Energy Flow & Ecological Succession

1 Mark Questions

1.State what does standing crop of a trophic level represent. [Delhi 2013]

Ans Standing crop represents the total mass of living material or energy content of all the organisms of a trophic level at a particular time and location

1. What is a detritus food chain made up of? How do they meet their energy and nutritional requirements? [All India 2013]

Ans. It is made up of decomposers, i.e. some bacteria and fungi. They meet their energy and nutrient requirements by degrading the dead organic matter of detritus

3. Mention the role of pioneer species in primary succession on rocks. [Foreign 2012]

Ans. Lichens are the pioneer species in the succession on rocks. They secrete acids to dissolve the rock and help in weathering and soil formation and pave way to small plant like bryophytes.

4.List any two ways of measuring the standing crop of a trophic level.[Foreign 2010]

Ans. Standing crop can be measured as:

1. Biomass of living organism in a unit area.

2 Marks Questions

1. Number in a unit area

5.A part from being a part of food chain, predators play other important roles. Mention any two such roles supported by examples.[Delhi 2014]

Ans. Apart from being a part of food chain, predators play important role in:

1. Maintaining the prey population and also regulates intraspecies competition.

(ii)Indicating ecological disturbances as predators are small in number and highly sensitive to ecological changes owing to their excessive adaptation.

6.It is possible that a species may occupy more than one trophic level in the same

ecosystem at the same time. Explain with the help of one example.[All India 2013,2008 C]

Ans. Yes, the trophic level of species represents the functional level of species in the energy ^ flow. The preference of food habit depends on the available food and worms. A single

species may occupy more than one trophic level at the same time in ecosystem. For example, sparrow is primary consumer when it eats seeds and secondary consumer when feeds on insects and worms.

1. Name the type of food chains responsible for the flow of larger fraction of energy in an

aquatic and a terrestrial ecosystem respectively. Mention one difference between the two food chains. [Delhi 2010]

Ans. Food chain in aquatic ecosystem is the grazing food chain. In terrestrial ecosystem, it is detritus food chain. Differences between grazing and detritus food chain are:

Grazing food chain Detritus food chain Transfer of energy Transfer of energy starts from producers. starts from detritus/decomposing organic matter. Less energy flows More energy flows through this. through this. In aquatic ecosystem, In terrestrial it is the major conduit ecosystem, it is the for energy transfer. major conduit for energy transfer.

1. Explain standing crop in an ecosystem. Draw a pyramid of biomass when a small standing

crop of phytoplanktons supports a large standing crop of zooplankton in the sea. [Delhi 2010]

Ans. Standing crop represents the total mass of living material or energy content of all the organisms of a trophic level at a particular time and location

Primary Consumer (PC) Primary Producer (PP)

Pyramid of biomass (standing crop)

Inverted pyramid of biomass small standing crop of phytoplankton supports large standing crop of zooplankton

Construct a grazing food chain and detritus food chain using the following five links each. Earthworm, bird, snake, vulture, grass, grasshopper, frog, decaying plant matter. [Foreign

2008]

Ans. Grazir ood chain

Grass - > Grasshopper - > Bird - > Snake -> Vulture

Detritus food chain

Dead and decaying plant matter -> Earthworm -> Bird -> Snake Vulture