EVOLUTIONARY THEORY JEAN BAPTISTE LAMARCK
JEAN BAPTISTE LAMARCK B:1774 D:1829 2 theories of how organisms changed over time Acquired characteristics Law of use and disuse Theories were determined to be incorrect BUT he was the first to publicly state that evolution of organisms occurs
EVOLUTIONARY THEORY CHARLES DARWIN
CHARLES DARWIN B:1809 D:1882 Man most famously credited for “discovering” evolution 5 basic principles of natural selection Individuals of species vary Some variations heritable More born than can survive Competition for resources Most fit individuals survive to reproduce
NATURAL SELECTION
NATURAL SELECTION Darwin’s explanation for how changes in organisms occur Nature is acting upon the phenotype of each individual organism; a favorable phenotype increases survival in the environment Organisms must adapt, migrate or die Darwin’s theory revolves around the reproductive success of organisms with favorable phenotypes
VARIATION MUTATIONS
MUTATIONS Driving force for evolution Origin source for new alleles in a population Random changes in the genotypes of members of a population Favorable/useful mutations increase organism’s chances for survival Mutations are rare so the effects are rarely seen in a specific population Cumulatively, mutations are why we are humans and not house plants
VARIATION FROM RECOMBINATION
VARIATION FROM RECOMBINATION Genetic variation by mutation alone tends to be a slow process (unless you are a bacteria) Genetic recombination through sexual reproduction speeds up this process dramatically Mechanisms: Crossing-over: exchange of genes between homologous chromosomes Independent assortment: genes segregate independently of each other
VARIATION FROM MIGRATION
VARIATION FROM MIGRATION Members of different populations of the same species are able to interbreed and produce fertile offspring As members migrate from one population to another, they take their specific genotypes with them Over time, this causes changes in the gene frequencies of the gene pools of each population
VARIATION FROM MIGRATION Examples of variations in populations: Morphological: differences in body shapes and colors Chromosomal: in some species, there can be a difference in chromosome number and shape; common in plants and insects Protein: amino acid substitutions that do not affect protein structure