questions.
(i) As per the number of organisms in the tropic level, which group of organisms are more in number and which are less in number ?
(ii) What happens if Secondary consumers disappear ?

Observe the following biogeochemical cycle.
(i) Mention the nutrient in the given cycle.
(ii) Write the activities from 'A' to 'D'.

a) What is ecological secession?
b) Represent an ideal pyramid of number in a grassland ecosystem.
c) Name the two types of nutrient cycles with an example each.

a) Distinguish between primary productivity and secondary productivity of an ecosystem.
b) Define food web.

Answer in 40 to 80 words:
With reference to ecological succession define the following terms:
i) Climax community
ii) Sere(s)
iii) Pioneer species.

Answer in 40 to 80 words:
What is ecological succession? Distinguish primary succession from secondary succession.

a) Draw an ideal pyramid of energy and mention the units.
b) What is an ecological succession?

Primary succession on rocks is known as xerosere. Answer the following related with xerosere.
(a) Name the pioneer community.
(b) Organic acids have important roles in this succession. Justify.

A list of different organisms in an ecosystem are given below
Arrange them in 1$$^{st}$$, 2$$^{nd}$$, 3$$^{rd}$$ and 4$$^{th}$$ trophic level.
(i) Phytoplankton
(ii) Man
(iii) Fish
(iv) Zooplankton

a. Briefly explain ecological pyramids
b. Define primary productivity. Give two factors which affect primary productivity.

Which of the following is correct with respect to the estuarine ecosystem?
A: Estuary constitutes one of the most productive ecosystems
B. It represents the transition zone between two populations of a species

Give specific reasons for the following statements:
We cannot distinguish colours in moonlight.

How do you explain the following statement?
Energy used by a leaping frog is actually the energy obtained from the Sun.

Short / Long Answer Type Questions :
Construct an ideal pyramid of energy when 1,000,000 joules of sunlight is available.Label all its trophic levels

Short / Long Answer Type Questions :
It is stated that the pyramid of energy is always upright. Justify

Short / Long Answer Type Questions :
Carbon cycle in nature is a biogeochemical event. Explain

Short / Long Answer Type Questions :
(a) Why is pyramid of energy always upright? Explain. Mention the limitations of an ecological pyramid
(b) Construct a pyramid of biomass starting with phytoplanktons. Label three trophic levels. Is the pyramid upright or inverted ? Why?

Fill in the blanks:
In an ecosystem dominated by trees, the pyramid of number is _______ type.

If you were to count the number of insects feeding on a big tree what kind of pyramid would you get? Now add an estimate of the number of small birds depending on the insects, as also the number of larger birds eating the smaller.

Draw the shape you would get from the above-mentioned data.

The pyramid of biomass represents the relationships that exist between the quantity of living matter (biomass) at different trophic level. In the terrestrial ecosystem, the biomass progressively decreases from producers to top carnivores.
What does the biomass pyramid represents?

Fill in the blank:
In aquatic ecosystems, the limiting factor for productivity is ________.

(a)Why is Charcoal considered better fuel than wood?
(b)Write one disadvantage of converting wood into Charcoal.

Define:
a) Stratification
b) Gross primary productivity
c) Leaching
d) Humification

The figure given below represents a food pyramid. Study it and answer the following questions.
i) Which trophic level has maximum energy ?
ii) Give one example for $$T_4$$ trophic level.

Give reason.

Energy flow through an ecosystem is 'one way'.

Give reason.

Equilibrium is necessary in the various bio-geo-chemical cycles.

Name the following.
Inert gases in the air.