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1.

Describe the components of an ecosystem

Answer»

An ecosystem is defined as an interacting unit that includes both the biological community as well as the non-living components of an area. The living and the non-living components of an ecosystem interact amongst themselves and function as a unit, which gets evident during the processes of nutrient cycling, energy flow, decomposition, and productivity. There are many ecosystems such as ponds, forests, grasslands, etc.
The two components of an ecosystem are:

  •  Biotic component: It is the living component of an ecosystem that includes biotic factors such as producers, consumers, decomposers, etc. Producers include plants and algae. They contain chlorophyll pigment, which helps them carry out the process of photosynthesis in the presence of light. Thus, they are also called converters or transducers. Consumers or heterotrophs are organisms that are directly (primary consumers) or indirectly (secondary and tertiary consumers) dependent on producers for their food.

Decomposers include micro-organisms such as bacteria and fungi. They form the largest population in a food chain and obtain nutrients by breaking down the remains of dead plants and animals.

  •  Abiotic component: They are the non-living component of an ecosystem such as light, temperature, water, soil, air, inorganic nutrients, etc.
Discussion
2.

Distinguish between(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

Answer»


(a) Grazing food chain and detritus food chain

Grazing food chainDetritus food chain
In this food chain, energy is derived from the Sun.In this food chain, energy comes from organic matter (or detritus) generated in trophic levels of the grazing food chain

It begins with producers, present at the first trophic level. The plant biomass is then eaten by herbivores, which in turn are consumed by a variety of carnivores.

It begins with detritus such as dead bodies of animals or fallen leaves, which are then eaten by decomposers or detritivores. These detritivores are in turn consumed by their predators.

This food chain is usually largeIt is usually smaller as compared to the grazing food chain. 

 (b) Production and decomposition

ProductionDecomposition
It is the rate of producing organic matter (food) by producersIt is the process of breaking down of complex organic matter or biomass from the body of dead plants and animals with the help of decomposers into organic raw material such as CO2, H2O, and other nutrients
It depends on the photosynthetic capacity of the producersIt occurs with the help of decomposers. 
Sunlight is required by plants for primary productionSunlight is not required for decomposition by decomposers 

(c) Upright and inverted pyramid

Upright pyramidInverted pyramid
The pyramid of energy is always upright.The pyramid of biomass and the pyramid of numbers can be inverted
In the upright pyramid, the number and biomass of organisms in the producer level of an ecosystem is the highest, which keeps on decreasing at each trophic level in a food chainIn an inverted pyramid, the number and biomass of organisms in the producer level of an ecosystem is the lowest, which keeps on increasing at each tropic level.

d) Food chain and Food we

Food chainFood web
It is a single linear sequence of organismsIt contains a number of interconnected food chains

Members present at higher trophic levels feed on single types of organisms

One organism has alternate food sources 

(e) Litter and detritu

LitterDetritus
Litter contains all kinds of wastes generated above the ground.Detritus is composed of the remains of dead plants and animals
Litter contains both biodegradable and non-biodegradable matter.Detritus contains only biodegradable matter.

f) Primary and secondary productivity

Primary productivitySecondary productivity
It is defined as the amount of organic matter produced by producers per unit area over a period of time.It is defined as the rate of production of organic matter by consumers over a period of time
Discussion
3.

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

Answer»

It is defined as the amount of organic matter or biomass produced by producers per unit area over a period of time.
Primary productivity of an ecosystem depends on the variety of environmental factors such as light, temperature, water, precipitation, etc. It also depends on the availability of nutrients and the availability of plants to carry out photosynthesis.
Discussion
4.

Define decomposition and describe the processes and products of decomposition.

Answer»

Decomposition is the process that involves the breakdown of complex organic matter or biomass from the body of dead plants and animals with the help of decomposers into inorganic raw materials such as carbon dioxide, water, and other nutrients. The various processes involved in decomposition are as follows:

  • Fragmentation: It is the first step in the process of decomposition. It involves the breakdown of detritus into smaller pieces by the action of detritivores such as earthworms.
  •  Leaching: It is a process where the water soluble nutrients go down into the soil layers and get locked as unavailable salts.
  •  Catabolism: It is a process in which bacteria and fungi degrade detritus through various enzymes into smaller pieces.
  •  Humification: The next step is humification which leads to the formation of a darkcoloured colloidal substance called humus, which acts as reservoir of nutrients for plants.
  •  Mineralization: The humus is further degraded by the action of microbes, which finally leads to the release of inorganic nutrients into the soil. This process of releasing inorganic nutrients from the humus is known as mineralization.

Decomposition produces a dark coloured, nutrient-rich substance called humus. Humus finally degrades and releases inorganic raw materials such as CO2, water, and other nutrient in the soil.
Discussion
5.

Fill in the blanks.(a) Plants are called as_________ because they fix carbon dioxide.(b) In an ecosystem dominated by trees, the pyramid (of numbers) is _________ type.(c) In aquatic ecosystems, the limiting factor for the productivity is _________.(d) Common detritivores in our ecosystem are_________.(e) The major reservoir of carbon on earth is_________.

Answer» (a) Plants are called as autotrophs because they fix carbon dioxide.
(b) In an ecosystem dominated by trees, the pyramid (of numbers) is of inverted type.
(c) In aquatic ecosystems, the limiting factor for productivity is light.
(d) Common detritivores in our ecosystem are earthwor
Discussion
6.

The second trophic level in a lake is(a) Phytoplankton(b) Zooplankton(c) Benthos(d) Fishes

Answer»

(b) Zooplankton
Zooplankton are primary consumers in aquatic food chains that feed upon phytoplankton. Therefore, they are present at the second trophic level in a lake.
Discussion