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[start]
[q] UNIT 7
[a] Natural Selection
[q] What is evolution?
[a] change in allele frequencies in a population over time
[q] What is a population?
[a] One species living together
[q] What are the five microevolutionary forces?
[a] 1. Mutation
2. Natural selection
3. Sexual selection
4. Gene flow
5. Genetic drift
[q] What observations did Darwin make about the Galapagos?
[a]
1. Overproduction: more babies than the environment can support
2. Limited resources: habitat, food, and mates are not infinit
3. Variation: no two individuals are the same
4. Conclusion: individuals best suited for the environment live longer and have more babies
[q] What is fitness?
[a] ability to survive and reproduce to pass genes on
[q] What is artificial selection?
[a] Selective breeding by humans
Ex: Strawberries have been selectively bred to be really big
[q] What is convergent evolution?
[a] Similar environments lead to similar phenotypes.
Ex: dolphins look like sharks, not closely related though
[q] What is sexual selection?
[a] Sexiest animals have the most babies
Ex: in humans, breast size, hip size, head size, and smell can all be indicators on if someone would be better to have kids with
[q] What is genetic drift?
[a]
When random events drive evolution.
This is more common in small populations because an individual in a small population dying has a greater effect than an individual dying in a large species
[q] What is the bottleneck effect?
[a] When a large population mostly dies off
this leads to leads diversity, which makes the population less likely to adapt to changes well.
[q] What is the founder effect?
[a] When a small part of a population is found in a new area like an island
This leads to less diversity in the new population
[q] How does migration and gene flow drive evolution
[a] 1. If two populations of the same species are separated by mountains, rivers, etc. they will evolve differently
2. If a species from one of these populations migrates to the other population, diversity will increase
[q] What happens with increased variation vs. decreased variation?
[a]
1. Decreased variation: the population will be worse at adapting and extinction is more likely
2. Increased variation: better at adapting so extinction is less likely
[q] What are the characteristics of a non evolving population?
[a] 1. No mutations
2. No migration
3. No natural selection
4. Random mating (no sexual selection)
5. Large population (no genetic drift)
[q] How is a non evolving population described?
[a] The population is at Hardy Weinberg Equilibrium
[q] What are the Hardy Weinberg equations for predicting allele frequencies in a non evolving population?
[a]
p^2 + 2pq + p^2 = 1
p + q = 1
p = A, q = a, p^2 = AA, q^2 = aa, pq = Aa
So, if you are given that the frequency of a recessive trait is .16, sub .16 in for q^2 because that would be aa
[q] What evidence suggests that eukaryotes have common ancestry?
[a]
1. They all have genes containing introns
2. They all have linear chromosomes
3. they all have membrane bound organelles
[q] What is phylogeny?
[a] Evolutionary relationships among organisms
[q] How is a phylogenetic tree interpreted?
[a] if you have a more recent common ancestor, you are more related.
An easy example of this is that you are more related to your sister than your cousin
[q] What is a sister group on a phylogenetic tree?
[a] Two species with the most recent common ancestor
[q] What is the out group on a phylogenetic tree?
[a] The most distant relative on the tree
[q] What conditions can indicate that organisms are different species?
[a]
1. Reproductive isolation: Can’t reproduce together
2. Geographic: won’t live together
3. Physiological: different cellular mechanisms
4. Behavioral: don’t recognize each other (will not mate)
5. Genetic: chromosome differences
[q] What ultimately determines if organisms are the same species?
[a] If they can breed in nature and produce fertile offspring
appearance doesn’t matter!
[q] What are the two ways a species can diverge?
[a]
1. Punctuated equilibrium: rapid speciation, usually after mass extinction
2. Gradualism: a species gradually diverges from two groups accumulating differences
[q] What is divergent evolution?
[a] Two groups from a common ancestor accumulate differences
Ex: dolphins and tigers have a more recent common ancestor than dolphins and sharks. Tigers have just accumulated many differences
[q] What is a mass extinction and why do they happen?
[a]
1. Definition: at least half of everything dies in a short period of time
2. Happens because of Environmental changes
[q] What are two theories about the origin of life?
[a] 1. Organic material came from a meteor
2. Primitive earth had free energy and no O2, allowing life to form
[q] What evidence is there that life formed on its own?
[a] Humans have been able to make biological molecules such as carbohydrates and DNA by simulating primitive earth. However, no onw has every made a cell.
[q] What is the RNA world hypothesis?
[a] RNA came first
life on earth began with a simple RNA molecule that could copy itself
[q] What are the classifications of organisms? What are humans in each of these classifications?
[a] 1. Kingdom: Animalia
2. phylum: chordata
3. class: mammalia
4. Order: primate
5. family: hominidae
6. genus: homo
7. species: sapiens
[q] directional selection
[a] one of the extremes are favored
[q] disruptive selection
[a] both of the extremes are favored
[q] stabilizing selection
[a] the majority is favored
[q] heterozygote advantage
[a] since you have both alleles, you can pass on the favorable one to your offspring so they will be successful
[q] sexual selection
[a] natural selection arising through preference by one sex for certain characteristics in individuals of the other sex
[q] genetic flow
[a] transfer of alleles or genes from one population to another, migration and emigration can causes this
[q] genetic drift
[a] A change in the allele frequency of a population as a result of chance events rather than natural selection.
