1. Evolution and Populations

2. EVIDENCE OF EVOLUTION STRUCTURAL ADAPTATIONS MIMICRY CAMOUFLAGE
Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

3. EVIDENCE OF EVOLUTION STRUCTURAL ADAPTATIONS MIMICRY CAMOUFLAGE
MILLIONS OF YEARS
PHYSIOLOGICAL ADAPTATIONS
CHANGE IN A METABOLIC PROCESS
WHAT DO YOU HEAR ABOUT IN THE NEWS ABOUT SOME BACTERIA?
Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

4. WHAT OTHER INDUSTRIES WOULD BE WORRIED ABOUT RESISTANCE?
WHAT OTHER INDUSTRIES WOULD BE WORRIED ABOUT RESISTANCE?
Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

5. OTHER EVIDENCE OF EVOLUTION
FOSSILS
ANATOMY
HOMOLOGOUS STRUCTURES indicate a related evolutionary ancestry, not just similarity
Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

6. OTHER EVIDENCE OF EVOLUTION
FOSSILS
ANATOMY
HOMOLOGOUS STRUCTURES
ANALOGOUS STRUCTURES similar in appearance and function but are not the result of shared ancestry.
Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

7. Convergent Evolution
Species from different evolutionary branches may come to resemble one another if they live in very similar environments.
Example:
1. Ostrich (Africa) and Emu (Australia).
2. Sidewinder (Mojave Desert) and
Horned Viper (Middle East Desert)

8. CONVERGENT EVOLUTION – WHAT IS AN EXAMPLE?
Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

9. Chapter 16—Populations
16.1
A population consists of all the individuals of a species that live together in one place at one time.
Population density is the number of individuals in a given area.
A population’s future survival is determined by its size, density, and dispersion.

10. Though a population’s growth is limited by factors such as predation and available sources, a population can grow rapidly and may eventually stabilize at a size that the environment can sustain.
 Species - a group of populations whose individuals have the ability to breed and produce fertile offspring. 

11. Some populations grow quickly in response to –density-independent factors (weather, climate). Ex. Mosquito populations
Some populations grow more slowly and their size is controlled by density dependent factors (limited resources—food, water). 

12. Mutation
• random, heritable changes in DNA that introduces new alleles into a gene pool

13. Gene pool– is the set of possible gene combinations in a given population (breeding options—different offspring trait choices/combinations)

14. 16.2
Natural selection means one species has a benefit that allows them to survive more than another.
Natural selection acts only on phenotype, not on genotype.

15. Modes of natural selection

16. Modes of selection

17. Polygenic traits are those which are influenced by several genes. Ex
Polygenic traits are those which are influenced by several genes. Ex. Skin color, height
The range of phenotypes controlled by polygenic traits results in a normal distribution when plotted on a chart. Figure

18. 2 Types of Natural selection:
Directional selection—shift phenotypes toward one extreme
Ex. Pesticide or antibiotic resistance

19. Directional selection
Beak size selection in a Galápagos population of the medium ground finch

20. 2. Directional Selection
Favors variants of one extreme.
Number of
Individuals
Size of individuals
Small Large

21. 3. Diversifying Selection
Favors variants of opposite extremes.
Number of
Individuals
Size of individuals
Small Large

22. Stabilizing selection

23. Stabalizing selection—range of phenotypes narrows
Ex. Increase the number of “average” individuals

24. 1. Stabilizing Selection
Acts upon extremes and favors the intermediate.
Number of
Individuals
Size of individuals
Small Large

25. Diversifying selection