1. Breeding Bunnies Lab Observe the graph and discuss with your lab mate.
What is the data showing?
Does it make sense? Why?

2. Population Genetics and Speciation

3. MISCONCEPTION ALERT Individuals DO NOT evolve!
Individuals do not change to match changes in the environment
POPULATIONS are acted upon by natural selection, where less fit individuals are less likely to pass on their genes
This causes a change in the genetic make-up of the population as a whole

4. Genetic Variation within Populations
A healthy population is one with a wide range of genetic diversity, without which evolution CANNOT occur
A wide range of genetic diversity causes there to be many different phenotypes

5. Genetic Variation within Populations
The greater the variation in phenotypes, the more likely it is that some individual can survive in a changing environment
Genetic variation is stored in a population’s gene pool – the combined alleles of all the individuals in a population
An allele frequency is a measure of how COMMON a certain allele is in a population

6. Genetic Change within Populations
Genetic change can occur because of the variations within populations
Genetic change causes a shift in the allele frequencies of certain traits
Genetic change within populations over time can occur in several ways…

7. Mechanisms of Genetic Change Over Time (Evolution)
Natural Selection
Occurs when nature selects for or against certain traits

8. Mechanisms of Genetic Change Over Time (Evolution)
2. Gene Flow
When genes are added or removed from a population
Caused by migration (emigration or immigration)

9. Mechanisms of Genetic Change Over Time (Evolution)
Genetic Drift
A CHANCE event that can cause the allele frequencies in a population (especially a small population) to change drastically
Can be caused by natural disasters such as fires, volcanoes, earthquakes and floods
Why?

10. Genetic drift (random)

11. Mechanisms of Genetic Change Over Time (Evolution)
4. Non-Random Mating
The cost of reproduction between males and females is different
Males produce many sperm continuously, while females are born with the number of eggs that they have
This allows females to be more choosy when it comes to selecting a mate
Non-Random mating occurs because certain traits in males increase mating success

12. Mechanisms of Genetic Change Over Time (Evolution)
5. Mutations
A random mutation can add a new allele to a population

13. Patterns of Natural Selection
When natural selection is NOT occurring, most populations have a normal distribution
If you were to collect one shoe from each student in your class and ordered and grouped them by size, you would probably form a hill-shape curve shown below, also known as normal distribution

14. Patterns of Natural Selection
When natural selection DOES occur, populations can respond in three major ways…

15. Patterns of Natural Selection
In directional selection, the “peak” of a normal distribution moves in one direction along its range
In this case, selection acts to eliminate one extreme from a range of phenotypes

16. Patterns of Natural Selection
In stabilizing selection, the bell-curve shape becomes narrower
In this case, selection eliminates individuals that have alleles for any extreme type

17. Patterns of Natural Selection
In disruptive selection, the bell-curve is pushed apart in two peaks.
In this case, selection acts to eliminate individuals with average phenotype values

18. Speciation Through Isolation
Do you remember what defines a species?
A species is defined as a group of organisms that can successfully interbreed
It is important to remember that species are not permanent, stable things…

19. Speciation Through Isolation
If gene flow between two populations stops for some reason, the populations are said to be isolated
As these populations adapt to their different environments, their gene pools may change
All of these changes add up over generations

20. Speciation Through Isolation
With time, the isolated populations become more and more genetically different from each other and may no longer be able to mate with each other (they become reproductively isolated)
Reproductive isolation between populations is the final step of becoming separate species

21. Speciation Through Isolation
The rise of two or more species from one existing species is called speciation
There are three ways in which population may become isolated
Behavioral Isolation: Caused by a difference in mating behaviors
Geographic Isolation: Involves physical barriers that divide a population into 2 or more groups
Temporal Isolation: Exists when timing prevents reproduction between populations

22. Which type of isolation is this?
GEOGRAPHIC

23. Convergent vs. Divergent Evolution
Convergent Evolution
Occurs when different species evolve in similar environments
When this occurs, the different species often evolve to have similar traits
These traits are said to be ANALOGOUS

24. Examples of Convergent Evolution
Bird
Insect
ANALOGOUS STRUCTURES!
(circle them in your notes!)
Dolphin
Shark

25. Convergent vs. Divergent Evolution
Occurs when closely related species evolve in different environments
When this occurs, the similar species evolve to have different traits
These traits are said to be HOMOLOGOUS

26. Examples of Divergent Evolution
HOMOLOGOUS STRUCTURES!

27. Coevolution
The process in which two or more species evolve in response to changes in each other
Species that involve predator-prey or parasite-host relationships often develop adaptations in response to each other