1. Population Ecology

2. Population Dynamics Population:
All the individuals of a species that live together in an area
Demography:
The statistical study of populations, allows predictions to be made about how a population will change
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

6. Population Dynamics Three Key Features of Populations Size Density
Dispersion
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

7. Three Key Features of Populations
Size: number of individuals in an area
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

8. Three Key Features of Populations
1 - Growth Rate = Birth Rate - Death Rate
How many individuals are born vs. how many die
Birth rate (b) = Births
Total population
Death rate (b) = Deaths
Doubling Time: The period of time required for a population to double in size. 
Doubling Time = 70% r
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

9. Three Key Features of Populations
2 - Density: measurement of population per unit area or unit volume
Population Density = # of individuals ÷ unit of space
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

10. Example 1
A population of 50 mice. 10 of them died and 20 were born.
Birth rate = 20 X 100 = 40% 50
Death rate = 10 X 100 = 20%
Growth Rate = Birth rate - Death rate
40% % = 20%
Doubling Time = 70% = 3.5 Years
20%
If the mice are occupying an area of 10 square miles.
Population density
= 50 = 5/sq m 10

11. Example 2
In a the population of 100 elephant, 20 of them died and 25 were born.
Birth rate
= 25 X 100 = 25%
100
Death rate
= 20 X 100 = 20%
Growth Rate
= Birth rate - Death rate
25% % =5%
Doubling Time
= 70% = 14 Years 5%
If the elephants are occupying an area of 5 square miles.
Population density
= = 20/sq m 5

12. Example 3
A population of 50 mice occupies 2 square miles.
A population of 50 elephants occupies 5 square miles.
Which one has the higher density?
Mice density = = = 25/sqmi 2
Elephant density = = = 10/sqmi 5

14. Three Key Features of Populations
Density: measurement of population per unit area or unit volume
Pop. Density = # of individuals ÷ unit of space
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

15. How Do You Affect Density?
Immigration: movement of individuals into a population
Emigration: movement of individuals out of a population
Density-dependent factors: Biotic factors in the environment that have an increasing effect as population size increases (disease, competition, parasites)
Density-independent factors: Abiotic factors in the environment that affect populations regardless of their density (temperature, weather)

16. Factors That Affect Future Population Growth
Immigration + + -
Population
Mortality
Natality -
Emigration

17. Population Dispersion

18. Three Key Features of Populations
Dispersion: describes the spacing of organisms relative to each other
Clumped
Uniform
Random
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

19. How Are Populations Measured?
Population density = number of individuals in a given area or volume
Count all the individuals in a population
Estimate by sampling
Mark-Recapture Method

20. How Do Populations Grow?
Idealized models describe two kinds of population growth:
Exponential Growth
2. Logistic Growth

21. Carrying Capacity Carrying Capacity (k):
The maximum population size that can be supported by the available resources
There can only be as many organisms as the environmental resources can support
Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

22. Exponential Growth Curve
Figure 35.3A

23. Logistic Growth Curve

24. Factors Limiting Growth Rate
Declining birth rate or increasing death rate are caused by several factors including:
Limited food supply
The buildup of toxic wastes
Increased disease
Predation

25. “Booms” and “Busts”

26. Reproductive Strategies
R Strategists
Short life span
Small body size
Reproduce quickly
Have many young
Little parental care
Ex: cockroaches, weeds, bacteria

27. Reproductive Strategies
K Strategists
Long life span
Large body size
Reproduce slowly
Have few young
Provides parental care
Ex: humans, elephants

28. Age Distribution
Distribution of males and females in each age group of a population
Used to predict future population growth

30. Human Population Growth
J curve growth
Grows at a rate of about 80 million yearly
r =1.3%
Why doesn’t environmental resistance take effect?
Altering their environment
Technological advances
The cultural revolution
The agricultural revolution
The industrial-medical revolution

31. The Human Population Doubled three times in the last three centuries
About 6.1 billion and may reach 9.3 billion by the year 2050
Improved health and technology have lowered death rates

32. History of the Human Population