1. The number of organisms per unit area
Population Density
The number of organisms per unit area

2. United States or New York City?
Which has a higher population size?
Which has a higher population density?

3. 3 Types of Dispersion
Fig. 4.2
Uniform
Clumped
Random

4. What type of dispersion….?
White-tailed deer?
Black bear?
Bison?
Mountain lions?
Seeds dispersed by wind?
Caribou?

5. What is a limiting factor?

6. Density-dependent limiting factors
a) Affect large, dense populations more than smaller, less- crowded populations
“Depends” on “density”

7. Density-dependent limiting factors
Predation:
Fig. 4.5
Wolves & Moose on Isle Royale

8. The amount of food for the mouse Disease among the wolf population
Isle Royale
In addition to the predator/prey relationship, the moose and wolf population were affected by:
The amount of food for the mouse
Disease among the wolf population

9. The “prey” always increases first.
Predator - Prey
The “prey” always increases first.

11. Density-dependent limiting factors
ii. Disease & Parasites:
Easily spread in large, dense populations

12. Density-dependent limiting factors
iii. Competition:
Fig Compete for available resources
Food, water, space

13. iv. Crowding & Stress:
The higher population density, the more crowding and stress on individual organisms

14. Density-independent factors
The density of the population DOES NOT MATTER
It doesn’t matter if the population is 5 or 5,000, they will be affected

15. Density-independent factors
Hot/Cold Weather
Fires
Floods/Hurricanes/Tornadoes
Human Activities – toxic waste spills, pesticides, deforestation

16. Population Growth Rate
How fast a population grows
It depends on 4 major factors

17. Population Growth Rate
a) Natality = birthrate
b) Mortality = death rate

18. Population Growth Rate
c) Emigration – “exit” or leaving population
d) Immigration – “in” or moving into a population

19. Population Growth Rate
Natality – Mortality + Immigration - Emigration

20. If natality is 10, mortality is 6, immigration is 3, and emigration is 2……
What is the net effect on the population size?
If the original population consisted of 10 individuals, what is the new population size?

21. Population Growth Rate
If birth rate > death rate
The population will…..
If birth rate < death rate
The population will….

22. Exponential Growth (J–shaped curve)
If ideal conditions (have everything!) continue, the population will continue to grow rapidly
Doubling and re-doubling
1, 2, 3, 8, 16, 32, 64, 128……..
Does NOT last long in nature – WHY?

23. Exponential Growth (J–shaped curve)
d) This is current human population growth worldwide
How long can it last?
Discuss
e) Draw graph
*Industrial revolution

24. Boom and Bust
As ideal conditions continue, population grows exponentially until it reaches a “peak” size (boom) and then crashes (bust)
Ex: Rabbit population
Draw graphs

25. Yeast Population Growth

27. Logistic Growth (S-shaped curve)
a) Exponential growth at first, eventually the population size levels off as the growth rate slows down b) Carrying capacity: Largest number of individuals that the environment can support

28. Logistic Growth (S-shaped curve)
Draw graph
Things that prevent the population from getting too big:
Lack of food or water
Home/shelter availability

29. Reproductive Patterns
r-strategy: rate strategy
Generally are small
Short life spans
Produce many offspring
rat, fruit fly, locusts (Fig. 4.9)

30. Reproductive Patterns
k-strategy: carrying capacity strategy
Larger organisms, long life span
Produces few offspring –better chance of survival
Take care of the offspring, usually for a long time
Kangaroo, elephant

31. Demography
The study of human population size, density, distribution, movement, and birth and death rates

32. Demographic Transition
A change in a population from high birth and death rates to low birth and death rates
(Read pg 102)

34. Demographic Transition
Stage 1: birth rate & death rate
Stage 2: birth rate & death rate
Stage 3: birth rate & death rate
Stage 4: birth rate & death rate
Discuss & answer questions on Notes handout

35. Zero Population Growth
Birth rate = Death rate

36. Age-Structure Diagram
# of males & females in 3 age groups:
Pre-reproductive stage
Reproductive stage
Post-reproductive stage

38. Age-Structure Diagrams
Fig – predict future population sizes…
Pyramid shaped
(pre-reproductive larger) 
Smaller at the bottom
(pre-reproductive #’s smaller) 

39. Education & Demographic Transition
What does the first graph tell us?
What does the second graph tell us?
What is a key factor in reducing the overall worldwide population growth?