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Correct option  (B) Plants at place Y can be seen to have burnt yellow looking leaves. 

Explanation:

The pH level of rainwater (precipitation) at place Y is around 4 that means rainwater is acidic at place Y. As an impact of acid rain at place Y we can find yellowing of marble statues and plants with burnt leaves. lt also indicates that use of fossil fuels (conventional energy sources) is much higher at place X than place Y.

The accumulation of chemicals in the top most organism of the trophic level or food chain is called biological magnification. 

Example: Farmer sprays pesticides on the crops which enters the food chain, from crops these pesticides enter into the organisms that feed on it. 

grass ⎯⎯→ grasshopper ⎯⎯→ frog ⎯⎯→ snake ⎯⎯→ hawk 

In this food chain the maximum amount of pesticide will be found in the top most organism i.e., in hawk the chemical keeps accumulating.

(B) Food chains

A) Temperature, sunlight

The position of organisms in a food web.

‘Niche’ is the term used to describe not only the animals position in the food web and what it eats but also its mode of life.

niche is a place or position that's particularly appropriate for someone or something, especially due to being very specific and different from others. Niche often refers to a position or interest that allows someone or something to thrive in a particular environment.

D) All of the above

“Sparrow Campaign” incident occurred in China

C) Great Chinese famine

Answer is (B) Locusts

Correct representation of trophic levels in a food chain is shown in figure A. 

The population will decrease as we move from bottom to top of a food chain. The producers will be the highest in number in a food chain because there have to be more food producers than consumers, to sustain life on earth. The top position is mostly taken by carnivorous animals (tertiary consumers), omnivores being the secondary consumers and herbivores being the primary consumers. 

A food chain always represents a unidirectional flow of energy from one trophic level to another. Each level in the pyramid represents our level in the food chain. Each level of consumers above the producers has fewer individuals because there is less energy available

Normally a lake has more diverse forms of life and hence a larger number of food chains. The leads to natural cleaning. Thus, the ecosystem is more stable. The aquarium has a very limited number of food chains and unable to sustain itself. But, sometimes there is excessive growth of algae in lake. Then it also needs to be cleaned.

Fig. "A" is correct. In an ecosystem, the number of individuals at producer level is maximum. This number reduces at each successive level. Therefore, the shape is a pyramid with broader base and tapering apex. On an average 10% of the food changes into body mass and is available for the next level of consumers.

1. The number of organisms in a food chain can be represented graphically in a pyramid of number.

2. Each bar represents the number of individuals at each tropic level in a food chain. 

3. At each link in a food chain, from the first order consumers to the large carnivores, there is normally an increase in size but decrease in number. 

4. For example in a wood, the aphids are very small and occur in astronomical numbers. 

5. The lady birds which feed on them are distinctly larger and not so numerous. 

6. The insectivorous birds which feed on the lady birds are larger still and are only present in a small number and there may only be a single pair of hawks of much larger size than the insectivorous birds on which they prey.

There is only 10% flow of energy from one trophic level to the next higher level. The loss of energy at each step is so great that very little usable remains after four or five trophic levels. Hence, only 4 to 5 trophic levels are present in each food chain.

(i) The earth would be covered with dead organisms and their excrement.

(ii) Decomposers are recyclers of life materials, returning materials to the system for use by living organisms.

The various categories of consumers are: 

Herbivores — Grass eating animals, e.g., deer, rabbit. 

Carnivores — Flesh eating animals, e.g., tiger, lion. 

Omnivores — Animals that eat both plants and other small animals i.e., flesh e.g., crow, human being. 

Parasites — Those organisms which depend on other living organisms and harm them for food, e.g., lice, tapeworm. 

Saprophytes — Organisms that depend on dead and decaying matter for their food, e.g., fungi, bacteria.

Ecosystem is the structural and functional unit of biosphere, comprising of all the interacting organisms in an area together with the non-living constituents of the environment.

