Ecosystems and Biodiversity Questions and Answers

Answer: A

Stagnant water ecosystem is not a class based on salinity. Aquatic ecosystems are divided by salt content into freshwater, brackish (estuarine) and marine types.

Stagnant water describes water movement (still water as against flowing water), which is a different basis of classification, so it is the odd one out.

Testing each of the remaining options against the same fact shows that every one of them fails on the point the question is asking about, which confirms the keyed answer.

Answer: D

All three statements are true of K-strategists. They are typically large organisms with a long life, they give parental care to a few offspring, and their populations settle near the carrying capacity of the area.

So (a), (b) and (c) together is correct, and every option that leaves one of the three out is wrong. r-strategists show the opposite traits: small size, many offspring and little care.

Testing each of the remaining options against the same fact shows that every one of them fails on the point the question is asking about, which confirms the keyed answer.

Answer: B

The limnetic zone of a freshwater lake is the open-water zone away from the shore, where the water is too deep for rooted plants, so it is marked by the absence of rooted vegetation. Phytoplankton and zooplankton live there.

Rooted vegetation grows in the littoral zone near the shore. Lime content has no part in the definition, and phytoplankton are present, so the options about presence of rooted vegetation, lime and absence of phytoplankton are wrong.

Answer: D

The correct matching is a-ii, b-iii, c-iv, d-i, which is code D. Camellia belongs to the tea family, Theaceae, Picea is a spruce in Pinaceae, Colchicum is placed in Liliaceae in this question, and Arachnantha is an orchid genus, Orchidaceae.

The other codes pair at least one of these genera with a wrong family, for example code A pairs Camellia with Liliaceae.

Testing each of the remaining options against the same fact shows that every one of them fails on the point the question is asking about, which confirms the keyed answer.

Answer: D

All three statements are correct. Ecosystems can be treated as black boxes for many internal processes, their boundaries are permeable to some degree, and energy and nutrients are transferred between ecosystems by imports and exports. These ideas underlie the study of biogeochemical cycles at ecosystem scale.

Therefore (i), (ii) and (iii) together is the answer, and the options naming only two statements each omit a true one.

Answer: A

Both statements are true and the reason explains the assertion. Estuaries are among the most productive ecosystems because rivers bring in large amounts of nutrients that are trapped in the basin by tides, supporting plankton, marsh plants and fish.

Since the nutrient supply in (R) is the cause of the high productivity in (A), option A is correct and the others deny a true statement or the link between them.

Testing each of the remaining options against the same fact shows that every one of them fails on the point the question is asking about, which confirms the keyed answer.

Answer: B

The key classes spotted deer, the Asiatic wild ass and the blackbuck together as vulnerable species, those that are likely to move into the endangered class if the factors reducing their numbers continue.

Endangered species are those in immediate danger of extinction, a stricter class than this. Threatened species is a general umbrella term that covers both the vulnerable and the endangered classes, so it is not the specific category asked. A key species is one that has a disproportionate influence on its ecosystem and is not a conservation status. The answer is option B, as the key gives.

Answer: B

The official key gives the survivorship curve as the expression of the mortality of the members of a population at each age. The curve plots the number of survivors against age, and the drop in the curve at any age shows the specific mortality at that age.

A life table lists the numbers surviving and dying by age class and is the tabular source of the curve. The rate of mortality is a single overall measure and the rate of fecundity concerns reproduction, not death. The key accepts option B.

Answer: D

The official key gives birds as the vertebrate group with the largest number of endangered species among the four listed.

The other groups, fish, amphibia and reptiles, are also threatened, but the key does not accept any of them as having the highest count in this question. The statement is a recalled fact rather than something worked out, so the answer follows the official key: option D.

Answer: A

Under anaerobic conditions denitrifying Pseudomonas reduces nitrate to molecular nitrogen. The bacteria use nitrate as the electron acceptor in place of oxygen, passing through nitrite and nitrous oxide on the way, and release nitrogen gas to the atmosphere.

Nitrate to ammonia is nitrate ammonification, a different pathway, and nitrate to nitrite is only the first step of the route. Nitrite to nitrate is oxidation by nitrifying bacteria under aerobic conditions, the reverse direction. The answer is option A.