Chapter 21 Flashcards
A group of individuals that can exchange genetic material through interbreeding to produce fertile offspring.
Species
All the alleles present in all individuals in a population or species.
gene pool
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.
Population
A mutation that occurs in somatic cells.
Somatic 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.
germ-line 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.
neutral mutations
Genetic changes that are harmful to an organism.
deleterious mutations
Genetic changes that improve their carriers’ chances of survival or reproduction.
Advantageous mutations
Among all the alleles of a gene in a population, the proportion that are of a specified allele.
allele frequency
Describes a population that exhibits only one allele at a particular gene.
fixed
A state in which particular 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.
Hardy-Weinberg equilibrium
The retention or elimination of mutations in a population of organisms.
selection
A change in the frequency of an allele due to the random effects of finite population size.
genetic drift
Mate selection biased by genotype or relatedness.
non-random mating
The current theory of evolution, which combines Darwin’s theory of natural selection and Mendelian genetics.
Modern Synthesis
Natural selection that increases the frequency of a favorable allele.
Positive selection
Natural selection that reduces the frequency of a deleterious allele.
Negative Selection
Natural selection that acts to maintain two or more alleles of a given gene in a population.
Balancing selection
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.
Heterozygote advantage
A form of selection that selects against extremes and so maintains the status quo.
Stabilizing selection
A form of selection that selects against one of two extremes and leads over time to a change in a trait.
Directional Selection
A form of directional selection analogous to natural selection, but without the competitive element; successful genotypes are selected by the breeder, not by competition.
Artificial Selection
A form of selection that operates in favor of extremes and against intermediate forms, selecting against the mean.
Disruptive Selection
A form of selection that promotes traits that increase an individual’s access to reproductive opportunities.
Sexual 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.
Intrasexual Selection
A form of sexual selection involving interaction between males and females, as when females choose from among males.
Intersexual Selection
The movement of individuals from one population to another.
Migration
The movement of alleles from one population to another through interbreeding of some of their respective members.
Gene Flow
An extreme, usually temporary, reduction in population size that often results in marked genetic drift.
Bottleneck
A type of bottleneck that occurs when only a few individuals establish a new population.
Founder Event
A reduction in fitness resulting from breeding among relatives causing homozygosity of deleterious recessive mutations.
Inbreeding depression
Evolution at the level of DNA, which in time results in the genetic divergence of populations.
Molecular Evolution
Estimates of the time when different taxa diverged, based on the amount of genetic divergence between them.
Molecular Clock
A gene that is no longer functional.
Pseudogene
What is the definition of biological evolution and how does it differ from other definitions of evolution?
Changes in gene frequencies in populations and it is different because other definitions describe evolution as organisms changing over time
What is the relevance of mutation to the process of evolution?
It generates new variation
How does a gene pool relate to levels of variation?
Individuals represent different combinations of alleles.
Why are populations important for understanding evolution?
It answers detailed questions about patterns of variations. Small differences, given enough time, can lead to the major differences we see among organisms today.
How does generation time relate to discussions of evolution?
How the allele frequencies change from generation to generation according to the allele’s impact on the survival and reproduction of individuals
How does gene flow differ from genetic drift?
Gene flow is the process of alleles moving from one population to another and genetic drift is the changes in allele frequency in a gene pool
Can genetic drift have a stronger effect than natural selection?
Yes, because genetic drift in a population can lead to elimination of an allele from a population by chance where as natural selection is over time
How does natural selection operate? What is necessary for natural selection to occur?
It is adaptations to the surrounding environment. Reproduction, heredity, variation in fitness or organisms, variation in individual characters among members of the population
What is biological fitness?
A measure of the extent to which an individual’s genotype is represented in the next generation
How do you determine whether a given trait is adaptive? What does it mean to be adaptive?
b
How do you determine whether a given trait is (or has been in the past) influenced by evolution?
b
Are any mechanisms of evolution random? Are any adaptive? Are any goal oriented?
b
