Chapter 15: VOCAB
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Adaptation: a particular structure, physical process or behavior that makes an organism better
able to survive and reproduce
Allele Frequency: how often certain alleles show up in a population; 5 factors cause a change in
allele frequency
o Gene flow
o Genetic Drift
o Mutation
o Natural selection
o Sexual selection/ non-random mating
o NONE OF THE ABOVE ARE FACTORED INTO THE H-W EQUILIBRIUM
Artificial Selection: selection by breeders of individuals with certain desirable traits
Directional Selection: phenotypes at one extreme of population distribution are favored
Disruptive Selection: phenotypes at both ends of a spectrum are favored, but not the ones in the
center; can create two new species at the extremes
Evolution: genetic change over time in biological populations
Evolutionary Theory: understanding and application of the mechanisms of evolutionary change to
solve biological problems
Evolve: change over time
Fecundity: average number of offspring produced by each female
Fitness: the contribution of a genotype or phenotype to the genetic composition of subsequent
generations, relative to the contribution of other genotypes or phentypes
Founder Effect: random changes in allele frequencies resulting from establishment of a population
by very small numbers of individuals; the only genes in the gene pool are the ones that were
introduced by the founders
Gene Duplication: the generation of extra copies of a gene in a genome over evolutionary time; a
mechanism by which genomes can acquire new functions
Gene Flow: genes from a different population introduce new alleles; ex: immigration, emigration;
greater in small population
Gene Pool: the genes available in a population; only way to change this is mutation or gene flow
Genetic Drift: allele frequency changes due to random chance; greater in small population; not
more fit, just mutated
Genetic Structure: the frequencies of different alleles at each locus and the frequencies of different
genotypes in a Mendelian population
Genotype Frequency: the proportion of a genotype among individuals in a population
Hardy-Weinburg equilibrium: no factors of evolution (hypothetical situation with no evolution);
frequency of allele in population remains constant from generation to generation; No sexual
selection/ mating is random; no mutations; large population size; no gene flow which would mess
with allele frequency; when numbers don’t line up, some evolutionary force is at work -> this
proves evolution
Homologous Features: traits shared by 2+ species inherited from a common ancestor
Homoplastic Features: results of convergent evolution
In-vitro evolution: based on natural molecular evolution that uses artificial selection in the
laboratory to rapidly produce molecules with novel enzymatic and binding functions
Lateral gene transfer: transfer of genes from one species to another; common among bacteria
Natural Selection: mechanism that produces change in a species based on differential survival and
reproduction of individuals based on variation in their traits.
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Neutral theory: a view of molecular evolution that postulates that most mutations do not affect the
aa being coded for, and that such mutations accumulate in a population at rates driven by genetic
drift and mutation rates
Non-synonomous substitution: a substitution of one nucleotide for another in a DNA sequence
that results in a different sequence than before; results change because of this substitution, there
is an effect!
Population bottleneck: a period during which only a few individuals of a normally large pop
survive
Population: a group of individuals of a species that can interbreed
Pseudogenes: A DNA segment that is homologous to a functional gene but is not expressed
because of changes to its sequence or changes to its location in the genome
Sexual selection: selection by one sex for characteristics in individuals of the opposite sex
Species: base unit on taxonomic classification, consisting of an ancestor/descendant group of
populations of evolutionarily closely related, similar organisms
Transposon (p232): Mobile DNA segment that can insert into a chromosome and cause genetic
change
Vestigial Features: features that apparently serve no function in an organism and are allegedly
holdovers from an evolutionary past.
QUESTIONS:
1. Fecundity is average number of offspring produced by each female. Longevity means long life.
Fecundity affects natural selection because the number of offspring that a female can have is
dependent on the amount of resources available and the time of gestation. Longevity determines
how long the lifespan is for the species and how long they have to reproduce.
2. Bullet 1: A population with a variety of phenotypes, like hair color, would not be evolution by
natural selection, but rather variety in the gene pool. Bullet 2: If a population is in an environment
where selective pressure is present, like competition for resources, then the population is bound
to adapt to better attain those limited resources. Therefore natural selection is occurring. Bullet 3:
If an individual is evolving, natural selection is occurring. Bullet 4: Individuals with advantageous
traits survive and reproduce better than others. This is an example of natural selection because
the advantageous traits are selected for and the non-advantageous traits are selected against.
3. A neutral mutation is one that doesn’t show any positive or negative effects. These build up
through genetic drift, which can eventually lead to speciation.
4. Gene flow is emigration and immigration, which introduced new genes into the gene pool. Genetic
drift is favoring of one extreme trait, which causes the spectrum of traits to shift. Small
populations have less genetic diversity and so changes in the spectrum are shown quickly and
dramatically over few generations.
5. Selfing is basically cloning of yourself, while sexual selection is choosing the optimal partner to
mate with. Selfing will have no change to the genome, unless mutations occur, while sexual
selection will produce genotypes that result in favorable phenotypes in the offspring.
6. NO Gene flow, Genetic Drift, Mutation, Natural selection, or Sexual selection/ non-random mating
will result in HW Equilibrium.
7. Stabilizing prefers the middle ground on a spectrum and the extremes are selected against.
Variation in the population decreases because there are fewer extremes. 200 years ago, babies had
a greatest chance of survival if their weight was right in the middle of the spectrum for birth
weight. Directional selection prefers one extreme over the other and variation will decrease unless
it is part of the favored extreme. During the industrial revolution, as pollution darkened the bark
on trees, the moths that camouflaged against the bark were selected for if they were dark in color.
In disruptive selection, both extremes are selected for and any variation in the middle of the
spectrum is selected against. Over time speciation will occur. If a population of finches has big
seed and little seeds as available food sources, disruptional selection will occur as the finches
pursue the separate resources.
8. You can tell if purifying/stabilizing selection is occurring because over time the species will have
genes closest to the median on the spectrum for that gene. Variation decreases.
9. Heterozygous advantage is when the heterozygous individuals are selected over the homozygous
recessive or dominant ones. Over time more heterozygous individuals will be present in a
population.
10. A gene family is a set of several similar genes formed by duplication of the original gene with
similar biochemical functions. The gene could mutate after it is duplicated but still be similar
enough to the original gene that it could be substituted in the genome.
11. Lateral gene transfer is transfer of genes from one species to another; it allows for genomes to
swap between separate species. This transfer is common in bacteria and archea and produced
antibiotic resistance. If one bacterium with antibiotic resistance releases its plasmids as it dies,
and another bacteria picks up those plasmids, the resistance can be transferred to the second
bacteria.
12. Studies of the origins, timing of emergence, and global diversity of many human pathogens (HIV
for example) depend on evolutionary principles and methods, as do efforts to develop effective
vaccines against these pathogens.