Ecology

group of individuals all of the same species living in the same area

group of population living in the same area

the interrelationships between the organisms in a community and their physical environment

all of the regions of the earth that contain living things

where and organism lives

all the biotic (living) and abiotic (nonliving) resources in the environment used by an organism

study of the growth, abundance, and distribution of populations

• represented by N
• total number of individuals in the population

total number of individuals per unity area or volume occupied

how individuals in a population are distributed

• description of the abundance of each age
• horizontal bars are tiers of the diagram that represent the frequency of individuals in a particular age group
• vertical line down divides each group into gender

how mortality of individuals in a species varies during their lifetimes

• describes most individuals survive to middle age
• after middle age, mortality is high
• ex. Humans

curve that describes organisms which length of survivorship is random

• describes that most individuals die young
• only a little bit survive to become adults

max growth rate of a population under ideal conditions with unlimited resources and without any growth restrictions

• age at reproductive maturity
• clutch size (number of offspring produced at reproductive event)
• frequency of reproduction
• reproduction lifetime
• survivorship of off spring to reproductive maturity

maximum number of individuals of a population that can be sustained by a particular habitat

• elements that prevent a population form attaining its biotic potential
• density-dependent-factors are those agents whose limiting effect becomes more intense as the population density increases. Ex. parasites nd diseases
• density-independent-factors occur independently of the density of the population. ex. natural disasters, and extreme climates

• occurs whenever the reproductive rate is greater than zero
• population size is plotted against time
• plot of exponential growth rises quickly forming a J-shaped curve

• occurs when limiting factors restrict the size of the population to the carrying capacity of the habitat
• S-shaped curve
• population increases, its reproductive rate decreases until at carrying capacity size stabilizes

fluctuations in population size in response to carrying effects of limiting factors

• exhibits rapid growth (Jshaped curve)
• opportunistic species-quickly invade a habitat, quickly reproduce, and then die

• one whose population size remains relatively constant
• produce a small number of large offspring that require extensive parental care until they mature
• reproduction occurs repeatedly during their lifetimes
• ex. humans

• increases in food supply-increase in food due to technological advances
• reduction in disease-advances in medicine reduced the death rate and increased the birth rate
• reduction in human wastes-water purification and sewage systems,health hazards from human waste were reduced
• expansion of habitat-better housing

concerned with the interaction of populations

competition between different species

• competitive exclusion principle (Gause's principle)
• resources partitioning
• character displacement (niche shift)
• realized niche

• when two species compete for exactly the same resources, one is likely to be more successful
• one species outcompetes that other and eventually the second species is eliminated
• no two species can sustain coexistence if they occupy the same niche

• some species coexist in spite of apparent competition for the same resources
• species that pursue slightly different resources or securing their resources in slightly different ways
• individuals minimize competition and maximize success

• result of resource partitioning, certain characteristics may enable individuals to obtain resources in their partitions more successfully
• selection for these characteristics reduces competition with individuals in other partitions and leads to a divergence of features or character displacement

• niche that an organism occupies in the absence of competing species is its fundamental niche
• when competitors are present one or both species may be able to coexist by occupying their realized niche, that part of their existence where niche overlap is absent where they do not compete for the same resources