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CBSE Questions for Class 12 Medical Biology Ecosystem Quiz 10 - MCQExams.com
CBSE
Class 12 Medical Biology
Ecosystem
Quiz 10
Which of the following aquatic ecosystems has very little primary productivity
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River
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Estuary
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Lake
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Marsh
Which of the following can explain the energy stored in an ecosystem?
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Pyramid of biomass
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Food chain
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Pyramid of energy
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Food web
Explanation
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 biomass" shows the relationship between biomass and trophic level by quantifying the biomass present at each trophic level of an energy community at a particular time. It is a graphical representation of biomass present in unit area in different trophic levels. The pyramid of biomass may be "inverted".
So the correct option is 'pyramid of biomass'.
Clements proposed the climax-pattern model of succession. Governing factors for this succession that he proposed were
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climate
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soil conditions
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each community modifies the environment
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all of these
Explanation
Every succession leads to the climax state. the governing factors for the succession are the type of soil, climatic conditions, the interaction of the community to the environment,
So, the correct option is 'all of these'
Primary succession takes much longer than secondary succession because it involves:
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time for development of the soil horizons
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more time for development of a seed.bank
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colonization by organisms that are farther away
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redevelopment of the atmospheric gases
Explanation
Primary succession takes much longer than the secondary succession because in the primary succession the, the horizons are soil are made from scratch. primary succession can take millions if years.
So the correct option is 'time for development of the soil horizons'
Choose the correct answers from the alternatives given.
Some species of Anopheles mosquito live in brackish water, some in running fresh water, and others in stagnant water. What type of reproductive barrier is most obviously separating these different species?
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Ecological isolation
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Temporal isolation
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Behavioural isolation
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Postzygotic barriers
Explanation
Populations may occupy the same territory but live in different habitats and so not meet are called Ecological isolation. Example the Anopheles maculipennis group consists of six species, some of which are involved in the transmission of malaria. Although the species are virtually indistinguishable morphologically, they are isolated reproductively, in part because they breed in different habitats. Some breed in brackish water, others in running fresh water, and still others in stagnant fresh water.
So, the correct answer is
Ecological isolation.
In a disturbed site in a community recovers and moves again toward the climax state.
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area effect
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primary succession
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distance effect
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secondary succession
Explanation
Secondary succession is the type of succession where the there were living species present before and it was an ecosystem Due to some natural calamity such as fire, or earthquakes the ecosystem got destroyed. If the succession starts in such place it is known as secondary succession and there are many nutrients available in the a4ea beforehand.
This succession is faster.
So, the correct option is 'secondary succession'
Which one of the following Clements would consider to be the climax community in a humid environment?
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The pioneer community
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Lichens, mosses, and ferns
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Large plants such as shrubs and trees
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Small native plants of the area such as grasses and herbs
Explanation
The climax community s the last stable community in the succession stage. The last climax stage involves large plants like trees, shrubs.
So, the correct option is 'Large plants such as shrubs and trees'
All of the following increase as community succession progresses, except for
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Relative amount of biomass produced by producers
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Number of species present
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Intricacy of trophic relationships
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Degree of specialization of species present
Explanation
During the course of evolution, the simple and less adaptable life forms change into complex forms. The number of organisms inhabiting the area increases substantially and hence a food web is created with intricacy of trophic relationships. The organisms become more specialized leading to their defined niches. There isn't a compulsory increase in amount of biomass produced by producers.
So, the correct option is 'Relative amount of biomass produced by producers'.
Choose the correct from the alternatives given.
Which one of the following organisms is the first to colonise a bare rock?
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Lichens
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Mosses
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Perennial plants
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Metazoans
Explanation
Plant succession occurs on bare rocks is called Xerosere.
A.Lichens - These are the special type of plants formed by the association of algae and fungi. These are typically the first organisms to colonize bare rock. They are therefore the pioneer species in primary succession.
B.Mosses - These are one type of bryophytes formed after lichens
C.Perennial plants - These are angiosperms constitutes climax community in xerosere
So the correct option is 'lichens'.
State whether the following statements are true or false.
Humans often disrupt natural succession to produce agricultural fields and managed forests.
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True
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False
Explanation
Humans cause a lot of destruction to the natural succession, through deforestation, starting forest fires, farming, and building things. When a forest is destroyed, secondary succession begins to take place. It is still slow, and habitats take hundreds of years to rebuild, and often are nothing like the habitat before it.
So, the correct option is 'True'.
State whether the following statements are true or false.
Clements called the first stage of secondary succession the climax community.
