evolution and adaptation Flashcards
deoxyribonucleic acid
molecule composed of two strands of nucleotides wound together in a double helix
4 nucleotides
Adenine, Guanine, Thymine, and Cytosine
chromosomes
compact structure containing DNA wound around proteins
gene
sequence of DNA that codes for a particular protein (influences traits)
alleles
alternate forms of a particular gene
gene pool
all genes/alleles in a population
polygenic
influenced by multiple genes
pleiotropy
when a single gene affects multiple traits
epistasis
when the expression of one gene is controlled by another gene
heterozygous
when an individual has two different alleles at a gene
homozygous
when an individual has two identical alleles at a gene
codominant
when two alleles both contribute to a phenotype (pink flower)
dominant
an allele that masks the expression of the other allele of a given gene (red flower)
recessive
an allele whose expression is masked by the presence of another allele (white flower)
random assortment
the process of making haploid gametes in which the combination of alleles that are placed into a given gamete could be any of those possessed by the diploid parent
recombination
the reshuffling of genes that can occur as DNA is copied during meiosis and chromosomes exchange genetic material
mutation
a random change in the sequence of nucleotides in regions of DNA that either comprise a gene or control the expression of a gene
-can be silent with no detectable effects
-can affect appearance or physiology
-can be lethal
genetic drift
a process that occurs when genetic variation is lost because of random variation in mating, mortality, fecundity, and inheritance
bottleneck effects
a reduction of genetic diversity in a population due to a large reduction in population size
founder effect
when a small number of individuals leave a large population to colonize a new area and bring with them only a small amount of genetic variation
selection
the process by which certain phenotypes are favored to survive and reproduce over other phenotypes
stabilizing selection
when individuals with intermediate phenotypes have higher survival and reproductive success than those with extreme phenotypes
directional selection
when individuals with an extreme phenotype experience higher fitness than the average phenotype of the population
disruptive selection
when individuals with either extreme phenotype experience higher fitness than individuals with an intermediate phenotype
strength of selection
difference between the mean of the phenotypic distribution before selection and the mean after selection
-measured in units of standard deviation
heritability
the proportion of the total phenotypic variation that is caused by genetic variation
artificial selection
selection in which humans decide which individuals will breed and the breeding is done with a preconceived goal for the traits of the population
natural selection
individuals interact with their environment, and traits that lead to greater fitness in an environment are passed on
speciation
the evolution of new species
phylogenetic trees
hypothesized patterns of relatedness among different ground such as populations, species, or genera
-depict which groups evolved from other groups
allopatric speciation
geographic isolation leads to genetic isolation
divergence hypothesis
closely related species should be found on adjacent islands and sequence of branching events should correspond to island formation
sympatric speciation
reproductive isolation without geographic isolation
polyploidy
changes in chromosome numbers isolate populations genetically
-particularly relevant in plants
migration
movement of individuals between populations
gene flow
movement of alleles between populations via immigration/emigration
genotype
set of alleles that an individual bears
positive assortative mating
mating of like with like partners
-increases the proportion of homozygotes
negative assortative mating
mating with unlike partners
-increases the proportion of heterozygotes in a population
selfing
extreme inbreeding
-mating with oneself or an identical genotype
