APBio Unit 8 Ecology

Population

a localized group of individuals of the same species that can interbreed, producing fertile offspring

Community

all the organisms that inhabit a particular area; as assemblage of populations of different species living close enough together for potential interaction

Ecosystem

all the organisms in a given area as well as the abiotic factors with which they interact

Biotic

pertaining to the living organisms in the environment

Abiotic

nonliving; referring to physical and chemical properties of an environment

Biosphere

the entire portion of earth inhabited by life; the sum of all the planet's ecosystems

Niche

the sum of a species' use of the biotic and abiotic resources in its environment

Clumped Distribution

individual aggregated patches, some organisms group together where food is abundant

Uniform Distribution

evenly spaced, some organisms maintain evenly distributed spacing to avoid aggressive interactions between neighbors

Random Distribution

unpredictable spacing, some plants grow in random groups if their seeds were windblown across an area

Population Ecology

the study of populations in relation to their environment, including environmental influences on populations, on population density and distribution, age structure, and variations in population size

Birth Rate

rate of annual birth within a population

Death Rate

rate of annual death within a population

Sex Ratio

ratio of females to males within a population

Age Structure

the relative number of individuals of each age in a population

Immigration Rate

the rate of influx of new individuals INTO a population from other areas

Emigration Rate

the rate of movement of individuals OUT of a population

Carrying Capacity

the maximum population size that can be supported by the available resources, (symbolized by K)

Density Dependent

any characteristic that varies according to an increase in population density

Exponential Growth

growth of a population in an ideal, unlimited environment, (represented by a J-Shaped curve when population size is plotted over time)

Logistical Growth

population growth that levels off as population size approaches carrying capacity

K-Selected

stabilize around carrying capacity, have fewer offspring later in life, mature later, live longer and invest more parental care

R-Selected

reside in unstable environment, have many offspring early in life, mature earlier, shorter life span, no parental care

Survivorship Curve

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

Type I Surivorship Curve

low death rates during early/middle life then increase among older age groups (humans)

Type II Surviorship Curve

constant death rate over the organism's life span

Type III Surviorship Curve

very high death rates for the young and then declines for those few individuals that survive the early period (insects)

Symbiosis

an ecological relationship between organisms of two different species that live together in direct and intimate contact

Commensalism

a symbiotic relationship in which one organism benefits but the other is neither helped nor harmed

Mutualism

a symbiotic relationship in which both participants benefit

Parasitism

a symbiotic relationship in which one organism (the parasite) benefits at the expense of another (the host) by living either within or on its host

Intraspecific Competition

interactions between the same species competing for resources

Interspecific Competition

competition for resources between individuals of two or more species when resources are in short supply

Predation

an interaction between species in which one species (the predator) eats the other (the prey)

Aposematic Coloration

the bright coloration of animals with effective physical or chemical defenses that acts as a warning to predators

Batesian Mimicry

a type of mimicry in which a harmless species look like a species that is poisonous or harmful to predators

Cryptic Coloration

camouflage that makes a potential prey difficult to spot against its background

Mullerian Mimicry

a mutual mimicry by two unpalatable species

Pioneer Species

the first species to colonize previously disrupted or damaged ecosystems, beginning a chain of ecological succession that ultimately leads to a more biodiverse steady-state ecosystem

Climax Community

in a community of organisms in a specific area where ecological succession has reached a steady state

Succession

the process by which the structure of a biological community evolves over time

Primary Succession

a type of ecological succession that occurs in an area where there were originally no organisms present and where soil has not yet formed

Secondary Succession

a type of succession that occurs where an existing community has been cleared by some disturbance that leaves the soil or substance intact

Herbivore

an animal that eats mainly plants or algae

Carnivore

an animal that mainly eats other animals

Detritivore

a consumer that derives its energy and nutrients from nonliving organic material such as corpses, fallen plant material, and the wastes of living organism (a decomposer)

Food Chain

the pathway along which food energy is transferred from trophic level to trophic level, beginning with producers

Food Web

the interconnected feeding relationships in an ecosystem

Trophic Levels

the positions organisms occupy in a food chain

Secondary Consumer

a carnivore that eats herbivores

Primary Consumer

a herbivore; an organism that eats plants or other autotrophs

Biogeochemical Cycles

any of the various chemical cycles, which involve both biotic and abiotic components of ecosystems

Carbon Cycle

forming the framework of organic molecules, photosynthesis & cellular respiration circulate this nutrient

Phosphorus Cycle

cycling of this nutrient through geologic processes such as erosion and sedimentation

Nitrogen Cycle

this nutrient is converted to compounds that can be assimilated by plants then returned in gas form to the atmosphere; all processes rely on bacteria

Nitrogen Fixation

the conversion of atmospheric nitrogen to ammonia

Water Cycle

this nutrient cycle involves evaporation from the earth & transpiration from plants and falls then by precipitation back down to the earth to begin the cycle again

Age Structure Diagrams

a visual representation of the relative number of individuals of each age in a population

Competitive Exclusion Principle

the concept that when populations of two similar species compete for the same limited resources, one population will use the resources more efficiently and have a reproductive advantage that will eventually lead to the elimination of the other population

Resource Partitioning

the division of environmental resources by coexisting species such that the niche of each species differs by one or more significant factors from the niches of all the coexisting species

Zero Population Growth (ZPG)

a period of stability in population size, when the per capita birth rate and death rate are equal

Gross Primary Productivity (GPP)

the total primary production of an ecosystem

Net Primary Productivity (NPP)

the gross primary production of an ecosystem minus the energy used by the producers for respiration

Keystone Species

a species that is not necessarily abundant in a community yet experts strong control on community structure by the nature of its ecological role or niche

Bottom-up Model

a model of community organization in which mineral nutrients influence community organization by controlling plant or phytoplankton numbers, which in turn control herbivores, which in turn control predator numbers

Top-down Model

a model of community organization in which predation influences community organization by controlling herbivore numbers, which in turn control plant or phytoplankton numbers, which in turn control nutrient levels; also called the trophic cascade model

Biological Magnification

a process in which retained substances become more concentrated at each high trophic level in a food chain

Decomposers

organisms that absorb nutrients from nonliving organic material such as corpses, fallen plant material, the wastes of living organisms and converts them into inorganic forms; a detritivore

Eutrophication

a process by which nutrients, particularly phosphorus and nitrogen, become highly concentrated in a body of water, leading to increased growth of organisms such as algae or cyanobacteria

Fundamental Niche

the niche potentially occupied by that species

Realized Niche

the portion of the fundamental niche that a species actually occupies in the environment

Invasive Species

a species often introduced by humans, that takes hold outside its native range

Altruism

behavior that increases fitness of another individual but decreases their own fitness

Kin selection

enhancing the reproductive success of one's relatives

Classical conditioning

association between neutral stimulus and natural response (ex: dogs salivating to sound of bell ringing)

Operant conditioning

trial and error learning; making associations between behavior and a reward or punishment

Communication

tactile, visual, auditory and chemical means of relaying messages to other members of ones species

Taxis

directed movement towards or away from a stimulus

Kinesis

movement in response to a stimulus that is not directional

Fixed Action Pattern

a sequence of unlearned actions that are unchangable and often carried to completion

Density dependent factor

factor that affects population based on size (disease, predation etc)

Density independent factor

factor that affect population regardless of size (weather, humans etc)

Species diversity

variety of organisms in a community

Species richness

the number of different species in a community

Relative abundance

evenness of distribution of individuals among species in a community