(i) Microevolution refers to the changes in allele frequencies within a population.
(ii) Allele frequencies in a population may change due to four fundamental forces of evolution such as natural selection, genetic drift, mutation and gene flow.

Genetic variation is the ALXl gene in the DNA of Darwin's finches is associated with variation in the beak shape. Mild mutation is the ALXl genes leads to phenotypic changes in the shape of the beak as in Darwin finches.

The evolutionary process which produces new species diverged from a single ancestral form becomes adapted to a newly invaded habitat is called adaptive radiation.
Eg: Darwin finches and Australian marsupials.

Artificial selection is a byproduct of human exploitation of forests, oceans, and fisheries or the use of pesticides, herbicides or drugs. For hundreds of years, humans have selected various types of dogs, all of which are variants of the single species of dog.

The organisms which possess the characters of two different groups (transitional stage) are called connecting links.
Eg: Peripatus (connecting link between Annelida and Arthropoda), Archeopteryx (connecting link between Reptiles and Aves).

Structures that are of no use to the possessor, and are not necessary for their existence are called vestigial organs.
Eg: Human appendix is the remnant of caecum which is functional in the digestive tract of herbivorous animals like rabbit.

Organisms having different structural patterns but similar function are termed as analogous structures.
Eg:  Wings of birds & Insects are different structurally but perform a similar function (flight) which brings about convergent evolution.

Structures which are similar in origin but perform different functions are called homologous structures that bring about divergent evolution.
Eg: Thorn of Bougainvillea is used for defense and tendrils of Cucurbita are used for climbing but both are homologous structures.

The age of fossils can be determined using two methods namely, relative dating and absolute dating. (a) Relative dating is used to determine a fossil by comparing it to similar rocks and fossils of known age. (b) Absolute dating is used to determine the precise age of a fossil by using radiometric dating to measure the decay of isotopes.

Coacervates (large colloidal particles that precipitate out in aqueous medium) are the first pre-cells which gradually transformed into living cells, according to theory of chemical evolution.

The term evolution is used to describe heritable changes in one or more characteristics of a population of species from one generation to the other.

According to the theory of spontaneous generation or Abiogenesis, living organisms originated from non-living materials and occurred through stepwise chemical and molecular evolution over millions of years. Thomas Huxley coined the term abiogenesis.

(i) The earliest fossils of the prehistoric man like Ramapithecus lived some 14mya. They were hairy and walked like gorillas and chimpanzees.
(ii) They had a brain capacity of 1300cc.
(iii) They lived on tough food consisting of seeds and savannah grasses and had well developed grains and heavy molars.
(iv) Australopithecus had a brain capacity of 461cc, teeth consisted of small canines and large molars. Good are softer foods consisting of grass, leaves and fruits.