This section provides examples of exponential decay.

Population Models: Exponential, Logistic, Beverton-Holt

In order to see how exponential decay affects a population, the link above displays an example of exponential decay. Follow the directions below.

1. Make sure a = 2 and b = 1.5.
2. If the graph stood for the birth rate of fish, the 1.5 means that for every pair of fish in one generation there are ____ fish for the next generation.
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   3
   
3. There are ____ fish after 4 generations.
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   10
   
4. If fish in the population are dying off and not reproducing, the populations will ________ instead of increase.
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   decrease
   
5. Set b = 0.5. For every pair of fish in one generation, only ___ of them will survive to the next generation.
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   one
   
6. Originally there was a growth rate of 1.5 and then there was a decay rate of 0.5. The graph shows the growth and then the decay. The two parts of the graph look like ________.
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   opposites
   
7. Move b to 0.8. Even though the decay is at a different rate the graphs still look like ____.
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   opposites

Try other rates and see how it changes the graph.

Answer the questions below in your notes.

1. What happens when a population experiences exponential decay?
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   The population decreases over time 3
   
2. For exponential decay to occur, the birth rate must be less than ____.
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   1