Evolution Final Concepts

BIOL 3013

Natural selection

Natural selection

difference in fitness of individuals leads causes some phenotypes (and thus their genes) to outcompete others

Descent with Modification

the passing of traits from parents to offspring

Mary Anning

British naturalist that discovered several species of extinct marine reptile

How mutations lead to evolutionary change

mutations provide the genetic variation; selection pressures can act on differences in phenotypes and subsequent differences in fitness allows for changes in allele frequencies, and thus evolution

Convergent evolution

the independent evolution of similar traits in separate lineages

Horizontal gene transfer

transfer of genetic material to another organism (other than parent to offspring)

Synapomorphy

derived form of a trait that is inherited from a common ancestor

Artificial selection

the selective breeding of animals and plants to encourage the occurrence of desirable traits

Zoonosis

transfer of disease between animals and humans

Viral reassortment

genetic material from different viral strains is mixed into new combinations within a single cell

Jean-Baptiste Lamarck

adaptation through inheritance of acquired changes; spontaneous generation; life evolved from simplicity to complexity

Charles Darwin and the Origin of Species

theory of evolution by natural selection

Homologous trait

similar trait that is inherited from a common ancestor

Analogous trait

serves the same function but differs in anatomy; evolved independently

Tetrapod evolution and divergence

evolved from lobe finned fish (load bearing limbs)

Phylogeny

visual representation of the evolutionary history of populations, genes, or species

Cladogram

shows relationships among species

Clade

represents an organism and all its descendants (a single branch in the tree of life)

Monophyletic

a common ancestor and all its descendants; forms a clade

Polyphyletic

a group that does not share an immediate common ancestor

Paraphyletic

a group that shares a common ancestor but doesn’t include all its descendants

Homoplasy

a character state similarity NOT due to shared descent

Meiosis generates genetic variation by

genetic recombination (crossing over) and independent assortment

Phenotypic plasticity

a single genotype produces multiple phenotypic possibilities in different environments

Post-mating (pre-zygotic) reproductive barrier

impedes gene flow after sperm has been transferred but before fertilization

Pre-mating (pre-zygotic) reproductive barrier

impedes gene flow before sperm can be transferred

Post-zygotic reproductive barrier

acts after a zygote is beginning to develop

Two-Fold Cost of Sex

disadvantages of being sexual (half the reproductive rate of asexual species)

Allopatric speciation

evolution of new species after populations have been separated geographically

Sympatric speciation

evolution of new species within a contiguous population with no physical barriers

Stabilizing selection

favors individuals in the middle of the distribution of phenotypes in a population

Directional selection

favors individuals on one end of the distribution of phenotypes in a population

Disruptive selection

favors individuals at the tails of the distribution of phenotypes in a population

Anisogamy

sexual reproduction involving the fusion of two dissimilar gametes

Ecological speciation

evolution of reproductive barriers between populations by adaptation to different environments or ecological niches

Red Queen Hypothesis

in a coevolving population each population must constantly adapt to the other to maintain relative fitness

Operational Sex Ratio

the ratio of male to female individuals who are available for reproducing at any given time.

Direct benefits

benefit that affects female directly (food, nest sites, protection)

Indirect benefits

benefit that affects genetic quality of female’s offspring

Antagonistic pleiotropy

a mutation with beneficial effects for one trait also causes detrimental effects on other traits

Nuptial gifts

nutritional gifts given by one partner during courtship and mating

Muller’s Ratchet

genomes of an asexual population accumulate deleterious mutations in an irreversible manner

Hardy-Weinberg

in the absence of drift, selection, migration, and mutation, allele frequencies will not change from one generation to the next

Bottleneck Effect

an event in which the number of individuals in a population is reduced drastically

Founder Effect

a small number of individuals leave a larger population and colonize a new habitat

Negative Frequency-Dependent Selection

occurs when rare genotypes have higher fitness than common genotypes; can maintain genetic variation within populations

Heterozygote Advantage

selection favors heterozygote individuals

Inbreeding depression

a reduction in the average fitness of inbred individuals relative to that of outbred individuals

Variance Components of a Quantitative Trait

additive genetic variance, dominance effects of alleles, epistatic interactions, environmental effects

Reaction norm

the pattern of phenotypic expression of a single genotype across a range of environments (often expressed in a graph)

Broad sense heritability (H^2)

proportion of the total phenotypic variance of a trait that is attributable to genetic variance, which is represented as a single value

Narrow sense heritability (h^2)

proportion of the total phenotypic variance of a trait attributable to the additive effects of alleles

Selection differential (S)

strength of phenotypic selection

Breeder’s Equation

R=h^2 x S evolutionary response equals the product of narrow sense heritability and selection differential

Ring species

a connected series of neighboring populations around a geographic barrier that can interbreed but the populations where the range meets around at the end of the barrier are reproductively isolated

Genetic linkage (or linked genes)

genes located near each other on a chromosome tend to be inherited together

Selective sweep

where strong selection can “sweep” a favorable allele to fixation within a population so fast that there is little opportunity for recombination

Preexisting sensory bias

biases in the female sensory system that existed prior to the evolution of the preferred trait

Sexual conflict

evolution of phenotypic characteristics that give a fitness benefit to one sex but a fitness cost to the other

Parental investment

may come at the expense of other reproductive options; females benefit from investing more bc they produce large nutrient filled eggs and certainty of maternity

Intersexual selection

sexual selection that occurs between two sexes (female choice)

Intrasexual selection

members of the same sex compete for mates (male-male competition)

Marie Curie

discovered radium; radioactive decay

Alfred Russel Wallace

father of biogeography; co-discovered theory of evolution