What evolution is not

2. What evolution is not • Organisms become better • Man represents the apex in evolution • Humans descended from apes • Only a theory • Only the strongest survive • It has an end purpose in mind

3. 1. Species produce more offspring than survive Thomas Malthus believed that there was an overproduction of young Resources would not be able to keep up with the population growth. Famine and misery would follow Darwin extended Malthus’ idea to include all organisms

4. Species produce more offspring than survive Malthus George Wallace and C. Darwin There was no ulterior motivation or social classes in nature. Organisms have biological desires to survive. • Believed that this was God’s way of keeping people from being lazy. • The lower class would have to “pick themselves up by their bootstraps” and compete to survive

5. 2. Individuals of a species possess different genetic traits, which help to compete for limited resources • The different traits do not lead to perfection. • They have to be good enough to get by. • Look around, no one is perfect.

6. 3. Organisms that don’t survive, don’t pass on their traits

7. 3. Advantageous adaptations will survive

8. Adaptation • Feathers= An adaptation is a feature produced by natural selection for its current function. • it must be genetically encoded—since natural selection cannot act on traits that don’t get passed on to offspring. • the trait must actually perform that task. • it must increase the fitness of the organisms that have it • did they evolve for insulation or flight?

9. 4. Most fit organisms survive and pass on traits to offspring

10. Natural Selection • Is mindless and mechanistic • Selects for whatever variation is available • Organisms do not “try”, “want” or “need” to adapt. • Is not random. • A mutation may be random, • But nature acts in a specific way.

11. Natural Selection • The change in the genetic frequency by selective pressure

12. Types of Selection • Directional selection - one trait is being favored and the other is being eliminated so the population shifts toward one trait • Stabilizing selection - range of a trait is narrowed • Disruptive selection - traits diverge toward the two extremes

13. No species lives in isolation • Ecological niche - describes either the role played by a species in a biological community or the total set of environmental factors that determine a species distribution • Generalist - has a broad niche (rat) • Specialist - has a narrow niche (panda) • Indicator species – sensitive to environmental change ( lichen) • Keystone species – provides ecosystem stability (American alligator) • Non-native invasive species (European starling)

14. Competitive Exclusion • Gause proposed the competitive exclusion principle which states that no two species can occupy the same ecological niche at the same time. The one that is more efficient at using resources will exclude the other. • Resource partitioning - species co-exist in a habitat by utilizing different parts of a single resource. Example: Birds eat insects during the day and bats eat insects at night.

15. Resource Partitioning

16. All species live within limits • Law of limiting factors: The factor in the shortest supply relative to its demand will limit its growth • Range of Tolerance: abiotic factor (light, nutrients, moisture) • Plants: N for terrestrial, P for aquatic

17. Range of tolerance

18. Genetic Engineering • Excise a gene with the desired trait • Insert the gene into the host cell’s genome • The host organism has the new trait • Bt corn

19. Factors that influence evolution • Mutations • Genetic drift • Genetic migration • Natural selection • Population size • Non-random mating