Natural Resources - Class 9 Biology - Extra Questions

It heats up the rocks during the day. Heating causes the rocks to expand. During night, the rocks cool and contract. Different parts of a rock expand and contract at different rates resulting in its cracking and breaking up into smaller pieces or fragments.

Yes, to dry the school uniform quickly, the uniform is spread near an anghiti or a heater. Higher the temperature faster is the rate of evaporation. So the uniform dries quickly.

The two main causes of the pollution of river Ganga are:

(i) Thermal pollution       

Water pollution can be caused by addition of:
(i) Undesirable substances like fertilizers and pesticides or any poisonous substances.
(ii) Sewage directly entering a water body.
(iii) Hot water from the power plant that increases the temperature and
reduces the dissolved oxygen in water thus killing the aquatic organisms.
(iv) Industrial effluents or radioactive substances in the water body.

• In the environment, the percentage of the gases like oxygen, nitrogen and carbon dioxide is maintained by their cyclic flow. The oxygen cycle, nitrogen cycle and carbon cycle respectively are operated by the constant interaction between the biotic and abiotic components of the biosphere. 
• This interaction includes the transfer of nutrient and energy between the different components of the biosphere. 
• Thus, the levels of oxygen, nitrogen and carbon dioxide in the atmosphere are maintained constantly up to a required limit.

Carbon mono-oxide is a colourless, odourless, non- irritating but very poisonous gas. It is produced by incomplete combustion of fuel such as natural gas, coal or wood. Vehicular exhausts are the largest source of carbon mono- oxide. It is, however, not a persistent pollutant. Natural processes convert CO to other compounds that are not harmful. In congested and closed places, it, however, proves quite harmful. Another source of CO is cigarette smoke.

Ozone when present on the Earth's surface is a very poisonous gas. Hence called bad.  

Ozone layer present in stratosphere functions as a shield against high energy and harmful ultraviolet radiations (l 00-320 nm). In the absence of ozone layer, the extremely harmful UV radiations will reach earth, cause large scale mutations to organisms, reducing photosynthesis, blinding of animals and humans, developing skin cancers and herpes leading to death of young ones. By filtering out harmful UV radiations, ozone protects the immune system of living beings against various diseases. It is therefore, essential for maintaining a healthy life on earth and survival of young ones.

During water cycle, water is found in three different states.
These are:
(a)Gaseous form (as water vapour)
(b)Liquid form (as rain, ground water and in water bodies).
(c) Solid form (as snow and ice)

Oxygen exists in two different forms in nature. These forms occur as oxygen gas 21% and combined form in the form of oxides of metals and nonmetals, in the earth's crust, atmosphere and water. It is also present in carbohydrates, fats, proteins.
Oxygen from the atmosphere is used up in three processes, namely combustion, respiration and in the formation of oxides of nitrogen. Oxygen is returned to the atmosphere by the process called as photosynthesis.

rain, snow or hail (precipitation). The water gets collected and joins the water bodies again.

Ozone layer, comprising high concentration of ozone about 18-50 km above in the atmosphere, is commonly called ozone blanket. It is being depleted by air pollutants. Chlorofluorocarbons (CFCs) are synthetic harmful chemicals which are widely used in refrigerators and air conditioners as propellants. These chlorofluorocarbons are air pollutants and are mainly responsible for the depletion ofozone layer in the atmosphere. When these are released in the air, these harmful chemicals produce active chlorine' (Cl and CIO radicals) and fluroine in the presence of UV radiation. These radicals, through chain reaction, then destroy the ozone by converting it into oxygen. Due to this, the ozone layer in the upper atmosphere (i.e, stratosphere) becomes thinner. A single chlorine atom can destroy one lakh ozone molecules. Cholorofluorocarbons are, therefore, termed major ozone depleting substances (ODS). Other ozone depleting substances are nitrogen oxides and hydrocarbons. The thinning of ozone layer allows more ultra violet (UV) radiations to pass through it which then strike the earth. These cause following harmful effects on man, animals and plants:
(i) Skin cancer.
(ii) Damage to eyes, also increase incidence of cataract disease in eyes.
(iii) Damage to immune system.
(iv) Increased embryonic mortality in animals and humans.
(v) In plants too, there will be increased death rate of seedlings, increased incidence of harmful mutations and reduction in yields.

Biosphere: It consists of the sphere where life exist. Life due to sun's heat. Plants also loose water during can exist if all the spheres given below are existing.
(a) Lithosphere: The crust of the earth also called as land which forms the upper layer of the earth i.e.-soil. The soil provides all the nutrients for all organism.
(b) Hydrosphere: Water available in various forms on the Earth is called hydrosphere. Water exists in solid ice, liquid water and gaseous water vapour forms. It is used by all life forms for their survival. Water helps in the. transportation of nutrients, dissolves nutrients minerals in it, make it available for the plants.
(C) Atmosphere: Atmosphere consist of air with different gases present in it like $$O_2, N_2, CO_2$$ another gases.
Ozone present in stratosphere helps the various gases present in the atmosphere are useful for combustion $$(O_2)$$ respiration $$(O_2)$$, Photosynthesis $$(O_2)$$ etc.

