Chapter 15 NotesChapter 15 Notes

Key TermsKey Terms

EvolutionEvolution: Changes in a population over : Changes in a population over time.time.

Natural SelectionNatural Selection: The environment favors : The environment favors individuals to survive and reproduce individuals to survive and reproduce successfullysuccessfully “AKA, Survival of the “AKA, Survival of the Fittest”Fittest”

Individuals do not evolve, populations do.

Darwin’s Theory: The Short VersionDarwin’s Theory: The Short Version

1. Organisms differ; variation is inherited1. Organisms differ; variation is inherited

2. Organisms produce more offspring than 2. Organisms produce more offspring than survivesurvive

3. Organisms compete for resources3. Organisms compete for resources

4. Organisms with advantages survive to pass 4. Organisms with advantages survive to pass those advantages to their childrenthose advantages to their children

5. Species alive today are descended with 5. Species alive today are descended with modifications from common ancestorsmodifications from common ancestors

Example: Colored MothsExample: Colored Moths

The traits that The traits that help an organism help an organism survive in a survive in a particular particular environment are environment are “selected” in “selected” in natural selectionnatural selection

Key Terms Key Terms

Adaptation: An inherited characteristic that increases an organism’s ability to survive and reproduce in its specific environment.

Fitness: The ability to survive and reproduce in a specific environment. Adaptations make an organism more fit.

Key Terms Key Terms

Artificial Selection: Nature provides the variation and human select those variances they find useful.

• Example: a farmer breeds only his best livestock.

Evidence for EvolutionEvidence for Evolution• 1. The Fossil Record

• 2. Homologous Body Structures

• 3. Similarities in Embroyology

• 4. Vestigial Structures

• 5. Similarities in DNA and RNA

Homologous Structures

Same structures-Different function

Example: Human arm, bird wing

Homologous StructuresHomologous Structures

EmbryologyEmbryology

Analogous Structures

Different structure, Same function

Example: Butterfly wing, bird wing

Vestigial StructuresVestigial Structures

Body structures that no longer have a useBody structures that no longer have a use

Example: Human appendixExample: Human appendix

Gene PoolGene Pool Gene PoolGene Pool: The combined collection of : The combined collection of

alleles for all traits in a population.alleles for all traits in a population.

Three Forms of Natural Selection

Sexual SelectionSexual Selection

Sexual SelectionSexual Selection: A special case of : A special case of selection that occurs when the choice of selection that occurs when the choice of mates is based on a trait (or traits). mates is based on a trait (or traits). Sexual selection may be directional, Sexual selection may be directional, stabilizing, or disruptive.stabilizing, or disruptive.

Sexual SelectionSexual Selection

Evolving New SpeciesEvolving New Species SpeciationSpeciation: The evolution of a new : The evolution of a new

species.species. In order for speciation to occur, populations In order for speciation to occur, populations

(or segments of populations) must (or segments of populations) must become become reproductively isolated.reproductively isolated.

There are 3 ways that a population can There are 3 ways that a population can become reproductively isolated.become reproductively isolated.

Reproductive IsolationReproductive Isolation Behavioral IsolationBehavioral Isolation; Occurs when two ; Occurs when two

populations are physically capable of populations are physically capable of interbreeding, but have different reproductive interbreeding, but have different reproductive behaviors.behaviors.

Geographic IsolationGeographic Isolation: Occurs when a : Occurs when a physical barrier (mountain, lake, etc.) physical barrier (mountain, lake, etc.) separates two populations.separates two populations.

Temporal IsolationTemporal Isolation: Occurs when populations : Occurs when populations are capable of interbreeding, but each breed are capable of interbreeding, but each breed at different times.at different times.

Courtship rituals, like Courtship rituals, like these, are critical for these, are critical for mating within a species, mating within a species, but ineffective for but ineffective for attracting members of attracting members of other species.other species.

Behavioral IsolationBehavioral Isolation

Geographic IsolationGeographic Isolation

Geographic IsolationGeographic Isolation

Temporal IsolationTemporal Isolation

Convergent and Divergent Convergent and Divergent EvolutionEvolution

Convergent EvolutionConvergent Evolution: Two unrelated : Two unrelated species develop similar traits due to species develop similar traits due to similar environments. Convergent similar environments. Convergent evolution causes evolution causes AnalogyAnalogy..

Divergent EvolutionDivergent Evolution: Two similar species : Two similar species develop differences due to different develop differences due to different environments. Divergent Evolution causes environments. Divergent Evolution causes HomologyHomology..

Genetic DriftGenetic Drift

Change in the frequency of alleles due to Change in the frequency of alleles due to natural disasters.natural disasters.

Example: tornado, hurricane, flood…Example: tornado, hurricane, flood…