Darwin's Theory of Evolution Textbook pages 274-292

Charles Darwin Charles Darwin, Alfred Wallace and others promoted the idea of evolution as they tried to make sense of the following question: “How could there be so many different kinds of living things (diversity) and at the same time how can all living things be so similar (unity)?

Charles Darwin given credit for the Theory of Evolution provided evidence for the theory “On The Origin Of Species By Natural Selection” made his observations and collected his evidence during a five year trip around the world on the H.M.S. Beagle

Galapagos Islands stop that influenced Darwin the most

Galapagos Islands Of all of the stops Darwin Made the one that influenced him the most was a small group of islands called the Galapagos Islands. He noted that the characteristics of many plants and animals varied considerably from one island to the next.

Evolution change in a gene pool over time

The Five Fingers of Evolution

The Five Fingers (causes) of Evolution Small Population Non-random mating Mutations Gene Flow Natural Selection

1. Small Population chance can have a large effect on a small population unlikely events can occur when a gene pool is small

1. Small Population Genetic Drift In small populations, individuals that carry a particular allele may leave more descendants than other individuals, just by chance. Over time a series of chance occurrences of this type can cause an allele to become common in a population. Remember genetics is controlled by the laws of probability Remember with small populations we may not get what is expected (deviation may be high)

1. Small Population Founder effect Loss of genetic variation when a new population is started by a small number of individuals

2. Non-random Mating Mating amongst individuals in a population is not always random Sexual Selection some features do not have a function that help individuals survive, but help them have more offspring

3. Mutations changes in genetic material can add new genes to a gene pool

4. Gene Flow movement of genes due to immigration and emigration

5. Natural Selection Individuals that have physical or behavioral traits that better suit their environment are more likely to reproduce more successfully than those without those traits.

Fitness the ability of an individual to survive and reproduce an organism’s fitness is the result of adaptations inherited traits or variations that increase the individuals chances for survival Darwin said organisms which are best adapted (fit) for the environment are the ones that survive survival of the fittest

Selective pressures environmental conditions that lead to one allele (trait or gene) being more beneficial to the survival and/or reproduction of members of a species Ex: moth population turning black selective pressure =

Homozygous Recessive Individual

Dominant allele creates a dark phonotype

Changing Environment = Selective Pressure

Selective pressures environmental conditions that lead to one allele (trait or gene) being more beneficial to the survival and/or reproduction of members of a species Ex: black colored individuals become more common within a moth population selective pressure = soot on trees from pollution

Convergent Evolution Organisms that are not closely related independently evolve similar traits Ex: sharks and dolphins; insect eaters having long, sticky tongues

Convergent Evolution

Adaptation Example Darwin’s Finches Adaptations beak size Improved Chance for Survival being able to eat available food sources

The Five Fingers of Evolution

Darwin’s Theory of Evolution Inherited variation exists within the genes of every population because of mutations and translation errors. In a particular environment, some individuals of a population are better suited to survive (because of variation) & have more offspring (natural selection).

Darwin’s Theory of Evolution Over time, the traits that make certain individuals of a population survive & reproduce tend to spread in that population Overwhelming evidence from fossils that living species evolved from organisms that are extinct.