1. Chapter 4 Population Ecology
4.1 Population Dynamics

2. Population Characteristics
Population Density: number of organisms per unit area
Spatial distribution: the dispersion or pattern of spacing of organisms
RANDOM
UNIFORM
CLUMPED

3. Principles of Population Growth
Population growth rate: explains how fast a given population grows.
Population growth measured in different ways

4. How Fast Do Populations Grow
Usually not linear

5. How Fast Do Populations Grow
Usually slow at first
Called a “J”-shaped curve
Slow at first because number of reproducing organisms is small
Called exponential growth: as a population gets larger it grows faster

6. Limits of the Environment
Population growth usually stops due to lack of resources
Food
Water
Shelter
Space
Population growth usually stops due to build up of waste products which poison the organisms

8. Carrying Capacity
Number of organisms of one species that an environment can support
“S”-shaped growth

9. Carrying Capacity
Fluctuations above and below carrying capacity are normal

10. “J”-shaped population growth pattern
Mosquito, bacteria
Rapid Life-history pattern
Reproduce very rapidly, produce many off spring in short period of time
Environment unpredictable and change rapidly
Small body size, mature rapidly, reproduce early, short life span
Populations increase rapidly then decline

11. ”S”-shaped population growth pattern
Slow Life-history pattern
Slow rate of reproduction, produce few offspring
Elephants, bears, whales, redwood trees, cacti
Live in stable environment
Large, reproduce and mature slowly, long-lived
Maintain population size near carrying capacity

12. Environmental Limits to Population Growth
Limiting Factors: biotic or abiotic factors that regulate size of a population
Two types of limiting factors
Density dependent factors
Density independent factors

13. Density Dependent Factors
Increasing effect as population size increases
Disease
Competition
Parasites
Food
The more dense the population the faster disease can spread
Big problem in agricultural crops

14. Density Independent Factors
Affect all populations regardless of their density
Most are abiotic factors
Temperature
Floods
Storms
Drought
Habitat destruction
Pollution

15. Organisms Interactions Limit Their Population Size
Predation affects population size
Predator prey relationships often show a cycle of population increases and decreases over time

16. Predator Prey Relationships
Hare
Lynx

17. Predator Prey Relationships
Important for health of natural population
Usually young, old or injured are caught

18. Effects of Competition
Competition for food, water, territory are density dependent factors
Only the best suited to the environment survive

19. Chapter 4 Population Biology
4.2 Human Population

20. Human Population
Demography: study of human population growth characteristics: size, density, distribution, movements, birthrates, and death rates.
People live longer and they’re able to produce more children, causing the population to grow.

22. Humans can control limiting factors by:
eliminating competing organisms
increasing food production
controlling disease organisms

23. Effects of Birth and Death Rates
Birthrate : the number of live births per 1000 people in a given year.
Death rate: the number of death per 1000 people in a given year

24. How to determine the growth rate of a population?
Population growth rate( PGR)=
birth rate – death rate
When is PGR = 0 ?
Zero population growth exists when birthrate equals death rate.

25. Zero population growth
It means that new people are entering the population (through birth) at the same rate that people are leaving the population (through death)
The population is changing but it is stable.

26. When PGR is above zero or positive
More people are entering the population
Less people are leaving the population
Population is growing
More births than deaths in the population
When PGR is less than zero or negative
Less people are entering the population
More people are leaving the population
More deaths than births in the population

27. Doubling time: is the time needed for population to double in size
Happen with growing population
( positive PGR)
Slow growth rate means it will take longer for population to double

28. What is the age structure of a population?
Age structure: refers to the number of people at each different age level. (ex: , 15-19)
Male or female
Is population is stable , growing , or becoming smaller?

29. Age Structure Graph: shows the age of the largest group in the population.
When a large amount of population is made up of children, then the population experiencing rapid growth.
When there are more adults than children, then the population is declining.
When the amount of population in the different age levels is about equal, then the population is stable.

30. Age Structure Graph

31. Does environment affect population growth?
Not enough food, water, or space for everyone
Population creates more waste than can be handled
Conditions of the environment cause disease to spread, or pollution affects the water

32. Homework: pages : 15-18
Due date: Monday October 10, 2016
Test on Monday October 10, 2016
Chapters chapter 4
Section 3.2 Biomes will NOT be on the test
Review on Friday