5 Agents of Evolution What is an Evolutionary

5 Agents of Evolution

What is an Evolutionary Agent? • Causes a change in heritable traits within a population Causes evolution to occur!

1. Natural Selection • The process by which beneficial traits become more common within a population because organisms with those traits have a higher chance of surviving to reproductive age and contributing to the offspring in the next generation.

2. Mutation • Any random change in the genetic material of an organism • Primary source of variation in natural selection • Must be passed down to contribute to evolutionary change • Mutation must be present in the gametes of an organism

Mutations: Speed of Evolution • Mutations occur randomly and at a low frequency • Alone, mutations do not have a huge effect on evolution. • HOWEVER, paired with another agent of change, such a natural selection or genetic drift, mutation can have a very drastic effect!

3 types of mutations 1. Positive: the mutation results in the production of a beneficial trait (increases fitness) 2. Negative: the mutation results in the production of a non-beneficial trait (decreases fitness) 3. Silent: the mutation does not affect the heritable traits of the individual

Sickle Cell Anemia • https: //www. youtube. com/watch? v=Qd 0 Hr. Y 2 Nlw. Y

Example: Snake Plant Mutant: Cylindrical Snake Plant Mutation occurred in the gene that is responsible for producing flat leaves.

Evolution before our eyes… • http: //news. harvard. edu/gazette/story/2016/09/acinematic-approach-to-drugresistance/? utm_source=twitter&utm_medium=so cial&utm_campaign=hu-twitter-general

Cat Mutations Manx (tailless) American Curl Polydactyl

3. Genetic Drift • Change in heritable traits in the population based on chance • Some organisms will contribute more offspring to the next generation • Not because they are more fit, because they are lucky

Bottleneck Effect • Quick reduction in a population often caused by a natural event (earthquake, flood, volcanic eruption, etc. ) • Gene pool of reduced population likely does not mirror original population • Future generations have different proportions of heritable traits than the previous generations

Visualizing the Bottleneck Effect See this video for an explanation! https: //www. youtube. com/w atch? v=c 1 zktd. T 2 un 4

Case Study: Northern Elephant Seal • Humans overhunted the Northern Elephant Seal population • In the 1890 s, the Northern Elephant Seal was reduced to only 20 individuals! • Today, the population is ~30, 000 individuals, but the population has reduced genetic variation • Why could this be a problem for the species?

Founders Effect • The loss in genetic variation that occurs when a new population is established by a very small number of individuals from a larger population

Case Study: Anoles • https: //www. youtube. com/watch? v=9 x 8 l. FXg. Xm. ZI

Founders Effect: Cultural Isolation • Amish populations in the United States tend to have grown from a few founding families and many have not recruited newcomers • Ellis-van Creveld syndrome is more common in Amish communities than in the entire American population • Symptom: extra fingers or toes

4. Gene Flow • A. k. a. migration • Changes in a population’s heritable traits as individuals migrate into or out of a population

Gene Flow: Examples • A young male lion leaves his mother’s pride and joins a pride with genetically unrelated females • How does gene flow occur in plant species?

5. Non-Random Mating • A. k. a. , sexual selection • An individual in a population does not have an equal chance of mating with any individuals of the other gender • (Individuals pick their mates) • Does this occur in humans?

Male competition • Male caribou grow large antlers every mating season. These antlers are for intimidating other males or used in combat. • These antlers are shed at the end of every season and regrown the next year! • Males who are able to grow large antlers are seen as more fit, and more females will mate with them.

Female Choice • Females choose their mate based on their traits • Can lead to some extravagant adaptations!

Heritable traits can be instinctive behaviours too! • https: //www. youtube. com/watch? v=bb. Lp. Zn 4 B 7 b 0

Looking to the future… • Monday: We have a guest presenter coming in from the organization Gene. Skool. They will be putting on an interactive workshop about evolution with us! • Wednesday: Group work to study the Agents of Evolution • Friday: Agents of Evolution Quiz! Also fun Halloween lecture