1. Chapter 15 – Mechanisms of Evolution
AP Biology
Chapter 15 – Mechanisms of Evolution

2. 15.1 Why is evolution the unifying principle in biology?
Things change all the time
These changes drive the origin of species
These changes drive the extinction of species
These changes drive the diversity of life
Evolution is change over time

3. 15.1 #2 What was the significance of Lamarck’s ideas?
His ideas led to the field of epigenetics – which is the study, in the field of genetics, of phenotypic trait variations that are caused by external or environmental factors that switch genes on and off and affect how cells read genes instead of being caused by changes in the DNA sequence

5. If Lamarck was right….

6. 15.1 What was the mechanism Lamarck proposed?
is the idea that an organism can pass on characteristics that it acquired during its lifetime to its offspring (also known as heritability of acquired characteristics)

7. 15.1 How does the present knowledge of molecular biology and genetics refute his mechanism?
Traits are passed down by genes and DNA, and changes in DNA (mutations) not by acquired characteristics

8. 15.1 Summarize Darwin’s theory of evolution by natural selection
Species change over time
Divergent (different) species share a common ancestor
What produces change in species is natural selection – the differential survival and reproduction of individuals in a population based on variation in their traits

10. 15.1 #6 What was the significance of Darwin’s theory of evolution by natural selection?
It provided the first, and only explanation of the existence of adaptations in nature.
It got proven and accepted after Mendel’s statistical analysis of genetic traits.

11. Bozeman Biology
Write down the evidence of evolution on your sticky note and add to notes.
Evidence of Evolution 10 minutes

12. 15.2

13. What affects the genetic makeup of populations over time?
Mutations – any change in DNA
Artificial Selection – selecting certain breeds for breeding on purpose
Natural Selection – survival and reproduction of the fittest
Gene Flow – Arrival and Leaving of species in a population
Genetic Drift – Change in genes due to random chance
Nonrandom Mating – Mating with preference

14. Natural Selection acts on individuals, but populations evolve
 The fittest organisms in a population are those that are strongest, healthiest, fastest, and/or largest. Natural selection is about survival of the very fittest individuals in a population. Natural selection produces organisms perfectly suited to their environments.
Individual organisms do not evolve, they retain the same genes throughout their life. When a populationis evolving, the ratio of different genetic types is changing -- each individual organism within apopulation does not change. ... Individuals are selected. Populations evolve.

15. 4. What is the difference between natural selection and adaptation?
Difference in fitness among organisms
Enhances the fitness of the organism
Like a trait

16. Raw material
Mutations

17. Populations evolve
Changes in the genetic makeup of organisms over time

18. 7. What is genetic drift? When is genetic drift especially potent in small populations?
Random changes in allele frequencies from one generation to the next
Small populations are affected the most because the random changes have a larger effect

19. 8. What is the net affect of a population bottleneck?
Loss of genetic variation

20. What are some potential causes of a population bottleneck?
Hunting
Habitat destruction
Disease

21. Founders Effect
Random changes in allele frequencies resulting from establishment of a population by a very small number of individuals.

22. Sexual Selection
Organisms phenotype influences its ability to attract males

23. 1. Fill out the chart Hardy Weinberg Equations P + Q =1
P2 + 2PQ + Q2 = 1
Required Conditions for HW Equilibruim
No net mutations
No natural selection
No gene flow
Large population size
Random Mating

24. 2. What is the significance of the HW equilibrium?
It allows us to see if evolution is occurring in a population

25. Summarize the effect of the following on allele frequencies
Mutations
If dominant mutation, p goes up; If recessive mutation, p goes down etc.
Gene Flow
Emmigration would lower p and q; Immigration would increase p and q
Genetic Drift
Random – p and q would change either way
Non-Random mating
Chosen traits (dominant or recessive) would go up
Natural Selection
Best fit traits for survival (dominant or recessive) would go up

26. 10.Define sexual selection
Preference by 1 sex for certain characteristics

27. 2 Bozeman Videos
Genetic Drift 12 minutes
Microevolution – 8 minutes

28. Bozeman Biology
Hardy Weinberg 12 minutes

29. 15.4 and 15.5
Ap Bio

30. Why do phenotypic variations in a population generally resemble a bell curve?
Because mutations occur and society stabilizes populations
Heavy babies sometimes don’t survive
The lower weight babies sometimes don’t survive

31. Type of Natural Selection
Effect and Example
Stabilizing Selection
Reduces variation (weight of babies is an example; height of humans is an example)
Directional Selection
One extreme is favored (giraffe neck length is an example)
Disruptive Selection
Both extremes are favored over mean (peppered moth is an example)

33. Bozeman Biology
Selection 12 min.

34. 15.5 Define fitness. How is fitness determined?
Contribution of a genotype or phenotype to the gene pool
It is determined by selection – the more “fit” you are, the more you are “selected” for and chosen for reproduction

35. Neutral Mutations Heterozygote Advantage Describe each.
Many mutations are never observed, because they are lethal and therefore those individuals are removed from the population; neutral mutations are not beneficial or detrimental so they have no effect on fitness.
Heterozygote Advantage
Because heterozygotes have both alleles, heterozygote advantage maintains both alleles, therefore maintaining genetic variation.