Biology Unit 6: Evolution

theory

a hypothesis that has been tested and supported by lots of evidence as well as been peer-reviewed

Evolution

the idea that there are changes in inheritable traits of a population overtime

What evidence is there for evolution?

1. Fossils

2. DNA/Biochem

3. Embryology

4. Homologous/Vestigial Structures

Homologous/Vestigial Structures

structures that are similar in shape, but have different functions/structures or bones that are not necessary for the modern organism anymore

Limitations for this: structures can be misleading to compare because species could have also evolved based on the environmental pressures

DNA/Biochem

the comparison of amino acids to find how similar organisms are

Embryology

the comparison of the development of an organism at an early stage

Fossil Evidence

helps us understand the time period in which an organism lived in

Darwin’s Natural Selection Idea

When he travelled to the Galapagos Islands, he saw that the finches were different than the ones on the mainland, despite their other oddly similar characteristics. He thought that because of the environment, they had adapted to it, creatin changes.

Natural Selection

the process by which organisms that are best suited to their environment are more likely to survive and reproduce

If a species improves its ability to survive and reproduce…

the trait will become more common throughout the population.

Random changes may happen in inheritable traits due to..

mutations

What happens if there are only so many resources for all these organisms?

• They must compete for resources

• Those that are the most fittest will survive and reproduce to pass down these traits

Directional Selection

when one extreme of a trait is favored over another

• Ex. Peppered Moths

• One left behind hump, one infront hump

Stabilizing Selection

when the intermediate form of the trait is favored

• Ex. Peacocks

• Longer hump is created in the thick hump

Disruptive Selection

both extremes of a trait are favored over the intermediate form

• Rock Pocket Mice

• results in 2 humps for the 2 traits

Individuals cannot evolve but…

populations can

It is not quite survival of the fittest but rather…

of who is fit enough

Divergent Evolution

when a species begins to create differences leading to speciation (2 species)

• Common ancestor —→ adapting different traits

• Caused by physical separation, gene flow, new predators, or changes in biotic and abiotic factors of environment

Convergent Evolution

when 2 species begin to evolve to become more similar

• Caused by random chance or same environenmental conditions

Co-evolution

when two species that share a symbiotic relationship evolve together

• As flowers evolved long nectar tubes, birds evolved long mouthparts

Genetic Drift

the change in a species due to random chance

• can lead to extinction

• reduce biodiversity

Gene Flow

when two isolated populations exchange genetic material

5 Agents of Natural Selection

Mutations

Gene Flow

Genetic Drift

Selection

Non-Random Mating