NEET Practice Questions (MCQs) with Answers & Solutions

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

Photosynthetically fixed carbon is evntually degraded by micro-organisms and two major forms of carbon result methane(${\mathrm{CH}}_4$) and carbon dioxide(${\mathrm{CO}}_2$). The micro-organisms breakdown the complex compunds of dead protoplasm of producers and consumers absorb some of the decomposition products and release simple substances. The slow rate of decomposition of fallen logs in nature is due to their low moisture content. 

The cellulose is in high amount in fallen logs. The environment around the fallen logs in aerobic, ie, ${\mathrm{o}}_2$ is present

Temperate deciduous forests grow in continental climates with summer rainfall and severe winters. They are dominated by broad leaved deciduous trees like Quercus virginiana, magnolias, boys and hallies as well as such tropical species as Ficus aurea, Lysiloma.

Tropical rain forests occupy low altitude zones near the equator where annual rainfall exceeds 80^" to 90^" distributed over the year. Trees generally form three storeys scattered very tall emergent trees, canopy layer and understorey stratum.

Tropical scrub forests develop in areas where moisture relations are intermediate between desert and savanna on one hand and rainforest on other.

Prodcutivity of tropical rainforest is highes. The tropical rain forest covering 300,000 km² area. They contain more than 50% of total flora and fauna of the world.

Ecological pyramids are the graphical representation of the trophic structure and function at successive trophic lveles. Ecological pyramids are of three general types, listed as here under:
(i) Pyramids of numbers, showing the number of organisms at each level.

(ii) Pyramid of biomass, showing the total dry weight flow/productivity at successive trophic levels.
Thus, fresh weight is not used for the construction of ecological pyramids.

(c) : Benthic zone is the bottom part of a water body. Light is not available here so it is dark. Micro-organisms and other benthic organisms are found in this region.

(c) : Benthic region or zone is the bottom of the quatic body which is made of sediments above. In deep lakes and sea, the benithic region is in perpetual darkness. Therefore, only consumers occur over here. They are either carnivorous or detrivorous. The common benthic organisms are snails, some specialised fishes and microorganisms.