Chapter 11 Infraspecific Population Regulation Flashcards
Density Dependent Population Regulation
how higher densities naturally lead to less births (decreasing fecundity) and more deaths (increasing mortality), leads the populations to slow the rate of population growth
Carrying Capacity (K)
maximum sustainable population size for the prevailing environment
Logistic model of population growth (dN/dt = rN (1 - N/K))… implications of K? where is growth maximized?
- maximizes growth rate of population at HALF the carrying capacity size (K/2)
- at K, population growth is 0
Competition
-OCCURS WHEN INDIVIDUALS USE A COMMON RESOURCE THAT IS IN SHORT SUPPLY RELATIVE TO THE NUMBER SEAKING IT
Scramble Competition
when growth and reproduction are depressed . equally across individuals in a population as the intensity of the competition increases… !!!!!!!!not any advantages for some individuals over others!!
Content Competition
when some individuals claim enough resources while denying others a share… some successful individuals do better than others
Exploitation competition
individuals don’t interact with one another… zebras eating the grass in the savanna don’t directly influence eachother but end up overgrazing and causing less grass to be available for other individuals
Interference Competition
denying other individuals access to the site and its resources (LIKE A BIRD DEFENDING ITS NEST DURING BREEDING SEASON)
Density independent factors meaning
natural influences… like a drought or excessive flooding
Density dependent growth meaning
inverse relationship between population density and growth… MORE DENSITY, LESS GROWTH
Influence of competition on growth
Less growth if more competition
Influence of competition on mortality rates/ survival rates
competition reduces survivial rates/ increases mortality rates
self thinning
progressive decline in density and increase in biomass of remaining individuals caused by combined effects of density dependent mortality and growth within a apopulation…. AS POPULATION STARTS TO DECREASE, SIZE OF REMAINING INDIVIDUALS GOES UP… something like this
Competition impact on reproduction
REDUCES REPRODUCTION… REDUCES FEDUNCITY… less resources for the population, less mass per individual, less babies for smaller animals
Home range
area that an animal normally uses during a year
How home range varies as a function of body size or trophnic group?
- carnivores require a larger home range than herbivores and omnivores of the same size
- bigger the body size, bigger the home range needs to be
Territory
home range that is defended by an animal
When there is an EXCESS of males and females of reproductive age unable to establish breeding territories…
the act of having territories would act as a density dependent regulator as reproduction would be limited.. but only if there is nowhere to have territory!
Allee Effect
density dependent mechanism have also been identified that function to reduce birth and survival rates of populations with LOW DENSITIES
Some examples of allee effect:
- organisms having too small pop densities in an area nd thus not being able to reproduce decreasing birth rates
- when a population is too small to sustain an effective herd or pack, the population may decline from increased mortality because of predation or starvation