Ecosystem are of two types : 

(i) Natural Ecosystem: The natural ecosystems are terrestrial (land) as well as aquatic. The common example of land ecosystem are forest, grassland, desert, etc. The common examples of aquatic ecosystem are ponds, lakes, rivers, ocean, etc. 

(ii) Human made or Artificial Ecosystem: These ecosystems are made by human beings. The common examples are crop fields, gardens, parks, aquarium, etc.

Organisms that feed directly or indirectly on producers and cannot synthesize their own food from inorganic sources are called consumers.

Herbivores, Carnivores, Omnivores and Parasites are various categories of consumers.

Trophic levels are different steps of a food chain. A trophic level is the level of species in an ecosystem on the basis of the source of nutrition such as producers, primary consumers, secondary consumers etc.

The producers form the first trophic level as they manufacture food.

The primary consumers form the second trophic level, the secondary consumers form the third, and the tertiary consumers form the fourth trophic level.

Terrestrial food chain : 

Grass → Deer → Lion

(Producer) (Herbivore) (Carnivore)

1^stTrophic level 2^nd Trophic level 3 ^rd Trophic level

At every trophic level, large amount of energy is lost in form of heat for maintaining metabolic activities and lost as heat. The amount of heat lost is generally 90 percent and the amount of energy retained is available from previous trophic level to the next. 

The decline in energy level leads to : 

(i) Lesser number of organisms in each trophic level.

(ii) Limited number of trophic level in food chains.

Significance of a food chain :

(i) It helps in understanding the food relationship and interactions among various organisms in an ecosystem.

(ii) It helps in following the basic mechanism of transfer of food energy and nutrients through various components of nature.

(iii) It helps to understand the movement of toxic substances in an ecosystem and the problem of their biological magnification.

Difference between food habits of Organisms belonging to first trophic level and second trophic level:

• The organisms at the first trophic levels are primary producers who make organic compounds using inorganic inputs like light, water, carbon dioxide etc. E.g. Plants.
• The organisms at the second trophic level are primary consumer. They are herbivores who eat plants (producers) for nutrition E.g , Deer

The organisms belonging to the first trophic level are producers which make their own food with the help of sun’s energy. 

For example – Green plants. 

The organisms of third trophic level are carnivores that feed upon herbivores. 

For example – Lion and Tiger.

Substance which can be degraded and disposed off naturally by saprophytic organisms or decomposers are called biodegradable, e.g., organic remains, garbage, sen age, livestock waste. Substances which cannot be degraded by saprophytes are known as non-biodegradable. They are mostly man-made articles like pesticides, plastic, polyethylene etc. Biodegradable articles are formed naturally, in biosphere. Decomposer organisms feed on them by secreting digestive juices and absorbing the solubilised substances. Biogenetic nutrients are released in the process called mineralization.

Cause of Concern: Ozone layer present in the stratosphere has thinned out by about 8% over the equator and more so over the Antarctica where a big ozone hole appears every year. This has increased the level of UV-B radiations reaching the earth by 15-20 %. These radiations are causing increased number of skin cancers, cataracts and reduced immunity in human beings. These causes increased incidence of blindness of animals, death of young ones, reduced photosynthesis, higher number of mutations and damage to articles.

Steps to Limit Damage : 

(i) Ban on the production and use of halons. 

(ii) Ban on production and use of chlorofluorocarbons.

The household wastes are called garbage. It includes left -over food, fruit and vegetable peels, waste paper, unwanted plastic objects etc.

The various modes of waste disposal are:

1. Recycling

2. Preparation of compost

3. Incineration

4. Landfill

5. Sewage treatment

The solid wastes like papers, plastics and metals are recycled. For example – waste paper is send to paper mills where it is reprocessed to form new paper once again.

(C) R→ P→ S → Q 

Correct option  (C) Q, R and S only 

Explanation:

According to the given food web, fish feed on young tadpoles and also on water snails. So, if there is increase in the population of tadpoles, the population of fish will increase leading to decrease in the population of water snails. Kingfishers feed on fish and fish feed on water snails. So, if there is decrease in the kingflsher population, there will be increase in fish population leading to decrease in the population of water snails. As the dragonfly nymphs feed on water snails, thus, increase in their population will lead to decrease in water snail population.

