Evidence of Evolution

I. Evolution Definition: gradual changes in a species over time

Jean Baptiste de Lamarck 1. First to propose that living things had descended from a similar extinct species a. Acquired traits passed on to offspring

2. Acquired Trait: a trait not determined by genes 2. Acquired Trait: a trait not determined by genes. Arises during an organisms lifetime due to their experience or behavior 3. Genetic Trait: a trait determined by genes

Charles Darwin: “Father of Evolution”

1. Studied organisms (finches, tortoises, iguanas) on the Galapagos islands.

2. Wrote the “Origin of Species”

3. Evolution occurs due to natural selection

Natural Selection: Organisms that are better adapted to their environment will have a better chance of survival, therefore they will reproduce more 1. Survival of the fittest

E. Steps to Natural Selection

Variation is necessary for natural selection a. Within a population there is a variation in traits (phenotypes)

Living things face a constant struggle for existence a. Produce more offspring than there is room and food for, so they must compete to survive

Only some individuals survive and reproduce a. Some individuals are more “fit” for the environment or for life in general ex. Resistance to disease

4. Each generation consists of individuals with traits(phenotypes) that made them more “fit”, so over time, alleles for those traits will increase in frequency

Species adapt to their environment a. selection tends to make organisms better suited to their environment

C. Lethal genes are kept in the gene pool if in the heterozygous form because those individuals will not show the lethal phenotype

Evidence of evolution: how do we know it occurs 1. Similarities in Embryology: during early stages of development, organisms that descend from common ancestor look the same

2. Homologous features: similar features that originated in a shared ancestor ex. Forelimbs of vertebrates

3. Analogous Features: serve similar function and they look similar, but the organisms don’t share a common ancestor ex. Wings in insects and birds

4. Vestigial Features: features that are apparently useless to the modern organism ex. Tailbone in humans, pelvic bones in whales

5. Similarities in DNA and macromolecules(proteins, carbs, etc.)

Patterns of Evolution: 1. Coevolution: change of two or more species in close association with each other. ex. Hummingbirds and the flowers they feed on

2. Convergent Evolution: organisms that are not closely related evolve to show similar trait ex. Sharks and Dolphins

Divergent evolution: two or more organisms evolve to become more and more dissimilar

a. Adaptive Radiation: many related species evolve from a single ancestral species

b. Artificial Selection: speeding up of divergent evolution ex. Dog breeding