2.2

Question 1

How is population growth determined?

Answer 1

B = Births, I = Immigration, D = Deaths, E = Emigration
B+I>D+E shows positive growth
B+I<D+E shows negative growth
B+I=D+E shows no growth

Question 2

What is exponential growth and what is logistic growth?

Answer 2

Exponential growth is the initial growth of a population when there are no limiting factors yet so the population can grow to enormous sizes. Logistic growth shows the population growing with limiting factors that make it level off at the carrying capacity.

Question 3

Where is population growth the highest in logistic and exponential growth?

Answer 3

When the amount of individuals in a population is halfway to the carrying capacity.

Question 4

What do the variables N, N0, r, t, K, dN/dt stand for in growth models?

Answer 4

N = population size
N0 = initial population size
r = maximum per capita growth rate
t = time
K = carrying capacity
dN/dt = population growth rate

Question 5

Define density-dependent and density-independent limiting factors.

Answer 5

Density-dependent limiting factors only have a major impact on growth when the population is large and the density is high, density-independent limiting factors always have a major impact on the growth of a population, no matter how dense it is.

Question 6

List examples of density-dependent and density-independent limiting factors.

Answer 6

Drought: Independent
Flood: Independent
Disease: Dependent
Competition for resources: Dependent

Question 7

How do exponential and logistic growth models change when r, N, or K change and why?

Answer 7

When r is increased, the slope of the line of the population increases sooner in time and much faster, vice versa for when it decreases, because r is the maximum per capita growth rate possible. When N is increased or decreased, the same thing happens as when r is increased or decreased, except when the number reaches the carrying capacity, then it starts slowing down and decreasing again. When K is increased, more individuals in the population can comfortably survive, so the population begins to grow again, and when it is decreased, the population can no longer live comfortably with the same number of individuals, so the population decreases in size and density.