ecology 8.3 8.4 8.5 8.6

population

group of individuals of a single species living in the same general area

population ecology

the study of populations in relation to their environment

• explores how biotic and abiotic factors influence the density, distribution, size, age structure of a population

what does the exponential model describe?

describes population growth in an idealized, unlimited environment

exponential growth

population increase under ideal conditions, characterized by a j shaped curve

density

number of individuals per unit area

carrying capacity

the max population size a particular environment can sustain (energy, shelter, refuge from predators, nutrient availability, water, nesting sites)

the logistic growth model

a new equation reduces the per capita rate of increase as the population grows, characterized by an s shaped curve

density independent

a birth or death rate that doesn’t change with population density

density dependent

a death rate that rises with population density

community

group of populations of different species living close enough to interact

species diversity

the variety of different kinds of organisms that make up the community has two components

species richness

the number of different species in the community

relative abundance

the proportion each species represents of all the individuals in the community

diversity and community stability

• higher diversity communities are more productive and better able to withstand and recover from environmental stress/change

• higher diversity communities are often more resistant to invasive species

trophic cascade

an ecological phenomenon where the addition or removal of top predators triggers a chain reaction in the populations of predator and prey, impacting multiple lower levels of the food chain, these interactions control entire ecosystems by altering predator density/behavior

competition

-/- interaction between the species involved

competitive exclusion principle

when two species are vying for a resource, eventually the one with the slight reproductive advantage will eliminate the other

• * invasive species can exploit new niches that are free of competition and outcompete other organisms for resources

ecological niche

sum total of biotic and abiotic resources that the species uses in its environment

fundamental niche

niche potentially occupied by a species

realized niche

the portion of the fundamental niche the species actually occupies

niche partitioning

the niche differentiation that allows similar species to coexist in ecological communities - each species in an area uses only a portion of the niche available to them

parasitism

(+/1) interaction where one organism (the parasite), derives its nourishment from another organism (host)

mutualism (+/+)

interspecific interaction that benefits both species

commensalism (+/0)

interspecific interaction where one species benefits while the other in unharmed

cooperation

the behavior that tends to increase the fitness of the individual and the survival of the population

altruism

a behavior that reduces an animal’s individual fitness but increases the fitness other individuals in the population

kin selection

natural selection that favours altruistic behavior by enhancing the reproductive success of relatives

keystone species

not usually the strong, dominant species but species that exert strong control on community structure because of the ecological role or niche

ecosystem engineers

species that dramatically alter the environment therefore influencing the community