Zoology MCQs for NEET — Practice Questions with Answers

(a) In the devonian period fishes were abundant in fresh water deposits, so that this period is called the age of fishes. By this time some fishes had already invaded the seas. the devonian period shows that much of the land was subjected to seasonal droughts in which abundant rainfall alternated with dry periods in which streams dried up. These conditions had a major influence on the history of fishes and development of terrestrial animals. At the end of the devonian appeared the first land vertebrates, the amphibians.

(b) Genetic drift is the random change in the frequency of alleles in a population over successive generations due to sampling error in the gametes. Each new generation differs from its parental generation with regard to allele frequencies simply because of random variation in the distribution of gametes. Over time, this may lead to certain alleles becoming fixed and others being lost altogether by chance. This process is more rapid in smaller populations or when the alleles are concerned confer no apparent benefit compared to their counterparts. hence, genetic drift can ultimately cause loss of genetic diversity if there are no counteracting factors.

(b) Because there are no living entities possible without the coded organic elements to define their required composite elements, Nucleic acids, are considered the most essential, with the conclusion that it is programmed with sufficient types and number of nucleic-acids. Enzymes and proteins are encoded through critically sequenced nucleic-acids and therefore only exist if programmed nucleic-acids are used.

(b) 

(c) There are some rare cases in medical literation which could be interpreted  as atavisms, that is the reappearance of our ancestor's organs, in which more prolonged traits, already lost by human beings throughout evolution, are expressed again. Such is the case of supranumerary mammary glands, sacral tail etc.   

(c) : Wings of pigeon, mosquito and bat show convergent evolution. It is the evolutionary process whereby organisms not closely related, independently evolve similar traits to adapt to their enviroment. Atavism is the regaining of same structures after a certain gap of few generations. Divergent evolution is the process where member of a species become more different resulting into new species. Examples, humans bats and whales (pentadactyl limbs.)

(b) The peppered moth (Biston betularia) is a temperate species of night-flying moth. Peppered moth evolution is often used by educators as an example of natural selection. Peppered moths are cryptically camouflaged against their backgrounds when they rest on the tree trunk.

(b)

(c) : The first fossil birds found in the rocks of Jurassic period belonged to genera Archaeopteryx and Archaeornis. These are considered as reptilian ancestors of birds. It was about the size of a crow and possessed feathers and wings but had a long reptilian tail very much unlike the modern birds and a toothed beak. Fossils of Hesperornis, an aquatic diving bird, and Ichthyornis, a powerful flying bird, have been found from Cretaceous.

(b)