Name ______

Date ______

The Predator-Prey Relationship

(Informational Text and Graphing Activity)

Key Terms:

Term / Part of Speech / Definition / Picture / Example
predator
prey
presence
limit
scarce
competition
reduced
odds
sufficient
pelt(s)

Introduction:

The predator-prey relationship is one of the most effective ways of controlling the size of a population. In this relationship, a predator species captures, kills and consumes the individuals of the prey species. The prey organism is the food for the predator. Predation can affect the number and types of species living in an area.

The presence of predators usually increases the number of different species that can live in a specific area. Since predators limit the size of prey populations, food and other valuable resources are less likely to become scarce. Competition between species is reduced as a result. The predator-prey relationship is important for the health of populations. Usually, the prey that are caught by the predators are the young, old, sick or injured members of the prey population. This increases the odds that there will be sufficient resources for the healthier members of the population.

During the 1800’s and into the early 1900’s, trappers collected and sold the pelts of both the Canadian lynx and the Snowshoe hares. The lynx, a member of the cat family, stalks, attacks and eats the snowshoe hare as a primary source of food.

The table below contains the data of the number of pelts bought by the Hudson Bay Company between 1845 and 1935. Make a graph of the data. Your graph will contain two lines. There will be one line for lynx and a second line for rabbits. Use separate colors for each line.

Year / Number of Lynx* / Number of Rabbits* / Year / Number of Lynx* / Number of Rabbits*
1845 / 39,000 / 21,000 / 1895 / 39,000 / 60,000
1850 / 10,000 / 71,000 / 1900 / 9,000 / 9,000
1855 / 38,000 / 69,000 / 1905 / 40,000 / 29,000
1860 / 17,000 / 22,000 / 1910 / 26,000 / 10,000
1865 / 51,000 / 129,000 / 1915 / 60,000 / 42,000
1870 / 71,000 / 9,000 / 1920 / 12,000 / 9,000
1875 / 38,000 / 56,000 / 1925 / 78,000 / 39,000
1880 / 29,000 / 70,000 / 1930 / 8,000 / 40,000
1885 / 40,000 / 47,000 / 1935 / 83,000 / 19,000
1890 / 30,000 / 21,000

* These figures have been rounded to the nearest thousand.

1. Describe the relationship between the number of lynx and the number of rabbits between the years of 1845 and 1900. Explain your answer.

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2. As the rabbit population increases, the lynx population increases. Why does this happen?

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3. What happens when the lynx population increases?

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4. What year is the rabbit population the highest? ______

5. Why do you think there was a huge (dramatic) increase in rabbit population during that year?

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6. What happened to the rabbit population in the year after the highest rabbit population year (Look at question #5)? Why did this happen?

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7. If the entire (all of the) lynx population disappears, what is could happen to the rabbit population? Explain your answer.

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8. Predict what might happen to the predator population if:

a) there is a lot of food for the prey species. ______

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b) a disease kills the prey population. ______

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c) a new predator species that feeds on same prey moves into the habitat. _

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9. List 2 traits that help predators survive. (They should be traits that make them good at catching their prey.)

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13. List 2 traits that help the prey survive. (They should be traits that help them not get caught by the predator.)

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