1. Mechanisms for Evolution
Level
Mechanisms for Evolution

2. Mechanisms of Evolution
Evolution is change over time in a population.
Population – group of the same species in the same area.
Species – organisms can mate and produce fertile offspring
Mechanisms of evolution
Natural Selection
Mutations

3. Natural Selection Natural selection
The driving force of evolution is natural selection
Natural selection
“Survival of the fittest”
Those individuals that are best suited to the environment survive, reproduce and pass on their favorable traits to their offspring.

4. Natural Selection
These favorable traits will become more common in future generations, so the population changes over time.
Example: Beetles with “brown genes” escape predation and survive to reproduce more frequently than beetles with “green genes,” so that more brown genes were prevalent in the next generation.

5. Natural Selection
Adaptation: process of adapting to environment, consisting of anatomical, physiological or behavioral changes, improving a population’s ability to survive.
Anatomical – Physical Traits
Physiological – How the body functions.
Behavioral – How the organism acts.

6. Natural Selection Natural Selection Requirements:
Genetic variation – the more diverse your population is, the more likely the population will survive during times of environmental change.
Sources
Sexual Reproduction – combines different genes
Mutations – changes in genotypes affects phenotypes.

7. Natural Selection Natural Selection Requirements: Competition
i. Limited recourses.
ii. Organisms produce more offspring than can survive.

8. Gene Flow Gene Flow (Immigration or emigration):
The transfer of genes from one population to another and can result in changes in the allele frequencies of a population.

9. Genetic drift: Chance Events
Changes in allele frequencies of a gene pool due to chance/random luck.
Genetic drift can cause big losses of genetic variation for small populations.

10. Artificial Selection
Artificial selection: human choice -process of breeding plants and animals for particular traits (selective breeding).
Changes here occur faster than in natural selection

11. Reproductive Isolation
Reproductive Isolation: Prevents gene flow – two populations can no longer breed together
Due to behavioral and geographical barriers.

12. Reproductive Isolation
Geographical Isolation: Physical barriers (e.g., rivers, oceans, mountains) prevent mixing of populations.
Behavioral Isolation: Species differ in their mating rituals (e.g., differing bird songs, mating colors).