The ozone hole is the depletion of the ozone layer. The ozone layer absorbs the harmful UV rays coming from the sun and therefore does not allow those rays to reach Earth's surface. 
Consequences of ozone depletion:
Due to its depletion, more radiation enters the Earth's atmosphere. UV radiations cause ageing of the skin, cataracts, skin cancer, and sunburns. Hence, they are harmful. They cause the death of phytoplanktons which leads to a decrease in fish productivity. Excess exposure may even cause mutation in the genetic material of organisms.

$$\textbf{Solution: }$$ 

$$\bullet$$Ozone layer absorbs 93-99% of sun's high frequency $$\textbf{Ultraviolet}$$ light.

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

$$\bullet$$This layer of ozone is protective in nature and is also known as ozone shield. 

$$\bullet$$This layer absorbs 93-99% of the sun's high frequency ultraviolet light. 

$$\bullet$$The entry of the ultraviolet radiation inside the earth atmosphere can result in the incidence of cataract, snow blindness, skin cancer and also reduces the functioning of the immune system of the human body. 

• Trapping of sun’s heat in the lower atmosphere due to increase in the pollution causing gases like carbon dioxide is called greenhouse effect.
  
• Greenhouse gases are water vapour, carbon dioxide, methane and ozone, nitrous oxide etc.
  
• Sun’s radiation is partly absorbed by earth and rest of the radiations are reflected back to the atmosphere which are escaped. But the greenhouse gases form blanket in the atmosphere and traps the radiation from escaping. This causes an increase in earth’s temperature resulting in Global warming.
  

Water keeps on circulating in nature through various states of matter; in the form of liquid, vapor and ice. Due to this, the water which disappears because of evaporation comes back in the form of rain. Thus, water becomes a renewable resource.

The process of changing water vapour into water is called condensation.This is due to the change of gaseous state of water into liquid state. Some common examples of condensation are:1. Formation of drops of water on the outside of a glass of ice water. 2. Formation of dew on grass overnight.

• The process in which water evaporates and falls on the land as rain and later flows back into the sea through rivers is called water cycle or hydrological cycle.
• The water cycle consists of four major processes: evaporation, condensation, precipitation, and collection.
  
• Evaporation is the initial stage of the water cycle. In this process, the water present in the water bodies gets heated in presence of sunlight and changes its state from liquid to vapour, and mixes up with the air.
  
• In condensation, the vapours formed from the evaporation process lose its thermal energy and changes its state from vapours to liquid and results in the formation of clouds.
  
• In precipitation, the clouds form water droplets which fall as rain, snow or hail back to the earth by the influence of gravity.
• The final stage is the collection of the water cycle. In this the water vapours which fall back to the earth in the form of rain and snow move to the different water bodies like rivers, oceans, lakes.

Leaching is a process in which water-soluble substances are washed out from the soil. These water-soluble substances may be nutrients, fertilizers or even pesticides. Leaching may occur due to many reasons like excessive rain or irrigation. Due to leaching, often fertilizers and other chemicals also get washed away with the water and reach natural water bodies.

Mineral resources are necessary to be conserved because 

Although ozone depletion is occurring widely in the stratosphere, the depletion is particularly more over the Antarctic region. This has resulted in the formation of a large area of thinned ozone layer, commonly called as the ozone hole.

Carbon dioxide creates greenhouse effect in the atmosphere.

The three main components of the environment are - the lithosphere, the atmosphere, and the hydrosphere. The lithosphere is the solid portion of the earth. The gaseous layer that surrounds the earth is the atmosphere. The atmosphere is made up of oxygen, nitrogen, argon, carbon dioxide, and other gases. The hydrosphere refers to the big area of water that covers the earth's surface. This water is in the form of ice, water, and water vapor.

Oxygen molecule splits into atomic oxygen (O) at higher levels of an atmosphere because of higher energy of UV radiations.

The fertility of the soil can be improved by the following two methods:

Using insecticides is safe at times when the insect population is increased, but besides, it also has disadvantages like the increasing infertility of soil. Long-term use of insecticides may have harmful impact on the soil quality, which ultimately can lead to a decrease of quality of plant growth and yield. Also, it may affect the surrounding habitat.

Soil fertility refers to the ability of soil to sustain agricultural and plant growth. It helps in obtaining sustained and consistent yields of high quality. Sources of soil fertility are manure, fertilizers etc. Plants absorb water and minerals from the soil, which is essential for growth, flowering, crop yield and other vital activities. The soil itself is a storehouse for organic and inorganic plant nutrients.

i) Photosynthesis

Nitrogen Cycle is a biogeochemical process through which nitrogen is converted into many forms, consecutively passing from the atmosphere to the soil to organism and back into the atmosphere.

