Ecosystem Test - 14

Correct Option: A

• The rate of accumulation of biomass at the primary consumer level is termed productivity. 
• The rate at which these consumers convert the chemical energy of their food into their own biomass is called secondary productivity. Secondary productivity is the rate at which animals produce their organic matter by feeding on other organisms. 
• The efficiency at which energy is transferred from one trophic level to another is called ecological efficiency. On average it is estimated that there is only a 10 percent transfer of energy.

Phosphorus is a major constituent of the biological membrane, nucleic acids and cellular energy transfer system. Detritus is leaf litter and other organic matter intermixed with soil, which is referred to as humus. Rocks are composed of one or more minerals. Primary producers are organisms in an ecosystem that produce biomass from inorganic compounds (autotrophs). Litterfall is dead plant material, such as leaves, bark, needles, and twigs, that has fallen to the ground. This detritus or dead organic material and its constituent nutrients are added to the top layer of soil, commonly known as the litter layer .

Secondary succession is the series of community changes which take place on a previously colonized, but disturbed or damaged habitat. Examples include areas which have been cleared of existing vegetation (such as after tree-felling in a woodland) and destructive events such as fires. Secondary succession refers to the concept of an ecosystem reviving itself after all or a portion has been destroyed. The primary concept is that the life was previously on the soil, eliminating the need for deposition of new seeds or soil. Secondary succession is a much more rapid process than primary succession because the soil and nutrients are already available.
Since, it involves the changes in the habitat the newly made habitat will not show the changes.

Gross primary productivity is the rate at which photosynthesis or chemosynthesis occurs. 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. Gross primary production (GPP) is the amount of chemical energy as biomass that primary producers create in a given length of time. 

Detrivores are heterotrophs that obtain nutrients by consuming detritus or decomposing plant and animal parts as well as faeces. Earthworm is a detrivore.
In succession, pioneer species like lichen, algae, and fungi, as well as other abiotic factors like wind and water start to 'normalize' the habitat.
Pollination is a type of ecosystem service which enhances the service provided by insects/birds through behavioral interaction.
Natality is the crude birth rate or specific birth rate and is the greatest influence on a population's increase.
Thus, the correct answer is option D.

• Sedimentary cycles involve the cyclic exchange of minerals from the earth's crust or the lithosphere  with the biotic components of the ecosystem
• examples of cycles under the sedimentary category are sulfur and phosphorus cycles. 
• Gaseous cycles involve the cyclic exchange  of minerals between atmosphere and the biotic world.
• Common examples of gaseous cycles are carbon and nitrogen cycles.

Partly upright pyramid of number is seen in the forest ecosystem where the number of producers are lesser and support a greater number of herbivores and which in turn support a fewer number of carnivores. In a tree community, single tree could supports many different consumers of larger numbers. Thus, the correct answer is option A.

Solution

Correct answer is option A.

Explanation for correct option:

• Xerarch succession takes place in dry areas and the series progress from xeric to mesic conditions.
• The correct order of succession in xerarch is:
• Lichen moss stage--> annual herb stage--> perennial herb stage--> shrub stage--> forest.
• Hydrarch succession takes place in ponds or any other water area.
• There is a progression from hydric conditions to mesic conditions.

• Time gradual and fairly predictable change in the species composition of a given area is called ecological succession.
• Ecological succession leads to a stable unchanging final state called climax community which is in equilibrium with the environment.
• During succession, some species colonize an area and their populations become more numerous, whereas populations of other species decline and even disappear.

Hence, during ecological succession, the gradual and predictable change in species composition occurs in a given area.