1. Adaptations and Population Genetics

2. Evolution
Evidence of Evolution
Types of Adaptation
An adaptation is a trait shaped by natural selection that increases an organism’s reproductive success.
Fitness is a measure of the relative contribution an individual trait makes to the next generation.

3. Allows organisms to become almost invisible to predators
Evolution
Evidence of Evolution
Camouflage
Allows organisms to become almost invisible to predators
Camouflage Pics
Leafy sea dragon
Camouflage Video

4. One species evolves to resemble another species.
Evolution
Evidence of Evolution
Mimicry
One species evolves to resemble another species.
Mimicry video
Western coral snake
California kingsnake

5. Shaping Evolutionary Theory
Mechanisms of Evolution
Population genetics
Hardy-Weinberg principle states that when allelic frequencies remain constant, a population is in genetic equilibrium.

6. Homozygous dominant (p2)
Evolution
Shaping Evolutionary Theory
This equation allows us to determine the equilibrium frequency of each genotype in the population.
Homozygous dominant (p2)
Heterozygous (2pq)
Homozygous recessive (q2)

7. 15.3 Shaping Evolutionary Theory
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory

8. Evolution
Shaping Evolutionary Theory
Genetic Drift
A change in the allelic frequencies in a population that is due to chance
In smaller populations, the effects of genetic drift become more pronounced, and the chance of losing an allele becomes greater.

9. Evolution
Genetic Drift
Founder Effect
Occurs when a small sample of a population settles in a location separated from the rest of the population
Alleles that were uncommon in the original population might be common in the new population.
Shown in this image is polydactyly -- extra fingers or sometimes toes -- one symptom of Ellis-van Creveld syndrome. The syndrome is commonly found among the Old Order Amish of Pennsylvania, a population that experiences the "founder effect." Genetically inherited diseases like Ellis-van Creveld are more concentrated among the Amish because they marry within their own community, which prevents new genetic variation from entering the population. Children are therefore more likely to inherit two copies of the particular recessive genes that lead to genetic disease.

10. Evolution
Genetic Drift
Bottleneck
Occurs when a population declines to a very low number and then rebounds

11. Evolution
Shaping Evolutionary Theory
Gene Flow
Increases genetic variation within a population and reduces differences between populations
Nonrandom Mating
Promotes inbreeding and could lead to a change in allelic proportions favoring individuals that are homozygous for particular traits

12. 3 types of Natural Selection
Evolution
3 types of Natural Selection
Stabilizing selection operates to eliminate extreme expressions of a trait when the average expression leads to higher fitness.
Example: Birth weight=average weight=survival
Directional selection makes an organism more fit.
Example: Peppered moths shifted to be mostly black after the industrial revolution.
Disruptive selection is a process that splits a population into two groups.
Example: Bees only pollenating certain flowers

13. Evolution
Shaping Evolutionary Theory
Sexual selection operates in populations where males and females differ significantly in appearance.
Qualities of sexual attractiveness appear to be the opposite of qualities that might enhance survival.
Birds of paradise mating dance

14. Evolution

15. Evolution
Shaping Evolutionary Theory
Prezygotic isolation prevents reproduction by making fertilization unlikely.
Different mating rituals, mating times, and other behaviors separate similar species.
Pre zygotic Video
Eastern meadowlark and Western meadowlark

16. Postzygotic isolation occurs when fertilization has occurred but
Evolution
Shaping Evolutionary Theory
Postzygotic isolation occurs when fertilization
has occurred but
a hybrid offspring
cannot develop
or reproduce (sterile).
Prevents offspring survival or reproduction
Liger
Post zygotic Video

17. Allopatric Speciation
Evolution
Shaping Evolutionary Theory
Allopatric Speciation
Video
A physical barrier divides one population into two or more populations.
Abert squirrel
Kaibab squirrel

18. A species evolves into a new species without a physical barrier.
Evolution
Shaping Evolutionary Theory
Sympatric Speciation
A species evolves into a new species without a physical barrier.
The ancestor species and the new species live side by side during the speciation process.
More common in plants due to polyploidy.

19. Shaping Evolutionary Theory
Video
Adaptive Radiation
Can occur in a relatively short time when one species
gives rise to
many different
species in
response to the
creation of new
habitat or some
other ecological
opportunity
Follows large-scale extinction events

20. Coevolutionary arms race
Shaping Evolutionary Theory
Coevolution
The relationship between two species might be so close that the evolution of one species affects the evolution of the other species.
Mutualism
Coevolutionary arms race
Video

21. Evolution
Shaping Evolutionary Theory
Convergent Evolution
Unrelated species evolve similar traits even though they live in different parts of the world.

22. Evolution
Shaping Evolutionary Theory
Rate of Speciation
Evolution proceeds in small, gradual steps according to a theory called gradualism.
Punctuated equilibrium explains rapid spurts of genetic change causing species to diverge quickly.
Video

23. 15.3 Shaping Evolutionary Theory
Chapter 15
Evolution
15.3 Shaping Evolutionary Theory
Kangaroo video