Life On Earth
A. Give one word for the following.
1. Cutting down of trees on a large scale.
= Deforestation;
2. The study of the interaction between living and non-living elements in an ecosystem.
= Ecology;
3. The water quotient on earth.
= Hydrosphere;
4. Average increase in the earth's temperature.
= Global warming;
5. Microorganisms that break down dead organic matter(dead plants and animals) to their simple elements.
= Decomposer;
6. The ultimate source of energy on earth.
= The Sun;
7. A resources that is liable to be depleted.
= Biodegradable;
8. Non-living elements in an ecosystem.
= Abiotic element;
B. Give two example for each of the following.
1. Fossil fuels.
= Coal and Petroleum;
2. Producers.
= Green Plants and Algae;
3. Decomposers.
= Bacteria and Fungi;
4. Artificial ecosystems.
= Park and Aquarium;
5. Fibres obtained from plants.
= Cotton and Coir;
6. Medicinal plants.
= Neem and Turmeric;
7. Sources of animal proteins.
= Eggs and Meat;
8. Primary consumers.
= Grasshopper and Frog;
C. Define the following terms.
1. Decomposers.
= Decomposers are some bacteria and fungi that bring about the decay and rotting of dead plants and animals. They break them down to their simple components. They bring about decomposition. Decomposers help replenishing the minerals to the earth. They also reduce the volume of dead mass on earth.
2. Environment.
= Environment is our surroundings. It comprises of both living and non-living elements, that is biotic and abiotic elements respectively.
3. Ecosystem.
= Ecosystem is a place where living and non-living elements coexist. There is a constant interaction between the biotic and abiotic elements in an ecosystem. This interaction forms the ecology of the region.
4. Producers.
= Producers are the green plants, algae and blue green algae that can prepare food. They are important because they convert the light energy of the sun into chemical energy by the process of photosynthesis. They are the sources of food and energy for life on earth.
5. Fossil fuels.
= Fossil fuels are made up of the decomposition of the plants and animals deep down the earth. The use of fossil fuels by man e.g. diesel, petrol releases oxides of carbon, sulphur and nitrogen into the air. This brings about global warming. It also spoils the quality of air.
6. Biodegradable.
= That can be broken down to simpler molecules by biological process.
7. Percolation.
= Percolation is the seepage of water down the layers of soil.
8. Biodiversity.
= Biodiversity is the variety of plants and animals and microbial elements.
D. State the importance of the following.
1. Decomposers.
= Decomposers help replenishing the minerals to the earth. They also reduce the volume of dead mass on earth.
2. Use of clean fuels.
= Use of clean fuels help to address the issue of pollution due to fossil fuels.
3. Atmosphere.
= The atmosphere acts as a blanket protecting the earth from the excessive heat of the sun.
4. Ozone layer of atmosphere.
= Ozone layer of atmosphere helps protect earth from the harmful ultraviolet radiations of the sun.
5. Water.
= Water is required to carry out the life processes, the activities of the cell. Hence, water sustains life.
6. Consumers.
= Consumers are the animals that consume the food prepared by the producers. They help the keep the ecological balance.
7. Food web.
= It means that an organism is not dependent on only one source for food. It can feed upon any organisms in the preceding step of the food chain.
8. Afforestation.
= Afforestation promotes soil formation, the ground water would also form. The effect of global warming would be lesser. The climate would be cooler since rains would be induced. It would also promote biodiversity hence the balance in nature could be maintained.
E. Answer the following questions.
1. Design a food chain in a forest. It should have at least four tropic levels.
i) Name the organism which possesses the greatest amount of energy.
ii) Name the tertiary consumer.
iii) Which organism would have the least energy available to go?
=
i) The producers posses the greatest amount of energy.
ii) The tertiary consumers are bear, wolf etc.
iii) The tertiary consumers would have the least energy available to go.
2. List the rules as regards energy flow, in a food chain.
= The transfer of energy from one trophic level to the next follows some basic rules in a food chain. These are listed below:
i)Plants trap only 1% of the sun's energy.
ii) Only 10% of the energy at every step is passed on to the next step, in a food chain. This is known as the 10% law of energy flow.
iii) The energy available at one step, cannot revert back to the previous step, in a food chain. Thus the flow of energy is unidirectional.
iv) Sun is the ultimate source of energy.
v) The energy keeps on decreasing as we proceed along a food chain.
3. State three important reasons as why earth supports life.
= Earth is the only planet in our galaxy that supports life. This is because it has the necessary conditions to support life. Among them three important reasons/conditions are -
i) It is at the right distance from the sun therefore has the right temperature. It is neither too warm nor too cold.
ii) It has an atmosphere comprising of nitrogen, oxygen, carbon dioxide, noble gases, water vapour and small amount of ozone. All the animals need oxygen to breathe. All the plants need carbon dioxide to make food. Nitrogen is needed for the growth of the plants and to make proteins.
iii) Water is present in the liquid form on earth. It is required to carry out the life processes, the activities of the cell. Hence, water sustains life. Nearly 70% of our body weight is water.
4. How does light, as an abiotic factor, affect life?
= Light is required for photosynthesis. It regulates the opening and closing of stomata. It affects transpiration. Flowering, germination of seeds and growth are influenced by light too.
5. State at least four parameters which are affected due to extensive deforestation.
= Man is carrying out extensive deforestation to built cities, industries, carry out mining, etc. Four parameters which are affected due to extensive deforestation are -
i) Deforestation is disturbing the balance of oxygen and carbon dioxide hence it is indirectly causing global warming.
ii) Deforestation is also reducing the rainfall, hence affecting climate.
iii) Soil erosion is also brought about due to deforestation.
iv) Deforestation also leads to loss of biodiversity.
6. What role can you play to improve/maintain/conserve your environment?
= To maintain/conserve/maintain our environment, I should play the following role -
i) I should plant trees and encourage others to do so.
ii) I should try to use cycle instead of bike or scooter and convince others to do the same.
iii) I would emphasise the use of clean fuels like CNG.
iv) I would encourage the shopping of CFC free products while buying electronic appliances.
v) I shall reduce the use of non-biodegradable substances such as plastic bags, plastic bottles etc. and encourage others to do so.
7. Why do you think acid rain is harmful to the environment?
= The oxides of sulphur and nitrogen, when mixed with rain water, form acid rain. Acid rain corrodes buildings, spoils plants and soil. It harms the skin of animals too.
8. Most of the food chains have 4-5 levels only. What could be the reason for this?
= Most of the food chains have 4-5 levels only because by the third or fourth tropic level, hardly any energy is left to be passed on.
9. Define how plants and animals can maintain the resources of air, soil, water?
= Plants and animals can maintain the resources of air, soil, water in the following ways -
i) Plants depend on soil to anchor themselves and to obtain nutrients and water. Some animals too live in the soil e.g. snakes, rats, ants.
ii) Plants and animals depend on ground water for their water requirement. Plants obtain many minerals like nitrogen, potassium, sulphur, etc. through the medium of water. These minerals are required to carry out the life processes of plants and animals.
iii) They depend on air for oxygen, for respiration. Plants depend on air for carbon dioxide also to carry out photosynthesis.
10. Which group of organisms are most important in a food chain? Why do you think so?
= I think the producers in a food chain are the most important. The producers trap the sun light and make food for the whole world. They use the carbon dioxide for making food and thus making the balance of oxygen and carbon dioxide in the atmosphere. They keep the environment cool and they bring rain. They resist soil erosion. They are the most responsible part of our ecosystem.