U5L2 - Changes in Population Size

Question 1

What factors influence population size?

Answer 1

Immigration (moving in)

Emigration (moving out)

Natality (birth)

Mortality (death)

Question 2

Changes in Population: Logistic Growth

Answer 2

A.k.a “S Shaped” and it has 3 phases
- Lag phase: small population, increasing slowly
- Log phase: rapid growth
- Resistance: growth slows, deaths increase
*Limited pop’n growth due to limited resources

Question 3

Logistic Growth

Answer 3

K = Carrying Capacity
- the maximum number of individuals that can be sustained by available resources
- At “K”, dynamic equilibrium occurs: the number of births = number of deaths

Question 4

Exponential Growth

Answer 4

A.k.a “J shaped” –> Smooth curve, continuous reproduction, rapid growth
Ideal conditions so Organisms reproduce at a constant rate

Question 5

r-selected strategy?

Answer 5

• short life span, reproduce large amounts of offspring, little or no parental care
• Insects, annual plants, and algae are examples of organisms that use r-selected strategies: They take advantage of favourable environmental conditions such as food, sunlight, warmer temperatures and they reproduce quickly. They experience exponential growth in the summer, but die quickly at the end of the season.

Question 6

K-selected strategy?

Answer 6

Long life span, reproduce fewer offspring, more parental care, closer to the carrying capacity (K)

Question 7

What Limits Growth of Populations?

Answer 7

Density Independent Factors – e.g. disasters, disease, climate change.

Density Dependent Factors – e.g. predator runs out of prey to eat, crowding of organisms (e.g. trees) leads to competition etc.