the scientific study of interactions among organisms and between organisms and their environment or surroundings (ecosystems).
a collection of the organisms that life in a particular place and their nonliving environment
organisms that can capture energy from sunlight or chemicals and use that energy to produce food; also known as producers.
process used by most autotrophs; creates food and oxygen from sunlight, carbon dioxide and water.
process used by some autotrophs; creates food from carbon dioxide and inorganic molecules without light.
organisms that rely on other organisms for their energy and food supply; also known as consumers
a diagram that links all the food chains in an ecosystem together to form a more realistic view of energy flow
a diagram that shows the relative amounts of energy or matter contained within each trophic level in a food chain or web. Three main types of pyramids are:
how elements, chemical compounds, and water are passed from one organism to another and from one part of the biosphere to another
when water is given off through the stomata of plants' leaves as a byproduct of photosynthesis
a single nutrient that either is scarce or cycles very slowly, limiting the growth of organisms in an ecosystem
determined by the number of births, the number of deaths, and the number of individuals that enter or leave the population
the type of growth seen when a population grows at a constant rate; represented by a "J"-shaped curve
when a population's growth slows or stops following a period of exponential growth; represented by an "S"-shaped curve
a factor that causes population growth to decrease; ex. climate, predators, food availability, or humans.
Density-dependent limiting factor
limiting factors that effect a population only when the population density reaches a certain level and operate most strongly when a population is large.
occurs when two organisms attempt to use the same resource; can occur between organisms or between species
when one species eats another for food; one of the best forms of natural population control.
Density-independent limiting factors
limiting factors that affect all populations in similar ways, regardless of the population size.
the change in a population from high birth and death rates to low birth and death rates
models that help demographers predict future growth of populations by showing the number of individuals in each age category