Semester 2, Day 11 Other Mechanisms of Evolution

Agenda  Review for Natural Selection Quiz  Turn in Homework  Take Quiz on Natural Selection  Lecture on Other Mechanisms of Evolution  Reading/Work Time

Review for Quiz  Genotype, Zygosity, and Phenotype  Define phenotype and genotype  Which does natural selection work upon and why?  Define the four conditions for natural selection  Define artificial selection  Define natural selection  Understand examples of each of the following TYPES of natural selection:  Directional selection  Disruptive selection  Sexual selection  Stabilizing selection  What is “fitness”?

Homework Due  Cornell Notes:  Pages  (stop BEFORE “Adaptations: Evidence for Evolution”)  Pages  (stop BEFORE “The Evolution of Species”)  Questions:  15.1 #1, 5  15.2 #1  Chapter 15 Assessment #2, 6, 9, 11, 16, 18-20

Quiz  Silently complete quiz  Keep eyes on your own paper  Flip quiz over when complete

Recall: Evolution  Change in a group of organisms over many generations  CANNOT OCCUR IN AN INDIVIDUAL!  5 Mechanisms of Evolution:  Natural Selection  Mutations  Gene Flow  Genetic Drift  Nonrandom Mating

Evolution  Mutations: change in DNA that results in a change in the gene expression  Recall Central Dogma:  3 types of mutations:  Beneficial: benefit organism = HIGHER fitness  Ex. faster runner can survive and reproduce more  Neutral: no effect of fitness  Ex. Eye color doesn’t necessarily help you to survive and reproduce more  Harmful: hurt organism = LOWER fitness  Ex. People with Huntington’s disease may not survive and reproduce. DNA  mRNA  Protein (Gene Expression)

Evolution  How are mutations related to natural selection?  Recall: Natural selection has four conditions:  Variation: differences  Heredity: parent to child  Overproduction: too many offspring  Reproductive Advantage: those able to survive & reproduce pass on their traits MORE.  Mutations are INHERITED, lead to VARIATION, and can provide ADVANTAGES  Without mutations, there would be no differences in organisms, which means no evolution could occur

Evolution  Gene Flow  Movement of organisms to different populations  Immigration: enter area  Emigration: leave area  Results:  MORE variation IN population  LESS differences BETWEEN populations.

Evolution  Genetic Drift  Taking a small population from a larger one  LOSE SOME VARIATION.  Founder Effect:  Individuals leave to start a population in a new area  Bottleneck Effect:  Catastrophic event reduces population

Evolution  Genetic Drift: Founder Effect  Genetic Drift: Bottleneck  Variation of INDIVIDUALS: ensures some INDIVIDUALS in a species will survive a catastrophic event  Recall: Biodiversity of SPECIES: ensures some SPECIES will survive a catastrophic event

Evolution  Nonrandom Mating: probability of mating with some individuals higher than with others  Higher chance of mating with those nearby  Higher chance of mating with those who look similar  Nonrandom mating can lead to INBREEDING:  Continued breeding of closely related individuals  Happens in nature: cheetah bottleneck  Happens artificially: breeding dogs for certain traits  Less Variation = Higher Risk for Disease!!!

Reading/Work Time  Cornell Notes on 14.3 and 14.4  Questions:  14.3 #1-3  14.4 #1-5  Chapter 14 Assessment #3, 4, 6, 10-14, 16, 20, 22a, 22c