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True
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False
Explanation
From about 1900 to 1960, however, understanding of succession was dominated by the theories of Frederic Clements, a contemporary of Cowles, who held that seres were highly predictable and deterministic and converged on a climatically determined stable climax community regardless of starting conditions. Clements explicitly analogized the successional development of ecological communities with ontogenetic development of individual organisms, and his model is often referred to as the pseudo-organismic theory of community ecology. Clements and his followers developed a complex taxonomy of communities and successional pathways.
So the given statement is false.
State whether the following statements are true or false.
After fire a primary succession starts at a very rapid rate
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True
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False
Explanation
After fire, secondary succession starts at a very rapid rate.
Secondary succession is the series of community changes which take place on a previously colonized, but disturbed or damaged habitat. Examples include areas which have been cleared of existing vegetation (such as after tree-felling in a woodland) and destructive events such as fires.
Secondary succession is usually much quicker than primary succession for the following reasons:
1. There is already an existing seed bank of suitable plants in the soil.
2. Root systems undisturbed in the soil, stumps and other plant parts from previously existing plants can rapidly regenerate.
3. The fertility and structure of the soil has also already been substantially modified by previous organisms to make it more suitable for growth and colonization.
So, the correct option is 'False'.
All successional trends lead towards relative xerophytism
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True
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False
Explanation
Based on the nature of the habitat, whether it is water (or very wet areas) or it is on very dry areas – succession of plants is called hydrach or xerarch succession respectively.
Both hydrarch and xerach successions lead to medium water conditions (mesic) – neither too dry (xeric) nor too wet (hydric).
So, the correct option is 'False'
State whether the following statements are true or false.
Ecological succession is directional, therefore a predictable process
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True
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False
Explanation
Succession is a directional non-seasonal cumulative change in the types of plant species that occupy a given area through time.
Succession begin when an area is made partially or completely devoid of vegetation because of a disturbance such as disease, fire, volcanic eruption etc.
Succession stops when species composition changes no longer occur with time, and this community is said to be a climax community.
So, the correct option is 'True'.
State whether the following statements are true or false.
Climax indicates a final and stable community in a successional series
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True
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False
Explanation
Climax community is a group of organisms that has undergone ecological succession in the given area over time and reached to a stable state.
So, the correct option is 'True'.
State whether the following statements are true or false.
Succession leads to the formation of a more or less stable community
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True
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False
Explanation
Gradual and fairly predictable change in the species composition of a given area is called ecological succession. Ecological succession is a community controlled phenomenon, in which the structure and composition of communities change in an orderly and sequential manner, leading ultimately to the establishment of a more or less stable climax community.
There is a gradual and fairly predictable change occurs in the species composition of a given area. Some species colonise an area and their populations become more. In the successive seral stages, there is a change in the diversity of species, increase in the number of species and organisms and also in the total biomass.
So, the correct option is 'True'.
What types of the ecological pyramid would be obtained with the following data?
Secondary consumer: 120 g
Primary consumer: 60 g
Primary producer: 10 g
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Upright pyramid of numbers
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Inverted pyramid of biomass
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Upright pyramid of biomass
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Pyramid of energy
Explanation
Biomass is the amount of living matter present at a trophic level. The inverted biomass pyramid has the least number of primary producers, which supports primary consumers and the secondary consumers are maximum in number.
The given data follows a trend where the biomass of the primary producer is less than the primary consumer and that of the primary consumer is less than the secondary consumer. So, the given data supports an inverted pyramid. So,
the correct answer is option B.
In order to estimate the gross primary productivity (GPP) of a pond containing phytoplankton and zooplankton, a student collected water samples from the pond in two bottles labelled X and Y. The dissolved oxygen (DO) of the samples immediately after collection was $$8$$mg $$ml^{-1}$$. The DO content when measured after $$24$$ hours of incubation was as follows:
Bottle X: $$2$$ mg $$ml^{-1}$$ after incubation in dark
Bottle Y: $$18$$ mg $$ml^{-1}$$ after incubation in light
GPP of the pond is?
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$$6$$
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$$10$$
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$$16$$
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$$20$$
Explanation
GPP or Gross Primary productivity is referred as the total rate of photosynthesis including the organic matter used up in respiration during the measurement period.
When the bottles X and Y containing pond water are kept in dark and light respectively, there is decline in Dissolved oxygen (DO) in bottle X because phytoplankton and zooplankton will not be able to photosynthesise and the oxygen will be used up in respiration whereas, there is increase in DO in bottle Y because
phytoplankton and zooplankton will photosynthesise in presence of light resulting in production of oxygen.
So, from the information given,
Respiratory activity can be calculated as : Initial DO - DO after incubation in dark = 8 - 2= 6 mg/ml
Net photosynthetic activity can be calculated as : DO after incubation in light - Initial DO = 18 - 8= 10 mg/ml
GPP = Net photosynthetic activity + Respiratory activity = 10 + 6 = 16.
