Get folders AND binders Also have out your natural selection reading assignment from the weekend Gene flow Gene pool Genetic drift

Species a group of individual organisms that are capable of interbreeding to produce fertile offspring in nature.

Population A group of organisms of one species that interbreed and live in the same place at the same time

Common Ancestor An organism which is the shared ancestor of two (or more) different descendant groups of organisms.

You will be able to describe Darwin’s theory of natural selection as well as give examples that support the theory. You will be able to describe the conditions required for natural selection.

Misconceptions Humans did not evolve from apes, gorillas or chimps. We are all modern species that have followed different evolutionary paths, though humans share a common ancestor with some primates, such as the African ape

Evolution: changes that transform life over an immense time. Darwin published, The Origins of Species making two main points for the mechanisms of evolution… 1. Descent with modification 2. Natural selection

Descent with Modification Species living today descended from ancestral species Species spread into various habitats over millions of years Species accumulated different modifications, or adaptations, to diverse ways of life as genes are passed on Results in diversity of species

Natural Selection Process by which individuals with inherited characteristics well-suited for their environment leave more offspring on average than do other individuals Survival and reproduction of the fittest

Theory of Natural Selection Flow Chart Population of Organisms OverproductionVariation Struggle for existence Differences in reproductive success Evolution of adaptations

What have you learned? What are the two main points that Darwin made in is book to ague the mechanisms of evolution? Descent with modification and natural selection What is natural selection? Process by which individuals with inherited characteristics well-suited for their environment leave more offspring on average than do other individuals Describe some conditions that could lead to a struggle for existence among individuals in a population. Over population, limited resources, changes occurring in the environment

Evidence of Evolution The fossil record= shows patterns of evolution over millions of years Comparative Anatomy Comparative Embryology (Not on foldable) Comparative Biochemistry: amino acid tables Geographic Distribution: similar organisms separated by land

Comparative Anatomy Homologous structures= anatomically similar structures inherited from a common ancestor

Comparative Anatomy Analogous structures= Structures of different species having similar or corresponding function but not from the same evolutionary origin

Comparative anatomy Vestigial structures= Vestigial structures are body parts that seemingly have no purpose or function. Perhaps they once did, but somewhere along the way they lost their functions and are now basically useless

Comparative Embryology Similar phases of development

Geographic distribution

Theory of Natural Selection Flow Chart Population of Organisms OverproductionVariation Struggle for existence Differences in reproductive success Evolution of adaptations

You will be able to discuss mechanisms of evolution other than natural selection such as genetic drift and gene flow.

Gene Pool Consists of all the alleles in all the individuals that make up a population. The process of meiosis (specifically crossing over) and fertilization shuffle alleles in the gene pool giving us genetic diversity

Genetic Drift A change in the population due to chance All populations are subject to some genetic drift; however, the smaller the population the greater the impact. Bottleneck effect- disasters can reduce the size of a population. By chance some alleles are represented more than others while others are completely eliminated Founder effect- when a few individuals colonize an isolated habitat. There is low genetic make- up

Bottleneck effect

Founder Effect

Demonstration for Genetic Drift Hypothesis: What would the populations look like generations from now if there were no environmental changes and the gene pool remained the same? Analysis: What are some deadly “chance” events? How did the removal of some of the marbles (change in the gene pool) affect each population? How did the impact of genetic drift contrast between the small population and the larger population?

Gene Flow The exchange of genes with another population Occurs when fertile individuals or their gametes migrate between populations Tends to reduce genetic differences between populations

What have you learned? What is a gene pool? All of the alleles in all of the organisms that make up a population What are the two main forces of evolutionary change in gene pools other than natural selection? Genetic drift and gene flow How can genetic drift cause a substantial change in allele frequencies in small populations? It can reduce genetic variations