FAQs: Ecology and Environment Class 12 Biology CBSE, CHSE
I. Organisms and Populations
Q1. Define Homeostasis. Give one example of a conformer and a regulator.
A. Homeostasis is the maintenance of a constant internal environment (like stable temperature and osmotic concentration) despite changes in the external environment.
Regulator: An organism that can maintain a constant body temperature/osmotic concentration (e.g., Mammals/Birds).
Conformer: An organism whose internal environment changes with the external environment (e.g., Most plants, most invertebrates).
Q2. What is the difference between Stenothermal and Eurythermal organisms?
A.
Stenothermal: Organisms that can tolerate only a narrow range of temperatures (e.g., Polar bear).
Eurythermal: Organisms that can tolerate a wide range of temperatures (e.g., Humans, most cats/dogs).
Q3. Differentiate between Hibernation and Aestivation.
A. Both are forms of temporary suspension to cope with stress:
Hibernation (Winter Sleep): Occurs during cold (winter) months to avoid low temperatures (e.g., Polar bear).
Aestivation (Summer Sleep): Occurs during hot and dry (summer) conditions to avoid heat and desiccation (e.g., Snails, some fish).
Q4. State the competitive exclusion principle (Gause's Principle).
A. Gause's Principle states that two closely related species competing for the same limited resources cannot coexist indefinitely. The competitively inferior species will eventually be eliminated.
Q5. What is the role of a predator in an ecosystem?
A. Predators play several important ecological roles:
They transfer energy across trophic levels.
They maintain the balance of the ecosystem by keeping prey populations under control.
They help maintain species diversity in a community by reducing the intensity of competition among competing prey species.
II. Ecosystem
Q6. Define Net Primary Productivity (NPP). What is the relationship between GPP and NPP?
A.
Gross Primary Productivity (GPP): The total rate of organic matter (biomass) production during photosynthesis in an ecosystem.
Net Primary Productivity (NPP): The remaining biomass available for consumption by the next trophic level (herbivores).
Relationship: NPP=GPP-R (where R is the respiration losses during the producer's metabolic activities).
Q7. State the Ten Percent Law of energy transfer in an ecosystem.
A. The Ten Percent Law, proposed by Raymond Lindeman, states that only 10% of the energy stored at one trophic level is transferred to the next higher trophic level. The remaining 90% is lost to the environment, mainly as heat, during metabolic processes.
Q8. Why is the pyramid of energy always upright?
A. The pyramid of energy is always upright because, at each successive trophic level, there is an enormous loss of energy (90%) in the form of heat, leaving only a small fraction (10%) for the next level. Therefore, the energy available at the producer level is always the highest.
Q9. Give one example of an inverted ecological pyramid.
A.
Pyramid of Biomass: In an aquatic ecosystem (e.g., ocean or large lake), the biomass of phytoplankton (producers) is often less than the biomass of the zooplankton (primary consumers) that feed on them.
