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Sophomore biology- Ecology and Population growth


the scientific study of interactions among organisms and between organisms and their environment or surroundings (ecosystems).


anywhere on Earth where life exists


a group of ecosystems that have the same climate and similar dominant communities


a collection of the organisms that life in a particular place and their nonliving environment


all of the different populations that live together in a defined area


group of individuals that belong to the same species and live in the same area


a group of organisms that are similar and can breed and produce fertile offspring


one single member of a species


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


eat only plants


eat only animals


eat both plants and animals


feed on dead plants and animals (detritus)


break down organic matter

Food chain

a series of steps in which organisms transfer energy by eating and being eaten

Food web

a diagram that links all the food chains in an ecosystem together to form a more realistic view of energy flow

Trophic level

each step in a food chain or food web

Ecological pyramid

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:

Energy pyramid

shows the relative amount of energy available at each trophic level.

Biomass pyramid

shows the total amount of living tissue within a given trophic level

Pyramid of numbers

shows the relative number of individual organisms at each trophic level

Biogeochemical cycles

how elements, chemical compounds, and water are passed from one organism to another and from one part of the biosphere to another


when liquid water absorbs energy and becomes a gas


when water falls from the sky as rain, snow, sleet, or hail


when water is given off through the stomata of plants' leaves as a byproduct of photosynthesis


when gaseous water vapor loses energy and becomes a liquid


when precipitation travels along the surface of the Earth until it reaches a body of water

Primary productivity

the rate at which organic matter is created by producers

Limiting nutrient

a single nutrient that either is scarce or cycles very slowly, limiting the growth of organisms in an ecosystem

Algal bloom

the sudden growth of algae in a body of water

Geographic distribution

the area inhabited by a population

Population density

the number of individuals per unit area

Growth rate

determined by the number of births, the number of deaths, and the number of individuals that enter or leave the population


the movement of individuals into an area


the movement of individuals out of an area

Exponential growth

the type of growth seen when a population grows at a constant rate; represented by a "J"-shaped curve

Logistic growth

when a population's growth slows or stops following a period of exponential growth; represented by an "S"-shaped curve

Carrying capacity

the largest number of individuals that a given environment can support

Limiting factor

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

Predator-pray relationship

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 study of human populations

Demographic transition

the change in a population from high birth and death rates to low birth and death rates

Age-structure diagrams

models that help demographers predict future growth of populations by showing the number of individuals in each age category


The process of using mathematical formulas to predict future events

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