MECHANISM OF EVOLUTION
As per Hardy Weinberg Principle, “Allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences. These influences include mate choice, mutation, selection, genetic drift, gene flow, and meiotic drive."
The gene pool remains a constant. The total genes and their alleles in a population make the gene pool. Sum total of all the allelic frequencies is 1.
Let us assume there are two alleles A and a of a gene. Let us assume that p represents the frequency of allele A and q represents the frequency of allele a.
Frequency of diploid AA individuals in population = p2
Frequency of diploid aa individuals in population = q2
Frequency of diploid Aa individuals in population = 2pq
Hence, p2 + 2pq + q2 = 1
When frequency differs from expected values, the difference (direction) indicates the degree of evolutionary change. Thus, disturbance in Hardy-Weinberg Equilibrium would then be said to result in evolution.
Factors that affect Hardy-Weinberg Equilibrium: Gene migration or gene flow, Genetic Drift, Mutation, Genetic Recombination and Natural Selection.
Evolution: The change in inherited traits in biological population over subsequent generations is called evolution. Scientists have proven that life evolved in the form of simple unicellular organisms on this earth; and all the organisms which are present today have evolved from a common ancestor. The idea of evolution is based on the premise of a common ancestry.
Speciation: The process of origin of a new species is called speciation. A species is a group of organisms in which most of the characters are similar and members of a species are able to breed among themselves. Speciation can happen if two groups of the same species are somehow prevented from interbreeding for several generations. This can happen because of geographical segregation or because of some genetic changes. Evolution of new species, because of geographical segregation is called genetic drift.
ORIGIN AND EVOLUTION OF MAN
- Dryopithecus and Ramapithecus existed around 15 mya. Ramapithecus was more man-like, while Dryopithecus was more ape-like.
- Man-like primates existed in eastern Africa around 3 to 4 mya.
- Australopithecines probably lived in East African grasslands around 2 mya.
- Homo habilis is an example of Australopithecines. Scientists still differ if Homo habilis should be kept under Australopithecines or among hominids. Its brain was of 650-800 cc capacity.
- Homo erectus existed about 1.5 mya. Its brain’s capacity was 900 cc.
- Neanderthal lives near east and central Asia between 100,000 to 40,000 years back. The brain capacity of Neanderthal was 1400 cc.
- Modern Homo sapiens arose in Africa between 75,000 to 10,000 years back.