1. What are the factors that form a stable ecosystem?
Both abiotic (non-living) and biotic (living) components of the biosphere constantly interact with each other to form a dynamic, but stable system. Such interaction includes transfer of matter and energy between the different components of the biosphere.
2. What are called bio - geochemical cycle?
The nutrient elements derived from the earth by the living organisms for use in their growth and development are called bio-geo chemicals. These bio-geo chemicals are used by the living organisms and are released to the environment, when the dead bodies of the organisms and their excreta are decomposed. These chemicals become available again for reuse and recycling.The cyclic flow of elements or compounds between non-living environment (soil, rock, air, water) and living organisms is known as bio-geo chemical cycle.
3. Name the abiotic components?
The abiotic components of the environment are air, water, soil, light and temperature.
4. What are biotic components?
The biotic components of environment include all living organisms including human beings. Plants and animals are interdependent.
5. Why are autotrophs important?
The green plants (autotrophs) are the producers of food for all living organisms. Solar energy is captured by autotrophs to synthesize food materials. The energy is transferred to herbivores when they consume plants. When carnivores feed on herbivores, the energy is transferred to carnivores.
6. What forms the food chain?
The energy trapped by green plants is relayed through a series of heterotrophic organisms. This forms the food chain.
7. How are plants and animals interdependent.
Man and animals take in oxygen during respiration and give out carbon dioxide. The plants absorb this CO2 during photosynthesis and liberate oxygen in to the atmosphere. Thus plants and animals are interdependent.
8. Define nitrogen cycle?
The process by which these forms get inter converted to maintain a constant amount of nitrogen in atmosphere, by physical and biological processes is called Nitrogen cycle.
9. Explain Nitrogen cycle.
The Nitrogen Cycle involves
- Nitrogen fixation
- Nitrogen assimilation
- Ammonification
- Nitrification
- Denitrification
11. What is Nitrogen fixation?
During nitrogen fixation, nitrogen is oxidized to by lightning and these oxides get dissolved in rain water and get oxides precipitated. During biological nitrogen fixation, the nitrogen fixing bacteria such as Azotobacter, Rhizoblum and blue green algae like Nostoc convert gaseous nitrogen to ammonia and nitrates.
12. Explain Nitrogen assimilation.
The nitrates absorbed by plants is utilized for making organic matter such as proteins, nucleic acids etc. Plant proteins and other nitrogenous compounds consumed by animals are converted into animal proteins.
13. What is ammonification?
Animal proteins are excreted out in the form of urea, uric acid or ammonia. When the plants and animals die, their proteins are broken down to release ammonia by the action of bacteria and fungi. This process of ammonia formation is called ammonification.
14. What is nitrification?
During this process, the ammonia is converted into nitrites and nitrates by soil bacteria such as Nitrobacter and Nitrosomanas which are then absorbed by plants through their roots.
15. What is Denitrification?
Free living soil bacteria such as Pseudomonas reduce nitrate ions of soil into gaseous nitrogen which returns to the atmosphere.
16. Chart out the activity and the name of the organisms involved in Nitrogen cycle.
| Activity |
Name of organism |
| Nitrogen Fixation |
Rhizobium, Axotobacter and Nostoc |
| Ammonification |
Ammonifying bacteria and fungi |
| Nitrification |
Nitrosomonas and Nitrobacter |
| Denitrification |
Pseudomonas |
17. Which are the three main sources of carbon?
The three main sources of carbon are CO2 of the air and CO2 dissolved in oceans , Carbonate rock in the earth's crust and, and Fossil fuels like coal and petroleum.
18. Where does CO2 basically come from?
The basic movement of carbon is from atmospheric reservoir to producers, to consumers and then to decomposers.
The respiratory activities at each trophic level return carbon dioxide quickly to the atmosphere. Carbon dioxide is also returned to the atmosphere through decomposition of dead organic materials, burning of fossil fuels and volcanic activities.
19. The role of CO2 in plants.
The atmospheric carbon dioxide enters into the living world, that is green plants, through the process of photosynthesis to form carbohydrates (food). The plant food is taken by herbivores and then passes through small and large carnivores.
20. Explain briefly oxygen cycle.
All living organisms require oxygen for respiration. Oxygen is one of the constituents of water and forms about 20% of the air in the atmosphere.
Oxygen enters the living world through respiration. It oxidizes the food materials and produces energy and carbon dioxide. Oxygen is also used up in the burning of the materials and carbon dioxide is produced.
Oxygen combines with nitrogen to produce oxides of nitrogen, which are taken up by the plants to produce amino acids and proteins. These compounds, after breaking down, release oxygen in the atmosphere and maintain balance in the environment.
21.Explain Water Cycle .
