Ch22
What are the 4 types of data document the pattern of evolution?
1. Direct observations
2. Homology
3. Fossil records
4. Biogeography
What is balancing selection? What are the two types?
Balancing selection = maintaining genetic diversity in a population by preserving multiple alleles
2 types:
- Heterozygote advantage
- Frequency-dependent selection
What must be reduced and eventually eliminated for speciation to eventually occur?
Gene flow
Horse + donkey = mule is an example of which reproductive barrier?
Reduced hybrid fertility
Only homozygotes are present
There are unicorns living on an island in the Caribbean. Another island in the Caribbean have horses that look very similar to the unicorns. These two populations have nothing else in common other than their physical structures. What does this represent?
Analogous structures
What are transposable elements? Are they present in prokaryotes or eukaryotes? Who discovered them?
Transposons = DNA that can move within genome
Occurs in both prokaryotes and eukaryotes
Discovered by Barbara McClintock
Two populations are mating, and their reproductive barriers are weakening. After multiple generations, how many populations will there be?
BONUS (5pts): This is an example of what?
One population
BONUS: Fusion!
BONUS 2pts each if you could describe each!
Prezygotic: temporal, behavioral, mechanical, gametic, habitat isolation Postzygotic: hybrid reduced viability, hybrid reduced fertility, hybrid breakdown
The speciation model that states that "specials appear to have changed gradually over time" is _________?
Gradual model
BONUS 5pts: what's the other model?
T/F
1. Individuals and populations both evolve.
2. Natural selection produces new traits in a population, thus increasing genetic variation.
3. One of two Darwin's observation was: all organisms produce more offsprings than the environment can support, and many of these fail to survive and reproduce.
1. False! Only populations evolve.
2. False! Natural selection only acts on existing traits.
3. True.
Bonus 5pts: What's the other observation?
A population of 200 longhorn live on one side of the Mississippi river. There are 33 longhorns with spotted color, a recessive trait. How many cows are heterozygotes, assuming the cows are in Hardy-Weinberg Equilibrium?
96 heterozygous cows
q2 = 33/200 = 0.165
q = 0.406
p = 1 - 0.406 = 0.594
2pq = (0.594)(0.406) = 0.48
0.48 x 200 = 96
3 types of sympatric speciation?
polyploidy
sexual selection
habit differentiation
Describe the 3 speciation concepts that we discussed in class
Biological - breeding of individuals that could produce viable fertile offsprings
Ecological - defined by the organism's interactions with the environment
Morphological - defined by structural similarity
BONUS: what are 2 limitations of the biological concept? Which concept can we use instead to overcome this?
FREE POINTS!
YAY
Determine what evolutionary process is associated with each of the following scientists
- James Hutton
- Charles Lyell
- Georges Cuvier
- Jean Baptiste de Lamarck
- Charles Darwin
- James Hutton: Gradualism
- Charles Lyell: Uniformitarianism
- Georges Cuvier: Catastrophism
- Jean Baptiste de Lamarck: Use/disuse + inheritance of acquired characteristics
- Charles Darwin: natural selection/descent with modifications
Give an example for each of the two types of sexual selection
Intrasexual selection
Intersexual selection
What are supergenes? What is unique about them? What is the example we went over in class?
Supergenes = inverted part of chromosome; resists recombination and inherited intact
Ruff supergenes!
Name 5 conditions for Hardy Weinberg Equilibrium
no mutation
no gene flow (migration)
large population
random mating
no natural selection
What's the difference between adaptation vs. acclimation?
Individuals do not adapt, they acclimate!
Acclimation - changing phenotypes to improve survival (not heritable unless in germ cells)
Describe the mechanism of bacteria's antibiotic resistance. How does it relate to natural selection?
When treated with antibiotics, some bacteria has mutations within their genomes that allow them to survive. These bacteria then reproduce and pass on the antibiotic-resistant genes to their offsprings.
This relates to concept of natural selection, where organisms with higher "relative fitness" possess traits that allow them to better adapt to the environment are more likely to survive and reproduce.
Differentiate between genetic drift and gene flow. What is their effects on genetic variation?
Genetic drift = allele freq. fluctuate due to chance
- decreases genetic variation within populations
Gene flow = movement of alleles among population
- decreases genetic variation among populations
Describe fusion, stability, and reinforcement.
- Compare hybrids vs. parents
- Effect on reproductive barriers?
Reinforcement
- hybrids < parents --> strengthening reproductive barriers
Fusion
- hybrids > parents --> weakening reproductive barriers
Stability
- hybrids = parents --> no change in reproductive barriers
Name all HWE equations and determine whether it's referring to genotypic or allele frequency.
allele frequency: p + q = 1
genotypic frequency: p2 + 2pq + q2 = 1
Describe stabilizing vs. directional vs. disruptive selection. Give example for each
Stabilizing = favors intermediate variants
ex: birth weight in humans
Directional = favors one extreme of trait
ex: white-colored mice better survive in snow
Disruptive: favors both extremes of trait
ex: beak size in finches