40 terms

chapter 6

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population- second level of complexity, composed of all individuals that belong to the same species and live in a given area at a particular time
evolution occurs here & factors may result in decrease or increase
community- third level complexity, incorporates all of the popluations of organisms in a given area
may be defined by state or federal agency responsible for managing it, also with population
population ecology- the study of factors that cause populations to increase or decrease
if birds birth and immigration exceeds deaths and emigration, population will grow, caused by factors
population size- (N) is the total number of individuals within a defined area at a given time
the California condor once ranged throughout California and the Southwestern US, eventually has decreased due to factors
population distribution- the description of how individuals are distributed with respect to one another
Random distribution, uniform distribution (rows), clumped distribution (many groups)
population density- the number of individuals per unit area (or volume, in the case of aquatic organisms) at a given time
with knowledge of population size, scientists can estimate whether a species is rare or abudnant
sex ratio- ratio of males to females in a population
typically sexually reproducing species, the sex ratio is close to 50:50
age structure- populations description of how many individuals fit into particular age categories
helps ecologists predicts how rapidly a population can grow
density-dependent factors- influence an individuals probability of survival and reproduction in a manner that depends on the size of the population
the amount of available food is a density- dependent factors, allows a certain # of organisms to live in area
limiting resource-a resource that a population cannot live without and which occurs in quantities lower than the population would require to increase in size
if a limiting resource decreases, so does the size of a population that depends on it
carrying capacity- population growth slowed as population size increased because there was a limit to how many individuals the food supply could sustain
limit of the environment and denoted as K, help us predict how many individuals an environment can sustain
Density-independent factors- have same effect on an individual probability of survival and amount of reproduction at any population size.
tornado can uproot and kill a large number of trees in an area, other examples- fires, floods, volcanoes, hurricane, and other climatic events
growth rate- the number of offspring an individual can produce in a given time period, minus the deaths of individuals or its offspring during the same time period
the # of offspring- deaths=positive #
intrinsic growth rate- under ideal conditions with unlimited resources available, every population has a particular maximum potential for growth
Denoted as r, when there is plenty of food available white tailed deer can give birth to twin fawns, the # of deaths also decreases
exponential growth model- used to estimate the populations future size after time has passed
the equation is N base t= N base 0 e exponents of rt
J-shaped curve- when graphed the exponential growth model creates a J shaped graph
when populations are not limited by resources, their growth is rapid as more births occur with each step in time
logistic growth model- describes a population whose growth is initially exponential, but slows as the population approaches the carrying capacity of the environment
if a population starts out small, its growth can be very rapid, but once the pop size reaches about one-half of the carrying capacity the population growth begins to slow
S shaped curve- the graph of a logistic growth model
graph has= early growth (exponential) and growth begins to slow, eventually growth falls to zero (k, carrying capacity)
K- selected species- because carrying capacity is denoted as K in population models, such species are referred as this
have certain traits in common, for example K-selected animals are typically large organisms that reach reproductive maturity relatively late
r selective species- because intrinsic growth rate is denoted as r in population models are referred as this
do not typically remain near their carrying capacity, but instead exhibit rapid population growth that often followed by overshoots and die-offs
survivorship curves- species can have distinct patterns of survival over time
plotted on a graph creates a pattern
corridors- strips of habitat provide some connectedness among the populations
cougars sometimes move between mountain ranges, often using strips of natural habitat that connect the separated populations
metapopulation- a group of spatially distinct populations that are connected by occasional movements of individuals between them
important part of each population's overall persistence, small populations are more likely to go extinct than larger populations
community ecology- the study of these interactions which determine the survival of a species in a habitat
interactions fall into four categories: competition, predation, mutualism, and commensalism
competition- the struggle of individuals to obtain a limiting resource
when two species grow together, one thrives while the other species goes extinct
competitive exclusion principle states that two species competing for the same limiting resource cannot coexist
when two species have the same realized niche, one species will perform better and will drive the other species to extinction
resource partitioning- when two species divide a resource based on differences in the species behavior or morphology
when two species overlap in their use of a limiting resource, selection favors those individuals of each species whose use the resource overlaps the least with that of the other species
predation- refers to the use of one species as a resource by another species
organisms of all sizes may be predators, and their efforts on their prey very widely, can be grouped as: true predators, herbivores, parasites, parasitoids
mutualism- third type of interspecific interaction that benefits two interacting species by increasing both species chances of survival or reproduction
each species in the interaction is ultimately assisting the other species in order to benefit itself
commensalism- type of relationship which one species benefits but the other is neither harmed nor helped
includes birds using trees as perches and fish using coral reefs as places to hide from predators
symbiotic- relationship of two species that live in close association with each other
commensalism, mutualism, parasitism are all symbiotic relationships
keystone species- species that plays a role in its community that is far more important than its relative abundance might suggest
loss of one species from community tht have a disproportionately large effect on entire community
predator-mediated competition-
Competition in which a predator is instrumental in reducing the abundance of a superior competitor, allowing inferior competitors to persist.
phenomenon commonly found in nature
ecosystem engineers- keystone species may create or maintain habitat for other species
beavers have a critical role in forest communities by creating damns and new habitats
ecological succession-type of change that occurs in virtually every community
its a predictable replacement of one group of species by another group of species over time
primary succession- occurs on surfaces that are initially devoid of soil,
abandoned parking lot, newly exposed rock left behind after a glacial retreat, or newly cooled lava
secondary succession- occurs in areas that have been disturbed but have not lost their soil
follows an event such as a forest fire or hurricane, removes vegetation but leaves the solid mostly intact
pioneer species- species with ability to colonize new areas rapidly and grow well in full sunshine
species such as trees aspen and cherry
theory of island biogeography- factors which demonstrates the dual importance of habitat size and distance in determining species richness
larger habitats typically contain more species of animals and organisms
pathogens-Microbes that cause disease
can be found in water and food, causes sickness and harm to organsim