Ecosystem Test - 64

A "pyramid of numbers" shows graphically the population of each level in a food chain. A large population of insects feeds upon a very big tree. The insects, in turn, are eaten by small birds which in turn are fed upon by big birds. It showing the interaction between trees, insects, birds and big birds. Pyramid of number is spindle-shaped as the number of insects is maximum. The number of trees and birds are less than the insects. The number is gradually decreasing at each trophic level.

The correct sequence is “C>D>B>A”.

So, according to this incorrect sequence is”D>A>B”

An ecosystem is a community of living organisms together with non-living components of their environment, functioning together as a system. The term 'ecosystem' was first proposed by Sir Arthur Tansley in 1935. The ecosystem can be recognized as a self-regulating and self-sustaining unit of 'landscape'. Hence, the correct answer is option B. ''landscape'.

• Ecological pyramids are a representation of the relationship between different trophic levels. These are shown with regards to biomass, energy, and number of organisms. 
• The producers are present at the base of pyramids and tertiary consumers are shown at the apex of the pyramids. In this, saprophytes/decomposers are not given any place although they play an important role in an ecosystem.

The gradual and fairly predictable changes in species composition of a given area is called ecological succession. The sere refers to the different stages that form and eliminate in the process of the ecological succession until the climax community colonozes the area.

The measure of vitality at each trophic dimension diminishes as it travels through a biological community. As meager as 10 percent of the vitality at any trophic dimension is exchanged to the following dimension; the rest is lost to a great extent through metabolic procedures as warmth.

• Every organism to establish a new ecosystem require a soil but lichens colonize in bare rock and secrete acid, which causes the breakdown of rock and produces the soil. That's why lichens are called pioneer species on rocks.
• Whereas, the phytoplankton establishes the primary succession in water and with time phytoplanktons are replaced by the free-floating angiosperms then the hydrophytes and finally the tress. 
• Phytoplanktons are called the pioneer species in hydrarch succession.
• So, the correct answer is 'Lichens'.

Pyramid of number can be inverted in a tree ecosystem because a single tree is occupying the primary trophic level, followed by insects as primary and secondary consumers, birds as tertiary consumer and hawk being the top consumer. The primary consumers will be large in number. So, the pyramid appears inverted.

Pyramid of energy is always upright because when energy flows from particular trophic level to next trophic level, some energy is always lost as heat at each step. So, the energy in subsequent trophic levels is always less than the energy in the previous level. Hence pyramid of energy is always upright and can never be inverted.

Ecological succession is the gradual process that describes the changes seen in the species structure of an ecological or biological community over time. It focuses on changes in animals, decomposers as well as vegetations. It is mainly of two types, namely primary ecological succession and secondary ecological succession. Primary succession occurs when an area that has never been supported by an ecological community is colonized by plants and animals. Secondary succession occurs when an area that has had an ecological community but was destroyed completely and is colonized by a new community. 

Correct Answer: C

Explanation:

• The pyramid of a number represents the number of individuals in per unit area at different trophic levels.
• It is forever upright in grassland, pond, and lake ecosystems.
• But in the forest or in the single tree ecosystem, and suppose if the parasitic food chain is considered, then it will be an inverted pyramid.
• Thus, the upright pyramid of number is not present in the forest.

So, the correct answer is 'Forest'.