BIOLOGY 1.5 Marks Questions

1. Forelimbs of cheetah and mammals: This is divergent evolution and these structures are homologous.
2. Flippers of dolphins and penguins: The example of convergent evolution they are not similar in structure but they perform a similar function.
3. Wings of butterflies and birds: The are look same in structure, they are not atomically similar is structure though they perform similar function they called analogues.
4. Forelimbs of whales and mammals: This is divergent evolution and these structures are homologous.

1. Analogous organs or structures are those that are similar in function but different in origin.

From the given options, following are the analogous structures:

• Eyes of octopus and mammals perform the same basic visual function but they differ in the origin of their retina.
• Tubers of sweet potato and potato perform the same function of food storage but they are modifications of root and stem, respectively.

2. The kind of evolution represented by analogous organs or structures is convergent evolution as they have different origins but evolve similar traits with evolution to perform the same function.

1. Forelimbs of whales and bats.

4. Thoms of Bougainvillea and tendrils of Cucurbita.

2. Divergent Evolution.

1. Pre-historic cave art.
2. Agriculture/Human Settlement.

1. First mammals.
2. First amphibians (lived both on land and in water)/fish with stout and strong fins which could move on land and go back to water.
3. First human-like being/hominid/brain capacity from 650-800 cc/did not eat meat.
4. Brain around 900 cc/ate meat.

Eg. Thron of Bougainvillea and Tendrils of Cucurbita represent homology.

This principle says that allele frequencies in a population are stable and is constant from generation to generation. The gene pool (total genes and their alleles in a population) remains a constant. this is called genetic equilibrium. Sum total of all the allelic frequencies is 1. Individual frequencies, for example, can be named p, q, etc. In a diploid, p and q represent the frequency of allele A and allele a. The frequency of AA individuals in a population is simply p². This is simply stated in another ways, i.e., the probability that an allele A with a frequency of p appear on both the chromosomes of a diploid individual is simply the product of the probabilities, i.e., p². Similarly of aa is q², of Aa 2pq. Hence, p² + 2pq + q² = 1. This is a binomial expansion of (p + q)². When frequency measured, differs from expected values, the difference (direction) indicates the extent of evolutionary change. Disturbance in genetic equilibrium, or Hardy-Weinberg equilibrium, i.e., change of frequency of alleles in a population would then be interpreted as resulting in evolution.

1. The characteristics which enable some population or individuals to survive better in natural conditions (foods, climate, physical factors) would outbreed others (survival of the finest).
2. Thus, those organisms, which are better fit or adapt well will survive and get selected by nature, which furthers their evolution. This is called natural selection.

• The biodiversity we see today is the story of evolution, i.e. evolution is considered as a process, that has resulted in various life forms.
• If we talk about the life on earth, evolution is considered as a consequence of the process, called natural selection.
• It is difficult to decide, whether evolution and natural selection are processes or end results of some unknown processes.

• Differential reproduction: The phenomenon in which all organisms who reach reproductive stage reproduce with varying degree of success, some reproduce more offsprings and some reproduce only few and other reproduce none depending upon their degree of fitness.

• Reproductive isolation: The biological phenomenon in which the individual belonging to same species reproduce among themselves, to maintain the species integrity. Both these terms are used in reference to natural selection.

• They have not evolved from common ancestors.
• It is the similar habitat that has resulted in similar adaptive features in different groups of organisms towards the same function.

1. Interbreeding among different populations or species.
2. Migration.

1. After industrialisation, the tree trunks became dark due to deposition of soot and smoke; under such a condition, the white winged moths stood out conspicuously and easily detected by the predators and hence they reduced in number
2. The dark-winged moths could merge with the black colour and they escaped the predators and hence increased in number.

1. It has beak and wings like that of a birds.
2. It has teeth and scales like that of a reptiles.

• Lamarck's theory is known as theory of Inheritance of acquired characters.
• According to this theory, organisms undergo certain changes to adapt themselves to the environment.
• These characters acquired by an organism during its life time, are passed on to the progeny, e.g. the long neck of giraffe was explained by Lamarck, as an outcome of these animals having to stretch their necks constantly to eat the leaves on the upper branches of the trees.

• Such structures in different groups of organisms which perform similar function, but are anatomically different, are called analogous organs.
• The tuber of potato (stem modification) and the tuber of sweet potato (root modification) are analogous as they perform the function of storage of food.