SPECIATIONA species is a population oforganisms consisting of similarindividuals which can breedtogether and produce fertileoffspring.The process by which new speciesdevelop from the existing species isknown as speciation.
FACTORS Geographical isolation of a population caused byvarious types of barriers. The geographicalisolation leads to reproductive isolation due towhich there is no flow of genes betweenseparated groups of population. Genetic drift caused by drastic changes in thefrequencies of particular genes by chance alone. Variations caused in individuals due to naturalselection.
GENETIC DRIFT Genetic drift or allelic drift is the change inthe frequency of a gene variant (allele) in apopulation due to random sampling. The allelesin the offspring are a sample of those in theparents, and chance has a role in determiningwhether a given individual survives andreproduces. Genetic drift may cause genevariants to disappear completely and therebyreduce 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 thatbirds are very closely related to reptiles.
EVOLUTION SHOULD NOT BE EQUATEDWITH PROGRESSEVOLUTION IS JUST THE PRODUCTIONOF DIVERSITY OF LIFE FORMS ANDSHAPING OF THIS DIVERSITY BY THEENVIRONMENTAL SELECTION. THEONLY PROGRESS IN EVOLUTIONAPPEARS TO BE THAT MORE AND MORECOMPLEX BODY DESIGNS OFORGANISMS HAVE EMERGED OVER THEAGES.