Evolution and Population Genetics
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What is comparative anatomy?
study of the evolution of the complex morphological systems possessed by vertebrates.
what are homologous structures?
morphologically similar structure with a common evolutionary origin that perform different functions.
similar structure/ common ancestor - diff function
ex) mammals display sim. kinds of forelimbs b/c share common ancestry, forelimbs of mammals are not identical b/c they have evolved to perform diff. fxns.
What are analogous structures?
body parts that resemble on another in diff. species because they have evolved independently as adaptations to similar environmental pressures, not because they have evolved from a common ancestor.
- diff species (no common ancestor) - same function
- Ex) wings of birds, bats, and insects are clearly diff. in design but because they serve the same function, they are analogous structures.
True or False. All vertebrate embryos follow a common developmental path due to their common ancestry.
True. They all have a set of very similar genes (homeobox genes) that define their basic body plan. As they grow, the differences that will distinguish the embryos as adults become more and more apparent. The study of this development can yield insight into the process of evolution.
True or False. Comparative biochemistry also reveals similarities btwn. organisms of different species.
True. For example, the metabolism of vastly diff. organisms is based on the same complex biochemical compounds. Another ex - genetic code.
what are vestigial structures? Give example.
structures in organisms that serve no useful function. Humans tailbone at the end of the spine.
How can vestigial organs or structures be viewed as evidence for evolution?
organisms have vestigial structures probably share a common ancestry w/ organisms in which the homologous structure is functional.
Do geographical barriers cause individuals in a population to evolve specific adaptations?
Yes, in general biogeographic distribution of species supports evolution. - species are distributed around the globe largely in relation to their relationship to one another w/ some understood exceptions
What are the two main theories of evolution that you should know?
Lamarckian evolution and darwinian evolution
What is Lamarckian Theory of Evolution: Use and Disuse?
This theory implies that organs of the body used extensively to cope with the environment become larger and stronger, while those organs not used deteriorate.
What is the Lamarckian Theory of Evolution: Acquired Characteristics
The modification an organism acquires during its lifetime can be passed along to its offspring. (ex: giraffes stretched their necks to reach for leaves on higher branches. The offspring were believed to inherit the valuable trait of longer necks b/c of parents use of necks)
however, modern genetics have disproved this theory. Studies have shown that if you cut off a mouse's tail, its offspring still have tails!
What is Darwin's Theory of Evolution, 3 concepts?
- involves the concepts of:
- survival of the fittest, adaptations and natural selection.
Certain organisms are better adapted to their environments and are "selected" to survive in greater numbers than less fit organisms. These well-adapted organisms reproduce and multiply, transmitting favorable variations to their offspring.
What are the 5 key points to Darwin's Theory of Evolution?
- 1. individuals from any given population vary from one another in many characteristics (due to mututations).
- 2. Genetic variations can be inherited.
- 3. Members of a population produce more offspring than the environment can support causes competition.
- 4. Those indiv. whose inherited characteristics fit them best to their environment are like to leave more offspring than less fit individuals.
- 5. Over many generations, natural selection, the favorable changes (adaptations) are perpetuated in the species. Accumulation of favorable changes eventually results in speciation.
what is convergent evolution?
is the independent development of similar structure in different species due similar ecological roles and selection pressures. These similarities are analogous.
diff species - similar structures
what is divergent evolution?
two or more related species becoming more and more dissimilar. It is the emergence of diff. species from an ancestral species. Two species have similar structures b/c they evolved from common ancestor. These similarities are homologous.
common ancestor species - similar structures become more and more different
What is genetic drift?
it results from what is known as sampling error. It is the change in the gene pool due to CHANCE!
How does the population size affect the effects of genetic drift?
The smaller the population, the greater the effect of small changes in allele frequency or of mutations on the gene pool of the next generation. In larger populations, the effects of a mutation in a certain allele may be drowned out by the fact that there are so many of the normal allele in the new population that the overall frequency of the allele does not change.
What is the founder effect?
is a form of genetic drift in which a small subset of a population becomes genetically isolated from the original population. "new island"
- - this occurs when a sm. grp. of indiv. colonizes a island or new isolated habitat, or become isolated from their pop.
- -group reps. sm. portion of alleles that existed in parent pop. so next gens. will be formed from only this subset of genes and the isolated "founder" population can diverge quite rapidly from the original one.
- -any mutations in this sm. subset of alleles and in this sm. group are likely to be disproportionally rep. in subsequent gens.
When observing a certain populations, its impt. to keep in mind that the environmental pressures constantly affect the gene pool of the group. what must we assume when examining the gene pool of a population? This assumption is the basis of what?
that the group is in a certain state of equilibrium.; Hardy-Weinburg principle
In order for a group to be in a certain state of equilibrium, what five assumptions must we make? Are these assumptions true, why or why not?
- 1 Random mating
- 2 No natural selection
- 3 No migration or emigration
- 4 Large population
- 5 No mutations
may not be entirely true for every pop. we study, the concept of equilibrium suggests that some of these factors will offset one another.
What can the Hardy-Weinburg equation be used to predict?
genotype and phenotype frequencies w/i the population of interest.
what are the two equations used to describe the genotype and phenotype frequencies of a particular population that is assumed to be under a Hardy-Weinberg equilibrium state? what does each variable stand for?
- p + q = 1
- p^2 + 2pq + q^2 = 1
- p= the frequency of the dominant allele
- q= the frequency of the recessive allele
- p^2= the frequency of homozygous dominant individuals
- 2pq= the frequency of heterozygous individuals
- q^2= the frequency of homozygous recessive individuals
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