Ecosystems and Biodiversity Questions and Answers

Answer: B

Allochthonous organisms are those that come from outside the ecosystem, so the allochthonous microorganisms are migrants. The indigenous ones, which originate in the ecosystem, are autochthonous. Parasitic and pathogenic describe a mode of life, not an origin. The answer is migrant.

Answer: D

Clostridium botulinum is the most dangerous spoilage organism in the canning industry: its spores resist heat and it produces the botulinum toxin in anaerobic cans. Clostridium cellulolyticum degrades cellulose, Bacillus subtilis is a common soil bacterium and E. coli is killed at much lower temperatures. The answer is Clostridium botulinum.

Answer: B

A generation time of 20 minutes means 3 generations per hour. To reach \(10^{3}\) cells takes about 10 generations (\(2^{10} = 1024\)), which is 3.3 hours as the question says. To reach \(10^{6}\) cells takes about 20 generations (\(2^{20} \approx 10^{6}\)):

\[ t = 20 \times 20 \text{ min} = 400 \text{ min} \]

\[ t \approx 6.6 \text{ h} \]

The answer is 6.6 hours, twice the time for \(10^{3}\) cells. The values of 5.3, 9.9 and 6.3 hours do not match 20 generations.

Answer: A

An ecotype is a genetically different form of the same species that is adapted to a local habitat. The key gives the first option: genetically different forms of the same organisms. The options of genetically similar forms and morphologically different forms are not the definition, and the option that combines the first two options contradicts itself.

Answer: A

Ultraviolet radiation is lethal because it damages and inactivates proteins, nucleic acids (by forming thymine dimers in DNA) and pigments. Minerals, water and air, carbohydrates, fats and vitamins and the gases \(\mathrm{O_{2}}\) and \(\mathrm{CO_{2}}\) are not the targets of lethal damage. The answer is the first option.

Answer: C

The species diversity of an ecosystem is greater when there is more richness (more species), more evenness (the individuals are spread evenly among the species) and less dominance (no species dominates). So the combination is (i), (ii) and (iv), option C. The other options include more dominance, less richness or less evenness, each of which lowers diversity.

Answer: B

Both statements are true, but the reason does not explain the assertion. If natality is greater than mortality, the population grows, and a very large excess leads to a population explosion. Demography is the scientific study of human populations, which is a true definition, but it has no bearing on why a surplus of births leads to growth. So the answer is option B.

Answer: D

In situ conservation protects species in their natural habitat. Reserve forests, national parks and sanctuaries are all protected areas of this kind, so all the above is correct. Ex situ methods keep species outside the habitat, in zoos, botanical gardens and gene banks.

Answer: B

The United Nations declared 2010 the International Year of Biodiversity.

It was chosen to mark the 2010 target to reduce the rate of biodiversity loss, and the Convention on Biological Diversity meeting at Nagoya, Japan, took place that year. The year 1972 is that of the Stockholm Conference on the Human Environment, and 2002 and 2020 are not the year of this declaration.

Answer: B

The keyed answer is Temperate forest.

By elimination: Boreal and Taiga are two names for the same northern coniferous biome, so they cannot be a single correct choice when the question asks for one biome. Tropical forests are the most species-rich of all, with many tree species in even a small area, so they are the opposite of the stated figure. This leaves the temperate forest, which has comparatively few tree species per unit area, and the official key accepts it.