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- 1The theory of genetic drift predicts two consequences of the founder effect. What are they and give an example of one of them.• Consequences of the founder effect are:
− Reduced genetic variation from the original population
− A non random sample of the genes in the original population
Example: − the Afrikaner population of Dutch settlers in South Africa is descended mainly from a few colonists. Today, the Afrikaner population has an unusually high frequency of the gene that causes Huntington's disease, because those original Dutch colonists just happened to carry that gene with unusually high frequency. This effect is easy to recognize in genetic diseases, but of course, the frequencies of all sorts of genes are affected by founder events. - 2What is population subdivision? How is it measured? Explain why population subdivision and inbreeding are similar.• Population subdivision: is smaller, isolated populations of a larger population.
• It can be measured using the Wrights Fixation Index
• It is similar to inbreeding because both lead to reductions in heterozygosity - 3Natural selection can maintain genetic variation within populations. Describe two ways this can occur.• Can cause microevolution (change in allele frequencies), with fitness-increasing alleles becoming more common in a population.
• Organisms with heritable (genetically determined) features that help them survive and reproduce in a particular environment tend to leave more offspring than their peers. - 4What is the difference between Parsimony and Maximum Likelihood methods of analysis?• Parsimony is based on the principle of parsimony, where the best tree is the one that requires the fewest evolutionary changes.
− Advantages: can be used to infer sequences from extinct species
− Disadvantages: can be fooled by Homoplasy.
• Maximum likelihood hypothesises a particular model of sequence evolution and then searches for the tree that maximises the probability of the observed sequences given the model
− Advantages: allows statistical inference
− Disadvantages: more time consuming - 5Natural selection can act to increase pre-zygotic isolation, but not post-zygotic isolation. Explain why.• Post zygotic isolation is only positively influenced by natural selection, since
• Individuals who mate with own species have advantage over those who mate with other species
• Natural selection cannot favour reductions in fitness - 6Island Model of Gene Flow. What is it?• Gene flow is the movement of genes between subpopulations within a species.
• Every population is exchanging migrants at a constant migration rate
• Stability is quite high
• Assumptions:
− Constant, equal N
− Equal contribution to pool of recruits
− Equal m
− No selection
− Equilibrium - 7Explain why sex has a 50% fitness disadvantage relative to asexual reproduction.• There are a number of reasons why sex might be disadvantageous. In species where males provide little or no resources to their offspring, females pay the full cost of reproduction yet only provide half of each sexually produced offspring's genes. In contrast, if a female were to produce an offspring asexually, she would transmit twice as many genes at the same energetic cost per offspring. This is the infamous ‘two-fold’ cost of sex. Such a cost does not exist if both parents contribute equal resources to the production of offspring; even in these cases, however, sex may be expensive because of the costs of searching for mates and the costs of engaging in mating, including an increased risk of predation or infection by a sexually transmitted disease.
- 8What is the nearly neutral theory?• Neutral: The neutral theory of molecular evolution holds that at the molecular level most evolutionary changes and most of the variation within and between species is not caused by natural selection but by genetic drift of mutant alleles that are neutral.
• Nearly Neutral: is a modification of the neutral theory of molecular evolution that accounts for the fact that not all mutations are either so deleterious such that they can be ignored, or else neutral. - 9Describe three species concepts and discuss their limitations• Biological
− Species are groups of interbreeding natural populations that are reproductively isolated from other such groups.
− Limitations: Does not apply to asexuals and fossils
• Ecological
− Set of species with shared ecological attributes
− Limitations: ecological and reproductive isolation is not always correlated
• Phenetic
− Set of individuals with shared morphological attributes
− Limitations: morphology and reproductive isolation is not always correlated - 10Discuss the importance of the G-Matrix• A table of the genetic variances and covariance’s between traits.
• Summarizes the inheritance of multiple, phenotypic traits - 11Types of Symmetry• Directional Asymmetry (DA)
− One side is larger than the other (e.g. human heart)
− Developmentally, one side develops on a different trajectory than the other
• Anti-asymmetry (AA)
− Left side is larger than the right, or right side is larger than the left
− E.g. major claw in fiddler crabs
− Developmentally, one side develops on a different trajectory than the other, but the side varies randomly
• Fluctuating Symmetry (FA)
− The differences between sides are randomly distributed around a mean of zero.
− E.g. most morphological traits
− Developmentally, both sides of the body develop on the same trajectories such that differences between sides are small and randomly distributed about perfect symmetry - 12What is frequency dependent selection?• Positive frequency dependent selection
− Fitness increases with the frequency of genotype
− Result: monomorphism
− Example: Mullerian Mimicry (both are palatable)
• Negative frequency dependent selection
− Fitness decreases with an increase in frequency of the genotype
− Result: possible polymorphism
− Example: Bateseian Mimicry (only one is palatable) - 13What is linkage disequilibrium?• Dependence of gene frequencies at two or more loci.
• Yes, there can be - 14Character State vs Distance• Character state uses actual sequence data whereases distance uses the measure of evolutionary distance between pairs of OTUs and the tree is based on those distances.
- 15What effects the effective population size- Unequal sex ratio
- Variation in population size
- Variation in family size
- Mitochondrial DNA
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- Flashcards on Untitled, created by Mitchell Hunter on 11/06/2018.
- Created by
- Mitchell Hunter · Jun 2018
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- Jun 11, 2018
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