Download Population Graphs: Learning Guide

Population Graphs: Learning Guide
What if there were no limits on population growth? What would happen to
the number of organisms in a species? The organisms would experience what
is known as exponential growth and the population size would double each
generation. Use the chart below to determine the population size of
snowshoe hares undergoing exponential growth for ten generations and then
graph your data for the first seven generations. Don’t forget to label your
axes and title your graph.
Generation # of Snowshoe Hares
1
2
2
4
3
4
5
6
7
8
9
10
Under normal conditions, however, there are limits to how large a population
can grow. If a population experiences exponential growth, then it does so
only for a limited amount of time. Eventually, populations reach their
carrying capacity. This is the maximum number of individuals of a
population that can occupy a certain habitat. Carrying capacity is regulated
by density dependent factors. Examples of density dependent factors
include resource availability, waste production, competition, predation, and
disease. There are also density independent factors (fire, drought,
landslides, earthquakes, temperature), but these factors influence the
population regardless of its size.
Imagine that the population of snowshoe hares from the first example has a
carrying capacity of 50. Draw a graph that would show this using the graph
below. Label the graph components (axes, title) as well as carrying capacity
and exponential growth.
Questions:
1. Some people describe the graphs you made as “S” and “J” shaped
graphs. Why do you think they have these names?
2. Which is the “S” shaped?
3. Which is the “J” shaped?
4. What is carrying capacity?
5. One of the factors that limit population size is resource availability.
What are examples of these resources?
6. Explain the types of competition the snowshoe hare might encounter.
7. What would happen to the snowshoe hare population if there was an
unusually harsh winter (weather)? What type of limiting factor is this
an example of?
8. Populations don’t actually stay constant at their carrying capacity.
Instead they fluctuate, a little above and then a little below. Explain
why this occurs.
9. What is the one species that continues to exhibit exponential growth
and has not reached its carrying capacity yet? Why do you think this
is?