1. Models of Population Growth
Chapter 8

2. Carrying Capacity
Carrying capacity (K) is the number of individuals that can be sustained in a given space.

3. Growth Curves
Two population growth curves: J-shaped (exponential) S-shaped (logistic)

4. Unlimited Growth Model
Unlimited resources. Not realistic due to carrying capacity. J

5. Density-dependent Growth Model
Resources become more and more limiting. S

6. Environmental resistance
Carrying capacity (K)
Population size (N)
Biotic
potential
Exponential
growth
Time (t)

7. Logistic Growth Model Population growth is SLOWED by limiting factors:
Density-dependent
Density-independent

8. Density-Dependent Factors
Factors include: Competition, Predation, Disease

9. Pause and Think What’s going on here?
Exponential increase in population size (number of bacteria).
Doubling every 20 min.
This assumes resources are unlimited.
J-shaped curve – unrealistic due to carrying capacity

10. Pause and Think What’s going on here?
P. aurelia and P. caudatum both show
exponential growth early on, then their growth slows down.
Resources are becoming more and more limited, which in turn affects growth. Carrying capacity is reached.
In a mixed culture, P. aurelia becomes a dominating species after 5 days. The growth of P. caudatum declines at this time. P. aurelia must be a better competitor for resources.

11. Predator-Prey Cycles
Low # predators = high # prey As # prey increase, # predators increases High # predators = low # prey As # prey decrease, # predators decrease

12. Which population peaks first in each cycle —
Think-Pair-Share
Which population peaks first in each cycle —
predator or prey? Why?

13. Population Curves in Nature

14. What is happening to the populations?
Think-Pair-Share
What is happening to the populations?

15. How/why did this lead to a population explosion?
Activity 1
How/why did this lead to a population explosion?
Industrial Revolution
(1800)

16. How did this lead to a population decline?
Activity 2
How did this lead to a population decline?
WWII
( )

17. How did this lead to a population increase? Medicine and Sanitation
Activity 3
How did this lead to a population increase?
Medicine and Sanitation

18. Pause and Think
What’s going on here?

19. Reproductive Strategies
Organisms can be divided into two categories of "strategies" for reproduction and survival:
r–strategist species
K–strategist species
© Brooks/Cole Publishing Company / ITP

20. r–strategist species
r–strategist species tend to live in environments where resources are not limiting. Such species tend to have high intrinsic rates of growth (high r).

21. ‘Quick and Many’
r-selected species are short-lived and produce very large numbers of offspring.
r-selection is directed to quantity of offspring (they put most of their energy into numbers).
The letter ‘r’ comes from the equation for population growth where r = rate of increase per generation.

22. K–strategist species
K–strategist species tend to do well in competitive conditions and live in environments where resources are limiting. They tend to have lower intrinsic rates of growth and characteristics that enable them to live near their carry capacity (population size near K).

23. ‘Slow and Few’
K-selected species produce small numbers of offspring at less frequent intervals
In general, K-selection is for quality of offspring (they put most of their energy into development).
The letter ‘K’ comes from the equation for population growth where K = carrying capacity of a habitat.

24. Carrying capacity K
K species;
experience
K selection
Number of individuals
r species;
experience
r selection
Time

25. Revisual

26. Revisual

27. Revisual

28. Characteristics of r–Strategist Species
© Brooks/Cole Publishing Company / ITP

29. Characteristics of K–Strategist Species
Fig. 10–7b
© Brooks/Cole Publishing Company / ITP

30. Biozone
146 – Factors Affecting Population Size 147 – Calculating Change in Population Size