ecology
the study of the ways organisms interact with each other and with their nonliving surroundings
environment
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
habitat
the space that an organism inhabits
niche
the functional role an organism has in its surroundings
genes
distinct pieces of DNA that determine the characteristics an individual displays
population
all the organisms of the same kind found within a specific geographic region
species
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
evolution
the changes that we see in the genes and the characteristics displayed by successive generations of a population of organisms over time
speciation
the production of new species from previously existing species
polyploidy
a condition in which the number of sets of chromosomes in the cells of a plant is increased. It results in a new species.
extinction
the loss of an entire species
coevolution
the concept that two or more species of organisms can reciprocally influence the evolutionary direction of the other
predation
occurs when one organism, a predator, kills and eats another, the prey
competition
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
symbiosis
a close, long-lasting, physical relationship between two different species
parasitism
a relationship in which one organism, the parasite, lives in or on another organism, the host, from whic it derives nourishment
vectors
animals that carry parasites from one host to another
ectoparasites
parasites that live on the host's surface
endoparasites
parasites that live inside the host's body
commensalism
a relationship between organisms in which one organism benefits while the other is not affected
mutualism
a relationship that is beneficial to both species involved
mycorrhizae
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
community
an assemblage of all the interacting populations of different species of organisms in an area
ecosystem
a defined space in which interactions take place between a community, with all its complex interrelationships, and the physical environment
producers
organisms that are able to use sources of energy to make complex, organic molecules from the simple inorganic substances in their environment
consumers
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
omnivores
animals that eat plants and animals
decomposers
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
biomass
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
detritus
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