So, the correct answer is C.
Nitrogen is a limiting nutrient for
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Natural ecosystem
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Aquatic ecosystem
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agricultural ecosystem
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Both (a) and (c)
Match column I with column II and select the correct option from the given codes.
Column I
Column II
A. Gross primary productivity
(i) Self-sustainable ecosystem
B. Net primary productivity
(ii) Aquatic ecosystem
C. Pond
(iii) $$O_2$$ requiring process
D. Aquarium
(iv) Photosynthesis production
E. Decomposition
(v) Available to secondary consumers
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A-(iv), B-(ii), C-(i), D-(iii), E-(v)
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A-(iv), B-(v), C-(i), D-(ii), E-(iii)
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A-(i), B-(iii), C-(ii), D-(iv), E-(v)
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A-(ii), B-(i), C-(iii), D-(v), E-(iv)
Explanation
Column I
Column II
A. Gross primary productivity
Gross primary productivity, or GPP, is the rate at which solar energy is captured in sugar molecules during photosynthesis (energy captured per unit area per unit time). Producers such as plants use some of this energy for metabolism/cellular respiration and some for growth (building tissues).
So the correct option is 'photosynthesis production'.
B. Net primary productivity
Net primary productivity, or NPP, is gross primary productivity minus the rate of energy loss to metabolism and maintenance. In other words, it's the rate at which energy is stored as biomass by plants or other primary producers and made available to the consumers in the ecosystem.
So the correct option is 'available to secondary consumers'.
C. Pond
Since a pond is a natural ecosystem, it has all the biotic and abiotic components in it. These components are interlinked with each other for ensuring the survival of the organisms there, hence it is a self sustaining unit.
So the correct option is 'self-sustaining ecosystem'.
D. Aquarium
In an aquatic ecosystem rocks are needed for shelter and plants provide oxygen for fish. An ecosystem is balanced when the natural animals and plants and non-living components are in harmony- i.e. there is nothing to disturb the balance. An aquarium comprises of green plants, fish and other aquatic animals. Water, sand (or gravel etc.), temperature, light, etc. are also present the abiotic factors.
So the correct option is 'aquatic ecosystem'.
E. Decomposition
The process of decomposition — the breakdown of raw organic materials to a finished compost — is a gradual complex process, one in which both chemical and biological processes must occur in order for organic matter to change into compost. The decomposition (stabilization) of organic matter by biological action has been taking place in nature since life first appeared on our planet. When organic materials decompose in the presence of oxygen, the process is called “aerobic.” The aerobic process is most common in nature. For example, it takes place on ground surfaces such as the forest floor, where droppings from trees and animals are converted into a relatively stable humus. There is no accompanying bad smell when there is adequate oxygen present.
So the correct option is 'O$$_2$$ requiring process'.
Primary productivity depends upon.
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Light and temperature
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Water and nutrients
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Photosynthesis capacity of producers
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All of these
Explanation
The primary productivity of an ecosystem is the rate at which biomass or organic matter is produced per unit area per unit time by plants(primary producers). Primary productivity depends upon plant species of the area, their photosynthetic capacity, availability of nutrients, solar radiations, precipitation, soil type and a number of other environmental factors.
Which one of the following is the most productive ecosystem?
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Temperature forest
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Grassland
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Desert
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Tropical rainforest
Explanation
Tropical rainforest shows the maximum diversity and also the maximum productivity. More solar energy and resources are available in tropics which promotes higher productivity. On land the maximum primary production rate is found in tropical rainforests followed by tropical deciduous forests, temperate forests, savannah, temperate grasslands and desert scrub.
Match column I with column II and select the correct option from the given codes.
Column I
Column II
A. Gross primary productivity
(i) Green plants
B. Secondary productivity
(ii) Rate of synthesis of organic matter by consumers
C. Transducers
(iii) Total organic matter produced from solar energy
D. Food web
(iv) Interconnection of food chains
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A-(i), B-(ii), C-(iii), D-(iv)
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A-(iii), B-(ii), C-(i), D-(iv)
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A-(iii), B-(iv), C-(i), D-(ii)
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A-(ii), B-(i), C-(iv), D-(iii)
Explanation
Column I
Column II
A. Gross primary productivity
Gross primary productivity, or GPP, is the rate at which solar energy is captured in sugar molecules during photosynthesis (energy captured per unit area per unit time). Producers such as plants use some of this energy for metabolism/cellular respiration and some for growth (building tissues).
So the correct option is 'total organic matter produced from solar energy'.
