TEST 02: ENVIRONMENT & ECOLOGY

Syllabus: Ecology, Functions of an Ecosystem, Terrestrial ecosystem, Aquatic ecosystem

1. Consider the following statements:

1. 1. Gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis.

2. 2. Net primary productivity minus respiration losses (R), is the Secondary productivity

 Which of the above-mentioned statements is/are NOT correct?

(A) 1 only

(B) 2 only

(C) Both 1 and 2

(D) Neither 1 nor 2

2. Consider the following statements on Ecological Pyramid

1. Pyramid of number can be either upright or inverted

2. Pyramid of Biomass is always upright

3. Pyramid of energy can be either upright or inverted

 Which of the statements given above is/are Correct?

(A) 1 only

(B) 2 and 3 only

(C) 1 and 2

(D) 1, 2 and 3

3. Consider the following statements on Ecological succession

1. In ecological succession, there is a definite point of the beginning but not a definite ending

2. The process of succession can be altered only by nature

3. Succession starts with a place where no living organism found is called primary succession

 Which of the statements given above is/are Correct?

(A) 1 only

(B) 2 and 3 only

(C) 1 and 3

(D) 1, 2 and 3

4. Consider the following statements on Grazing food chain and Detritus food chain

1. Grazing food chain gets energy from the sun

2. Detritus food chain gets energy from the soil

3. Both the food chain helps in fixing inorganic nutrients

 Which of the statements given above is/are Correct?

(A) 1 only

(B) 2 and 3 only

(C) 1 and 3

(D) 1, 2 and 3

5. Which of the following have Mangrove forest?

1. Andaman and Nicobar Islands

2. Gulf of Kutch

3. Gulf of Mannar

4. Sunderbans

Select the correct answer using the code given below.

(A) 2 and 3 only

(B) 1, 2 and 4 only

(C) 1 and 3 only

(D) 1, 2, 3 and 4

6. The flow of energy from lower to higher trophic level in the ecosystem is mainly explained by

1. First law of thermodynamics

2. The second law of thermodynamics

3. Third law of thermodynamics

 Select the correct answer using the following Code:

(A) 1 only

(B) 2 only

(C) 3 only

(D) Both 1 and 2

7. Which of the following statements best describes biotic potential?

(A) It refers to the potential biomass of a population measured as dry weight per unit area.

(B) It refers to the possible functional roles a species can play in an ecosystem.

(C) It refers to the maximum reproductive capacity of an organism under optimum environmental conditions.

(D) It refers to the minimum population of a species required to sustain a food web.

8. Consider the following pairs:

          Population Interaction      Feature

1. Mutualism: Both the species are benefited

2. Competition: Both the species are harmed

3. Commensalism: One species is harmed and the other is unaffected

4. Amensalism: One species is benefited and the other is unaffected

Which of the pairs given above is/are correctly matched?

(A) 1 and 2 only

(B) 3 and 4 only

(C) 1, 2 and 3 only

(D) 1, 2, 3 and 4

9. Which of the following is known as the Rain forests of the oceans?

(A) Mangroves

(B) Coral reefs

(C) Sea grass

(D) Oysters

10. With reference to ecology, which among the following correctly describes the Allen’s rule?

(A) It states that the growth and productivity of a plant is always limited by availability of a critical nutrient.

(B) It states that if two species have completely overlapping niches they cannot continue to coexist.

(C) It states that mammals from colder climates generally have shorter ears and limbs to minimize heat loss.

(D) None of the above.

11. Which of the following statements is/are correct about a biosphere reserve?

1. A biosphere reserve focuses on protection of a single species rather than the entire ecosystem.

2. Human activity is completely prohibited in both core and buffer zones of a biosphere reserve.

Select the correct answer using the code given below.

(A) 1 only

(B) 2 only

(C) Both 1 and 2

(D) Neither 1 nor 2

12. With reference to ‘decomposition’, which of the following statements is/are correct?

1. Humus is highly susceptible to microbial action and undergo decomposition at fast rate.

2. Decomposition is slower if detritus is rich in nitrogen.

3. Low temperature and anaerobiosis inhibit the decomposition.

Select the correct answer using the code given below.

(A) 3 only

(B) 2 and 3 only

(C) 1 and 2 only

(D) 1, 2 and 3

13. Which of the following is/are examples of Mutualism?

1. Algae and lichens.

2. Rhizobium bacteria and plants.

3. Coral polyps and Zooxanthellae

4. Leech and cattle

Select the correct answer using the code given below:

(A) 1 and 3 only

(B) 2 and 4 only

(C) 1, 2 and 3 only

(D) 1, 2, 3 and 4

14. Consider the following statements with regard to responses of organisms to stressful environment:

1. Hibernation and Aestivation refers to temporary movements of organisms from the stressful habitat to a more hospitable area.

2. Diapause is animal dormancy due to adverse environmental conditions in which growth or development is suspended.

Which of the statements given above is/are correct?

(A) 1 only

(B) 2 only

(C) Both 1 and 2

(D) Neither 1 nor 2

15. Which of the following statements is/are correct regarding freshwater ecosystems?

1. Lotic ecosystems are still water ecosystems whereas Lentic ecosystems are running water ecosystems.

2. Thermocline in an aquatic ecosystem is the zone of constant temperature.

Select the correct answer using the code given below:

(A) 1 only

(B) 2 only

(C) Both 1 and 2

(D) Neither 1 nor 2

 

ANSWERS

1. D

• The Primary productivity can be divided into: Gross Primary Productivity (GPP) of an ecosystem is the rate of production of organic matter during photosynthesis. considerable amount of GPP is utilized by plants in respiration. Net Primary Productivity is gross primary productivity minus respiratory losses.

