FREE NEET Biology Practice MCQ Test: Ecosystem Exercise 4 Questions Answers With Detailed Explanations [PDF]

Answer: (b)

Answer: (c)

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.

Answer: (b)

Answer: (b)

Answer: (b)

Statements I and II are correct, while statement III is incorrect. It can be corrected as Energy for detritus food chain (not grazing food chain) comes from organic remain or detritus. Grazing food chains are directly dependent on influx from solar radiations. Green plants with the help of solar radiation manufacture food by the process of photosynthesis.

Answer: (a)

Trophic level is a step or division of food chain which is characterized by the method of obtaining its food. The two fundamental trophic levels are producers and consumers. Producers belong to the first trophic level. In a lake the producers are mainly some rooted or floating plants and phytoplanktons.

Primary consumers form the second trophic level. They feed on living plants or plant parts. The primary consumers are zooplanktons.

Answer: (c)

Answer: (d)

Series of biotic communities that develop one after the other in a newly formed pond or lake is called hydrosere. It starts as soon as the muddy water becomes clear. The pioneer stage of hydrosere is plankton stage. Death and decomposition of planktons in the first seral stage of hydrosere produces organic matter which mixes up with clay and silt at the bottom to form soft mud which is favourable for growth of submerged hydrophytes in the next seral stage. Hence, the second stage of hydrosere is occupied by submerged hydrophytes like Vallisneria.

Answer: (b)

A standing crop is the quantity or total weight or energy content of the organism, which are in a particular location at a particular time.

Answer: (a)

The dead organic matter of plants or animals is called as detritus. While a part of it remains on the soil surface as litter, the other part enters the soil. Many animals such as protozoans, nematodes, insects etc., depend on detritus and hence they are called as detritivores. Even the human beings are detritivores when they eat cooked food. From detritus, the chain proceeds to detritivores, then to carnivores and finally to top carnivores.

Answer: (d)

Answer: (c)

The bare rocky habitat is extremely hostile to living beings. There is no water, as the substratum does not absorb rainwater. There is no nutrient holding mechanism. Plants cannot grow on these rocks. The first inhabitants or pioneers of such a habitat are usually lichens as they are resistant to desiccation and extreme temperatures.

Answer: (b)

Answer: (b)

Answer: (a)

Answer: (b)

Carbon constitutes 49% of dry weight of organism and is next only to water. Among the total quantity of global carbon 71% is found in oceans in dissolved form whereas only 1% is found in atmosphere. Carbon cycling occurs through atmosphere, ocean and living or dead organism.

Answer: (d)

The sequences of communities of primary succession in hydrosere is phytoplankton (pioneer stage) → rooted submerged hydrophytes → floating hydrophyte (floating stage) → reed swamp → sedges → meadow and woodland (trees). The other options are incorrect.

Answer: (c)

Pyramid of number in ecosystems can be inverted or upright. In terrestrial ecosystem, pyramid of number is upright. In case of successive decrease in members of trophic level like a big tree it is inverted.

Answer: (b)

Answer: (d)

Climax community is the stable, self perpetuating and final biotic community that develops at the end of biotic succession and is in perfect harmony with the physical environment.