Populations Flashcards
what stops a population from rising above a certain level?
limiting factors
limiting factor definition
an environmental resource or constraint that limits population growth
what is used to show the growth of a population
a population growth curve
3 main phases of population growth curve
- phase 1 , slow growth
- phase 2 , rapid growth
- phase 3 , a stable state/ stationary phase
name and explain Phase 1
small numbers if individuals that are present reproduce, and because the birth rate is higher than the death rate, the population increases in size.
name and explain phase 2
in rapid growth, the number of breeding individuals increases, so the total population grows exponentially. no constraints limit population growth yet.
name and explain phase 3
in a stable state, further population growth is limited by external constraints. population size fluctuates but remains stable. birth and death rates are equal.
what accounts for fluctuations in population size during the stable state
- limiting factors such as the presence of predators
name the two categories of limiting factors
abiotic factors
biotic factors
define density dependant factors
limiting factors that are caused by a populations abundant size (disease, competition, build up of toxic byrproducts from metabolism)
define density independent factors
limiting factors that affect the population regardless of size (natural disasters)
what other names are used for the slow and rapid growth phases on the population curve?
LAG and LOG phases respectively
carrying capacity
the maximum stable population an ecosystem can hold
logarithmic scales
increments on this scale increase quickly by large numbers
what limiting biotic factors might affect abundance
- competition (inter and intra specific)
- predators
- disease
biotic factor that affects population abundance, not a limiting factor
migration ( immigration into a population, emigration away from a population)
what abiotic limiting factors might affect population abundance
- nesting sites
- light
- availability of water and oxygen
- pH
What abiotic factors might affect distribution
- soil and water pH
- temperature
- sunlight
- water availability
- altitude
what biotic factors may affect distribution?
- predation
- interspecific competition because it leads to the reduction of a resource that multiple species are fighting for.
interspecific competition
competition between different species
intraspecific competition
competition between members of the same species
explain outcompetition
when in interspecific competition, one organism is better adapted and therefore the other species will decline.
explain competitive exclusion principle
the less well adapted species will continue to decline until it can no longer exist in the habitat with the better adapted species. the better adapted organism will effectively eliminate the other.
intraspecific competition leads to
fluctuations of the number of organisms present in a given time
How many stages are in intraspecific competition?
3
intraspecific competition stage 1
resource is plentiful, population abundance increases
intraspecific competition stage 2
larger population means less food and space available. not enough resources for sll organisms to survive, population decrease.
intraspecific competition stage 3
less competition due to fewer organisms competing for the same resources, population grows
when an organism kills and eats another
predation
predation is a type of..
interspecific competition
stage 1 of predator-prey relationship graph
increase in prey, more food for predators, increase in predators
stage 2 of predator-prey relationship graph
more predators means less pray
birth rate of prey population is lower than death rate
stage 3 of predator-prey relationship graph
reduced prey population can no longer support increased predator population. predator abundance decreases
stage 4 of predator-prey relationship graph
reduced predators, less of prey being killed, more of prey. cycle begins again.
what other factors affect the predator prey relationship?
availability of plants, presence of other predators
How does interspecific competition (biotic) affect population size?
fewer resources available for both populations. Both populations reduce in size.
How can the variability of temperature affect population size?
When the temperature is significantly lower/higher than organism’s optimum temperature, mammals have to use up enrgy to maintian body temperature, so less energy is available for growth and reproduction. Population size decreases.
Population size
Total number of organisms of one species in a habitat
