1. Think / Pair / Share
What factors affect the human population of Brampton/Caledon?
Are these the same factors that affect other cities?

2. Population Dynamics

3. Population a group of organisms of the same species living in a particular area
Population Density the number of organisms living in a given unit of space, such as a square metre (m2)
D= N/S
D= Population density
N= Number of organisms
S= Unit of space

4. Factors Affecting Population Size
There are four main factors that affect population size in an area:
BIRTHS (Natality = Birth Rate) - number of new individuals being added to a population by births
2. DEATHS (Mortality = Death Rate) - number of individuals dying from all causes
3. Immigration – number entering an area (Moving into)
4. Emigration – number leaving an area (Moving out)

5. Types of Populations Open populations Closed populations
All 4 factors (birth, death, immigration and emigration) are acting on the population
most natural ecosystems
Closed populations
Not affected by migration; only affected by birth and death rates
Some islands, laboratory, and zoos

6. Growth Rate of a Population
Tells how much population size changes in one year
Expressed as a percentage
Growth Rate = (births-deaths) + (immigration – emigration) x 100%
initial population size
= ______ %

7. Some fun facts Field mice have litters with 6 or more pups
They can reproduce every 6 weeks
They reach sexual maturity at an age of 6 weeks
In 6 months, a population of 20 could reach 5120

8. Exponential Growth
Without limits population growth of a species will accelerate!

9. Limiting Factors
All population growth is limited! It can not grow forever!
Limiting factor: a factor that stops the growth of a population in an ecosystem
Light
Temperature
Food
Predators
diseases
Examples of limiting factors:
Availability of water & food would affect how many, if any, organisms can live in an area
Predators to an area would affect the number of organisms (prey) living in the area
Temperature of the area affects which animals live there (ex., polar bears will not be in a desert)
Common limiting factors: amount of sunlight, climate, temperature, water, nutrients/food, fire, soil, chemistry, space, other organisms

10. Abiotic Biotic Adequate food supply Suitable habitat
POPULATION SIZE
GROWTH FACTORS
Favorable light
Favorable temperature
Favorable chemical environment
Abiotic
Biotic
Adequate food supply
Suitable habitat
Ability to compete for resources
Ability to defend against predators
Ability to resist diseases
& parasites
Decrease factors
Too much or too little light
Temperature too high or too low
Unfavorable chemical environment
Inadequate food supply
Unsuitable or destroyed habitat
Too many competitors
Insufficient ability to hide from or
Defend against predators
Inability to resist diseases and
parasites

11. Limiting Factors
DENSITY DEPENDENT: factors that are based on population size (e.g. disease, predators, food, etc.)
DENSITY INDEPENDENT: factors that are NOT based on the populations size (e.g. temperature, weather, volcano, earthquake, ozone holes, etc.)

12. Limited Growth Growth is slowed by limiting factors.
Growth levels off when factors are in balance.

13. Carrying Capacity
Carrying capacity is the largest number of individuals that an ecosystem can support
when a population is maintained at its carrying capacity, the size of the population is at an equilibrium
Births + Immigration = Deaths + Emigration
If a population is NOT maintained at its carrying capacity, the population will eventually crash

14. Limited Growth
Carrying Capacity.

15. Population Crashes

16. Something to Consider…
Today: 7.1 Billion People
2040: 12 Billion People

17. UN 2010 predictions

18. Credits
Mrs K Casha