Limiting population size and its examples

the bigger the population grows…

the more resources such as water, oxygen, or food are taken from the environment

what is carrying capacity

the maximum size of a population that an environment can support

what do all environments have

a finite carrying capacity

what does the finite carrying capacity mean

past a certain limit, the population cannot increase anymore

what factors affect carrying capacity

abiotic and biotic factors

what is an example of these abiotic factors

• light availability

• temperature

• soil mineral availability

what are some examples of these biotic factors

• competition for resources

• predation

• disease

what can population also be limited by

density dependent and independent factors

what will density dependent factors do

cause population size to fluctuate due to negative feedback control

what is meant by the term “negative feedback”

feedback that counteracts any deviation from equilibrium and promotes stability

what are density dependent limiting factors

factors that depend on population size e.g. competition, predation, food, (biotic factors)

what are density independent limiting factors

factors that affect all populations in a similar way, e.g. drought, wild fire, hurricane (abiotic factors)

what are the three main groups od density dependet factors

• competition

• predation

• disease and parasitism

competition

a higher density will reduce the amount of available resources such as food, water, etc., so competition will be higher

predation

becomes more intense if a population of prey becomes denser and therefore easier to find

disease and parasitism

higher density = more likely to spread/transmission of diseases

what happens to the prey population when a predator kills its prey

the prey population becomes one smaller

why doesn’t the prey population change much despite predation

birth and death rates are balanced

what is the term for when predator and prey populations remain stable due to balanced birth and death rates

dynamic equlibrium

what is sometimes observed in communities instead of dynamic equilibrium

cyclic oscillations in predator and prey populations

in a food chain, how many interactions between members of different species in a community can operate in how many directions

two directions

what does it mean that species interactions in a food chain operate in two directions

species can influence both those they eat (downward effects) and those that eat them (upward effects)

what is top-down control

acts from a higher trophic level to a lower one, an increase in predator number will decrease the pop size of the prey

what is bottom-up control

vice-versa, a population of producers may be limited by the number of nutrients in soil or water

what have some organisms developed to deter potential competitors from their ecological niche

special metabolic pathways

what do these special metabolic pathways produce

secondary metabolites

what is the purpose of secondary metabolites

deter potential competitors from the organism’s ecological niche

what are the two main methods of chemical defense in plants

• production of antibiotics

• allelopathy

what do many fungi produce to prevent the growth of other species?

antibiotic substances

what do these substances do

prevent the growth of other species by interfering with cell wall components

what will this cause the bacteria to do

burst and die

what is allelopathy

The release of secondary metabolites by plants to prevent nearby competitive plants from growing