B. Secondary productivity
Secondary productivity The rate of biomass formation or energy fixation by heterotrophic organisms, such as grazers and decomposers (see heterotrophic nutrition). These derive all their energy from photosynthetic plants and other autotrophs, either directly or indirectly, and their productivity determines the number of trophic levels and the lengths of the food chains within an ecosystem – both of which are likely to be increased by greater secondary productivity.
So the correct option is 'rate of synthesis of organic matter by consumers'.
C. Transducers
Transducers are the one who converts one form of energy into another form of energy. Energy types can be electrical, mechanical, electromagnetic (including light), chemical, acoustic, and thermal energy. plants receive light energy and convert it into chemical energy that viruses and animals use.
So the correct option is 'green plants'.
D. Food web
A food web (or food cycle) is a natural interconnection of food chains and a graphical representation (usually an image) of what-eats-what in an ecological community. Another name for food web is consumer-resource system. To maintain their bodies, grow, develop, and to reproduce, autotrophs produce organic matter from inorganic substances, including both minerals and gases such as carbon dioxide. These chemical reactions require energy, which mainly comes from the Sun and largely by photosynthesis, which is then passed on to the next consumer.
So the correct option is 'interconnection of food chains'.
Arrange the following ecosystems in increasing order of their mean NPP(tons/ha/year).
A. Tropics deciduous forest
B. Temperature coniferous forest
C. Tropical rainforest
D. Temperate deciduous forest.
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B $$<$$ A $$<$$ D $$<$$ C
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D $$<$$ B $$<$$ A $$<$$ C
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A $$<$$ C $$<$$ D $$<$$ B
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B $$<$$ D $$<$$ A $$<$$ C
Explanation
Net primary productivity is the rate at which all the plants in an ecosystem produce net useful chemical energy.
So, the correct option is $$B<D<A<C$$
Productivity at the second trophic level is always.
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Greater than the productivity at the first trophic level
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Less than the productivity at the first trophic level
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Equal to the productivity at the first trophic level
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Extremely variable compared to the productivity at the first trophic level
Explanation
Productivity at second trophic level is always less than productivity at first trophic level. This is because only $$10\%$$ of energy is transferred from one trophic level to another. Thus, decrease in energy would result in decrease in productivity.
Character of a stable community is that it
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should not show too much variations in year-to-year productivity
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must be resistant to occisional natural or manmade distribances
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should be resistant to invasions by alien species
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all of these.
Explanation
A stable community is self-perpetuating and final biotic community that is in perfect harmony with the physical environment. It does not show much of changes and is usually resilient to natural or man made disturbances.
Which one of the following exhibits least productivity?
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Salty marshes
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Grasslands
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Open oceans
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Coral reefs
Explanation
In oceans, there are lots of nutrients but no sufficient sunlight is available in deep areas hence, oceans have the least productivity. Grasslands are less productive ecosystem with annual productivity of 200−1000 gm/m2. Maximum productivity can be seen in coral reefs followed by estuaries. Salt marshes are estuaries where brackish and salt water mix. Salt marsh plants(halophytes) are salt tolerant and adapted to water levels that fluctuate with tides. Tides carry in the nutrients that stimulate plant growth in marshes.
So, the correct answer is 'Open oceans'.
The rate of conversion of light energy into chemical energy of organic molecules in a ecosystem is?
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Net primary productivity
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Gross primary productivity
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Secondary productivity
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Gross secondary productivity
Explanation
In ecology, productivity is the rate at which energy is added to the bodies of organisms in the form of biomass. Biomass is simply the amount of matter that's stored in the bodies of a group of organisms. Productivity can be defined for any trophic level or other group, and it may take units of either energy or biomass. Gross primary productivity, or GPP, is the rate at which solar energy is captured in sugar molecules during photosynthesis (energy captured per unit area per unit time). Producers such as plants use some of this energy for metabolism/cellular respiration and some for growth (building tissues).
So the correct option is 'gross primary production'.
In a grassland ecosystem, if the number of primary producers(plants) is approximately $$6$$ million, the number of top carnivores, which may be supported by them will be.
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$$3$$ million
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$$30$$ million
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$$6$$ million
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$$60$$ million
Explanation
In a grassland ecosystem, the pyramid of numbers is upright. If primary producers are approximately $$6$$ million plants, then number of top carnivores must be less than $$6$$ million. Hence, according to the options given, there would be $$3$$ million top carnivores.
Which of the following statements describe natural extinction?
(i) Extinctions abetted by human activities
(ii) Slow replacement of existing species
(iii) Also known as background extinction
(iv) A small population is most likely to be extinct
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(i) and (ii)
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(i), (ii) and (iii)
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(ii), (iii) and (iv)
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(i), (ii), (iii) and (iv)
Explanation
Natural or background extinction is a slow process of replacement of existing species with the better adapted species due to alternate evolution, changes in environmental conditions, predators, and disease.
