1. Populations

2. Population Density The number of individuals in a specific area.
Population Density = number of individuals
unit area
Example: Supposed there are 30 turtles in a 15 square foot area.
30/15= 2 or 2 turtles per square feet

3. Determining Population Size
Direct Observation
Actually count all of the members of that population
Indirect Observation
Observe tracks or other signs of the organism
Example : There are an average of 4 birds in a nest, there are 30 nest. 4*30= 120 birds in the area
Sampling-
Estimate the number of the population in a small area then multiple.
Example: There are 3 turtles in 2 square feet. If the area is 50 square feet. 3*50= 150 turtles in the area.

4. Changes in Population Size
Births and Deaths- population size when new members enter or when members leave.
Birth rate-number of births in a certain amount of time
Example- If 500 turtles are born in a populations in a year. The birth rate is 500 turtles per year
Death rate- number of deaths in a certain amount of time
Example- If 200 turtles die in a population in a year. The death rate is 200 turtles per year.

5. Changes in Population Size
The Population Statement-
If the birth rate is greater than the death rate in a population, the population with increase in size
Birth rate > Death rate = population increase.
If the death rate is greater than the birth rate in a population, the population with decrease in size
Death rate > Birth rate = population decrease.
Immigration and Emigration
Immigration- Moving into a population
Emigration- Moving out of a population

6. Limiting Factors
Limiting Factor- an environmental factor that prevents a population from increasing
Food- all animals need food, when food is scarce it is a limiting factor.
Space
Weather
When factors are good, populations tend to increase.
Carrying capacity- the largest population an environment can support.

7. 5 Levels of Environmental Organization
Organism- (one living thing)
Population- (all of the same living thing *species*)
Community- (all of the living things)
Ecosystem- (all biotic and abiotic factors in an area)
Biosphere- (all of the ecosystems in the world)