Ecosystem Test - 23

The succession which thus takes place through the process of living, growing and interactions of organisms with  the effect of the environment  within an area is referred as  biotic succession.  

Geographical succession is the directional change in the plant and animal community over a period of time in a specific area.

Physiographic succession is the directional change in the plant and animal community over a period of time in a specific area due to physical factors.

Climate succession is the directional change in the living community in a particular area over a period of time due to prevailing climatic conditions.

So, the correct answer is option B.

Solution

Correct answer is option C
Explanation for correct option:

• Biotic or ecological succession is the successive development of different biotic communities at the same site till a climax community develops there.
• Primary Succession is the ecological succession on a primary base area like rock, or outcrop. It takes a long time of 1000 years or more. 
• Secondary succession is biotic succession on the secondarily bare areas e.g., an area devastated by forest fire or deforestation. It takes 50 to 100 years for grassland and 100 to 200 years for the forest. Ferns are generally the first to grow after forest fire because of their underground rhizomes. 
• Secondary succession is not completed if invaded by weeds like Sphagnum, Lantana, Eichhornia, Eupatorium. 

• Ecological succession is the gradual process by which ecosystems change and develop over time. 
• With the habitats, constantly changing, succession is of two types- primary and secondary.
• Succession develops through increasing complexity until it becomes stable or self-perpetuating as a climax community where the ecosystem is balanced and there is less risk of any interfering event or change to the environment. 

Pyramid of energy is ecological pyramid that gives graphic representation of amount of energy trapped by different trophic levels per unit area. It is always upright because during transfer of energy from one trophic level to the next a lot of wastage occurs in feeding, digestion, assimilation and respiration i.e metabolism at each trophic level. Hence, organisms of each trophic level have more energy than each succeeding trophic level and less energy than organisms at previous trophic level.

 A) Correct option (A)
B) Explanation of the correct option 

• When the ecosystem in an area changes, it is called ecological succession. New species come into existence at this place. 
• Apart from this, ecological succession is of 2 types. One is primary succession, in which a barren land with no species affiliation shows the development of a new species. 
• Another is secondary succession where the species develop again in a land that was previously occupied by different organisms and was destroyed due to certain reasons. 

• The stability of an ecosystem depends on species diversity, the complexity of food webs, and the rate of nutrient cycling. 
• More the species diversity, the greater the complexity of the food web, and the higher the rate of nutrient cycling; the greater will be stability. 
• More the stability more will be the productivity of the ecosystem. 
• If an ecosystem can be easily damaged it means that stability is low. For example, man-made or artificial ecosystems have low stability. But if the ecosystem can recover fast it means high resilience. 
• High resilience may be due to human intervention or secondary colonization of fast-growing plants and rapidly settling animals.

Sere is a sequence of developmental stages from pioneer to climax communities. Plants that are first to invade a bare area are called as pioneer species. Hence, primary succession in a sere is pioneer sere.

The nitrogen cycle is a gaseous biogeochemical cycle and pyramid of biomass is inverted in aquatic food chains, where the primary producers are phytoplanktons.