8.4: Effect of Density of Populations

What is population density?

how close individuals within a population live near one another

How does food availability affect population density?

When an abundance of food is available, the population can become dense and space is limited.

When food is limited, the density of the population may decrease and individuals can spread out in the limited space.

What are density dependent factors?

abiotic or biotic factors whose affect on population size relies on a populations density

What are some examples of density dependent factors?

1) competition for resources

2) predation

3) territoriality

What are density independent factors?

abiotic or biotic factors that affect population size regardless of population density

What are some examples of density independent factors?

1) natural disasters(floods, forest fires)

2) pollution

What are the three stages of growth shown in the logistic growth curve?

1) initially slow start

2) exponential growth

3) relatively stable maximum growth

What would a graph of population size in a population experiencing logistic growth look like?

an S-shaped curve

What is carrying capacity?

the maximum number of individuals an environment can sustain

What causes a population to reach carrying capacity?

both density-dependent and density-independent limiting factors

What is the equation for logistic growth?

change in population size/change in time = maximum per capital growth rate of the population * population size ((carrying capacity - population size)/carrying capacity)

dN/dt = r,max * N ((K - N)/K)

How does the change in population size(dN)/change in time(dt) change as the population size(N) gets closer to the carrying capacity(K)?

change in population size(dN)/change in time(dt) decreases