Ecosystem Test - 62

Gross primary productivity is the rate of production of organic matter during photosynthesis and its considerable amount is utilized by plants during respiration.

In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through chemosynthesis, which uses the oxidation or reduction of inorganic chemical compounds as its source of energy. Almost all life on Earth relies directly or indirectly on primary production. The organisms responsible for primary production are known as primary producers or autotrophs, and form the base of the food chain. Net primary production is the rate at which all the plants in an ecosystem produce net useful chemical energy; it is equal to the difference between the rate at which the plants in an ecosystem produce useful chemical energy (GPP) and the rate at which they use some of that energy during respiration. Some net primary production goes toward growth and reproduction of primary producers, while some is consumed by herbivores.

Primary succession includes changes which occur when living things become established on a previously uninhabited area such as a newly exposed sea or lake sediments or sand dunes.

Triangular age pyramid has high proportion of preoperative
 individuals, moderate number of reproductive individuals and fewer post-reproductive individuals. It represents young or rapidly growing population. 
In urn-shaped age pyramid, the number of reproductive individuals is higher than the number of pre-reproductive individuals. It represents declining or diminishing population with negative growth. 
In bell-shaped age pyramid, the number of pre-reproductive and reproductive individuals is almost equal. Post reproductive individuals are comparatively fewer. It represents stable or stationary population, neither growing nor diminishing. 

According to the mechanism of resource partitioning (supported by Mac Arthur), if two species compete for the same resource, they could avoid competition by choosing, for instance, different times for feeding or different foraging patterns. Two species evolve to become different too reduce competition, so that species can co-exist. 

Ecollogy is the study of interactions among organisms and between the organisms and their biotic and abiotic environment. The study of reciprocal relationships between every stage of development of a population/species/individual and its environment is called autecology. composition, organisation and development of communities and their environment. 

A keystone species plays a important role in maintaining ecosystem and keystone species may be top predator so, the removal of it will affect the ecosystem but not producers , decomposers or consumers. So the correct option is "ecosystem"

The number of organisms in a food chain can be represented graphically in a pyramid. Each level shows the number of individuals at each trophic level in the food chain. Usually, from one level to next, the number of individuals decreases by 10%. If in a forest, producers are 14000, then primary consumers (herbivores) will be 1400 and secondary consumers (carnivores) will be 140. The tertiary consumers (top carnivores) will be 14.

Answer: (B) Lithosere.