1. How are new species created?
Speciation
How are new species created?

2. Warmup: Get out your learning targets paper
In the warmup section of your lab book: Create a concept map using at least 12 of the terms listed in part b) on the front side

3. Share current events article Notes:
Directional selection, stabilizing, disruptive
Genetic Drift
Founder Effect
Speciation
Ensatina eschscholtzii salamanders
Create a scenario…
Homework

4. Natural Selection on Polygenic Traits
Low mortality,
high fitness
Directional Selection
High mortality, low fitness
Food becomes scarce
Individuals at one end of curve have higher fitness
Range of phenotypes shifts

5. Natural Selection on Polygenic Traits
Individuals near center of curve have highest fitness
Keeps center of curve at same position and narrows graph
Stabilizing Selection
Low mortality,
high fitness
High mortality,
low fitness
Selection against both extremes keeps curve narrow and in same place
Percentage of Population
Birth Weight

6. Natural Selection on Polygenic Traits
Disruptive Selection
Largest and smallest seeds become more common
Population splits into two subgroups specializing in different
seeds.
Low mortality,
high fitness
Number of Birds
in Population
Number of Birds
in Population
High mortality,
Low fitness
Beak Size
Beak Size
Individuals at upper and lower ends of the curve have higher fitness than individuals in the middle
Selection acts strongly against individuals of the intermediate type

7. Speciation Speciation = formation of new species
Species = group of organisms that breed with one another and produce fertile offspring
As new species evolve, populations become reproductively isolated from each other
Members of same species share same gene pool
Genetic change that occurs in one individual can spread through the population
Gene pools must become separated for speciation to occur
When two population cannot interbreed and produce fertile offspring, reproductive isolation has occurred

8. Isolating Mechanisms (lacewing interactive)
Behavioral Isolation
Differences in courtship rituals or other reproductive strategies
Geographic Isolation
Two populations separated by geographic barrier such as rivers, mountains or bodies of water
Temporal Isolation
Two or more species reproduce at different times of the day or year

9. Reproductive Isolation
results from
Isolating mechanisms
which include
Behavioral isolation
Temporal isolation
Geographic isolation
produced by
produced by
produced by
Behavioral differences
Different mating times
Physical separation
which result in
Independently evolving populations
which result in
Formation of new species

10. Speciation
In a phylogenetic tree, it is represented by a branching point
Example: Drosophila

11. A new species of fruit fly
Example: Fruit flies
A population of wild fruit flies on several bunches of rotting bananas, laying their eggs in the mushy fruit...

12. A new species of fruit fly
Disaster strikes: A hurricane washes the bananas and the fruit flies out to sea. The banana bunch washes up on an island off the coast of the mainland. The two portions of the population, mainland and island, are now too far apart for gene flow to unite them.

13. A new species of fruit fly
The populations diverge: Conditions are slightly different on the island, and the island population evolves under different selective pressures and experiences different random events than the mainland population does.
Food preferences, and courtship displays change over the course of many generations of natural selection.

14. A new species of fruit fly
So we meet again: When another storm brings the island flies back to the mainland, they will not mate with the mainland flies since they've evolved different courtship behaviors.
The few that do mate with the mainland flies, produce inviable eggs because of other genetic differences between the two populations.
Two separate species now exist since genes cannot flow between the populations.

15. Geographic Isolation
Populations are separated by geographic change or dispersal to geographically isolated places
Rivers change course
Mountains rise
Continents drift
Organisms migrate
Roads are built
Note: a barrier for one species may not be a barrier for another species
Add graphics of river, Grand Canyon

16. Small populations face risks
Founder effect: when only a few individuals colonize a new place, genetic variation is low
Genetic drift: changes in gene pool due to chance (which individuals reproduce)
Bottleneck effect: disasters that eliminate a large number of individuals and greatly reduce the gene pool

17. Genetic Drift Section 16-2 Sample of Original Population Descendants
Founding Population A
Founding Population B

18. Genetic Drift Section 16-2 Sample of Original Population Descendants
Founding Population A
Founding Population B

19. Genetic Drift Section 16-2 Sample of Original Population Descendants
Founding Population A
Founding Population B

20. A new species: If a group splits off from the main population
evolves to adapt to its environment
the changes accumulated make it unable to breed with the larger population
Then a new species has been formed

21. Other reasons for reproductive isolation:
Timing (Temporal Isolation): Different breeding seasons
Example: Spotted skunks
Western skunks breed in the fall, Eastern skunks breed in the late winter

22. Other reasons for reproductive isolation:
Behavior (Behavioral Isolation): Different courtship or mating behaviors
Example: Eastern and Western Meadowlarks
Different songs

23. Other reasons for reproductive isolation:
Habitat: Adapted to different habitats in the same general location
Example: Stickleback fish in British Columbia
Live in different levels of water, have different diets

24. Other reasons for reproductive isolation:
Others: different reproductive structures, insects only transfer pollen to certain plants, hybrid offspring is sterile

25. Speciation of Darwin’s Finches
Founders Arrive
Separation of Populations
Changes in the Gene Pool
Reproductive Isolation
Ecological Competition
Continued Evolution

27. Speciation in the Andes (Ecuador)
Hummingbird video
Explain the hypothesis presented by the scientists profiled in this segment to explain the process of speciation in hummingbirds and possibly other species.
How does this hypothesis differ from the traditional view that speciation often requires geographic separation of populations?
Why were the researchers collecting blood from the populations they studied? Discuss at least two possible analyses that could be performed on those samples and, identify at least two different questions that might be answered with sufficient data.

28. Ensatina Salamanders California salamanders
Live and lay eggs on land
Studied by R.C. Stebbins in the 1940s
You used his data to map the locations of various subspecies
Video of mating behavior:
Pictures of each subspecies:

30. Ring Species
All subspecies interbreed with their immediate neighbors EXCEPT at southern end
E. klauberi and E. eschscholtzii do not interbreed
Where should speciation be marked?

31. Did you get it? Watch this!
Link to video about Ensatina salamanders in California (3 minutes)

32. Do Now!
Devise a scenario in which a particular type of selection leads to speciation.
Use the 5 tenants of natural selection
What type of selection is at work?

33. Homework
Read section 17-4 in your textbook (pg ), Patterns in Evolution
Answer the three learning targets for this section (#3, 4 and 5 under chapter 17) from your LEARNING TARGETS paper.