Ch. 5 Ecology


the study of the ways organisms interact with each other and with their nonliving surroundings


everything that affects an organism during its lifetime

abiotic factors

nonliving things that influence an organism

biotic factors

all forms of life with which an organism interacts

limiting factor

a shortage or absence of a factor that can restrict the success of the species

range of tolerance

the degree to which a species is able to withstand environmental variation


the space that an organism inhabits


the functional role an organism has in its surroundings


distinct pieces of DNA that determine the characteristics an individual displays


all the organisms of the same kind found within a specific geographic region


a population of all the organisms potentially capable of reproducing naturally among themselves and having offspring that also reproduce

natural selection

the process that determines which individuals within a species will reproduce and pass their genes to the next generation


the changes that we see in the genes and the characteristics displayed by successive generations of a population of organisms over time


the production of new species from previously existing species


a condition in which the number of sets of chromosomes in the cells of a plant is increased. It results in a new species.


the loss of an entire species


the concept that two or more species of organisms can reciprocally influence the evolutionary direction of the other


occurs when one organism, a predator, kills and eats another, the prey


two organisms strive to obtain the same limited resource

intraspecific competition

competition between members of the same species

interspecific competition

competition between members of different species

competitive exclusion principle

the concept that no two species can occupy the same ecological niche in the same place at the same time


a close, long-lasting, physical relationship between two different species


a relationship in which one organism, the parasite, lives in or on another organism, the host, from whic it derives nourishment


animals that carry parasites from one host to another


parasites that live on the host's surface


parasites that live inside the host's body


a relationship between organisms in which one organism benefits while the other is not affected


a relationship that is beneficial to both species involved


root-fungus associations. The fungus obtains organic molecules from the roots of the plant, and the branched nature of the fungus assists the plant in obtaining nutrients


an assemblage of all the interacting populations of different species of organisms in an area


a defined space in which interactions take place between a community, with all its complex interrelationships, and the physical environment


organisms that are able to use sources of energy to make complex, organic molecules from the simple inorganic substances in their environment


organisms that require organic matter as a source of food

primary consumers

herbivores - animals that eat producers

secondary consumers

carnivores - animals that eat other animals


animals that eat plants and animals


organisms that use nonliving organic matter as a source of energy and raw materials to build their bodies

keystone species

a species that has a critical role to play in the maintenance of specific ecosystems

trophic level

each step in the flow of energy through an ecosystem


the weight of living material in a trophic level

food chain

a series of organisms occupying different trophic levels through which energy passes as a result of one organism consuming another


small bits of nonliving organic material on which food chains rely

food web

when several food chains overlap and intersect

biogeochemical cycles

atoms are cycled between the living and nonliving portions of an ecosystem

carbon cycle

the processes and pathways involved in capturing inorganic carbon-containing molecules, converting them into organic molecules that are used by organisms, and the ultimate release of inorganic carbon molecules back to the abiotic environment

nitrogen cycle

the cycling of nitrogen atoms between the abiotic and biotic components and among the organisms in an ecosystem

nitrogen-fixing bacteria

bacteria that are able to convert nitrogen gas (N2) that enters the soil into ammonia that plants can use

free-living nitrogen-fixing bacteria

nitrogen-fixing bacteria that live freely in the soil

symbiotic nitrogen-fixing bacteria

nitrogen-fixing bacteria that have a mutualistic relationship with certain plants and live in nodules in the roots of legumes and certain trees such as alders

nitrifying bacteria

bacteria that can convert ammonia to nitrite, which can be converted to nitrate

denitrifying bacteria

under conditions where oxygen is absent, these bacteria can convert nitrite to nitrogen gas (N2), which is ultimately released into the atmosphere