unit 5 bio

life history

includes the traits that affect the pattern of reproductive events and survival

trade-offs

inescapable compromises between traits, because they must perform different functions and are limited by available resources

r-selection

selection for traits that maximize reproductive success at low population densities

K-selection

selection for traits that maximize reproductive success at high population densities

density independent

factor that does not change with population density

density dependent

factors that increase or decrease as population changes

territoriality

defense of an area against other individuals – competition for space

allelopathy

the release of chemicals that inhibits growth of other plants

density dependent factors

regulate populations through negative feedback

fitness

measure of how many offspring an individual organism produces

evolution

a change in the genetic composition of a population from generation to generation

population

same species that are living together

genetic variation

the differences among individuals in their genes or DNA sequences

mutation

a change in the nucleotide sequence of an organism’s DNA

neutral variation

arises from mutations in non-coding regions or mutations that do not alter the protein

phenotype

the observable physical traits of an organism

allele

any version or form of a gene that may result in a difference in phenotype

genotype

the genetic makeup of an organism

heterozygote

individuals with two different alleles for a gene

homozygote

individuals with two identical alleles for a gene.

locus

a specific place in the genome.

gene pool

the combination of all copies of every type of allele at every locus in every individual in a population

hardy weinberg equilibrium

null model used to test whether a population is changing in genetic composition over time

homozygous genotypes

p2 and q2

heterozygous genotypes

2pq

genetic drift

when populations are small, random chance causes allele frequencies to fluctuate unpredictably from one generation to the next

gene flow

transfer of alleles into or out of a population through the movement of reproductive individuals or their gametes

selection

when individuals with different phenotypes (and underlying genotypes) have differential reproductive success (fitness), the allele frequencies within the population change

genotype frequencies

the proportion of individuals in a population that carry a specific genotype

inbreeding

when individuals mate with close relatives

assortative mating

the tendency to mate with individuals that have similar (positive) or opposite (negative) phenotypes

isolation by distance

a pattern that results when individuals tend to mate with others that are nearby.

allele frequencies

the relative proportion of a specific gene variant (allele) at a particular genetic locus in a population

founder effect

occurs when few individuals colonize a new area

population bottleneck

a sudden, drastic reduction in population size

adaptive evolution

in which traits that increase survival and reproductive success tend to increase in frequency

directional selection

occurs when phenotypes at one extreme are favored -the frequency curve shifts in one direction

disruptive selection

occurs when phenotypes at both extremes are favored over individuals with intermediate phenotypes. The frequency curve becomes bimodal (has two peaks)

stabilizing selection

occurs when intermediate phenotypes are favored over phenotypes at the extremes. The frequency curve narrows as variation in the population is reduced

sexual selection

occurs when individuals with certain inherited characteristics are more likely than others of the same sex to obtain mates

balancing selection

occurs when variation is preserved at a locus, maintaining two or more phenotypes in a population

frequency dependent selection

a form of balancing selection in which the fitness of a phenotype depends on its frequency in the population

heterozygote advantage

a form of balancing selection in which heterozygotes for a particular locus have greater fitness than both homozygotes

community ecology

examines how interactions between different species affect their distribution and abundance

community

includes populations of different species living in close enough proximity to interact with one another.

trophic structure

the feeding relationships between organisms in a community.

species diversity

variety of different organisms present

species richness

the number of different species in a community

relative abundance

the proportion of individuals in the community represented by each species

Shannon Diversity Index

calculate the diversity of a community based on both species richness and relative abundance

biomass

the total mass of all organisms in a habitat

introduced species

organisms that have been moved to new regions outside of their original range

primary producers

plants and other autotrophs

primary consumers

herbivores

secondary, tertiary, and quaternary

carnivores

food chain

linear sequence showing how energy and nutrients move from one organism to another in an ecosystem

food web

multiple food chains

bottom up model

lower trophic levels have influence on higher trophic levels

top down model

higher trophic levels influence lower trophic levels

foundation species

have large effects within their communities because of their high abundance and often large size. They often provide habitat or food for other species

keystone species

have large effects within their communities although they are not usually abundant; often they have important ecological roles that influence community structure

ecosystem engineers

influence their communities by changing the physical environment

pathogens

disease-causing organisms

zoonotic pathogens

transferred from other animals to humans

vector

intermediate species

species discovery curve

curve that shows that more sampling effort leads to higher detection

interspecific interactions

relationships between individuals of two or more species in the community

competition

individuals compete for resources

competitive exclusion

inferior competitor is eventually eliminated from the area because limited resources prevent them from coexisting

ecological niche

specific set of biotic and abiotic resources

resource partitioning

differentiation of their niches

character displacement

traits diverge in geographically overlapping populations of two species compared to populations of those species living in different areas

fundamental niche

the set of conditions that a species could potentially occupy.

realized niche

portion of the fundamental niche where it actually occurs

exploitation

+/- interaction in which individuals of one species benefit by feeding on individuals of another species

predation

predator killing and eating its prey

cryptic coloration

camouflage making them hard to see

warning coloration in animals with chemical defenses