Temperature is considered as the most ecologically relevant environmental factor because it affects ________ of organisms
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physiology
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morphology
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geographical distribution
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all of these
Explanation
Temperature is the most relevant environment factor. The temperature varies seasonally. The physiological functions, morphology and the geographical distribution of many plants and animals is governed by temperature.
What kind of pyramid is represented by the given figure?
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Pyramid of numbers in a pond ecosystem
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Pyramid of numbers in a parasitic food chain
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Pyramid of biomass in a forest ecosystem
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It is a wrong pyramid
Explanation
Correct Option: C
Explanation:
Biomass
is defined as the mass of living organisms present in a particular area.
A biomass pyramid shows the level of biomass in each
trophic level
.
The given pyramid shows
secondary
consumers on the top.
As we move down, there are the
primary consumers
and then, the
producers
.
Hence, the
p
yramid of biomass in a forest ecosystem
is represented by the given figure.
An exotic species that is introduced to a new area, spreads rapidly and eliminates native species is called
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immigrant species
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invasive species
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destructive species
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none of these.
Study the following statement and select the incorrect one.
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Shorter food chains provide more energy as compared to longer food chains
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Ecological factors connected with physical geographical of earth are called topographic factors
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The pyramid of biomass is upright in a grassland ecosystem and the pyramid of number is upright in a parasitic food chain
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None of these
Explanation
Pyramid of biomass for terrestrial ecosystems (grasslands, forests) the biomass generally decreases at each higher trophic level from plants via herbivores to carnivores. This is evident from the fact that the terrestrial producers’ viz. grasses, trees and shrubs have a much higher biomass than the animals that consume them, such as deer, zebras and insects. A single plant or animal in a parasitic food chain may support numerous parasites, which might be further supporting a larger number of hyperparasites. Thus, the pyramid of numbers in a parasitic food chain is inverted.
So the correct option is 'the pyramid of biomass is upright in a grassland ecosystem and the pyramid of number is upright in a parasitic food chain'.
Study the following ecological pyramids carefully. Match the following statements (i), (ii) and (iii) with given pyramids A, B and C and select the correct answer.
(i) Inverted pyramid of biomass depicting small standing crop of phytoplanktons supporting a large standing crop of zooplanktons.
(ii) Pyramid of numbers in a grassland ecosystem showing about $$6$$ million producers.
(iii) Upright pyramid of biomass.
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A-(ii), B-(iii), C-(i)
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A-(ii), B-(i), C-(iii)
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A-(i), B-(iii), C-(ii)
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A-(i), B-(ii), C-(iii)
Explanation
When the biomass of producer is less and that of the consumer is more the pyramid will have an inverted shape. It occurs in a pond and lake ecosystem. Here the biomass of diatoms in planktons is negligible as compared to their date of crustaceans and small fishes. inverted pyramid soil found in that ecosystem where the number and biomass of producers of more and those of consumers are less.
In most of the ecosystems, the number of the biomass of producers is more than those of a consumer is less. This type of ecosystem has a pyramid where the apex is pointed upwards. This type of pyramid is known as upright pyramid.
In some ecosystem, the number of the producers is more than the consumers. The apex is pointed upwards. This is known as the upright pyramid of the number. Found in the grassland ecosystem.
So, the correct option is 'A-(ii), B-(iii), C-(i)'
Given figure represents a pyramid of biomass in an aquatic ecosystem. Identify A and B and select the correct answer.
(i) A is the crop which supports and B is the crop which is supported.
(ii) A is the crop which is supported and B is the crop which supports.
(iii) A is phytoplanktons and B is zooplanktons.
(iv) A is zooplanktons and B is phytoplanktons.
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(i) and (iv)
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(ii) and (iii)
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(i) and (iii)
0%
(ii) and (iv)
Explanation
The given pyramid represent pyramid of biomass in an aquatic ecosystem. In this pyramid, the biomass of phytoplankton, i.e., producers (represented by A) is smaller than that of zooplanktons, i.e., primary consumers(represented by B). Phytoplanktons support zooplanktons as the latter feed upon them.
So the correct answer is option C.
Primary succession occurs on
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Area destroyed due to forest fire
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Newly formed river delta
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Harvested crop field
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All of these
Explanation
Primary succession starts from the primitive substratum, where previously there was not any sort of living matter. The first groups of plants establishing there are known as the pioneers, primary community or primary colonisers. Newly formed river delta, newly exposed sea floor, igneous rocks, sand dunes, new cooled lava sediments are some examples of primary bare area. Primary succession takes a long time for completion, several hundred to several thousand years.
