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Give an account of energy flow in an ecosystem.

Different components for a universal model of energy flow are :

A generalised energy flow model of ecosystem—Boxes represent biotic components and the arrows show the pathways of energy transfer

When a herbivore eats a plant, then it digests and oxidizes the ingested food to liberate energy which is equal to that used in synthesizing the organic biomass by the plant. Some of the released energy is lost as heat while only a part of energy is used in building the biomass of the herbivore, called gross secondary productivity. The same is repeated when the herbivore is eaten by a primary carnivore and so on. At each transfer, about 80-90% of potential energy is dissipated as heat while only 10-20% of energy is available to next trophic level. Thus, there is a decline in the amount of energy passing from one trophic level to the next trophic level. The study of energy transfer was called bioenergetics.

Secondary productivity tends to be about 10 per cent at the herbivore level, although efficiency may be higher, as 20 per cent at the carnivore level.

So regarding the energy flow, an ecosystem is characterized by :

1. Unidirectional flow of energy.

2. Decrease in useful energy.

3. Return of radiant energy of sun to non-living system as heat.

Fill in the blanks with suitable words :
1. Plants are called as .......................because it fixes carbon dioxide.

2. In ecosystem, dominated by trees, the pyramid is.......................type.

3. In aquatic ecosystems, the limiting factor for the productivity is.......................

4. Common detritivores in our ecosystem are.......................

5. The major reservoir of carbon is.......................

Define ecological pyramids and describe with examples, pyramids of number and biomass.

Define decomposition and describe the processes and products of decomposition.

Write important features of a sedimentary cycle in an ecosystem.

Outline salient features of carbon cycling in an ecosystem.

Which one of the following has the largest population in a food chain ?

The second trophic level in a lake is :

Secondary producers are :

What is the percentage of photosynthetically active radiation (PAR), if incident solar radiation is considered 100% ?

Distinguish between the following :
(a) Grazing food chain and detritus food chain

(b) Production and decomposition

(c) Upright and inverted pyramid.

(d) Food chain and food web

(e) Litter and detritus

(f) Primary and secondary productivity.

Describe the components of an ecosystem.

What is primary productivity ? Give brief description of factors that affect primary productivity.

Describe the advantages for keeping the ecosystems healthy.

Explain the carbon cycle with the help of a simplified model.

Explain how does:

(a) a primary succession start on a bare rock and reach a climax community?
(b) the algal bloom eventually choke the water body in an industrial area?

(a) Explain primary productivity and the factors that influence it.

(b) Describe how do oxygen and chemical composition of detritus control decomposition?

It is often said that the pyramid of energy is always upright. On the other hand, the pyramid of biomass can be both upright and inverted. Explain with the help of examples and sketches.

(a) Explain the significance of ecological pyramids with the help of an example.
(b) Why are the pyramids referred to as upright or inverted?

(a) Taking an example of a small pond explain how the four components of an ecosystem function as a unit.
(b) Name the type of food chain that exists in a pond.