Ecosystems and Biodiversity Questions and Answers

Answer: A

The full range of physical, chemical and biological conditions a species could use if there were no competition is its fundamental niche. When competitors, predators and other interactions restrict the species to a smaller part of that range, the part it actually occupies is the realized niche, so the realized niche is the smaller of the two. Ecological niche is a general term for the species' role and does not mean the competition-free potential. Competitive exclusion is a principle, stating that two species competing for the same limiting resource cannot coexist, and is not a kind of niche.

Answer: A

The raven can fill several trophic roles in different food chains. It eats seeds and fruit as a primary consumer, small animals and insects as a secondary or tertiary consumer, and carrion as a scavenger, so it is an omnivore and opportunist. A tiger is a top carnivore and is not a primary consumer or scavenger in the normal case. A snake is a carnivore, a secondary or tertiary consumer, with no plant-eating role. Phytoplankton are producers, not consumers at all.

Answer: A

The tendency of biological systems to resist change and remain in a state of equilibrium is homeostasis. It is maintained by feedback, but feedback mechanism is the process by which output regulates the system, not the name for the tendency itself. Ecological efficiency is the percentage of energy transferred from one trophic level to the next. Carrying capacity is the maximum population an environment can support over time. Homeostasis is the term that names the resistance to change and the steady state.

Answer: B

The correct sequence of the threatened categories in the older classification is Vulnerable, Rare, Endangered, Extinct, which runs from the least to the most severe threat. A vulnerable species is likely to move into the endangered category if the causes continue, a rare species has a small population that is not yet at risk, and an endangered species is in danger of extinction. Extinct is the end point, so it must come last. The orders that begin with Extinct, or put Extinct before Endangered, or start with Rare, break this progression.

Answer: C

Wildlife sanctuaries are not an ex situ method, because they protect species in their natural habitat, which is in situ conservation. Botanical gardens, zoological parks and gene banks all conserve organisms or their genetic material outside the natural habitat. Botanical gardens keep living plants, zoos keep animals under managed care, and gene banks store seeds, gametes or tissue, often at low temperature. Only the sanctuary keeps the species in the wild, so it is the item that is not ex situ.

Answer: A

As succession proceeds, the P/B ratio is high at the developmental stage and low at the mature stage. In young communities, production exceeds the biomass present, so the ratio is high. As biomass accumulates, more of the production goes to maintenance and respiration, and the ratio falls toward about one at the climax. The option saying the ratio is low in early stages and high at maturity is the reverse of this. The statement that the ratio stays unchanged denies succession-related change. The third statement allows a ratio below one in early stages, which does not fit a developing community, so the first option is the answer.

Answer: C

The keyed answer is alpha divided by 2 beta. The growth equation dN/dt = alpha N - beta N^2 is the logistic model with carrying capacity K = alpha/beta. The growth rate dN/dt is greatest when N = K/2, which is alpha/(2 beta), and harvesting at that population gives the maximum sustainable yield. So the keyed option is the population size at which the maximum yield is obtained. The yield itself would be alpha^2/(4 beta), which is not listed, so the question is loosely worded. The expression alpha - beta N is the per capita growth rate, alpha/beta is the carrying capacity, and alpha^2/beta is not a meaningful quantity here.

Answer: D

The tropical Western Ghats lie in the southwestern part of India, and among the states listed it is Kerala that contains them. The range runs along the west coast from Gujarat in the north, through Maharashtra, Goa, Karnataka and Kerala to Tamil Nadu in the south. Punjab and Rajasthan are in the north and northwest, with no part of the ghats, and Gujarat has only the northern end, with a dry climate. The tropical wet forest belongs to the southern part, in Kerala.

Answer: C

The variety of species, the genetic variability among individuals within each species and the variety of ecosystems together constitute biological diversity, or biodiversity. Species diversity refers only to the variety of species, genetic diversity to the variation within a species and ecological diversity to the variety of ecosystems and habitats. Each of these is a single level, while the question names all three together, which is the definition of biological diversity.

Answer: D

Net primary productivity per unit area follows this decreasing order in the standard ecosystem tables: tropical rain forest (about 2,200 g per square metre per year), tropical seasonal forest (about 1,600), woodland and shrubland (about 700) and temperate grassland (about 600). So the sequence is tropical rain forest, tropical seasonal forest, woodland and shrubland, temperate grassland. The other options put the seasonal forest above the rain forest, or temperate grassland above woodland, which reverses the table.