1. Microevolution (Ch 23) and Macroevolution (Ch 24)

2. Gene Pools A gene pool is the sum of alleles within a population
A population is a localized group of organisms of the same species

3. Microevolution Macroevolution Changes occurring in a population
Adaptations result in evolution
Evolution above the species level
Origin of new taxonomic groups

4. Hardy-Weinberg Equilibrium
To assume Hardy-Weinberg equilibrium all of the following must be true:
The population must be very large (no sampling error/genetic drift)
There must be no mutation
There must be no natural selection
No migration between populations
Random mating

5. Hardy-Weinberg Equation
p=frequency of one allele (A); q=frequency of
the other allele(a);
p+q= p=1-q q=1-p
p2 =frequency of AA genotype; 2pq=frequency of Aa genotype; q2 =frequency of aa genotype
frequencies of all individuals must add to 1 (100%)
p2 + 2pq + q2 = 1

6. Hardy Weinberg Equilibrium
Population of cats
n=100
16 white and 84 black
bb = white
B_ = black
Can we figure out the allelic frequencies of individuals BB and Bb?

7. Using Hardy-Weinberg equation
population: 100 cats
84 black, 16 white
How many of each genotype?
q2 (bb): 16/100 = .16
q (b): √.16 = 0.4
p (B): = 0.6
p2=.36
2pq=.48
q2=.16 BB Bb bb

8. Hardy Weinberg Ex 1
If only 6% of the population displays pale eyes (recessive gene e), what is the frequency of genotype Ee in this population?
q2 = > q = 0.24
p + q = > p = 0.76
Ee = 2pq = 2(0.76)(0.24) = 0.36

9. Hardy Weinberg Ex 2
If the statistics for people who have PKU is 1 in 10,000, what percentage of the US population carries the gene but does not exhibit the disease?
q2 = > q = 0.01
p + q = > p = 0.99
2pq = 2(0.99)(0.01) = or 1.98%

10. Genetic Drift
Genetic drift is random fluctuation in allele frequency between generations.

11. A Genetic Bottleneck is a Form of Genetic Drift
In a genetic bottleneck, allele frequency is altered due to a population crash.
Once again, small bottlenecked populations = big effect.

12. Genetic Bottleneck – A Historical Case
A severe genetic bottleneck occurred in northern elephant seals.
Other animals known to be affected by genetic bottlenecks include the cheetah and both ancient and modern human populations.

13. Founder Effect- new habitat
The South Atlantic island of Tristan da Cunha was colonized by 15 Britons in 1814, one of them carrying an allele for retinitis pigmentosum. Among their 240 descendents living on the island today, 4 are blind by the disease and 9 others are carriers.

14. Gene Flow
genetic exchange due to the migration of fertile individuals or gametes between populations (reduces differences between populations)
seed & pollen distribution by wind & insect
migration of animals

15. Migration (Gene Flow)

16. Mutations Mutation creates variation
a change in an organism’s DNA (gametes; many generations); original source of genetic variation (raw material for natural selection)

17. Nonrandom Mating Inbreeding
assortive mating- choosing a mate with either similarities or differences (both shift frequencies of different genotypes)

18. Sexual selection
It’s FEMALE CHOICE, baby!

19. Natural Selection
differential success in reproduction;
climate change
food source availability
predators, parasites, diseases
toxins
only form of microevolution that adapts a population to its environment
provides “fitness” increase in the population

20. Genetic Variation
Polymorphism- 2 or more distinct forms (morphs) within a single population of organisms

21. Geographic Variation-cline
differences in genetic structure between populations

22. Mutation and Sexual Recombination
-random changes to DNA
errors in mitosis & meiosis
environmental damage
-Recombination
mixing of alleles
new combinations=
new phenotypes

23. Diploidy 2nd set of chromosomes hides variations in the heterozygote
Balanced polymorphism heterozygote advantage (hybrid vigor; i.e., malaria/sickle-cell anemia);

24. In reality there is little random mating
Inbreeding can occur within small or isolated populations
Mate selection- choosing a mate similar to one’s self.(Homogamy)

25. Sickle-Cell Prevalence
Selection by malaria exposure

26. Evolutionary Fitness
Contribution an individual makes to the gene pool for the next generation.
The alleles of this individual promotes the survival or reproductive success of others that share the same allele.

27. Modes of Selection
Stabilizing Selection- favors the middle and eliminates the extremes in a population
Directional Selection- natural selection or evolutionary changes in the population
Disruptive Selection- favors the two extremes creating polymorphism.

28. Modes of Selection

29. Two distinct forms in the sexes of some species
Sexual Dimorphism
Two distinct forms in the sexes of some species

30. Sexual Selection

31. Macroevolution: the origin of new taxonomic groups Chapter 24
Speciation: the origin of new species
1- Anagenesis (linear evolution): accumulation of heritable changes
2- Cladogenesis (branching evolution): budding of new species from a parent species that continues to exist (basis of biological diversity)

32. What is a species?
Biological species concept: a population whose members have the potential to interbreed and produce viable, fertile offspring

33. Other Species’ Concepts
Biological Species Concept
Reproductive Isolation
Not necessarily easy to apply
Morphological Species Concept
Phenotypic differences
Paleontological Species Concept
Fossil species
Ecological Species Concept
Filling of ecological niches
Phylogenetic Species Concept
Evolutionary lineages/genetic history

34. Reproductive Isolation (isolation of gene pools)
Pre-zygotic barriers: impede mating between species or hinder the fertilization of the ova
Habitat (snakes; water/terrestrial)
Behavioral (fireflies; mate signaling)
Temporal (salmon; seasonal mating)
Mechanical (flowers; pollination anatomy)
Gametic (frogs; egg coat receptors)

35. Reproductive Isolation
Post-zygotic barriers: fertilization occurs, but the hybrid zygote does not develop into a viable, fertile adult
Reduced hybrid viability (frogs; zygotes fail to develop or reach sexual maturity)
Reduced hybrid fertility (mule; horse x donkey; cannot backbreed)
Hybrid breakdown (cotton; 2nd generation hybrids are sterile)

36. Modes of speciation (based on how gene flow is interrupted)
Allopatric: populations segregated by a geographical barrier; adaptive radiation – diversification due to habitat change (Darwin’s finches)
Sympatric: reproductively isolated subpopulation in the midst of its parent population

37. Sympatric Speciation Polyploidy-more than 2 paired chromosomes
Allopolyploidy- infertile hybrid
Sexual selection- intraspecies competition

38. Tempo of speciation
Gradualism- species diverge more and more as they adapt
Punctuated Equilibrium- periods of apparent stability and then a sudden change

39. Evolutionary Novelties
Exaptation- structures becomes better adapted for another function- bird feathers originally kept the bird warm but later were better suited for flight
Heterochromy- change in the rate of evolution- foot development in salamanders
Paedomorphosis- retaining some juvenile characteristics

40. Analogies are products of convergent evolution