People have more children than are able to survive There are builtin population checks disease famine and war Darwin based his theory on his own observations and the writings of Thomas Malthus ID: 1046842
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1. Malthus was a British social scientist who made these observations about humans: People have more children than are able to survive. There are built-in population checks: disease, famine, and war.Darwin based his theory on his own observations and the writings of Thomas Malthus.KEY POINTS
2. You will need your notebook a packet from the welcome table.You will have 5 minutes from the bell to get them cut out and tabs folded
3. You will need your notebook and each of these from the welcome table.Please put your cell phone in the phone pouch.
4. The gradual change in a species over time.Evolution is…
5. Things to keep in mind…Populations, not individuals, evolve.It’s all about the genes!Occurs over a LONG period of time.
6. Evidences of EvolutionFossil RecordBiochemical - DNAComparative AnatomyBiogeographyObservable Events
7. How does evolution occur?Mechanisms of Evolution
8. A mechanism for change in a population.Natural Selection is…Survival of the FittestOrganisms with favorable genetic variation survive to reproduce and pass on their genesFitness: the ability of an individual to survive and reproduce in its specific environment. Fitness is a result of adaptations.
9. Requirements for Natural SelectionInherited Variation within the speciesProduction of more offspring than can surviveFinite (limited) supply of environmental resourcesCompetition for resources
10. Types of Natural SelectionStabilizingDirectionalDisruptive
11. Stabilizing Selection:When the average is favored over either of the extremes in a population.
12. Stabilizing Selection:
13. Directional Selection:This happens when one of the “extremes” is favored in an environment over the other extreme or the old average.
14. Directional Selection:
15. Disruptive Selection:This situation happens when either extreme is favored over the average.
16. Disruptive Selection:
17. Genetic Drift The alteration of allelic frequencies by chance events.
18. Genetic Drift
19. Bottleneck Effect An event that kills off a large number of members of a species randomly by chance therefore reducing the genetic diversity.
20. Bottleneck Effect
21. Founder Effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population.
22. Founder Effect
23. Founder Effect
24. Mutations Random genetic changes that occur in a populations DNA.
25. MutationsMost mutations either silent and do not affect the organism or are harmfulSome are advantageous
26. Mutations
27. Gene Flow The transfer of alleles from one population to another population through immigration or emigration of individuals.
28. Gene Flow
29. Gene Flow
30. Speciation: the evolution of a new speciesHow are new species made?
31. Speciation is always caused by isolationTypes of isolation:GeographicReproductiveHow are new species made?
32. Types of IsolationGeographic Isolation A single species can become two different species because they are isolated by mountains, rivers, canyons, etc.
33. Types of Isolation2. Reproductive IsolationAnimals in different areas of the country may develop different actions and behaviors.These different behaviors can cause groups to separate from each other and become different species.
34. Types of Isolation2. Reproductive Isolation Organisms may develop different mating seasons which do not correspond to one another
35. Individuals die, species go extinctExtinction
36. As the environment changes, organisms must have variations that allow them to survive (adapt) to those changes or dieIf an entire population of a species cannot adapt, that species becomes extinct.Extinction
37. There have been at least 5 MASS extinctions during Earth’s history where a huge % of the living species were destroyedAt least one of these has been attributed to meteor impact and its consequences.Mass Extinction
38. Mass Extinction