Population Dynamics
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What four factors is population controlled by?
births deaths immigration emigration
Equation to determine population size
past population + births + immigration - deaths - emigration = current population
Factors affecting birth rates
ratio of females:males sexual maturity number of offspring produced length of gestation period life cycle predation nutrient availability
Factors affecting mortality rates
food availability water availability predators pathogens
What does carrying capacity mean?
the biggest population a habitat can support without degrading
What is a density independent factor?
a factor that affects the size of a population independent or regardless of the population density (e.g. forest fires, flooding, seasons)
What is a density dependent factor?
a factor whose effects on the size or growth of a population vary with the population density (e.g. food availability, predation, competition, disease)
What is sigmoidal population growth?
a pattern of growth in which, in a new environment, the population density of an organism increases slowly initially, then rapidly, then slowly declined and fluctuates once carrying capacity is reached
Lag phase
numbers and therefore rate of reproduction is low
Log phase
rapid growth
Stable fluctuating phase
population is no longer increasing in size
Examples of artificial population control
culling of deer removal of invasive species pest control
What is meant by an r-selected species?
a species that has many young with low parental investment short gestation period large amount of offspring die sexual maturity is reached early
Examples of r-selected species
frogs insects small fish
What is meant by a K-selected species?
species that give birth to very few young and have high parental investment long gestation period large amount of offspring survive
Examples of K-selected species
elephants orcas gorillas
r-selected vs K-selected species: population drop
r-selected = recover much faster after a drop in population K-selected = may take hundreds of years
r-selected vs K-selected species: supporting in conservation
r-selected = cheap and fast K-selected = captive breeding programmes, require soft release, time consuming