1. Chapter 4
Population Biology

2. What is a population?
Group of organisms, all of the same species that live a specific area

3. How fast do populations grow?
Increase slow at first, then faster because there are more reproducing individuals
Populations do not increase forever
Populations will level out due to limited factors
Examples of limited factors: predation, disease, lack of space, food supply

4. Exponential Population Growth

5. Let's look at the graph in your book on pg. 94

6. Population Growth Graph
J-shaped curve showing exponential growth of a population
This population has not yet reached its carrying capacity.
S-shaped curve shows how a population becomes limitied by environmental factors
Carrying Capacity: the maximum size of a population that an area can support

7. Population Growth Steady State Carrying Capacity Exponential Phase
Lag Phase

8. Carrying Capacity
The number of organisms of one species that an environment can support indefinitely
Developing environment: more births than deaths and the population increases until it reaches its carrying capacity
When it reaches carrying capacity, more deaths than births due to limited resource
Population fall below carrying capacity again

9. Limiting Factors
Any biotic or abiotic factors that restricts the existence, numbers, reproduction or distribution of organisms.
Ex. Soil, food, organism, strong winds, temperatures, high elevations, water

10. Tolerance
Ability of an organism to withstand fluctuations in biotic and abiotic environmental factors
Example: too much water or too little water on corn plants

11. Ranges of Tolerance
Range over which a population or organism can successfully survive and grow
Too much or too little of an environmental factor can be limiting

12. What affects population density
What affects population density? Population density: number of individuals in a given area
Density-dependent factors: affect the size of a population and depend on the size of that population
Examples: disease, predation, parasites, limited resources, competition, stress from overcrowding
Density-Independent Factors: affect the size of a population but do not depend on the size of that population
Examples: volcanic eruptions, temperature, storms, floods, droughts, chemical pesticides

13. Organism interactions limit populations size
Population size are not limited only by abiotic factors
Examples: Predator-Prey Relationships, Competition

14. Predator-Prey Relationships
Predation can be a limiting factor on population size
Predator-Prey relationships show a predictable cycle of population increases and decreases over time

15. Competition within a Population
What happens when organisms within the same population compete for resources?

16. DEMOGRAPHY
The study of human population size, density, and distribution, movement, and its birth and death rates
Factors that have lead to human population living longer and producing offspring that live long enough to produce offspring
Vaccines
Producing more food
Technology to supply clean water
Infant mortality rate decrease

17. Calculating growth rate
Birthrate: number of live births per 1000
Death rate: number of deaths per 1000
Immigration: movement of individuals into a population
Emigration: movement of individuals out of a population
Birthrate – Death rate = Population Growth Rate (PGR)
PGR above zero population is growing
PGR below zero, fewer individuals are enter than leaving

18. Age Structure Graph

19. Age Structure Graph

20. Ways To Estimate Populations 1. Random Sample 2. Mark & Recapture