[q] bottleneck effect
[a] some type of catastrophe wipes out a large segment of a population and survivors are not a representation of the original population
[q] mutations
[a] create new alleles, advantageous alleles will increase over generations
[q] cline
[a] there are different environments and the same species looks different because of it ex. black bears
[q] deme
[a] small, localized population
[q] divergent evolution
[a] one species goes 2 different way and becomes 2 different species, usually due to environment changes
[q] convergent evolution
[a] Process by which unrelated organisms independently evolve similarities when adapting to similar environments
[q] parallel evolution
[a] Two related species that have made similar evolutionary adaptations after their divergence from a common ancestor
[q] Habitat (geographic) isolation
[a] A type of reproductive isolation due to separation by an impassable geographic barrier such as a mountain range, body of water, etc.
[q] behavioral isolation
[a] Form of reproductive isolation in which two populations have differences in courtship rituals or other types of behavior that prevent them from interbreeding
[q] temporal isolation
[a] form of reproductive isolation in which two populations reproduce at different times
[q] mechanical isolation
[a] reproductive parts do not fit
[q] gametic isolation
[a] A prezygotic (pre zygote) reproductive barrier where the sperm of one species may not be able to fertilize the eggs of another species
[q] sterile offspring
[a] reduced hybrid fertility (offspring cannot reproduce- postzygotic) i.e. mule
[q] hybrid inviability
[a] offspring dies during development (postzygotic)
[q] hybrid breakdown
[a] Some first-generation hybrids are fertile, but when they mate with another species or with either parent species, offspring of the next generation are feeble or sterile
[q] Hardy-Weinberg equilibrium
[a] condition in which a population’s allele frequencies for a given trait do not change from generation to generation
[q] descent with modification
[a] principle that each living species has descended, with changes, from other species over time
[q] phylogenetic tree (cladogram)
[a] a diagram that depicts the ancestral relationships between organisms
[q] explain differential reproductive success as it relates to the struggle for existence
[a] more successful you are at reproducing, the more you will pass on your genes and your offspring will be fit
[q] Natural selection
[a] A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.
[q] explain what the statement “natural selection depends on time and place” means
[a] what traits are passed on depends on the environment and it takes generations for natural selection to take effect
[q] homologous structures
[a] Structures in different species that are similar because of common ancestry. Same structure, different function
[q] Analogous structures (convergent evolution)
[a] various structures in different species having the same function but have evolved separately, thus do not share common ancestor
[q] how are the founder effect and the bottleneck effect the same, yet different
[a] the founder effect and the bottleneck effect are the same because the number of organism within a population changes and the frequency of a population changes but they are different because the founder effect happens when emigration or immigration occur and the bottleneck effect happens when a catastrophe wipes out a segment of a population
[q] what 4 conditions must be met for a population to be in Hardy-Weinberg genetic equilibrium
[a] 1. no mutations
2. large population
3. random mating (no sexual selection)
4. no immigration or emigration
[q] how can gene flow affect genetic equilibrium in a population
[a] if more organisms come or more leave, then there can be more organisms or less organisms and can change the frequency of alleles and effect equilibrium
[q] how can cline lead to speciation
[a] a cline is when a species looks different because they live in different environments and this can lead to speciation because a new species can be created
[q] what were Lamarck’s 2 methods that organisms changed over time and was he correct
[a] 1. use and dis-use of characteristics (go away)
2. acquired characteristics
he was not correct because characteristics do not go away unless they are harmful and if an organism acquires a characteristics during its lifetime it will not pass it to its offspring
[q] how does the term differential reproductive success relate to natural selection
[a] if you are more successful at reproducing then natural selection will be successful and the offspring will be fit
[q] describe how selection pressures can change allelic frequencies
[a] if there is a catastrophe and you are only able to mate with an organism with certain genes, then the allelic frequencies will change because then there will be more of one gene and less of another
[q] can an individual organism adapt to its environment
[a] no because if an organism is not born with the genes then it can not make a gene in order to survive, only a population can adapt because mutations can occur and then will pass that gene along and then adaption will occur
[q] why do vestigial structures disappear over time
[a] because organisms that have that harmful structure will not mate and the structure will be lost
[q] what are 4 types of evidence that can be used to determine common ancestry
[a] 1. structural evidence (homolgous and analogous) structures
2. molecular evidence (DNA sequencing, amino acid sequencing, and RNA types)
best way to determine common ancestry
3. embryological evidence
[q] using darwins terms be able to explain the adaptive radiation of the finches and how they filled different niches
[a] overproduction could have occurred and there was an abundance of food and the finches filled that niche
[q] anagenesis
[a] perfect species
[q] cladogenesis
[a] creates new species
[q] allopatric speciation
[a] new species is created due to geographic barriers
[q] sympatric speciatin
[a] new species is created within the orginial population
[q] how can frequencies change over time
[a] 1. mutations
2. bottleneck effect
3. genetic drift
4. founder effect
5. genetic recombination
[q] genetic recombination
[a] sexual selection (mate choice and handicapping principle)
[q] name 4 things that cladograms show
[a] 1. number of shared characteristics
2. all these species are alive today
3. how closely organisms are related to each other
4. when characteristics came about
[q] how did Darwin explain the diversity of like on the Galapagos
[a] 1. overproduction
2. variation (Darwin could not explain)
3. speciation
4. heritability
5.adaptation
6. competition
differential reproductive success
[q] what did darwin notice about the animals on the south american continent
[a] -they looked like they should in the environment that they live in
-they looked different than european animals, but some looked similar
[q] what did darwin notice about the organisms on the Galapagos
[a] -some were similar to mainland organisms
-organisms were different on different islands
[q] natural selection acts on ___________, not ____________
[a] populations not individuals
[q] natural selection acts on ______________ frequencies
[a] gene
[q] Hardy-Weinberg equation
[a] p^2 + 2pq + q^2 = 1
[q] Vistigual Structures
[a] A structure that is no longer needed (i.e. hipbones in whales, wisdom teeth in humans, goosebumps in humans)
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