NEET Practice Questions (MCQs) with Answers & Solutions

(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)

(a) The disruptive selection favours both the small and large sized (two different traits) individuals of a population. It eliminates the members with mean expression, thus producing two peaks in trait distribution. This may lead to development of two different populations.

(c) Natural selection is shown by the reproductive success of the members of a population best adapted to the environment. The organisms which adapt useful variations and successfully survive in changing environment and reproduce.

Sympatric speciation is the formation of species within a single population by reproductive isolation or without geographical isolation, eg., polyploids.

Richard Owen introduced the term homologous. The organs which have the same fundamental structure but are different in functions are called homologous organs like wings of mosquito and butterfly. But wings of butterfly is analogous to wings of a bird. Analogous organs are those which performing same function but having different basic structures.

Electron spin resonance method is the relatively most accuate method for dating fossils. Electron spin resonance dating is a relatively new, more precise and most accurate method of dating. 

In radioactive carbon method, C-14 is used. Its half life is 5730 years.

In Uranium-lead method, the uranium (${\mathrm{U}}^{238}$) is used. The half-life period of $\left(U^{238}\right)$ is $4.5\times {10}^{10}$ years. It means one-half of $U^{238}$ will convert to $L{d}^{206}$.