SPECIATION

A species is a population of organisms consisting of similar individuals which can breed together and produce fertile offspring.

The process by which new species develop from the existing species is known as speciation.

FACTORS

Geographical isolation of a population caused by various types of barriers. The geographical isolation leads to reproductive isolation due to which there is no flow of genes between separated groups of population.

Genetic drift caused by drastic changes in the frequencies of particular genes by chance alone.

Variations caused in individuals due to natural selection.

GENETIC DRIFT

Genetic drift or allelic drift is the change in the frequency of a gene variant (allele) in a population due to random sampling. The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces. Genetic drift may cause gene variants to disappear completely and thereby reduce genetic variation.

EVOLUTION OF EYESRUDIMENTARY EYES IN PLANARIATHEY CAN DETECT LIGHT.

EVOLUTION OF FEATHERS

Pterosaurs were flying reptiles The presence of feathers on birds tells us

that birds are very closely related to reptiles.

EVOLUTION BY ARTIFICIAL SELECTION

KOHLRABI &KALE

EVOLUTION SHOULD NOT BE EQUATED WITH PROGRESSEVOLUTION IS JUST THE PRODUCTION OF DIVERSITY OF LIFE FORMS AND SHAPING OF THIS DIVERSITY BY THE ENVIRONMENTAL SELECTION. THE ONLY PROGRESS IN EVOLUTION APPEARS TO BE THAT MORE AND MORE COMPLEX BODY DESIGNS OF ORGANISMS HAVE EMERGED OVER THE AGES.

HUMAN EVOLUTION