Exponential vs. Logistic Growth Note Packet - E

Name: _____________________________________________ Date:_________ period:_____
Unit 3 Ecology, Populations, & Human Impact
5.1 Types of Population Growth
Essential Questions: How can I help to maintain a sustainable planet?
How do I affect the planet? How does the planet affect me?
Background: It is really important for scientists to understand how populations grow and the factors that
impact that growth.
Let’s Review!
Directions: In the image below record 4 factors that you learned about that can change how a population
Different Types of Population Growth:
All populations, if given enough resources, will reproduce so fast that each generation will be larger than the
generation before it. Assuming each organism had a mate, one organism reproduces two and two organisms
producing four and four eight, etc. Assuming these ideal conditions remain, this exponential growth will
occur for an unlimited amount of time.
1. Look at the two graphs below and circle which model you think shows exponential population
growth based on the description above.
Model A
Model B
2. Self Check: Look at the image below; did you pick the correct graph showing exponential growth?
Compare and Contrast: As time goes on, what is…
…similar about the two graphs?
…different about the two graphs?
3. Predict: Why do you think the population size in the second graph begins to level off?
Key Idea: Population growth cannot go on forever, unless both the environment and its resources are
unlimited. Therefore, exponential growth only occurs for a limited time before slowing down and eventually
4. Identifying Phases of Logistic Growth:
A. Phase 1: When populations are small and resources are abundant, such as when organisms move
to an new area, these populations tend to grow exponentially (very fast)! Circle only the area of the
graph that shows exponential growth and label it “Phase 1: Exponential Growth).
B. Phase 2: As time goes on, individuals making up that population will find resources harder to
find the bigger that population gets. Circle only the area of the graph that shows population growth
slowing and label it “Phase 2: Growth Slows).
C. Phase 3: At some point the environment will no longer have enough resources to support more
organisms because it hit the maximum number of individuals it could support. The population will no
longer grow or decline….it will just stay the same. When this happens the environment is said to
have reached its carrying capacity. Circle only the area of the graph that shows when the
population size has stabilized and label it “Phase 3: Growth Stops – Carrying Capacity Hit).
This type of population growth which all organisms experience is known as logistic growth.
Self-Check: Look at the image below; did you correctly identify where each phase was on the graph?
5. Predict: Do you think the carrying capacity of an environment is always the same? Explain.