1. During the 1990s, the United States experienced high levels of immigration (people moving to the United States), which contributed to slow population increase. The birth, fertility, and death rates did not change substantially during this decade

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.

3. 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.

4. 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
A limiting factor is something that limits population growth. Food, water, and living space are all examples of limiting factors. Without access to these resources, populations cannot grow and eventually decline

5. 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.

6. Three Key Features of Populations
Growth Rate:
Birth Rate (natality) - Death Rate (mortality)
How many individuals are born vs. how many die
Birth rate (b) − death rate (d) = rate of natural increase (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.

7. 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.

8. 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
Carrying capacity is the maximum population size that an environment can support. In general, populations increase when they are below the carrying capacity because there are plenty of resources available for the entire population. However, populations decrease when they are above carrying capacity because resources are not available for everyone
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. 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)

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

11. Doubling time is the period of time required for a population to double in size. Measuring the doubling time of a population requires that the growth rate be constant over long periods of time

12. Population Dispersion

13. 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.

14. 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

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

16. Exponential Growth Curve
Figure 35.3A

17. Logistic Growth Curve

18. “Booms” and “Busts”

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

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

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

22. In the United States women had fewer children in 1995 than in 1955 (the baby boom era). Also, women are having children later in life; there is a clear shift away from women having children in their early twenties in 1955 to women now having children in their early thirties

23. 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

24. 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

25. History of the Human Population