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Midterm

BIOL 1001 Study Guide - Midterm Guide: Allopatric Speciation, Evolutionary Taxonomy, Sympatry


Department
Biology
Course Code
BIOL 1001
Professor
Tamara Kelly
Study Guide
Midterm

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D9. Differentiate between the different types of evolutionary mechanisms; the conditions
under which they occur; their effects on a population’s genetic structure (e.g., variation,
and mean character value); their relative effects on evolution; and factors that can impact
their effects. Given a scenario, determine the type(s) of mechanism(s) acting, and predict
the effects on the population, justifying your choices.
Gene Flow- important source of genetic variation and can change frequency of alleles
Mutation- Sources of new alleles: mutations- cannot account for big changes in allele
frequencies in one generation
b. Describe the impact of gene flow between two populations
Any movement of genes from one population to another. Gene flow includes lots of different
kinds of events, such as pollen being blown to a new destination or people moving to new
cities or countries. If genes are carried to a population where those genes previously did not
exist, gene flow can be a very important source of genetic variation
Reduces genetic variation as populations become more alike
Original Population: where people came from
Founder Population: people that are stranded and starting new population
New Population: descendants of founders
c. Relate and explain the effects of drift as a function of population size; relate these effects
to conservation biology.
Greater effects in smaller populations sizes due to sampling error
d. Compare founder and population bottleneck events (causes and outcomes).
1) Founder Effect: few individuals begin new population
2) The Bottleneck effect: Populations reduce in size because due to a random event where
surviving individuals do not represent random genetic sample of original population.
e. Compare genetic drift and natural selection in terms of: how they work; their potential
outcomes with respect to fitness, adaptation, and genetic variation; and random vs. non-
random processes.
Genetic drift: causes random changes in allele frequency and for a small isolated population
elimination of alleles by chance. It happens to ALL populations—there’s no avoiding chance.
Pseudogenes have reached to fixation and some codons that code for a particular amino acid
have reached fixation even though we can’t see the changes: genetic drift can effect large
populations given enough time
Comparison between Genetic Drift and Gene Flow: gene flow also allows some
populations to remain reasonably identical in the frequency of alleles and tends not to cause
speciation, gene flow requires populations to be in contact with each other and to be able to
move between these populations.

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D10. Compare inbreeding and sexual selection, and their potential effects on a population;
given a scenario, determine which is acting.
Inbreeding: reproduction from the mating of pairs who are closely related genetically,
meaning that they have a common ancestor therefore they share similar alleles
1) Increasing homozygosity, which can increase the chances of offspring being affected by
recessive deleterious traits 2) Does not cause evolution as it does not change a population as
a whole and does not change allele frequencies
Sexual Selection: acts on an organism's ability to obtain or successfully copulate with a mate
Often powerful enough to produce features that are harmful to the individual’s survival.
a. Describe the impact of inbreeding on a population’s genetic variation, phenotypes, and
heterozygosity; explain how non-random mating may not result in evolution.
Decreases heterozygosity
b. Explain how sexual selection has resulted in showy structures in males, commenting on
what this indicates about the males (relating to fitness tradeoff, handicap hypothesis,
honest signals etc.); provide examples of male traits/behaviours to explain it.
Handicap Hypothesis: reliable signaling between animals which have an obvious
motivation to bluff or deceive each other
Honest signals: reliable signals must be costly to the signaler, costing the signaler as a
fitness trade-off. Receivers know that the signal indicates quality because inferior quality
signalers cannot afford to produce such wastefully extravagant signals
Deceitful communication: get fooled by other males
c. Differentiate between inter- and intra-sexual selection; given a scenario, identify which is
acting, which sex will show the greater variation in reproductive success, the extent of
sexual dimorphism, justifying your answer.
Reproductive success: number of offspring

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Variation in reproductive success: some individuals have more offspring then others
Intersexual selection: male attract females- female choice driving evolution of male traits
Intrasexual selection: male-male competition and forming territories Greater variation in
reproductive success: males, comparing reproductive success of males to other males vs
females with other females
Greater Variation: females
Sexual Dimorphism: in humans: breasts, muscle mass, and height
d. Compare founder and population bottleneck events (causes and outcomes)
Outcome: same
Cause: F: move to new population B: original population wiped out
e. Compare genetic drift and natural selection in terms of: how they work; their potential
outcomes with respect to fitness, adaptation, and genetic variation; and random vs. non-
random processes.
Genetic Variation: NS: maintains GD: neutral, generally decreases
NS: non-random based on fitness
Genetic Drift: random
D10. Compare inbreeding and sexual selection, and their potential effects on a population;
given a scenario, determine which is acting.
Comparisons between Sexual Selection and inbreeding: both violate assumptions of HW
principle, but SS causes alleles to increase and decrease in frequency and results in evolution
and inbreeding does not
d. Describe the phenomena of assortative mating (positive and negative) and its potential
impact on a population.
Positive Assortative Mating: mate with individuals that share a particular phenotype
Impact: greater number of homozygous
Negative Assortative Mating: mate with individuals that do not share a particular phenotype
Impact: greater number of heterozygotes
DO NOT change specific allele frequencies
e. Explain the adaptive value of sexual cannibalism and self-sacrifice.
Male Redback spiders: get ready to be eaten as very few find a mate and it is an adaptive
trait to constrict organs to save time so that the spider can insert to sperms into the female
and produce more kids
Genetic marker: specific allele that causes a distinctive phenotype
Bateman-Trivers hypothesis: Pattern: sexual selection acts strongly on males Mechanism:
Eggs are expensive and sperm is cheap. Females fitness limited by ability to gain resources and
produce more eggs, males fitness limited by the number of females he can mate with.
Sexual dimorphism: any trait that differs between males and females
Monogamy: 1 male + 1 female
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