It involves several processes such as nitrogen fixation, nitrification, denitrification, decay and putrefaction.

The nitrogen gas exists in both organic and inorganic forms. Organic nitrogen exists in living organisms, and they get passed through the food chain by the consumption of other living organisms.

Inorganic forms of nitrogen are found in abundance in the atmosphere. This nitrogen is made available to plants by symbiotic bacteria which can convert the inert nitrogen into a usable form – such as nitrites and nitrates.

Nitrogen undergoes various types of transformation to maintain a balance in the ecosystem. Furthermore, this process extends to various biomes, with the marine nitrogen cycle being one of the most complicated biogeochemical cycles.

Gangotri glacier in Himalaya has started melting because of global warming.

(i) Police man is wearing a mask.
(ii) He is wearing mask to protect himself from air pollution caused by automobiles and dust present in the air.
(iii) The air quality of the place is very poor as it is polluted with harmful gases produced by the engines of various vehicles.

A) Oil and water are both liquids with different densities and can be separated by decantation.

Nitrogen obstructs burning of things. So if there is no nitrogen in the atmosphere, things will burn at a faster rate. No nitrogen means more chances of dehydration. The plant cycle will be disturbed due to disturbed nitrogen cycle.

The evaporation of water from oceans and its arrival back into oceans is called water cycle. 

Decrease of the concentration of ozone in the stratosphere is the cause of formation of ozone holes.

Constituents of air	Uses
Oxygen	Necessary for respiration and combustion
$$CO_2$$	Used by plants to make their foods. Used in fire extinguishers.
$$N_2$$	Used in Nitrogen fixation by bacteria.
Helium	Used for generating lifts in airships

Chlorofluorocarbons are responsible for the depletion of the ozone layer.
Chlorofluorocarbon released into the atmosphere reach the stratosphere and breakdown by the action of ultraviolet radiation releasing chlorine the chlorine decomposes ozone molecules into oxygen. This disturbs the equilibrium in the ozone - oxygen cyclic process. Hence the depletion of ozone in the atmosphere reduces the absorption of ultraviolet rays.

The ozone layer is responsible for most of the absorption of harmful UV rays. Depletion of the ozone layer allows the harmful UV rays to enter the Earth's surface causing various damages to the living organisms. Exposure to UV rays can lead to skin cancer, defective eyesight, reduction in immunity, increased number of mutations, and reduction in crop yield.

Excessive release of carbon dioxide in the atmosphere is the cause of the greenhouse effect which causes global warming.

The ozone layer prevents the harmful ultraviolet radiation of the sun to reach the earth.

• Ozone at the higher levels of the atmosphere is a product of UV radiation acting on oxygen ($$O_2$$) molecule. 
• The higher energy UV radiations split apart some molecular oxygen ($$O_2$$) into nascent Oxygen (O) atoms. 
• These atoms then combine with a molecular Oxygen to form Ozone as shown.

Ozone depletion is mainly caused by the active chlorine atoms generated from CFC in the presence of UV radiation. 

CFC’S are decomposed by UV rays to highly reactive chlorine, which is produced in its atomic form.
$$ CF_2Cl_{2 {\text{(g)}}} \xrightarrow{{\text{UV rays}}} CF_2 Cl{\text{(g)}} + Cl_{{\text{(g) (free radical)}}} $$ 

This free radical of chlorine reacts with ozone to form chlorine monoxide
$$ Cl_{\text{(g)}} + O_{3{\text{(g)}}} \rightarrow ClO_{\text{(g)}} + O_{2{\text{(g)}}} $$
This causes Ozone depletion.

It protects us from harmful solar radiation, it is a medium that provides solutions to some harmful gases.
Explanation:
The atmosphere is incredibly important. It protects us from harmful solar radiation (such as in the case of the ozone layer). It circulates dust, gases and clouds. The oxygen-rich lower atmosphere is good for life. It is also important for birds and other flying creatures. It regulates the temperature.

D is the right answer as at stage D the water from the clouds precipitates and fall on the surface of the earth in the form of rains liquid form of water.

The main difference between carbon and phosphorus cycle is that the carbon cycle interacts with the atmosphere whereas phosphorus cycle does not interact with the atmosphere. 

An aerosol is defined as a colloidal system of solid or liquid particles in a gas. An aerosol includes both the particles and the suspending gas, which is usually air. Aerosols need to be banned because CFC's (Chlorofluorocarbons) are used in them as propelling agents that keep the pressure in the can constant. CFCs are air pollutants that can have several adverse effects. So, a ban on aerosols is in demand.

Depletion of the ozone layer takes place mainly over Antartica circle.