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scientific study of interactions among organisms and between organisms and their environment
part of Earth in which life exists including land, water, and air or atmosphere
group of similar organisms that can breed and produce fertile offspring
group of individuals of the same species that live in the same area
assemblage of different populations that live together in a defined area
collection of all the organisms that live in a particular place, together with their nonliving environment
group of ecosystems that have the same climate and dominant communities
organism that can capture energy from sunlight or chemicals and use it to produce its own food from inorganic compounds; also called a producer
process by which plants and some other organisms use light energy to convert water and carbon dioxide into oxygen and high-energy carbohydrates such as sugars and starches
process by which some organisms, such as certain bacteria, use chemical energy to produce carbohydrates
organism that obtains energy from the foods it consumes; also called a consumer
organism that relies on other organisms for its energy and food supply; also called a heterotroph
organism that feeds on plant and animal remains and other dead matter
food chain
series of steps in an ecosystem in which organisms transfer energy by eating and being eaten
food web
network of complex interactions formed by the feeding relationships among the various organisms in an ecosystem
trophic level
step in a food chain or food web
ecological system
diagram that shows the relative amounts of energy or matter within each trophic level in a food chain or food web
total amount of living tissue within a given trophic level
biogeochemical cycle
process in which elements, chemical compounds, and other forms of matter are passed from one organism to another and from one part of the biosphere to another
loss of water from a plant through its leaves
chemical substance that an organism requires to live
nitrogen fixation
process of converting nitrogen gas into ammonia
conversion of nitrates into nitrogen gas
primary productivity
rate at which organic matter is created by producers in an ecosystem
limiting nutrient
single nutrient that either is scarce or cycles very slowly, limiting the growth of organisms in an ecosystem
algal bloom
an immediate increase in the amount of algae and other producers that results from a large input of a limiting nutrient
greenhouse effect
natural situation in which heat is retained in Earth's atmosphere by carbon dioxide, methane, water vapor, and other gases
biotic factor
biological influence on organisms within an ecosystem
abiotic factor
physical, or nonliving, factor that shapes an ecosystem
any necessity of life, such as water, nutrients, light, food, or space
competitive exclusion principle
ecological rule that states that no two species can occupy the same exact niche in the same habitat at the same time
relationship in which two species live closely together
ecological succession
gradual change in living communities that follows a disturbance
primary succession
succession that occurs on surfaces where no soil exists
pioneer species
first species to populate an area during primary succession
secondary succession
succession following a disturbance that destroys a community without destroying the soil
organism's capacity to grow or thrive when subjected to an unfavorable environmental factor
climate within a small area that differs significantly from the climate of the surrounding area
material formed from decaying leaves and other organic matter
biome in which the winters are cold but summers are mild enough to allow the ground to thaw
layer of permanently frozen subsoil in the tundra
population of algae and other small, photosynthetic organisms found near the surface of the ocean and forming part of plankton
tiny animals that form part of the plankton
ecosystem in which water either covers the soil or is present at or near the surface of the soil for at least part of the year
particles of organic material that provide food for organisms at the base of an estuary's food web
salt marsh
temperate-zone estuary dominated by salt-tolerant grasses above the low-tide line and by seagrasses under water
mangrove swamp
coastal wetland dominated by mangroves, salt-tolerant woody plants
photic zone
well-lit upper layer of the oceans
aphotic zone
permanently dark layer of the oceans below the photic zone
prominent horizontal banding of organisms that live in a particular habitat
coastal ocean
marine zone that extends from the low-tide mark to the end of the continental shelf
organisms that live attached to or near the ocean floor
population density
number of individuals per unit of area
movement of individuals into an area occupied by an existing population
movement of individuals out of an area
exponential growth
growth pattern in which the individuals in a population reproduce at a constant rate
logistic growth
growth pattern in which a population's growth rate slows or stops following a period of exponential growth
carrying capacity
largest number of individuals of a population that a given environment can support
limiting factor
factor that causes the growth of a population to decrease
density dependent limiting factor
limiting factor that depends on population size
predator prey relationship
mechanism of population control in which a population is regulated by predation
density independent limiting factor
limiting factor that affects all populations in similar ways, regardless of population size
scientific study of human populations
demographic transition
change in a population from high birth and death rates to low birth and death rates
age structure diagram
graph of the numbers of males and females within different age groups of a population
farming strategy in which large fields are planted with a single crop, year after year
green revolution
the development of highly productive crop strains and the use of modern agricultural techniques to increase yields of food crops
sustainable development
using natural resources at a rate that does not deplete them
soil erosion
wearing away of surface soil by water and wind
in areas with dry climates, a process caused by a combination of poor farming practices, overgrazing, and drought that turns productive land into desert
the raising of aquatic organisms for human consumption
acid culture
rain containing nitric and sulfuric acids
biological diversity; the sum total of the variety of organisms in the biosphere
ecosystem diversity
variety of habitats, living communities, and ecological processes in the living world
species diversity
number of different species in the biosphere
genetic diversity
sum total of all the different forms of genetic information carried by all organisms living on Earth today
habitat fragmentation
splitting of ecosystems into small fragments
biological magnification
increasing concentration of a harmful substance in organisms at higher trophic levels in a food chain or food web
invasive species
plants and animals that have migrated to places where they are not native
wise management of natural resources, including the preservation of habitats and wildlife
ozone layer
atmospheric layer in which ozone gas is relatively concentrated
global warming
increase in the average temperatures on Earth

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