So, the correct answer is 'Newly formed river delta'.
Match column I with column II and select the correct option from the given codes.
Column I
Column II
A. Bacteria
(i) Prisere
B. Green plants
(ii) Transducers
C. Primary succession
(iii) Lithosere
D. Succession on bare rock
(iv) Micro-consumers
Report Question
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A-(iv), B-(ii), C-(i), D-(iii)
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A-(iv), B-(iii), C-(i), D-(ii)
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A-(i), B-(iii), C-(ii), D-(iv)
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A-(iv), B-(ii), C-(iii), D-(i)
Explanation
Bacteria are important decomposers of ecosystem. Because of their small size, they are also called as micro consumers. Green plants(producers) are also called transducers because they convert light energy into chemical energy.
Primary succession(=Prisere) is the biotic succession that occurs on a previously bare area. Lithosere(or Xerosere) refers to the sequence of successional stages that occur on bare rock.
So, the correct answer is 'A-(iv), B-(ii), C-(i), D-(iii)'
Which one of the following statements regarding CO gas is correct ?
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It is produced by the complete combustion of fossil fuels.
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It combines with haemoglobin to form carbamino-haemoglobin.
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It impairs oxygen transport resulting in giddiness, headache, asphyxia and even death.
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All of these
Explanation
Carbon monoxide ( CO ) is produced due to incomplete combustion of fossil fuels, metallurgical operations, automobile emission, cigarette smoking. CO combines with haemoglobin, produces carboxyhaemoglobin which impairs oxygen transport resulting in headache, decreased vision, cardiovascular disease, asphyxia.
The rate of secondary succession is faster than primary succession because.
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Soil or sediment is already present
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Water is available in large quantity
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Climax community is already present
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pH of soil is favourable
Explanation
Correct option: A
Explanation:
The rate of secondary succession is faster than primary succession as inorganic substrate is already present in them.
In Primary succession, no soil is present and pioneer species have to colonize and die to form substrate, this takes lots of time.
While in secondary succession, due to some factors vegetations is no longer present but soil is present. And there is no need of pioneer species to form topsoil as it has already been done.
Thus, Option A is correct. The rate of secondary succession is faster than primary succession because the soil or sediment is already present in secondary succession.
Match column I with column II and select the correct option from the given codes.
Column I
Column II
A. Pioneers
(i) Vegetation which modifies its own environment and thus causing its own replacement
B. Autogenic succession
(ii) Replacement of existing community by external conditions
C. Allogenic succession
(iii) Establishment of organisms in an area into which they have come by dispersal or migration
D. Ecesis
(iv) Primary colonizers
Report Question
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A-(iv), B-(i), C-(ii), D-(iii)
0%
A-(i), B-(ii), C-(iii), D-(iv)
0%
A-(ii), B-(i), C-(iv), D-(iii)
0%
A-(i), B-(iv), C-(iii), D-(ii)
Explanation
Pioneers or primary colonisers are the first organisms to inhabit an area. In ecology, autogenic succession is succession driven by the biotic components of an ecosystem whereas allogenic succession is succession driven by the abiotic components of ecosystem. In other words, we can say that, in autogenic succession, the vegetation(biotic components) itself modifies it own environment and causes the succession to occur. In allogenic succession, replacement or modification of existing community occurs by external(or abiotic) factors such as volcanic eruptions, flooding, human interference, etc. Ecesis refers to the establishment of organisms in a new environment or area, into which they have come by dispersal or migration.
So, the correct answer is 'A-(iv), B-(i), C-(ii), D-(iii)'.
As the succession proceeds number and types of _________ change.
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Vegetation
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Animals
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Vegetation and animals
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Vegetation, animals and decomposers
Explanation
Ecological succession usually describes changes in vegetation but vegetational changes in turn affect food and shelter for various animals. Thus, number and types of animals and decomposers also change during succession.
Correct sequence of stages of succession on a bare rock is?
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Lichens $$\rightarrow$$ Mosses $$\rightarrow$$ Grasses $$\rightarrow$$ Shrubs $$\rightarrow$$ Trees
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Trees $$\rightarrow$$ Shrubs $$\rightarrow$$ Lichens $$\rightarrow$$ Mosses $$\rightarrow$$ Grasses
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Mosses $$\rightarrow$$ Shrubs $$\rightarrow$$ Trees $$\rightarrow$$ Lichens $$\rightarrow$$ Grasses
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Mosses $$\rightarrow$$ Lichens $$\rightarrow$$ Grasses $$\rightarrow$$ Shrubs $$\rightarrow$$ Trees
Explanation
Correct option: A
Explanation:
The various seral stages of lithosere (succession on bare rock) is as follows-
Lichens (Pioneers community) $$\rightarrow$$ Mosses
$$\rightarrow$$
Annual grasses
$$\rightarrow$$
Perennial grasses
$$\rightarrow$$
Shrubs
$$\rightarrow$$
Trees (Climax community).
