Bio II: Exam 3

aka the FINAL

population density and population structure

• number of individual per unit of area or volume

• ex. number of nests, fecal deposit, tracks, mark-recapture

Clumped dispersal

Individuals are in patches

uniform dispersal

evenly spaced pattern of dispersion and direct interactions between individuals

Random dispersal

When each individual in a population is independent of other individuals

life history

traits that affect an organisi’s schedule of reproduction and survival

semelparity

• a one-shot pattern of reproduction

• all offspring are made in one reproductive event

• die after reproduction and common in invertebrates

• usually occurs in harsh environments

iteroparity

• reproduces several times throughout life

• low chance of survival for juveniles, hence the repeated reproductions

• can be seasonal or continuous

Stable population

when populations grow with many young individuals and decline with few evenly distributed

life tables

summarizes the survival and reproductive rates of individuals in specific age-groups within a population

cohort

group of individuals of the same age, from birth until all of the individuals are dead

survivorship curve

a plot of the proportion/numbers in a cohort still alive at each age

type I

• Common in humans and mammals

• few offspring

• high parental care

• die at old age due to sickness or predation

type II

• annual plants, rodents, lizards, birds

• survival probability does not change with age

• occasional parental care

type III

• high death rates for the young

• alot of offspring

• no parental care

• those that survive reach old age

exponential growth

• potential to expand greatly when resources are abundant

• population growth is constant

carrying capacity (K)

the maximum population size that a particular environment can sustain

logistic growth

the per capita rate of population growth while it approaches zero as the population size nears the carrying capacity (more realistic)

biological community

an assemblage of populations of various species living close enough for potential interaction

intraspecific interactions

relationships among individuals of a population

interspecific interactions

relationships between species in a community

competition

• (-/-) interaction

• different species compete for a resource in short supply

• can lead to competitive exclusion → local elimination of competition species

competitive exclusion principle

two species competing for the same limiting resource cannot exist in the same place (1 species per niche)

resource partitioning

differentiation of ecological niches, enabling similar species to coexist in a community

predation

• (+/-) interaction

• one species kills (predator) and eats the other (prey)

defensive adaptations

• mechanical defense, chemical defense, aposematic coloration (warning), cryptic coloration (camouflage)

• Batesian mimicry (harmless species mimics harmful one) and Mullerian mimicry (unpalatable species mimic each other)

herbivory

• (+/-) interaction

• eats part of plants or algae

• secondary compounds = chemical defenses

• mechanical defenses = often osmoregulated

symbiosis

• can be (+/+), (+/0), (+/-))

• a dependent relationship where two or more species live in direct and intimate contact with one another (long term)

ecological niche

total of a species’ use of biotic and abiotic resources

parasitism

• (+/-) interaction

• one organism, the parasite derives nourishment from the host who is harmed in the process

mutualism

• (+/+) interaction

• interspecific interaction that benefits both species

commensalism

• (+/0) interaction

• one species benefits and the other is apparently unaffected

species richness

total number of different species in the community

relative abundance

the proportion each species represents of the total individuals in the community (any dominant species?)

Shannon diversity index (H)

index of diversity based on species richness and relative abundance

• higher H = more diversity)

Trophic structure

the feeding relationships between organism in a community

bottom-up model

community organization has a unidirectional influence from lower to higher trophic levels

• primary producers → herbivores → predators

top-down model

proposes that control comes from the trophic levels above

• predators → herbivores → primary producers