1. Agents of Evolutionary Change
Or Disruption of Genetic Equilibrium

2. Last Class Chapter 15 Review Fossils Evolutionary Theorists
Evolutionary Evidence
Processes of Evolution
Build-A-Beast Workshop (Due Monday Oct 5, along with presentation)
Test – Evolution- Wednesday Oct 7

3. Today We will discuss how Evolution occurs in populations
Agents of Evolutionary change
AKA Disruption of Genetic Equilibrium
Genetic Drift Activity
Computer Lab time

4. But First… Evolution Quiz!
Everything off your tables except for a writing utensil!
5 min (shouldn’t take too much longer…)

5. Back to the Lesson…
But First…
Let’s do a Think- Pair- Share
What traits would a NON-EVOLVING population have?
What factors would keep this population from evolving?

6. Hardy-Weinberg Genetic Equilibrium
Of course we know by now, that populations do evolve… but typically not at any rate which we can really see.
populations tend to remain the same from generation to generation, unless enacted on by an outside influence
This is what is known as the Hardy-Weinberg Genetic Equilibrium (HWE)

7. Hardy-Weinberg Genetic Equilibrium
It is based on a set of assumptions about a hypothetical and ideal population that is not evolving;
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

8. HWE Continued
Of course, there is no population like that…
The HWE is used to measure the rate of evolutionary change in a population, by comparing it to an ideal, never evolving population

9. Let’s Look Back at the “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
An Evolutionary change in a population would therefore involve one of these changes to occur.

10. Agents of Evolutionary change
Mutation, Genetic Drift, Migration (Gene Flow), Non-Random Mating, Natural Selection

11. Mutations Insertion Deletions
We have learned how mutations are copying errors during DNA replication. Mutations can happen in different ways:
Substitutions
ACTGCGA  ACTGCCT (sickle cell anemia)
Insertion
ACTGCGA  ACTGACGA
Deletions
ACTGCGA  ACTCGA G
Insertions and Deletions lead to Frameshifts

12. Mutations (cont’d) Types of mutations: Neutral
Most common. Change in DNA sequence that has no affect on protein synthesis
Harmful
Second most common: change in DNA sequence leads to harmful trait
Beneficial
Least common, mutation leads to trait which serves beneficial to organism. Driving force of evolution

13. Genetic Drift
The Hardy-Weinberg equilibrium does not hold for small or medium populations
Genetic drift is the phenomenon by which allele (genetic traits) frequencies in a population change as a result of RANDOM events or CHANCE
In a small population the FAILURE or GREATER THAN NORMAL RATE of one organism to reproduce can significantly disrupt gene frequency

14. Loss in genetic variation means there is nothing for natural selection to act upon
- Positive or Negative traits can’t be selected if all genes across population are similar

15. Genetic Drift- Bottleneck effect

16. Genetic Drift- Founders Effect

17. Now let’s see genetic drift in action…
In groups of 3, grab one cup of candy, and one worksheet
Follow directions, and complete questions
When finished
In your Notebook
Explain in your own words the positives and negatives of mutations on an INDIVIDUAL.
Why might mutations be more beneficial on a POPULATION?
Why are species in danger of extinction if there is no variation in allele (gene) frequencies in the population?

18. Next Class Look at the other 3 agents of Evolutionary change
Migration (Gene Flow)
Non-random mating
Natural Selection