Finishing Off Evolution! Agents of Evolutionary Change Migration, Non-Random Mating, Selection Types

Last Class Discussed 2 agents of Evolutionary Change We discussed the HWE… Which stands for…? The Hardy-Weinberg (Genetic) Equilibrium Discussed 2 agents of Evolutionary Change Mutations Substitutions, Insertions, Deletions, Frameshifts Neutral, Harmful, Beneficial Genetic Drift Bottleneck and Founders Effect How small populations can be hit hard by evolution

Today Finish up Agents of Evolutionary Change As promised Migration Non-Random Mating Selection As promised Time IN CLASS to work on Build-a-beast project/ Evol. Research Project Time IN COMPUTER LAB to work on Evol. Research Project

REMINDER EVOLUTION PROJECT PRESENTATION- TUESDAY MARCH 10. IF it is an ELECTRONIC presentation PLEASE submit by MIDNIGHT MARCH 9!!! EVOLUTION UNIT TEST- THURSDAY MARCH 12 Start preparing now.

Back to the Action… 1. No Net Mutations occur Last class, we looked at the 5 assumptions of a hypothetical, “ideal” non-evolving population: 1. No Net Mutations occur 2. Individuals do not enter or leave the population 3. The population is large (ideally, infinitely) 4. Individuals mate randomly 5. Selection does not occur

Migration (Gene Flow) 2. Individuals do not enter or leave the population Immigration  The movement of animals into a population Emigration  The movement of animals out of a population Both can play a role in gene frequencies

Migration (Gene Flow) Consider the Baboon Common baboons live together in groups called “troops” Troops are dominated by a small number of adult males. Females remain with troops they are born into, but young adult males tend to leave their birth troop, and join another troop. This disrupts the genetic variation in the original population, as well as the immigrated population

Non-Random Mating Most species undergo some process of mate selection Usually due to geographic proximity, and some degree of kinship

NON RANDOM MATING Mating between closely related individuals can amplify certain traits, resulting in disorders caused by recessive genes Animals will often seek out mates with similar physical traits, meaning they will have similar genes This is known as Assortive mating

Sexual Selection (Goes with non-random mating) Consider the feathers of the peacock Very easy for predators to see Why would these be advantageous? A male must be “selected” by a female. Big elaborate feathers, or other traits are a sign of an organisms health and fitness Represents good genes, and are selected by females.

Natural Selection The fifth requirement of the HWE was that Selection does not occur in a population Natural selection is a key process in which the environment “selects” for certain traits (genes) to be passed on to the next generation Three Selection patterns: Stabilizing, Directional, Disruptive

Stabilizing Selection Individuals with the average form of a trait have the highest fitness. Ex. A species of lizard in which larger individuals would be spotted easily by predators, and smaller species are not fast enough to escape predators

Stabilizing Selection Fig 16.7a

Directional Selection Individuals that display a more extreme form of the trait will be selected. Ex. The length of an anteaters tongue. The longer the tongue, the more insects they would be able to eat which were buried deeper in the ground.

Disruptive Selection Individuals with EITHER EXTREME of the trait will have more fitness than the average form of the trait Ex. Shell color of a clam. Individuals who are dark are able to camouflage themselves in dark rock or in shadows, individuals with light colouring will be able to hide in the light coloured sand. Individuals that are between light and dark will not be able to hide as easily.

And That wraps up Evolution! To do now: 16.2 Review Sheet in front of you Finish Chapter 15 Review in back of textbook Finish any journal entry you are behind on/ want to finish off (They will be given a completion mark at the end of the Evolution Unit) Work with your groups to finish: Build-a-beast project Evolution Research Project Study for DNA retest/Evolution Unit Test