12 Questions with Answers and Explanations on “Ecosystem” for Biology Students:
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Q.1. What are the two basic categories of ecosystem? Give two examples to each.
Ans.
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Terrestrial
Ex- Grassland
Forest
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Aquatic
Ex- Pond
Wetland
Q. 2. Describe the components of an ecosystem.
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Ans. Ecosystem consists of abiotic and biotic components.
Abiotic components:
These components are the non-living components. Light, temperature, soil, water are the abiotic factors that make the habitat for living beings.
They affect the living organisms behaviour and physiology. The survival of living organisms is directly or indirectly effected by these factors and thus they are dependent on it.
Biotic components:
These are the living components. Plants and animals.
They live in a habitat and show inter dependance on each other and on the abiotic components.
The components of the ecosystem are seem to function as a unit when we consider the following aspects:
Productivity, decomposition, energy flow and nutrient cycling.
Q. 3. Define stratification with an example.
Ans. The vertical distribution of different species occupying different levels is called stratification. It is clearly visible in case of forests.
For example, trees occupy the top vertical strata, shrubs occupy the second and bottom layers/floor are occupied by hurbs and grasses.
Q. 4. What is primary productivity? Give brief description of factors that affect primary productivity.
Ans. The amount of biomass/organic matter produced per unit area over a time period by plants during photosynthesis is called primary productivity (PP).
It depends on the plant species, environmental factors, availability of nutrients and photosynthetic capacity of plants. Thus, the PP is variable in different types of ecosystems.
Q. 5. Give an account of energy flow in an ecosystem.
Ans. The energy flow in the ecosystem is unidirectional. It taken place towards higher trophic levels and its dissipation and loss of heat to the environment takes place following both the laws of thermodynamics.
The green plants revive solar energy from sun in the form of solar radiation of which 50% of it is photosynthetically active radiation (PAR).
Plants absorb on 2-10% of it and use in converting it into their biomass. The consumers depend on the chemical energy source on food.
The energy trapped by producer consumers of all levels. Energy amount decreases at successive trophic levels.
When any organism dies it is convert to ditritus or dead biomass. This serves the energy source for decomposers.
Q. 6. What are the limitations of ecological pyramids?
Ans. The limitations of ecological pyramids are:
(a) It does not consider the same species belonging to two or more levels. (.b) It considers/assumes a simple food chain that does not exist in nature.
(c) It does not accommodate a food web in its depiction.
(d) It does not give any significance to saprophytes.
Q. 7. (i) What is ecological succession?
(ii) Define the terms—sere.
Ans. (i) The gradual and fairly change in the species composition of an area is called ecological succession.
(ii) The sequence of communities that successively change in a given area are called sere.
Q. 8. Arrange the following plant species in the sequential manner of their appearance during a succession. Mention the end product/changes that take place in the habitat. Bigger plants, stable climax forest, smaller plants, lichen, bryophytes, bare rocks.
Ans. Bare rocks -> lichen bryophytes -» smaller plants bigger plants -» stable climax forest. ‘
The xerophytic habitat is converted into a mesophytic habitat as the result of above succession.
Q. 9. What are the various kinds of nutrient cycles? Give it with examples.
Ans. Gaseous cycles
Examples- Nitrogen
Carbon
Sedimentary Cycles
Examples- Phosphrous
Sulphur
Q. 10. (1) Mention the various ecosystem services provided to us. (2) Should these services be priced? If yes, why?
Ans. (1) Ecosystem services:
(i) Supply of pure air, water.
(ii) Mitigation of drought, floods
(iii) Nutrient cycling, fertility of soils,
(iv) Provision of wild life habitat, biodiversity, storage of a carbon,
(v) Pollution of crops—food resources.
(vi) Provision for aesthetic, cultural and spiritual values.
Yes, some of the ecosystem services should be priced to put a check on the greed and exploitation of natural resources.
Q. 11. Write important features of a sedimentary cycle in an ecosystem.
Ans. Important features are:
(1) The mineral/nutrient is not released through respiration in the atmosphere.
(2) The atmospheric inputs of (phosphorus) nutrients through rainfall is smaller as in comparison to carbon.
(3) There is no gaseous exchange of the nutrient between the organism and the environment.
Q. 12. Outline salient features of carbon cycling in an ecosystem.
Ans. Salient features:
(1) It is a gaseous cycle. It undergoes exchange between the organism, rocks, air and water.
(2) It forms 49% of dry weight of organisms.
(3) It is returned to atmosphere by respiration, combustion, decomposition and other human activities.
