Observed that similar environments have different plant or animal populations
Georges-Louis Leclerc Comte de Buffon published a book about a mechanism for evolutionary change
James Hutton, Charles Lyell
Proposed that geological change occurred gradually by the accumulation of small changes
Jean-Baptiste Lamarck
Proposed a mechanism for evolutionary change
Mechanisms of evolution
Natural selection
Mutation
Genetic drift
Gene flow
Natural selection
An inevitable outcome of three principles that operated in nature: 1) Characteristics of organisms are inherited, 2) More offsprings are produced that able to survive; resources for survival and reproduction are limited, 3) Offsprings vary among each other in regard to their characteristics
Whether or not a trait is favorable depends on the environment at the time. The variations in the finch beaks shifted from generation to generation providing adaptation to food availability.
Mutation
The change in the DNA sequence of a gene
Mutation
Harmful - gives reduced fitness
Beneficial - positive effect on fitness
Neutral - no effect on fitness
Harmful mutations are removed from the population by selection, beneficial mutations will spread through the population through selection, its effect on evolution is small, unless it interacts with natural selection, mutation is the ultimate source of genetic variation of all populations
Genetic drift
The effect of chance, has a stronger effect on small/finite populations, it happens because the alleles in an offspring generation are a random sample of the alleles from each parent, can lead to the elimination of an allele from a population by chance
Genetic drift
Bottleneck effect - when a species goes through an event that suddenly and significantly reduces its population, the genetic structure of the next generation may be very different from the previous generation
Founder effect - a scenario in which a new population is started by a small group from a larger population
Gene flow
The flow of alleles in and out of a population resulting from the migration of individuals, can occur when an individual travels from one geographic location to another and joins a different population of the same species, or when plant seeds get sent far and wide through wind or animals and may introduce new alleles to another population
Theodosius Dobzhansky: '"Nothing makes sense in Biology except in the light of Evolution."'
