Botany MCQs for NEET — Practice Questions with Answers

Page 251, XII NCERT

Answer:    2

Read page 250,XII NCERT

(a) Biomass refers to the amount of living organic matter. Forest ecosystem have the maximum biomass, because it includes organisms of all tropic levels as compared to pond, lake or grassland ecosystem. In forest ecosystems productivity is also high that contributes to maximum biomass.

(b) The primary producers of the deep-sea hydrothermal vent ecosystem are archaebacteria.

These have chemosynthetic mode of nutrition. Thus option (b), i.e., chemosynthetic bacteria is the correct option.

(d) In primary succession on rocks, lichens secrete acids to dissolve rock, helps in weathering and soil formation. So, lichens are pioneer species to colonize the bare rock.

(a) The term ecosystem was coined by AG Tansley in 1935. Ecosystem is a self regulated and self sustaining structural and functional unit of nature. It consists of living beings and their physical environment.

(b)Vertical distribution of different species occupying different levels in a biotic community is known as stratification. It refers to the vertical layering of a habitat; the arrangement of vegetation in layers. It classifies the layers of vegetation largely according to the different heights to which their plants grow. The individual layers are inhabited by different animal and plant communities.

Secondary succession is the series of community changes which take place on a previously colonized, but disturbed or damaged habitat. It is the process of regrowth of an ecosystem which undergoes a destructive event. 

The rate of production of organic matter (chemical energy) as biomass that primary producers (via photosynthesis) created in a given duration of time is called Gross Primary Productivity (GPP).

Net primary production is the rate at which all plants (producers) in an ecosystem produce net useful chemical energy, it is equal to difference between the rate at which plants in an ecosystem produce useful chemical energy (GPP) and the rate at which they use some of that energy during respiration.

NPP = GPP - respiration (by plants)

Secondary productivity is the generation of biomass or organic matter by heterotrophic (consumers) in a system.

Net productivity is the amount of energy trapped in organic matter during a specific interval at a given trophic level less than that lost by the respiration of the organisms at that level.

(c) Secondary productivity is the rate of formation of new organic matter by consumers. Primary productivity depends on the producers inhabiting a particular area.