natural selection
the fittest individuals passing their traits to the next generation more successfully
selection pressures
some mutations are thought to have given those individuals an advantage under these in the environment (some mutations have a negative effect on fitness)
critical factor
the single factor in shortest supply relative to demand is the ________ ________ determining where a species lives
tolerance limits
each environmental factor has both minimum and maximum levels beyond which a particular species cannot survive or is unable to reproduce
indicators
the presence or absence of such species indicates something about the community and the ecosystem as a whole
habitat
the place or set of environmental conditions in which a particular organism lives
ecological niche
the role played by a species in a biological community and the total set of environmental factors that determine a species distribution
generalists
species that have a wide range of tolerance for many environmental factors
specialists
species that have a more exacting habitat requirement, tend to have lower reproductive rates and care for their young longer
endemic species
habitat specialists found exclusively in one specific type of habitat
competitive exclusion principle
states that no two species can occupy the same ecological niche for long (the one that is more efficient is using available resources will exclude the other)
resource partitioning
allows several species to utilize different parts of the same resource and coexist within a single habitat
speciation
the development of a new species
geographic isolation
a type of speciation where two organisms can't interbreed with each other due to different environmental conditions in a separate geographical area, thus, gradually becoming different species
allopatric speciation
new varieties arise in non-overlapping geographic locations (separated by a barrier)
sympatric speciation
a new species arises in the same location as the ancestor species
directional selection
the shift toward an extreme of a trait
stabilizing selection
shift that narrows the range of a trait
disruptive selection
shift that causes traits to diverge to the extremes
binomials
another name for the scientific name that is used to identify species
intraspecific competition
competition among members of the same species
interspecific competition
competition between members of different species
predator-mediated competition
a superior competitor in a habitat builds up a larger population than its competing species; predators take not and increase their hunting pressure on the superior species, reducing its abundance and allowing the weaker competitor to increase its numbers
coevolution
the response of predator to prey and vice versa, over thens of thousand of years, produces physical and behavioral changes
Batesian mimicry
certain species that are harmless resemble poisonous or distasteful ones, gaining protection against predators who remember a bad experience with the actual toxic organism
M�llerian mimicry
involves two unpalatable or dangerous species who look alike
symbiosis
two or more species live intimately together, with their fates linked
mutualism
a relationship where both species benefit (+,+)
commensalism
a type of symbiosis in which one member clearly benefits and the other apparently is neither benefited nor harmed (+,0)
parasitism
a form of predation, may also be considered symbiosis because of the dependency of the parasite on its host
keystone species
species that plays a critical role in a biological community that is out of proportion to its abundance
biotic potential
the maximum reproductive rate of an organism, given unlimited resources and ideal environmental conditions
exponential
population growth that has no limit and possesses a distinctive shape when graphed over time
J curve
a graph of exponential growth is described as a _____ curve
carrying capacity
the number or biomass of animals that can be supported (without harvest) in a certain area of habitat
logistic growth
population dynamic that is categorized by its growth rate change over time
S curve
a graph of logistic growth describes a population whose growth rate decreases if its numbers approach or exceed the carrying capacity of the environment - a ______ curve
density-dependent
factors that influence population size - as population size increases, the effect intensifies
r-selected species
species that are adapted to employ a high reproductive rate to overcome the high mortality of virtually ignored offspring
K-selected species
species that are adapted for slower growth conditions near the carrying capacity (K) of their environment
diversity
the number of different species per unit area
abundance
the number of individuals of a species in an area
community structure
patterns of spatial distribution of individuals, species and communities
core habitat
a mostly uniform environment big enough to support nearly all the plants and animals that are typically found in that community
ecotone
the border between two communities (sometimes the borders are sharp and some are blended together)
edge effects
the penetrating influences of a border may extend hundreds of meters into an adjacent community
complexity
the number of trophic levels in a community and the number of species at each of those trophic levels
resilience
the ability of a community to resist or recover quickly from disturbance
primary productivity
a community's annual output of biomass or energy, is expressed as units of biomass or energy per unit area per year
net primary productivity
the amount of biomass stored after respiration
stability
the ability of a community to resist changes despite disturbance - can support the same species in about the same numbers as before the disturbance
climax community
the community that developed last and lasted the longest
primary succession
land that is bare of soil is colonized by living organisms where none lived before
secondary succession
an existing community is disturbed, a new one develops from the biological legacy of the old
pioneer species
the first colonists of an area
disturbance
any force that disrupts the established patterns of species diversity and abundance, community structure, or community properties
disturbance-adapted species
species that survive fires by hiding underground, or resist the flames and then reseed quickly after the fires