Ecosystem MCQs for NEET — Botany Questions with Answers

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

Phosphorus cycle is a sedimentary bigeochemical cycle. It describes the movement of phosphorus through the lithosphere, hydrosphere and biosphere and the main reservoir pool is lithosphere. Atmosphere does not play any significant role in the movement of phosphorus because phosphorus and phosphorus based compounds are usual solids at the typical ranges of temperature and pressure found on Earth. The production of phosphine gas occurs only in specialized, local conditions.

Green Plant   ->   Insect   ->   Frog   ->   Cobra     ->    Eagle
(producer)                  (Primary          (Secondary       (Tertiary              (Top
                                  consumer         consumer         consumer           consumer
                                      or                or Primary        or secondary       or Tertiary
                                 Herbivore)         carnivore)         carnivore)          carnivore)

Secondary succession or subsere is ecological succession that takes place in a recently denuded area which still contains a lot of organic debris, remains and propagules of previously living organisms. It is more common and caused by baring of an area due to forest fires, deforestation, excessive overgrazing, Landslides, earthquakes, repeated floods, etc. Only 50 to 100 years are required for establishment of a grassland over a recently denuded area. Formation of forest requires 100 to 200 years.

Pyramid of energy is graphic representation of energy per unit area sequence-wise in various rising trophic levels with producers at the base and top carnivores at the apex. Pyramid of energy is upright in all the cases. It is also more accurate than other types of ecological pyramids.

The amount of having matter present in an ecosystem in its different trophic levels is called standing crop. It is expressed in the form of number or biomass per unit area. Biomass is measured as either fresh weight or dry weight.

Dry weight is preferred over fresh weight as it is not liable to change with moisture content. Standing crop indicates the productivity and luxurience of growth.

PAR (Photosynthetically active radiation) designates the spectral range of solar radiation from 400 to 700 nm that photosynthetic oganisms are able to use in the process of photosynthesis. Of the total incident solar radiation the proportion of PAR is less than 50%

Net Primary Productivity (NPP) is the weight of organic matter stored by producers in a unit area/volume per unit time. NPP is equal to the rate of organic matter created by photosynthesis minus the rate of respiration and other loses. Stored biomass is tansferred from one trophic level to another trophic level.

Secondary Productivity is the rate of energy storage at consumers levels-herbivores, carnivorous and decomposers.

Gross Primary Productivity (GPP) is reffered as total rate of photosynthesis including the organic matter used up in respiration during the measurement period.

Stratification is the characteristic of biological community. Stratification is the vertical layering or the phenomenon of having more than one stratum including formed by different plants/organisms in the same place. A forest may have 5-7 strata including large or canopy trees, medium tees, short trees, shrubs, herbs, ground flora etc. Stratification is useful as it can accommodate a large number of organisms of different types and more efficient use of resources. The animals that occupy such similar strata or ecological niches although geographically seperated are called ecological equivalents.

(c) The atmosphere is the source of carbon dioxide, which is utilized by plants in photosynthesis reduced to form carbon compounds. The total mass of carbon currently in the atmosphere is about 7x10¹⁷ g, i.e., 700000 million tonnes. Oceans regulate the CO₂ content in the atmosphere and thus play a very important role. Sea water contains 50 times more CO₂ than air, i.e., about 70% of total global carbon is found in oceans. This is in the form of carbonates and bicarbonates