Thus, Option A is correct.
Correct sequence of stages of succession of a lithosere is?
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Foliose lichens $$\rightarrow$$ Crustose lichens $$\rightarrow$$ Mosses $$\rightarrow$$ Annual grasses $$\rightarrow$$ Perennial grasses $$\rightarrow$$ Shrubs $$\rightarrow$$ Trees
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Crustose lichens $$\rightarrow$$ Foliose lichens $$\rightarrow$$ Mosses $$\rightarrow$$ Perennial grasses $$\rightarrow$$ Annual grasses $$\rightarrow$$ Shrubs $$\rightarrow$$ Trees
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Crustose lichens $$\rightarrow$$ Foliose lichens $$\rightarrow$$ Mosses $$\rightarrow$$ Annual grasses $$\rightarrow$$ Perennial grasses $$\rightarrow$$ Shrubs $$\rightarrow$$ Trees
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Crustose lichens $$\rightarrow$$ Foliose lichens $$\rightarrow$$ Mosses $$\rightarrow$$ Annual grasses $$\rightarrow$$ Shrubs $$\rightarrow$$ Perennial grasses $$\rightarrow$$ Trees
Explanation
A lithosere (a sere originating on rock) is a plant succession that begins life on a newly exposed rock surface, such as one left bare as a result of glacial retreat, tectonic uplift as in the formation of a raised beach, or volcanic eruptions. The following points highlight the the seven main stages of lithosere in plants. The stages are:- 1. Crustose Lichen Stage 2. Foliose and Fruticose Lichen Stage 3. Moss Stage 4. Herb Stage 5. Shrub Stage 6. Trees Stage.
Crustose Lichen Stage: Lichen species like Graphis Rhizocarpon, Rinodina and Lecanora forms are the pioneer community in a lithosere, as they can tolerate desert or extreme hot condition. Organic acids produced by lichens leach the rock surface and release minerals for proper growth of lichens. Crustose lichens can adhere to the surface of rock and absorb moisture from atmosphere; therefore, these colonize the barren surfaces of rocks first. When these lichens die their thalli are decomposed and add humus. This promotes soil formation and the environment becomes suitable for growth of foliose and fruticose type of lichens.
Foliose Lichen Stage: Foliose lichen retain more water and accumulate more soil particles, helping in the development of a fine layer of soil on the rock surface. As the soil formation proceeds it leads to the growth of foliose lichens. They can absorb and retain more water and are able to accumulate more dust particles. Their dead remains are decomposed to humus which mixes with soil particles and help building substratum and improving soil moisture contents further.
Moss Stage: Accumulation of soil and humus leads to the growth of mosses. The spores of xerophytes mosses, are brought to the rock where they succeed lichens. Their rhizoids penetrate soil on the rocks. The bodies of mosses are rich in organic and inorganic compounds. When these die they add these compounds to the soil, increasing the fertility of the soil. As mosses develop in patches they catch soil particles from the air and help increase the amount of substratum.
Herb Stage: Death and decay of mosses produce a mat of organic moss rich in organic soil, that help the germination to seeds of hardy grasses. Their roots penetrate deep down, secrete acids and enhance the process of weathering. Leaf litter and death of herbs add humus to the soil. As a result the xeric conditions begin to change and biennial and perennial herbs and xeric grasses. These climatic conditions favor growth of bacterial and fungal populations, resulting in increase in decomposition activity.
Shrub Stage: The herb and grass vegetation is replaced by shrub species. This results in dense organic soil and making conditions unfavorable for the growth of herbs, which then begin to migrate. The soil formation continues and its moisture content increases. Further weathering or rocks and death of herbs make the habitat more suitable for the growth of shrubs. Since the shrubs are larger in size and their roots penetrate more deeply in the rocky substratum causes more weathering and soil formation.
Tree stage: Change in environment favors colonization of tree species. The trees begin to grow among the shrubs and establish themselves. The kind of tree species inhabiting the area depends upon the nature of the soil. In poorly drained soils oaks establish themselves. The trees form canopy and shade the area.
So the correct option is 'crustose lichens $$\rightarrow$$ foliose lichens $$\rightarrow$$ mosses $$\rightarrow$$ annual grasses $$\rightarrow$$ perennial grasses $$\rightarrow$$ shrubs $$\rightarrow$$ trees'
An ecosystem which can be easily damaged but can recover after some time if damaging effect stops, will be having.
