1. Chapter 5 POPULATIONS
Lab Biology CP

2. Red Crabs on Christmas Island in the Indian Ocean- What assumptions can you make about this population???

3. What problems does this population impose on other populations??

4. Chapter 5: POPULATIONS 5.1: How Populations Grow 5.2: Limits to Growth
5.3: Human Population Growth

5. 5.1 How Populations Grow

6. What is a Population?
A population is a group of organisms of a single species that lives in a given area

7. How do Ecologists Study Populations???
1.) Geographic Range
2.) Density and Distribution
3.) Growth Rate
4.) Age Structure

8. 1. Geographic Range Geographic Range:
The area inhabitated by a population
Can vary in size
Small - Bacteria in a rotting pumpkin (<1 cubic meter)
Large - Cod in the Atlantic (hundreds of miles)

9. 2. Density and Distribution
Population Density:
The number of individuals per unit area
Vary in densities
Distribution:
How individuals in a population are spaced out across the range of the population
1.) Randomly
2.) Uniformly
3.) Clumps (most concentrated)

10. 3 Types of Population Distribution

11. 3. Growth Rate
Growth rate determines whether the size of a population increases, decreases, or stays the same.
Examples:
Zero growth rate:
When the population size stays the same
Positive growth rate:
Population increases
Negative growth rate:
Population decreases

12. 4. Age Structure Age structure:
The number of males and females of each age a population contains
WHY?
Because most plants and animals can’t reproduce until a certain age
Only females reproduce

13. What factors affect population growth?
1.) Birthrate
2.) Death rate
3.) Immigration
4.) Emmigration
Reasons for 3 & 4:
Food shortage
Overcrowding
Looking for mates

14. Why does a population grow?
Has food
Has space
Protection from predators
Protection from disease
Has removal of waste products

15. Exponential Growth Exponential Growth:
The size of each generation of offspring will be larger than the generation before it
The larger the population gets, the faster it grows
Under ideal conditions, a population will grow exponentially

16. Rates of Growth Reproduce Rapidly: Reproduce Slowly: Bacteria
1 day = 4,720,000,000,000,000,000 individual cells
Reproduce Slowly:
Elephants
1 offspring every 2-4 years

17. Logistic Growth Logistic Growth:
Occurs when a population’s growth slows then stops, following a period of exponential growth
3 Phases:
Phase 1 – Exponential Growth
Phase 2 – Growth slows down
Phase 3 – Growth stops
When birthrate and death rate are the same
When emigration equals immigration

19. Carrying Capacity Carrying Capacity:
The maximum number of individuals of a particular species that a particular environment can support

20. 5.2 Limits to Growth

21. Limiting Factors Limiting factors:
A factor that controls the growth of a population
Determine the carrying capacity of an environment for a species
Examples:
Competition
Predation
Parasitism
Disease
Natural disaster
Unusual weather

22. How might each of these factors increase the death rate in a population?

23. Density Dependent Limiting Factors
Operates strongly only when population density reaches a certain level
Examples:
1. Competition
2. Predation
3. Herbivory
4. Parasitism
5. Disease
6. Stress from overcrowding

24. 1. Competition
Organisms compete for:
Food
Space
Water
sunlight

25. 2 & 3. Predation and Herbivory
Predator-prey relationships
Cycle up and down over time
Herbivory effects
Herbivores are predators to plants
Cycle up and down
Humans as predators

26. 4 & 5. Parasitism and Disease
Parasites make their hosts weak and may cause disease or death

27. How does predation affect population growth?

28. Density-Independent Limiting Factors
Affect all populations in similar ways, regardless of population size and density
Examples:
Hurricanes
Droughts
Floods
Wildfires

29. Controlling Introduced Species
How to control runaway populations???
Remove them
Herbicides
Problems:
Only temporary solution
Expensive

30. 5.3 Human Population Growth

31. Has human population size changed over time?
Tends to INCREASE
Reasons:
Medication
Sanitation

32. Patterns of Human Population Growth
Demography:
The scientific study of human populations
Predicted by:
Birthrates
Deathrates
Age structure

33. The Demographic Transition
Dramatic change from high birthrates and death rates to low rates
3 stages