AP-ENVIR A | K-Selected and R-Selected Species

K-Selected Species

>Also called equilibrium species because their populations have little fluctuation, birth rate continually offsets death rate. >Population hovers at carrying capacity, k, which is where the term k-selected comes from. >Exhibit logarithmic or logistic growth, s shaped curve. >Exhibit type I survivorship, or late loss. >Are more affected by density dependent factors (disease/competition/predation), which more greatly affect larger, more concentrated/dense populations. >Inhabit more stable environments. >Are better able to adapt to changes in environmental conditions. >Large, strong, long lifespan, long gestational period, high parental care, fewer offspring, intelligent, low sex drive, longer maturation time, higher reproductive age, more energy efficient, large at birth.

R-Selected Species

>Also called opportunistic species because they capitalize and their populations soar when environmental conditions become favorable and plummet when environmental conditions are unfavorable, populations have considerable fluctuation. >Population growth is at r, or the intrinsic growth rate, which is where the term r-selected comes from. >Reproduce at their biotic potential, or maximum offspring possible during their lifespan, >Exhibit exponential growth, J-shaped curve. >Exhibit type III survivorship, or early loss. >Are more affected by density independent factors (natural disasters/weather and climatic changes), which affect populations equally regardless of size and concentration/how dense they are. >Inhabit less stable environments. >Are less able to adapt to changes in environmental conditions. >Small, weak, short lifespan, short gestational period, low parental care, lots of offspring, low intelligence, high sex drive, shorter maturation time, lower reproductive age, less energy efficient, small at birth.

Generalist Species

>Can occupy several ecological niches. >Can adapt to a wide range of environmental conditions. >Exploit a wide variety of resources. >Are better adapted to environmental changes and are more likely to survive. >Not great competitors.

Specialist Species

>Occupy one specific or a few specific ecological niches. >Have special adaptations to particular environmental conditions. >Exploit one or few resources. >Adapt less to environmental changes and are less likely to survive. >Great competitors.

R-Selected Species Examples

Flies, mosquitos, cockroaches, gnats, oysters, mice, weeds, wind/spore pollinated plants such as grasses, and ocean sunfish/mola mola.

Generalist Species Examples

Humans, cockroaches, and raccoons.

K-Selected Species Examples

Humans, elephants, eagles, chimpanzees, whales, tortoises, and sequoia trees.

Specialist Species Examples

Koala and giant panda.