Ch 20: Evolution Flashcards
Species
A group of individuals that can exchange genetic material through interbreeding to produce fertile offspring.
Gene Pool
All the alleles present in all individuals in a population or species.
Population
All the individuals of a given species that live and reproduce in a particular place; one of several interbreeding groups of organisms of the same species living in the same geographical area.
Somatic Mutation
A mutation that occurs in somatic cells.
Germ-line Mutation
A mutation that occurs in eggs and sperm or in the cells that give rise to these reproductive cells and therefore is passed on to the next generation.
Neutral Mutation
Genetic changes that have no effect or negligible effects on the organism, or whose effects are not associated with differences in survival or reproduction.
Deleterious
Genetic changes that are harmful to an organism.
Advantageous
Genetic changes that improve their carriers’ chances of survival or reproduction.
Allele Frequency
The proportion of a specified allele among all the alleles of a gene in a population.
Fixed Population
In genetics, describes the situation in which all individuals in a population are homozygous for the same allele of a particular gene; the noun form is fixation. In metabolism, refers to the processes by which simple inorganic molecules are converted into biologically available forms, especially carbon fixation and nitrogen fixation.
Genotype Frequency
The proportion of a specified genotype among all the genotypes for a particular gene or set of genes in a population.
Hardy-Weinberg Equilibrium
A state in which allele and genotype frequencies do not change over time, implying the absence of evolutionary forces. It also specifies a mathematical relationship between allele frequencies and genotype frequencies.
Selection
The retention or elimination of mutations in a population of organisms.
Genetic Drift
A random change in the frequency of an allele due to the statistical effects of finite population size.
Non-random Mating
Mate selection biased by genotype or relatedness.
Fitness
A measure of the extent to which an individual’s genotype is represented in the next generation.
Modern Synthesis
The current theory of evolution, which combines Darwin’s theory of natural selection and Mendelian genetics.
Positive Selection
Natural selection that increases the frequency of a favorable allele.
Negative Selection
Natural selection that reduces the frequency of a deleterious allele.
Balancing Selection
Natural selection that acts to maintain two or more alleles of a given gene in a population.
Heterozygote Advantage
A form of balancing selection in which the heterozygote’s fitness is higher than that of either of the homozygotes, resulting in selection that ensures that both alleles remain in the population at intermediate frequencies.
Stabilizing Selection
A form of selection that selects against extremes and therefore maintains the status quo.
Directional Selection
A form of selection that results in a shift of the mean value of a trait in a population over time.
Artificial Selection
A form of directional selection similar to natural selection, but with selection done intentionally by humans, usually with a specific goal in mind, such as increased milk yield in cattle.
Disruptive Selection
A form of selection that operates in favor of extremes and against intermediate forms, selecting against the mean.
Sexual Selection
A form of selection that promotes traits that increase an individual’s access to reproductive opportunities.
Intrasexual Selection
A form of sexual selection involving interactions between individuals of one sex, as when members of one sex compete with one another for access to the other sex.
Intersexual Selection
A form of sexual selection involving interaction between males and females, as when females choose from among males.
Bottleneck Effect
An extreme, usually temporary, reduction in population size that may result in marked loss of genetic diversity and, in the process, genetic drift.
Founder Event
A type of genetic drift that occurs when only a few individuals establish a new population.
Migration
The movement of organisms from one place to another, including the movement of individuals from one population to another.
Gene Flow
The movement of alleles from one population to another through interbreeding between members of each population.
Inbreeding Depression
A reduction in fitness resulting from breeding among relatives causing homozygosity of deleterious recessive mutations.
Molecular Evolution
Evolution at the level of DNA, which in time results in the genetic divergence of populations.
Molecular Clock
The observation of rate constancy in molecular evolution. The extent of genetic divergence at a gene in two taxa is thus a reflection of the time since the taxa last shared a common ancestor.
Pseudogene
A gene that is no longer functional.
All the alleles present in all individuals in a species are referred to as the _____ of that species.
gene pool
Allele frequency can be measured using what technique?
DNA sequencing
What does the term 2pq represent in the Hardy-Weinberg equation?
the frequency of heterozygotes
How does gel electrophoresis allow researchers to observe genetic variation?
Gel electrophoresis enables scientists to distinguish allele variants of a gene.
T/F: Sexual reproduction of diploid individuals is one of the conditions of the Hardy-Weinberg equilibrium.
True
Genetic variation has two sources: mutation and:
recombination
When calculating the allele frequency of allele A in a population, you multiply the frequency of individuals who are homozygous for A by 2 because:
each individual who is homozygous for A has two copies of the allele.
A population in biology refers to a group of individuals in the same geographic area that:
are the same species.
A researcher is studying the color of grasshopper exoskeletons. Assume that this phenotype is caused by the action of two alleles. Green grasshoppers have the genotype AA and brown grasshoppers have the genotype aa. If the frequency of the A allele in this population is 0.2, what is the frequency of the a allele?
0.8
What is the fundamental concept that causes gel electrophoresis of proteins to work?
Different proteins have different charges and sizes.
T/F: Evolution typically occurs when all conditions of Hardy-Weinberg equilibrium are met.
False
As a population geneticist, you find a species of snails with more genetic diversity than humans. What does this mean?
There is more variation in the gene pool of snails than humans.
If there are 100 diploid individuals in a population and 20 are homozygous for B, 60 are heterozygous, and 20 are homozygous for b, what is the allele frequency of B?
50%
Why is Hardy-Weinberg such a valuable tool when examining populations?
It enables us to identify whether a population is evolving.
If a gene has two alleles, and allele A has a frequency of 83 percent, then allele a has a frequency of:
17%
