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The scientific study of the interactions of organisms with their environment

Biotic Factors

all living things operating directly or indirectly to influence the lives of each other

Abiotic Factors

Non living, physical, and chemical conditions in an environment (winds, temperature, availability of water, solar energy, natural disturbances)


A group of individual organisms of the same species living in a particular area


The total amount of organisms that inhabit a particular area


A community that includes living communities and nonliving communities living together


All the parts of the planet that are inhabited by living things; sum of all earth's ecosystems


Specific environments in which organisms live (both biotic and abiotic factors included)

What are the levels of organization in the size of an ecosystem?

organism, population, community, ecosystem, biosphere

*Population Density

The number of individuals of a particular species within a population in a certain area


Pop density sampling technique-
1.mark off a particular area
2.count # of a particular species within this boundary
3.repeat the procedure in several locations
4.average results to estimate pop density

*Indirect counting

sampling technique for organisms that move around-count nests, burrows, or tracks rather than the organisms themselves


1.capture animals in area and mark them
2.animals are released
3.ecologists then capture them again(1 yr later) from the population and counts the marked and unmarked individuals in the 2nd sample

Limiting Factor

physical, chemical, and biological characteristics that restrict a populations growth (space, availability of food, disease)

Exponential Growth

The population multiplies by a constant factor at constant time intervals= every number of mins, population grows at the same time without stopping. Unrealistic. a pop. increases by a fixed percent (j-shaped curve)

Population Distribution

special arrangement of organisms in one area (clumped, close, spread apart from one another)(random, uniformed, clumped)

Logistic Growth

A rapid increase for a time, followed by stabilized growth when the population reaches the carrying capacity of the environment

Carrying Capacity

The number of organisms in a population that the environment can maintain with no net increase or decrease(s-shaped curve)

Density-Dependent Factor

A factor that limits a population more as population density increases (food availability, water, space, disease, predators)

Density-Independent Factor

A factor that limits populations but are unrelated to population density (extreme weather events, hurricanes, blizzards, ice storms, droughts)


Organisms that take in light energy from sunlight to make its own food and then produce chemical energy that serve as food for other organisms in an ecosystem (photosynthesis, base of food chain) PRODUCE energy


Organisms that make its own energy by eating producers or other consumers


Organisms that break down wastes and dead organisms in their environment (role important for constant recycling of chemicals)

Trophic Level

The feeding level in an ecosystem

Food Chain

The pathway of food from one trophic level to another


A consumer that only eats producers (horse)


A consumer that only eats other consumers (lion)


A consumer that eats consumers and producers (bear)

Primary Consumer

A consumer that feeds directly on producers (insects, antelope, deer, birds that eat seeds and fruit)

Secondary Consumer

Consumer that eat primary consumers (small mammals that eat insects)

Teritary Consumers

Consumers that eat secondary consumers (snake eating mouse)


The wastes and remains of dead organisms

Food Web

Combined food chains within ecosystems to create a pattern of feeding

Sampling Techniques

Quadrats, mark and recapture, indirect counting

Interspecific Competition

occurs between 2 species if they both require the same limited resource (food, space, mates)


Helpful for parasite but harmful for the host


When both species benefit from a relationship


When one organism benefits while the other is neither helped nor harmed

Competitive Exclusion

two species cannot coexist in a community if their niches are identical(if they do, they adapt different niches)

Symbiotic Relationship

A close interaction when one thing lives in or on another species


A unique living arrangement of an organism defined by its habitat, food sources, time of day its most active, and other factors

Energy Flow

not all sunlight is taken in by producers and other parts of the trophic level. they take in what they need and give back what they dont


water loss from the leaves of trees after it precipitates and is absorbed into the ground

*food chain

stepwise flow of energy and nutrients- to herbivores, carnivores, decomposers

*food web

network of interconnecting and branching food chains-more realistic structure of ecosystem


decomposers(animal scavenger, fungi, prokaryotes) *all decomposers=detritvores but not all detritvores=decomposers...decomposers break stuff down, detritvores break down waste

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