ABIO 330 - Speciation and Selection Vocab

Descent with modification

offspring carry traits from their parents that may be in different combinations from each parent (mom's nose/hair, dad's eyes/build)

Directional Selection

Populations average phenotype shifts directionally toward an extreme based on environmental shifts/changes

Diversifying/disruptive Selection

Average trait no longer "best fit" and become less prevalent as two extremes both become more common

Stabilizing/purifiying seleciton

Average phenotype (already most common) becomes more prevalent and those on edges of curve disappear -- loss of phenotypes

Negative Frequency-Dependent Selection

a rare trait makes individual more attractive for mates, less interesting to predators, or better fit --- trait becomes more common in few generations

Positive Frequency-Dependent Selection

common traits are favored and become more common, while rare traits are selected against and tend to disappear.

Overdominance

heterozygotę has higher fitness

Underdominance

lower fitness in heterozygote than in either homozygote. favored gene depends on frequency of alleles in a population

Balanced Polymorphism

multiple alleles are maintained in a population because selection favors genetic diversity, often due to heterozygote advantage or varying selective pressures.

Antagonistic Pleiotropy

negative affect on one characteristic and a positive affect on another

Adaptation

heritable trait that serves a specific function and improves an organism's fitness or survival

Exaptation

trait that evolved for one function but is now used for another

Environmental unpredictability model

sexual reproduction is favored in unpredictable environments, not in predictable

Multiple niche model

sexual reproduction is favored when there are a large number of different available niches in environment, not only a few

Red Queen hypothesis

sexual reproduction is favored when parasite load is high, not low

Evolution

changes in allele frequencies in a population over time (driven by 5 processes)

Natural selection

process by which environmental conditions determine individuals best fit to survive and reproduce

Mate choice

selection based on an individual's ability to obtain a mate

Anisogamy

One species with gametes (egg and sperm) of drastically different sizes -typically a drastically larger number of sperm compared with number of eggs permating pair

Isogamy

One species with gametes (eggs and sperm) of very similar size and similarnumber - more equal contribution to offspring in terms of biomass.

Fundamental asymmetry of sex

unequal parental investment between males and females (typically females invest more)

Sexual dimorphism

any trait that differs between males and females of the same species

Intrasexual selection

males compete among themselves, female mates with winner; competition within the same sex for access to mates

Intersexual selection

males display specific traits, females mate with male with best display; selection on interaction between sexes

Post-copulatory sexual selection

Selection that occurs after mating, such as sperm competition or female choice of which sperm fertilizes eggs.

Handicap hypothesis

a male that can support a costly and unwieldy ornament is likely to be a vigorous individual whose overall genetic quality is high

Sexy son hypothesis

Females choose attractive males so their sons will inherit those traits and be more successful at attracting mates.

Morphological species concept

grouping by phenotypic/physical characteristics

Phylogenetic species concept

species defined as the smallest monophyletic group distinguished by a shared derived characteristic

Biological species concept

Groups that interbreed (or have the potential to interbreed) and produce viable, fertile offspring.

Prezygotic isolation

prevents successful mating or fertilization between different species.

Postzygotic isolation

the hybrid offspring do not survive or reproduce.

Vicariance

geographic barrier splits a population

Allopatric speciation

speciation due to geographic isolation

Sympatric speciation

speciation without geographic separation

Parapatric speciation

speciation between neighboring populations with limited interaction

Hybrid zone

region where interbreeding between diverging populations occurs and hybrid offspring are frequent

Secondary reinforcement

Stronger reproductive isolation due to low hybrid fitness