NEET Biology Ecosystem MCQs Set 26

Answer: (b) thorn forests

Explanation:
1. Prosopis, Acacia and Capparis are thorny, drought-adapted plants of tropical thorn forests.

Teacher's Note:
1. Thorn forests occur in dry regions.
2. Thorny plants form thorn forests.

Answer: (d) gross primary productivity

Explanation:
1. Gross primary productivity is the rate at which producers convert light energy into chemical energy of organic matter.

Teacher's Note:
1. Net primary productivity is GPP minus respiration.
2. GPP is rate of photosynthetic storage.

Answer: (a) T1

Explanation:
1. Producers (T1) capture solar energy and hold the maximum energy of all trophic levels.

Teacher's Note:
1. Energy falls at each higher level.
2. T1 has the most energy.

Answer: (d) Tropical rain forests

Explanation:
1. Tropical rain forests have the greatest species richness and density of organisms because of warm, moist, stable climate.

Teacher's Note:
1. Deserts have few organisms.
2. Rain forests have highest density.

Answer: (a) Fishes

Explanation:
1. Toxic substances increase at each higher trophic level (biomagnification), so the top consumer, the fish-eating bird, accumulates the most.

Teacher's Note:
1. DDT biomagnification is a classic example.
2. Top consumer has most toxin.

Answer: (d) free-floating micro-algae, cyanobacteria and nanoplankton

Explanation:
1. In oceans the main autotrophs are free-floating microalgae, cyanobacteria and nanoplankton, which have the greatest biomass.

Teacher's Note:
1. Seaweeds are limited to coasts.
2. Plankton are major oceanic producers.

Answer: (c) Gause’s competitive exclusion principal

Explanation:
1. Gause's competitive exclusion principle states that two closely related species competing for the same resources cannot coexist indefinitely.

Teacher's Note:
1. Experiment was done on Paramecium.
2. Gause stated competitive exclusion.

Answer: (c) Both

Explanation:
1. Mimicry helps an organism to avoid attack as prey and also helps predators to approach prey, so it serves defence and offence.

Teacher's Note:
1. Batesian and Mullerian mimicry are defensive.
2. Mimicry gives protection and aid in attack.

Answer: (c) Utricularia, Drosera, Dionea

Explanation:
1. Bladderwort is Utricularia, sundew is Drosera and venus fly trap is Dionaea; all are insectivorous plants.

Teacher's Note:
1. Nepenthes is the pitcher plant.
2. Match insectivorous plants to genera.

Answer: (b) Random mating

Explanation:
1. With random mating and no other evolutionary force, gene frequencies stay constant as in Hardy-Weinberg equilibrium.

Teacher's Note:
1. Mutation, selection and gene flow change frequencies.
2. Random mating keeps ratio constant.

Answer: (a) Cuscuta — Parasite

Explanation:
1. Cuscuta (dodder) is a total stem parasite. Dischidia is an epiphyte, Opuntia a xerophyte and Capsella a mesophyte weed.

Teacher's Note:
1. Parasites take food from the host.
2. Cuscuta is a parasite.

Answer: (b) Reproductive isolation

Explanation:
1. Reproductive isolation prevents gene exchange between populations and is the key step in forming new species.

Teacher's Note:
1. Geographical isolation often comes first.
2. Reproductive isolation drives speciation.

Answer: (c) polyploidy

Explanation:
1. Polyploidy can create a new, reproductively isolated species in a single generation, which is common in crop plants.

Teacher's Note:
1. Wheat and cotton are polyploids.
2. Polyploidy gives rapid speciation.

Answer: (c) symbiotic relationship

Explanation:
1. Mycorrhiza is a mutual association of a fungus and plant roots, a symbiotic relationship.

Teacher's Note:
1. It is not parasitism.
2. Mycorrhiza is symbiosis.

Answer: (d) faecal matter

Explanation:
1. E. coli lives in the human gut, so its presence in water shows contamination with faecal matter.

Teacher's Note:
1. Coliform count is a standard test.
2. E. coli indicates faecal pollution.

Answer: (c) real basic units of classification

Explanation:
1. A species is regarded as the real basic unit of classification, a natural group of interbreeding individuals.

Teacher's Note:
1. It is a natural group, not a man-made one.
2. Species is the basic unit.

Answer: (a) A species which makes up only a small proportion of the total biomass of a community, yet has a huge impact on the community’s organization and survival

Explanation:
1. A keystone species may have low biomass yet an enormous effect on community structure and survival.

Teacher's Note:
1. Dominant species are different.
2. Small biomass, large effect.

Answer: (c) Gross Production (GP)

Explanation:
1. Gross production is total production before respiration losses, so it is higher than net or secondary production.

Teacher's Note:
1. NPP is GPP minus respiration.
2. Gross production is highest.

Answer: (c) camouflage

Explanation:
1. The praying mantis is coloured and shaped like leaves or twigs to blend with surroundings, which is camouflage.

Teacher's Note:
1. Warning colouration is bright.
2. Mantis shows camouflage.

Answer: (d) Gene flow does not occur between the populations of a species

Explanation:
1. Different populations of a species can exchange genes, so the statement that gene flow does not occur is false.

Teacher's Note:
1. Members of a species interbreed.
2. Gene flow occurs within a species.

Answer: (d) Fresh weight

Explanation:
1. Ecological pyramids use dry weight, numbers or energy flow. Fresh weight varies with water content and is not used.

Teacher's Note:
1. Dry weight is a more reliable measure.
2. Fresh weight is not used.

Answer: (c) sharing of one or more resources between the two species

Explanation:
1. Niche overlap means that two species share one or more resources, which leads to competition.

Teacher's Note:
1. The greater the overlap the stronger the competition.
2. Niche overlap is resource sharing.

Answer: (a) Tropical rain forest

Explanation:
1. Tropical rain forests have the highest annual net primary productivity because of warm, wet conditions all year.

Teacher's Note:
1. Productivity falls toward the poles.
2. Rain forest has highest NPP.

Answer: (b) intraspecific competition

Explanation:
1. A dense population of one species (elephants) increases competition among its own members, which is intraspecific competition.

Teacher's Note:
1. Interspecific competition is between different species.
2. Same species competing.

Answer: (c) oceans

Explanation:
1. The oceans contain about 71 percent of global carbon, mostly dissolved, so they are the largest reservoir.

Teacher's Note:
1. The atmosphere has only about 1 percent.
2. Oceans hold most carbon.