(3)

Change in the population of the organism at any trophic level can distress the whole food chain in the ecosystem. This can be detrimental to the balance of energy transfer in the ecosystem.

(1)

The correct sequence of the food chain is:
$Sunlight \to Producers \left(Phytoplanktons\right) \to Herbivores \left(Zooplanktons\right) \to Carnivores (Small fish) \to Top Carnivores (Large fish).$

(4)

In any food chain, all the trophic levels are of equal importance. They maintain ecological balance.

(2)

The given image shows a food web in the ecosystem. A food web is formed when the different food chains are interconnected in the ecosystem. Food chain comprising:
$Plants \to Frog \to Snake \to Owl$ is not the part of this food web.

(3)

At each trophic level, some amount of energy is lost; hence, food chains can have maximum 3–4 trophic levels. After four levels, there is no significant amount of energy left to pass on.

(4)

Different food chains interconnect to form food webs.

(4)

Phytoplanktons are the primary producers. They should occupy the first trophic level in the aquatic food chain.

(1)

The energy flow in an ecosystem is always unidirectional. Energy coming from the sun in most natural ecosystems, is used by producers, and then passed on to subsequent trophic levels in the form of food. Energy never flows in the reverse direction, it always gets transferred from the prey to the predator.

(4)

The sun is the ultimate source of energy in an ecosystem, and green plants capture it and convert it to chemical energy, which is then stored in the form of carbohydrates. This chemical energy, in the form of food, is transmitted down the food chain in the ecosystem from one trophic level to the next following 10 per cent law according to which only 10% of the chemical energy is transferred from one trophic level to subsequent higher trophic level.

(4)

The flow of energy is always unidirectional. It flows from the sun to the producers and ultimately to the consumers. According to the 10% law, only 10% of the energy is transferred from one trophic level to the next.

(3)

Energy flows in a unidirectional manner in an ecosystem from the lower trophic level towards the higher trophic level.

(1)

Cutting a large number of trees would affect all the other organisms dependent on those plants. Many organisms would even die. Some would migrate to other places. All such events would disturb the ecological balance and thus would decrease the stability of the ecosystem.

(2)

Crop rotation can gradually reduce the occurrence of pests, thereby reducing damage to crops year by year without affecting the environment.

(1)

Biological magnification occurs when the harmful chemicals used in the crop fields get washed into water bodies and enter the food chains.

(1)

The accumulation of harmful chemicals at each trophic level is called biological magnification.

(4)

Different agricultural activities are affecting the environment. Fertilisers and pesticides are non-biodegradable. They cause soil and water pollution. Soil loses fertility due to extensive cropping and water table is lowering due to the overuse of groundwater for irrigation.

(1)

Pesticides can disturb the balance within the ecosystem by indiscriminately killing pests and the predators of these pests.

(4)

Being eco-friendly refers to a way of life that is better for the environment. It involves taking little measures towards ensuring that the Earth’s environment is properly maintained for current and future generations. Carrying cloth bags to put purchases in while shopping, switching off unnecessary lights and fans, walking to school instead of getting your mother to drop you on her scooter are all examples of environment friendly practices.

(3)

The lead storage batteries use sulphuric acid which is acidic in nature while soaps and detergents are basic in nature.

(3)

UV rays are extremely hazardous to humans, animals, and even plants. It can cause skin cancer, cataracts in the eyes, and immune system damage by reducing the body’s response to infections.

(2)

If UNEP has not controlled the CFC levels, then after 20 years there would have been major destruction of the ozone layer due to an increase in CFC levels in the environment.

(2)

Ozone is formed by the action of UV radiations on the oxygen atoms in the upper layers of the atmosphere.

(4)

Ozone acts as a blanket around the earth and prevents the UV rays from entering the earth’s atmosphere. However, at the surface level, it acts as a pollutant.

(2)

The high energy of UV rays help in the formation of ozone from oxygen.

(3)

Gases that maintain the temperature of the earth by trapping the solar energy in the earth’s atmosphere are called greenhouse gases. Increase in the amount of greenhouse gases in the atmosphere can lead to global warming. Carbon dioxide and methane are the greenhouse gases.

(3)

CFCs are used in refrigerators. They are dangerous for the ozone layer that acts as a blanket around the earth and prevents UV rays from the sun to enter the atmosphere.

(1)

Reuse involves using again the same substance for some other purpose. Recycle involves forming a new substance from the old substance to be used for the same or different purpose.

(1)

Each enzyme has a specific substrate and has a specific function to perform. Each enzyme is a protein and each protein is made by a specific gene.

(4)

There are some substances that cannot be acted upon by decomposers and hence, these items are called as non-biodegradable. Examples: plastics, chemicals like DDT, etc. When items like disposable plastic plates are used they persist in the environment because they cannot be degraded and may cause hazardous effects on the other biotic components of the ecosystem. Therefore, usage of disposable plastic should be avoided as they have hazardous effects on the environment.

(1)

Some waste materials are non-biodegradable. Decomposers cannot break them into simpler forms. Therefore, these materials stay in the environment for a longer duration.