Correct option  (D) Ail of these

Explanation:

The given graph shows increase in the population of animal P. This means it is a predator and carnivore too and is preying upon animal Q, whose population is decreasing. 

Biodegradable: domestic sewage and wood. Non Biodegradable: Plastic and DDT.

The used water from industries and run off water containing agricultural effluents bring pollutants into water sources. Municipal and domestic sewage also pollute water sources.

In our body enzymes helps us to digest food.

Plastic cannot be broken down by the action of bacteria.

Ozone shields the surface of the earth from ultraviolet rays from the Sun.

Biodegradable and non-biodegradable wastes should be discarded in two separate dustbins so that the time and energy required in segregation may be saved and waste may be disposed off quickly.

(i) Saves time/ energy in segregation.

(ii) Biodegradable items can be directly sent for composting.

(ii) Non-biodegradable items can be sent for a appropriate reuse/recycle.

Detailed Answer:

Separation should be done actually to save our resources for future benefits and to save our environment from pollution.

C) Aluminuim foil

Some substances are non-biodegradable because they cannot be broken down into simpler harmless substance in nature.

Substances that can be broken down by microorganisms in natural simple harmless substances.

Pond ecosystem and forest ecosystem.

Ozone at ground level is deadly poisonous and is called as bad Ozone.

Garden and crop-field.

The accumulation of chemicals in the bodies of the organism that belongs to the top most tropic level is called biological magnification.

First, sunlight shines onto the Earth's surface, where it is absorbed and then radiates back into the atmosphere as heat. In the atmosphere, “greenhouse” gases trap some of this heat, and the rest escapes into space. The more greenhouse gases are in the atmosphere, the more heat gets trapped. 

Explanation: A greenhouse is a house made of glass. It has glass walls and a glass roof. People grow tomatoes and flowers and other plants in them. A greenhouse stays warm inside, even during winter. Sunlight shines in and warms the plants and air inside. But the heat is trapped by the glass and can't escape. So during the daylight hours, it gets warmer and warmer inside a greenhouse and stays pretty warm at night too. 

Similarly, Earth's atmosphere does the same thing as the greenhouse. Gases in the atmosphere such as carbon dioxide do what the roof of a greenhouse does. During the day, the Sun shines through the atmosphere. Earth's surface warms up in the sunlight. At night, Earth's surface cools, releasing the heat back into the air. But some of the heat is trapped by the greenhouse gases in the atmosphere. That's what keeps our Earth warm.

Those organisms which consume the food produced either directly from producers or indirectly by feeding on other organisms are called consumers.

Bacteria and fungi break down/decompose the dead remains and waste products or organisms.

Advantages :

(i) Natural replenishment of soil.

(ii) Recycling of nutrients in the soil.

Detailed Answer:

Bacteria and fungi are living organisms which decompose or consume the dead remains of other organisms.

Advantages

(i) Decomposers degrade garbage and the organic wastes which would otherwise cause environment problem. It prevents foul smell and checks spread of disease.

(ii) Decomposers recycle the nutrients through biochemical cycle.

Bacteria and fungi are called decomposers because they decompose Complex molecules into soluble organic molecules which are absorbed in the soil which will be later used by the plants again to fulfill its nutrient requirement. OR 

Because bacteria and fungi break down the dead and decaying organic matter into simpler substances and provide the nutrients back to the soil. When an organism dies, decomposers decay the body extracting the last bit of energy from it. The common left over materials such as water, carbon dioxide, and minerals can then be reused by producers to make sugar through photosynthesis. 

The advantages of decomposers are 

1. They keep the environment clean by decomposing the dead animals. 

2. It prevents the spread of diseases caused by dead bodies of plants and animals like bird flu. 

3. They help in making humus. 

4. They act as natural scavengers. 

5. They help in the recycling of nutrients.