1. Ch. 5 Populations

2. Characteristics of Populations
**3 important characteristics of a population are
Population Density

3. Population Growth ** 3 factors can affect pop size:
Birth rate
Death rate
Individuals entering and leaving the pop.
* birth rate > death rate =
* death rate > birth rate =
* birth rate = death rate –

4. Immigration / Emigration
Add or subtract?
Emigration

5. Population Growth
Put 4 bacteria cells in a culture of infinite food / unlimited about of bacteria can grow.
After 5 mins.  the bacteria reproduce to make 2x the original # of bacteria

6. Exponential Growth 1 0 min 4 2 5 min 8 3 10 min 16 15 min 32 5 20 min
GEN TIME # BACT 1
0 min 4 2
5 min 8 3
10 min 16
15 min 32 5
20 min 64

7. Does not happen in nature. Why?
Exponential growth
Happens only at near perfect conditions
Does not happen in nature. Why?
In natural populations, 100 % of new offspring do not survive to reproduce
What adds and subtracts members from a population?

8. Growth Rate
All these factors; birth, death, immigration, and emigration determine growth rate.

9. Carrying Capacity Carrying Capacity
* When death rate = birth rate* at capacity.
What factors determine carrying capacity?

10. 2 factors that limit population growth
Density – dependent limiting factors

11. Competition Competition
The struggle for use of the same resources that are limited.
Animals 
Plants 
Competition is most fierce between the same species. Why?

12. Predation All consumers are predators
The organism eaten by the consumer
Prey
Changes in the size of a predator – prey population often occur in cycles.
Ex lynx and hare populations

13. The S – Shaped Curve Population begins to grow – little competition
Grows until

14. Logistic Growth
Growth that has a carrying capacity

15. Density – Independent limiting factors
Winters, droughts, seasons
Specific organisms – insects and grasses
DILF  exponential growth followed by a sudden collapse of the population

16. Human Population
How do factors such as improved medical care and increased availability of food impact the birth rates of humans?
Scientist believe the earth’s total carrying capacity for humans is 15 to 20 billion people. What changes in lifestyle would be required in order to accommodate 15 to 20 billion people?

17. Exponential growth of humans
Currently, the human population is growing at an exponential rate. 7 billion now.

18. Projected Population Growth

19. Patterns of Population Growth
Demography
Demographic transition
A dramatic change in birth rates and death rates
Age – Structure Diagrams

20. Figure 5-13 Age Distribution
Section 5-3
U.S. Population
Rwandan Population
Males
Females
Males
Females

21. There must be a carrying capacity.
What happens when a population starts to reach it’s carrying capacity?
What type of graph represents this?
Can you predict what will happen if the population does not level off?