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Populations & Ecological Succession

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Presentation on theme: "Populations & Ecological Succession"— Presentation transcript:

1 Populations & Ecological Succession
Chapters 4 & 5

2 What is a population? A group of organisms of the same species that live in the same area.

3 3 Major Characteristics of Populations
1) Geographic distribution 2) Density 3) Growth Rate

4 Geographic Distribution AKA “range”
Where the population is located.

5 Density How closely the individuals live to one another.
The lower the density, the more personal space each individual has.

6 Growth Rate How quickly the size of the population is changing. Can be
getting bigger or smaller

7 What causes changes in population size?
Increase in size Births Immigration (In-migration) Decrease in size Death Emigration (Exit – migration)

8 Common Growth Patterns
There are two very common patterns of growth. Exponential Logistic

9 Exponential Growth “J-shaped” growth
Growth starts out slowly, then skyrockets. Occurs only in “perfect” conditions: No disease No predators Unlimited space Unlimited food and water

10 Logistic Growth “S-shaped” growth
Starts out like exponential growth, but eventually levels out. Growth pattern of most real populations.

11 Carrying capacity (K) The maximum number of individuals of a particular species that the environment can support. Determines the point at which a population stops growing.

12 Limiting Factors Anything that causes a population to stop growing.
Can be: a shortage of food, water, nutrients or shelter.

13 Density-Dependent Factors
Things that only slow/stop population growth when there is a high density. This is because you now have many organisms living close to one another. Disease Predation Parasites Competition (food, water, shelter, mates, etc.)

14 Density-Independent Factors
Things that slow any population’s growth, regardless of density. Natural disasters (tornados, hurricanes, earthquakes, etc.) Seasonal changes (winter freeze) Human activity (Pollution, deforestation, global warming, etc.)


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