NEET Practice Questions (MCQs) with Answers & Solutions

(a) Prosopis are tree found in scrub. Saccharum is grass which is cultivated. Shorea robusta (Sal) is tree found in moist tropical forest. Acacia catechu is tree found in dry deciduous forests.

(c) : Genetic diversity is the diversity in the number and types of genes as well as chromosomes present in different species and the variations in the genes and their alleles in the same species. Variations in the genes of a species increase with the increase in size and environmental parameters of the habitat. It helps in speciation and evolution of new species.

(b) : Light is the visible part of electromagnetic radiations. Sunlight or solar radiations reaching the earth have wavelength between 300 nm to 2600 nm. Part of the spectrum used in photosynthesis  has a wavelength between 400-700 nm. It is called photosynthetically active radiation (PAR).

(d) : Bacteria attacking the dead animals represent the end of the food chain and are decomposers. These are the organisms that obtain energy from chemical breakdown of organisms. They secrete enzymes onto dead matter and then absorb the breakdown products. Bacteria are specialised to breakdown organic materials that are difficult for other organism to digest. They also fulfil a vital role in the ecosystem, returning the constituents of organic matter to the enviroment in inorganic forms so that they can again be assimilated by producers.

(a) A single species might show high diversity at the genetic level over its distributional range. India has more than 50,000 genetically different strains of rice, and 1,000 varieties of mango.

(b) : Phosphorus is a major constituent of biological membranes, mucleic acids and cellular energy transfer systems. Many animals also need large quantities of this element to make shells, bones and teeth. The natural reservoir of phosphourus is rock, which contains phosphorus in the form of phosphate. When rocks are weathered, minute amounts of these phosphate dissolve in soil solution and are absorbed by the roots of the plants. Herbivores and other animals obtain this element from plants.

(b) Benthos is the community of organisms which live on, in, or near the sea bed, also known as the benthic zone. As no light is available in this zone of sea, the energy source for deep benthic ecosystem is often organic matter from higher water column which drifts down to the depths. This dead and decaying matter sustains the benthic organisms, and therefore, most organisms in benthic zone i.e., in deep oceanic waters, are scavengers or detritivores.

(d): Keystone species are species which have significant and disproportionately large influence on the community. Removal or decrease in their number causes disruption in structure and function of community. For example in intertidal regions starfish feeds on mussels. Removal of starfish leads to dominance of mussels that excludes algae and browsing species. In tropical rain forests, fig trees function as keystone species as they provide fruits to a number of animals during the period of food scarcity.

Energy flow is always unidirectional and it follow IInd law of thermodynamics. Energy is transferred from one tropic level to another trophic level but does not revert back.