1. Evolution By Natural Selection

2. Isn’t Evolution Just A Theory
Isn’t Evolution Just A Theory? Video clip: learning and teaching evolution NP-VT min 0-7
How does the scientific meaning of a term like theory differ from the way it is used in everyday life?
Can the “facts” of science change over time? If so, how?

3. Evolution Scientific theories
Concepts based on the conclusions of observations and experiments.
A well tested explanation that unifies a broad range of observations.
Supported by a large number of observations and not yet found lacking.

4. Evolution Cell All organisms are composed of cells. Biogenesis
Life comes only from life.
Gene
Organisms contain coded information that dictates their form, function, and behavior.
Evolution
All living things have a common ancestor. Genetic changes in a population or species over generations have led to the diversity of life on Earth.

5. Introduction
Evolution: change over time by which modern organisms have descended from ancient organisms.

6. How Does Evolution Really Work
How Does Evolution Really Work? Video clip: learning and teaching evolution NP-VT min 20-27
What are the 4 components of natural selection?
What determines an individual hummingbird’s beak length?
What factors in the environment might select for beak length and shape within the hummingbird population?

7. Introduction Natural selection:
Individuals that are better suited to their environment are more likely to survive and reproduce than those that do not have such traits.
testable scientific explanation of the process by which life on earth has changed over time.

8. Modern understanding of Natural selection
In nature populations produce more offspring than environment can support
 struggle for existence
 survival of the “fittest”

9. Modern understanding of Natural selection
Populations of a species have genetic variation
-random mutation creates new alleles for the gene pool
-Sexual reproduction shuffles genetics to create unique individuals

10. Evolution by Natural selection overview
2) Certain phenotypes are better suited to an environment

11. Modern understanding of Natural selection
3) Over time, the genetic traits that make certain individuals better at surviving & reproducing have more offspring

12. Modern understanding of Natural selection
4) Natural selection selects for phenotypes (physical characteristics) - ex. Lizard color coded for by genes.
Alters the gene frequency (microevolution)
Predict what it will the gene frequency be at Gen 40

13. Natural selection and Heterozygous individuals
Lethal recessive alleles – how can they hide in a gene pool?
Dominant allele: functioning chloride ion channel  healthy lungs
Recessive cystic fibrosis allele: nonfunctioning ion channel  airways clogged with mucus and early death
Sickle cell Heterozygous advantage
Natural protection against malaria parasite
No complications of being homozygous
For sickle cell X

14. How Do We Know Evolution Happens Video clip: learning and teaching evolution NP-VT 576.8 min 14-20
How do fossils give us a picture of change over time?
What distinguishing feature of the fossil Pakicetus skull identified it as related to a whale? Why was this surprising?
Why do scientists seek fossils that are intermediate in form and time between modern forms and their probable earliest ancestors?

15. Review of Current Evidence of Evolution*

16. Review of Current Evidence of Evolution*

17. Genetic Drift
Genetic drift may occur when a small group of individuals colonizes a new habitat.
Individuals may carry alleles in different relative frequencies than did the larger population from which they came.
The new population will be genetically different from the parent population.

18. Species and Speciation
Species: a group of organisms that breed with one another and produce fertile offspring
Speciation: the formation of new species
Isolating Mechanisms: As a new species evolves, populations become isolated from one another

19. Isolation Temporal Isolation
prezygotic
can live in same place but breeds at different times
Frog example 

20. Isolation
Behavioral isolation: courtship rituals
prezygotic

21. Isolation

22. Isolation Geographic isolation:
population split by barrier (ex: river, mountain…)
Evidence Common ancestor
Separated 10,000 years ago
different sides of the Grand Canyon

23. Macroevolution: back to the big picture
Macroevolution refers to large-scale evolutionary patterns and processes that occur over long periods of time.

24. Macroevolution: back to the big picture Auxiliary video 4 Billion Year war – 1hr movie: McKay
Extinction
More than 99% of all species that have ever lived are now extinct.
In the past, most researchers looked for a single, major cause for each mass extinction.
Many paleontologists now think that mass extinctions were caused by several factors.

25. Macroevolution: back to the big picture
What effects have mass extinctions had on the history of life? Mass extinctions have:
provided ecological opportunities for organisms that survived
resulted in bursts of evolution that produced many new species
Punctuated equilibrium is a pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change.