2.A

• Pyramid of energy is always upright, can never be inverted, because when energy flows from a particular trophic level to the next trophic level, some energy is always lost as heat at each step. In most ecosystems, the pyramid of energy, biomass and number are always upright but this is not generalized, there are some exemptions like sea ecosystem, Tree ecosystem and many others.

3. C

• Succession can be altered by either naturally or anthropgenic. Say for example, destroying the forest for agricultural activities.

4. C

• Statement 2 is incorrect, it derives energy from decaying matters.

5. B

• List of Mangroves in India – West Bengal Sunderbans Orissa 2. Bhaitarkanika 3. Mahanadi 4. Subernarekha 5. Devi 6. Dhamra 7. Mangrove Genetic Resources Centre 8. Chilka Andhra Pradesh 9. Coringa 10. East Godavari 11. Krishna Tamil Nadu 12. Pichavaram 13. Muthupet 14. Ramnad 15. Pulicat 16. Kazhuveli Andaman & Nicobar 17. North Andamans 18. Nicobar Kerala 19. Vembanad 20. Kannur (Northern Kerala) Karnataka 21. Coondapur 22. Dakshin Kannada/Honnavar 23. Karwar 24. Manglore Forest Division Goa 25. Goa Maharashtra 26. Achra-Ratnagiri 27. Devgarh-Vijay Durg 28. Veldur 29. KundalikaRevdanda 30. Mumbra-Diva 31. Vikroli 32. Shreevardhan 33. Vaitarna 34. Vasai-Manori 35. Malvan Gujarat 36. Gulf of Kutchh 37. Gulf of Khambhat 38. Dumas-Ubhrat

6. B

• The Second Law of Thermodynamics states that “energy of all kinds in our material world disperses or spreads out if it is not hindered from doing so.” In other words, the randomness (entropy) of the universe is always increasing. The second law of thermodynamics is definitely the most applicable of the four laws to ecology.
• It is consistent with Elton’s Pyramid of food webs that states that although sometimes total size or number of organisms can either increase or decrease with increasing trophic levels, the total biomass ALWAYS decreases with increasing trophic levels, as energy is constantly being lost to the atmosphere.

7. C

• Biotic potential, the maximum reproductive capacity of an organism under optimum environmental conditions. It is often expressed as a proportional or percentage increase per year, as in the statement “The human population increased by 3 percent last year.” It can also be expressed as the time it takes for a population to double in size (doubling time).
• Full expression of the biotic potential of an organism is restricted by environmental resistance, any factor that inhibits the increase in number of the population. These factors include unfavorable climatic conditions; lack of space, light, or a suitable substrate; deficiencies of necessary chemical compounds or minerals; and the inhibiting effects of predators, parasites, disease organisms, or unfavorable genetic changes.

8. A

• Mutualism is the interaction in which both the interacting species benefit, for example, the association between fungi and the roots of higher plants. The fungi help the plant in the absorption of essential nutrients from the soil while the plant in turn provides the fungi with energy-yielding carbohydrates.
• Competition is the interaction in which species compete with each other to utilise the limited available resource. In this interaction both the species lose as they try to outdo each other, for example, the herbivores animals compete with each other to access limited grazing resources..
• Commensalism is the interaction among species in which one species benefits and the other is neither harmed nor benefited, for example, an orchid growing as an epiphyte on a mango branch. In this interaction while orchid benefits, the mango tree remains unaffected.
• Amensalism is the interaction in which one species is harmed while the other is unaffected, for example, some higher plants like black walnut secrete substances that inhibit the growth of or kill the nearby competing plants.

9. B

10. C

• Allen’s rule states that the mammals from colder climates generally have shorter ears and limbs to minimise heat loss. Liebig’s law of the minimum states that the rate of growth of a plant, the size to which it grows, and its overall health depend on the amount of the scarcest of its essential nutrients that is available to it.
• Competitive exclusion principle, sometimes referred to as Gause’s law of competitive exclusion, is a proposition that states that two species competing for the same resource cannot coexist at constant population values, if other ecological factors remain constant.

11. D

12. A

• Statement 1 is incorrect, because humus is highly resistant to microbial action and undergoes decomposition at an extremely slow rate.
• Statement 2 is incorrect, because Decomposition is faster if detritus is rich in nitrogen.
• Statement 3 is correct, because low temperature and anaerobiosis inhibit the decomposition. Cold Storages are used to preserve the perishable product, by slowing the growth of decomposer microorganism.

13. C

• Leeches feeding on cattle is an example of Parasitism i.e. association between two different species where the symbiont benefits and the host is harmed. All the others are examples of Mutualism in which both the organisms benefit.
• Algae provides food and seeks water and protection from lichens.
• Rhizobium bacteria receives carbohydrates from plants and in reverse plants get nitrogen fixed by bacteria
• Coral polyps provide protection and supply raw materials and Zooxanthellae provides food to host.

14. B

• Hibernation, aestivation and diapause are the forms of Suspend response of organisms to the abiotic components of the environment.
• Statement 1 is not correct. Hibernation and Aestivation are not related to movement of organisms from one place to another; rather they are escape in time. Bears go into hibernation during winter while some snails and fish go into aestivation to avoid summer related problems like heat. These are not forms of migration of the organisms.
• Statement 2 is correct. Under unfavourable environmental conditions certain organisms like insects and many zooplanktons enter in the phase of diapause which sees diminished physiological activity by these organism as well as suspended development.

15. D

• Freshwater ecosystems can be divided into two types:

1. Standing water or lentic (lenis, meaning calm) ecosystems like a lake, pond, marshes, or swamps. These are also known as pond ecosystems.
2. Running water or lotic ecosystems are that of a river or Spring.Hence statement 1 is incorrect.

• Statement 2 is incorrect. Thermocline is the zone of aquatic ecosystem in which temperature of the water changes rapidly.