1. Populations
Population: All the individuals of the SAME species that live in the same area
Population Density: The number of individuals of a species live in a given area (#/area)
Populations of organisms are limited by various factors.
Biotic Potential: The maximum number of offspring a
Species can produce in and ideal setting.
Biotic potential is regulated by 4 factors:
Birth potential: Maximum number of offspring per year
2. Capacity for Survival: # of offspring that reach reproductive age
3. Procreation: # of species that reproduce each year
4. Length of reproductive life: # of years you can reproduce

2. B. Environmental Factors: The biotic and abiotic factors that limit populations
Light
Amount of Food
Temperature
Number of Predators
Space
Competition
Intraspecific- within the same species
Interspecific- within other species
Let’s see if we really understand

3. Community Interactions
Carrying Capacity:
The maximum number of individuals that can be supported by an ecosystem, determined by the available resources.
Density Independent Factors:
Affect the number of individuals in a
Ecosystem regardless of the population
Density.
Density Dependent Factors:
Affect the number of individuals in a
Ecosystem BECAUSE of the population
Density.
Community Interactions
Community:
All living things in an Ecosystem
The organisms within a community have specific interactions:
Competition: Intraspecific (within same species) and Interspecific
(within different species)
2. Predations: Predator (hunter) and prey (hunted)

4. Examples: MUTUALISM PARASITISM COMMENSALISM
3. Mutualism: Both organisms benefit (+,+)
4. Commensalism: One organism benefits and the other is unharmed (+, 0)
5. Parasitism: One organism benefits and the other is harmed (+, -)
Examples:
Green algae live inside the shell of the clam and provides it with Oxygen and
and food the clam needs to survive. In turn, the clam provides the algae with
protection, carbon dioxide an nutrients(from it’s waste-ewww)
MUTUALISM
A deer tick gets food from a white-tailed deer (poor bambi). The tick eats and
The deer loses blood and can get infection
PARASITISM
An American robin builds a nest in a Red Maple tree
COMMENSALISM

5. Population Growth Patterns
Changes in population size occur when individuals are added or removed from an area
There are four factors that affect population size:
1. Natality = Birth
2. Mortality = Death
3. Immigration = moving into the area
4. Emmigration = Leaving the area
Remember this formula:
Population Growth = (Natality + Immigration) – (Mortality + Emmigration)
Example: In March 2004 the deer population in a forest(terrestrial) Ecosystem was 45.
During deer were born, 9 died, 3 left the area and 6 moved in. Calculate the what
The population is in March 2005 54

6. Factors that act on populations
SPACE: Need proper space to feed and reproduce
WEATHER: Can affect space and food (extreme weather)
PREDATORS: Increase in predators, decrease in prey and vice versa
FOOD : Supply and Demand
THE COMBINED EFFECT OF THESE FACTORS CONTROLS THE NUMBER OF INDIVIDUALS THE HABITAT SUPPORTS