Test: Ecosystem–Structure and Function & Productivity (February 20) - NEET MCQ

Biosphere is one of the layers surrounding the earth along with the lithosphere(land) ,hydrosphere(water),atmosphere (air).

The relationship between any system and its surrounding environment can be described in one of three ways. In an isolated system, neither matter nor energy is exchanged with its environment. In a closed system, energy, but not matter, is exchanged. In an open system, both matter and energy are exchanged between the system and its surrounding environment. Any ecosystem is an example of an open system. 

A biome is defined as a community of various plants and animals, that inhabit a particular type of geographic region of Earth. Biomes are often defined by their climate, rainfall/water characteristics, elevation, and plant characteristics (leaf type, spacing, etc). Biomes can be divided into two major classifications, terrestrial (land-based) and aquatic (water-based). 

Interaction of biotic and abiotic components result in a physical structure, that is characteristic of each type of ecosystem. Components of ecosystem function as one single unit. Four important functional aspects of the ecosystem are:
(i) Productivity,
(ii) Decomposition,
(iii) Energy flow and
(iv) Nutrient cycling.
Ecological pyramids are graphical representation of number, biomass and energy flow in an ecosystem.

Ecological equivalents are the organisms which occupy same niche in different habitats (or geographical areas) e.g. both owl and cat feed on shrews and mice hence they occupy the same niche though their habitats are different.

Dry, freezed storage of germplasm at -196°C in liquid nitrogen is called cryopreservation. At such temperature, all biological activities are near stoppage. In situ conservation is the maintenance of biological diversity in natural habitats like national parks, wildlife sanctuaries and biosphere reserves. Ex situ conservation is the conservation of selected rare plants/animals in place outside their natural home.

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:

(1) 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.

(2) Leaching: It is a process where the water soluble nutrients go down into the soil layers and get locked as unavailable salts.

(3) Catabolism: It is a process in which bacteria and fungi degrade detritus through various enzymes into smaller pieces.

(4) Humification: The next step is humification which leads to the formation of a dark-coloured colloidal substance called humus, which acts as reservoir of nutrients for plants.

(5) 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.

The components of the ecosystem are seen to function as a unit when the aspect is energy flow. It is the calorific amount of energy that moves from the sun and up to each subsequent level of the food chain in an environment.

Soil has five components with different compositions: Mineral matter - 40%, water - 25%, organic matter - 10%, air-25% and soil organisms (variable).

Tropical rainforest shows the maximum diversity and also the maximum productivity. More solar energy and resources are available in tropics which promotes higher productivity. On land the maximum primary production rate is found in tropical rainforests followed by tropical deciduous forests, temperate forests, savannah, temperate grasslands and desert scrub.