Evolution MCQs for NEET — Zoology Questions with Answers

(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 $L{d}^{206}$.

According to Hardy- Weinberg equation,

P² + 2PQ + Q² = 1

Where P = dominant allele frequency

          Q = Recessive allele frequency

          P² = Homozygous dominant genotype

          2PQ = Heterozygous genotype 

          Q² = Homozygous recessive genotype 

here p = 0.6 and Q= 0.4

therefore, 2PQ = 2 $\times$ 0.6 $\times$ 0.4 = 0.48

(b) Speciation of sympatric species is the formation of species within a single population without geographic isolation. Thus the subpopulation becomes reproductive isolated in the midst of its parent population.