04 Feb Populations are always changing. Sometimes changes are the result of humans interfering with food webs or habitats. But even

Hare and Lynx Populations Name____________________

Populations are always changing. Sometimes changes are the result of humans interfering with food webs or habitats. But even when humans do not interfere, populations will still naturally shift up and down or fluctuate. For example, let us study the relationship between the Canada lynx and its primary prey, the snowshoe hare.

1. Graph the number of hares and the number of lynx vs the generation number, then answer the questions below.

2. What patterns on your graph do you notice? Describe what is happening in your graph.

First, let’s think about the hares.

Scientists observe that as the hare population gradually increases, they eat more and more grass and seeds each year until the food supply, particularly during the winter, becomes scarce. At that point, young hares have a difficult time finding enough food to survive and fewer babies are born. On your graph, label these periods of hardship with arrows and a short description of what is happening in your own words.

3. As the number of hares decreases, what do you think happens to the population of grass and seeds that the hares eat? Why?

4. After a few years, the hare population begins to increase. On your graph, label these periods of prosperity with arrows and a short description of what is happening. Make sure you address all of the biotic factors involved.

Now, let’s think about the lynx which eats the snowshoe hares.

5. In general, are there more lynx or more hares? Why? (think in terms of energy transfer in a system).

6. What do you think is the biggest problem for the lynx population living in the mountains of Colorado?

7. When the hare population increases, what happens to the lynx population? Why? On your graph, label these periods of prosperity with arrows and a short description of what is happening in your own words.

8. Ecologically speaking, is the presence of lynx helping the hares or hurting them? Why?

When the hare population declines, the lynxes compensate by switching to other prey such as squirrels, gophers, mice and other rodents. Even though there are other prey around, there is not enough to support a large lynx population so the carrying capacity is reduced. When females are in poor condition, fewer will breed and not all of those bred will produce litters. Litters will be smaller, and most, if not all, of the few kittens born will die soon after birth.

9.  On your graph, label these periods of hardship with arrows and a short description of what is happening in your own words.

10. When predators such as lynx are eliminated from an ecosystem by humans, predict what the consequences are to other plants and animals in that area? Don’t skimp on your answer! (think about the food web that we made, and how those animals and plants would be affected.)

11. Define the word “niche” from your text book. What is the niche of the lynx? The hare?

12. What are some factors that affect the carrying capacity of the lynx and hare’s environment?

13. In this simulation, what was the primary consumer?______________________________

Secondary consumer? __________________________

Primary producer ?_______________________________________________

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