Bio 1B MT2: Ecology

clumped dispersion

individuals are aggregated in patches

uniform dispersion

individuals are evenly spaced

random dispersion

position of each individual is independent of each other

territorial

defends space against encroachment by others

demography

study of birth/death/migration characteristics and how they change over time

life tables

summarize survival/reproductive rates of individuals in specific age groups within a population

cohort

group of individuals of the same age

Survivorship curves

plot of percent of cohort still alive at each age

type 1 survivorship curve

low death rates during early/middle life, increased death rate in old age. common in large mammals that produce few offspring but provide them with good care

type 2 survivorship curve

constant death rate over lifespan, ex. rodents, invertebrates, lizards, annual plants

type 3 survivorship curve

high mortality rate among young, later death rate declines. common among organisms that produce large amounts of offspring and provide little care, ex. long lived plants, fish, oysters

R = deltaN / deltaT = B - D

calculates rate of change of population size

dN / dT = rN

represents population growth as rate of change at each instant in time

exponential growth model

only works for ideal environment with unlimited resources

logistical growth model

accounts for the fact that as population increases, resource access decreases

carrying capacity (K)

max population size that a particular environment can sustain

r (K - N) / K

per capita growth rate

rN (K - N) / K

population growth rate

life history

traits that affect organism’s schedule of reproduction/survival

semelparity

individual reproduces once and makes many offspring

iteroparity

individual reproduces multiple times across lifespan

K-selection

selection for traits advantageous in high densities near capacity: nurturing young, etc

r-selection

maximizes intrinsic rate of increase (r ), occurs when density is well below capacity

density dependence

birth/death rate changes based on population density

density independence

birth/death rate does not change with population density

regulated population

1+ density dependent factors cause size to decrease when pop. is large, and size to increase when pop. is negative

resource competition

increasing population density leads to competition between population members for nutrients and toher resources, reducing reproduction rate

metapopulation

when local populations are linked

principle of allocation

individual organisms have a limited amount of resources to invest in functions/activities: there is a trade off

community structure

number of species in community, species that are present, and relative abundance

competitive exclusion

two species competing for the same limiting resource cannot coexist permanently in the same place and eventually the inferior competitor will be eliminated

aposematic coloration

warning bright colors on poisonous species

resource partitioning

differentiation of niches that enable similar species to coexist in a community

fundamental niche

nice potentially occupied by a species

realized niche

portion of fundamental niche actually occupied

character displacement

morphological characteristics diverge more in sympatric species versus allopatric species

cryptic coloration

camoflauge

batesian mimicry

“dishonest”, harmless species mimics appearance of harmful one

Mullerian mimicry

“honest”, 2+ harmful speceis resemble each other so predators learn to avoid them

endoparasites

live inside of hosts

ectoparasites

live outside of hosts

mutualism

(+/+) benefits individuals of both species

commensalism

(+/0) helps one species but is neutral to the other

trophic structure

feeding relationships between organisms

energetic hypothesis

length of food chain is limited by inefficiency of energy transfer along chain

foundation species

have strong effects on communities because of large size or high abundance

keystone species

exert strong control on community structure not by numerical might but by their pivotal ecological roles

ecosystem engineers

species that create / dramatically alter environment

bottom up control

abundance of organisms at each trophic level is limited by nutrient supply/food availability of lower trophic levels

top down

abundance of organisms at each trophic level controlled by abundance of consumers at higher levels. effects move down trophic structure as alternating (+/ -) effects

non equilibrium model

most communities arfe constantly changing after disturbance

climax community

stable equilibrium solely controlled by climate

disturbance

event that changes community by removing organisms or altering resource availability

intermediate disturbance hypothesis

moderate levels of disturbance foster greater species diversity than do high or low levels

small scale disturbances

can create patches of different habitats, maintaining diversity

species diversity

variety of different kinds of organisms in community

relative abundance

proportion that each species represents of all individuals in community

species richness

number of different spedcies in community

Shannon diversity index

-summation (pi ln(pi))

primary succession

process starts on lifeless area. 1st life forms: prokaryotes, protists. 1st macroscopic photosynthesizers: lichenss, mosses from windblown spores. Soil develops gradually and grasses/shrubs can grow

facilitation

when early arrivals in ecological succession make the environment more favorable for later species

secondary succession

recolonization of area after major disturbance removes most organisms in community

species-area curve

the larger the geographic area of community, the more species it has

Island equilibrium model

number of species on an island represents thte balance between immigration of new species and extinction of already present species

intraspecific competition

competition between individuals of the same species

interspecific competition

competition between individiauls of different species

indirect mutualism

if three species are herbivorized by the same herbivore and two of the plants are less palatable, the third plant is eaten more and the other two plants indirectly help each other

Lotka Voterra Predator prey model

negative density dependence enables coexistence, populations fluctuate with each other

spacial grain

characteristic scale where measurements are reported

spacial extent

overall region in which measurements are made at selected spacial grain

abundance

number of individuals

richness

total number of species

evenness

relative similarity in abundance of species

composition

identities of species that are present

alpha diversity

number of species in local site

beta diversity

difference between alpha and gamma diversity

gamma diversity

number of species across all sites

latitudinal diversity gradient

increases in species richness the closer you get to the equator

dispersal

movement of individuals/gametes away from original location

Hadley Cell

air circulation pattern where tropical air heats up, rises, moves away from equator, cools, and moves down

mountain precipitation

precipitation increases at high elevation on windward side of mountains

GPP

total amount of energy from light converted to chemical energy of organic molecules per unit time

NPP

GPP minus energy used by primary producers for cellular respriation

NEP (Net Ecosystem Production)

measure of biomass accumulation by producers and consumers

secondary production

amount of chemical energy in food that consumers convert to their own new biomass

Ecological efficiency

fraction of energy later available to other organisms as growth

assimilation fraction

fraction of energy used by organism for growth/respiration

sociometabolism

metabolism of humans accounting for bodily energy use and indirect consumption through appropriation of ecosystems and other energy sources

flux

rate of movement between compartments

Haber-Bosch process

method of producing nitrogen for fertilizer

Janzen/Connel effect

diseases that increase when hosts have high density population cause negative density dependence for hosts

dI/dt = bSI - mI

rate of infection

R0

bs / m

pyromes

fire dependent biomes

dispersal corridors

pathways that promote persistence of species metapopulation across multiple patches

portfolio effect

higher diversity communities perform better