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Low stability and high resilience
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High stability and low resilience
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Low stability and low resilience
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High stability and high resilience
Explanation
Correct option: A
Explanation:
If an ecosystem is easily damaged, that means it is not very stable. But since, it recovers fast when the damaging effect stops, it certainly has high resilience.
Thus, Option A is correct. A damaged ecosystem is having low stability and high resilience.
Which one of the following is not one of the three aspects studied in biogeochemical cycling?
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The nature and size of natural reservoir
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The rate of movement between reservoirs
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Interaction between different biogeochemical cycles
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Creation of their own biogeochemical cycles by new species
Explanation
The cyclic movement of the elements from the abiotic system to the biotic system and back again is the biogeochemical cycle. These chemicals form the compounds of food, so these are also known as nutrient cycles.
Some of the important biogeochemical cycles are carbon cycle, Oxygen cycle nitrogen cycle, Phosphorus cycle.
Following aspect are studied in biogeochemical cycling-
The nature and size of the natural reservoir
The rate of movement between reservoirs
The interaction between different biogeochemical cycles
The correct option is the 'creation of their own biogeochemical cycles by new species'
The sequence of communities of primary succession in water is?
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Phytoplankton, sedges, free-floating hydrophytes, rooted hydrophytes, grasses and trees
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Phytoplankton, free-floating hydrophytes, rooted hydrophytes, sedges, grasses and trees
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Free-floating hydrophytes, sedges, phytoplankton, rooted hydrophytes, grasses and trees
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Phytoplankton, rooted submerged hydrophytes, floating hydrophytes, reed swamp, sedges, meadow and trees
Explanation
Primary succession in water is also called as hydrarch, which will lead from hydric to mesic conditions. Phytoplanktons(autotrophic) are generally the first to appear. Later zooplanktons feeding on phytoplanktons also appear. Next stage is characterized by the soft mud on the bottom having organic matter favouring the growth of rooted submerged plants. They are replaced by free-floating hydrophytes (
Lemna, Wolffia
etc). Rapid growth of these plants build up bottom as that water becomes shallow on periphery. In this shallow water, comes the reed-swamp stage(e.g.,
Typha
). They produce abundant organic matter. Next stages are sedge or marsh-meadow stage which transpire rapidly and build up soil, on which the next stage, trees can grow.
So, the correct answer is 'Phytoplankton, rooted submerged hydrophytes, floating hydrophytes, reed swamp, sedges, meadow and trees'.
Given is an imaginary pyramid of numbers.
Which of the following could be a possibility regarding it?
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Level PC is "insects" and level SC is "small insectivorous birds"
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Level PP is "phytoplanktons" in sea and "whale" on top level TC.
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Level PP is "pipal trees" and the level SC is "sheep".
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Level PC is "rats" and level SC is "cats".
Explanation
An ecological pyramid is the graphic representation of the number, biomass, and energy of the successive trophic levels of an ecosystem.
As the number of insects is always greater than the number of its predators in any ecosystem.
So the correct option is 'Level PC is "insects" and level SC is "small insectivorous birds'''.
Pyramid of numbers is?
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Always upright
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Always inverted
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Either upright or inverted
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Neither upright nor inverted
Explanation
Ecological pyramids are a pictorial representation of a relationship between organisms at different trophic levels, regarding energy, biomass or number. Pyramid of numbers can be either upright or inverted. For example in a grassland ecosystem, pyramid of number will be upright because number of primary consumers are less than primary producers and that of secondary consumers are less than primary consumers and so on. On the other hand, in a parasitic food chain the pyramid of number will be inverted.
So, the correct answer is 'Either upright or inverted'.
The reservoir for the gaseous type of biogeochemical cycle exists in-
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Stratosphere
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Atmosphere
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Ionosphere
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Lithosphere
Explanation
$$\textbf{Correct answer:}$$ (B)
$$\textbf{Explanation for correct answer:}$$
$$\bullet$$ The movement of nutrient elements through various components of an ecosystem is called as Nutrient cycling/ Biogeochemical cycling.
$$\bullet$$
Nutrient cycles are of two types- Gaseous and Sedimentary
$$\bullet$$
The Reservoir for Gaseous type of nutrient cycle (Nitrogen and Carbon cycle) exists in the atmosphere.
$$\bullet$$
The reservoir for Sedimentary type of nutrient cycle ( Phosphorus and Sulphur cycle) is located in earth's crust.
$$\bullet$$
Hence the correct option is (B).
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Practice Class 12 Medical Biology Quiz Questions and Answers
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