Adapted from an activity at M. Poarch – 2005

Deer: Predation or Starvation

6th Grade, Science Unit 2: Ecosystems

Relationships of Organisms and Environmental Impact of Organisms

GOAL:

  • Students will indentify how predator prey relationships impact one another.
  • Students will examine the changes that populations undergo to keep a balance in the ecosystem
  • Students will examine changes in populations due to human intervention
  • Students will create a graph illustrating population changes in a predator prey relationship.

Big Idea: All life forms, including humans, are part of a global food chain in which food is supplied by plants, which need light to produce food. Ecosystems continually change with time as environmental factors and populations of organisms change

GLCE Alignment:

L.EC.06.23Predict and describe how changes in one population might affect other populations based upon their relationships in the food web.

L.EC.06.41 Describe how human beings are part of the ecosystem of the Earth and that human activity can purposefully, or accidently, alter the balance in ecosystems.

L.EC.06.42 Predict and describe possible consequences of overpopulation of organisms, including humans, (for example: species extinction, resource depletion, climate change, pollution).

S.IP.06.15 Construct charts and graphs from data and observations.

Background Information:

Students need a basic understanding of how to complete a double bar graph.

Students need to understand the energy flow in an ecosystem (food chains and food webs) and be able to identify the importance of producers and consumers interaction.

Students need to understand the definition of resource depletion in an ecosystem.

An increase of a population of predators can decrease the population of the prey.

Vocabulary:

ecosystem

population

producers

consumers

predator

prey

competition

resource depletion

balance in ecosystems

Materials:

Two colored pencils to complete double bar graph

Handouts:

  • Scenario
  • Data table of population changes for deer and wolf population
  • Graph form for deer and wolf population change
  • Analysis questions

Procedure:

  • Copy handouts
  • Read through all information
  • Make an answer key for the graph and analysis prior to beginning the activity
  • Make a poster with three columns to use for predicting the outcomes.
  • Deer are better off with the wolves
  • Deer are better off without the wolves
  • Deer are about the same with the wolves

1-Have students read through the scenario independently and discuss the situation as a class.

2-Ask students to hypothesize how this might or might not work. Have students predict what might happen to each population.

3-Point out the poster headings. Ask students to place a sticky note on the column that has the outcome with which they agree.

4-Hand out the predation/starvation worksheets (data table and graph sheet) Have students complete the data table and graph independently or with a partner .

5-Discuss the table and graph as a class.

6-Have students complete the analysis questions, discuss questions 1 &2 as a class.

7-Have students take a sticky note of a different color and place it on the poster in the column they most agree with now.

8-As a class discuss the following:

a)How did your first opinion compare with your second?

b)If you changed your opinion, what caused you to change it?

c)If you didn’t change your opinion, why?

9-Group students by final perspective and have they share ideas, then choose a spokesperson to share their ideas.

Adapted from an activity at M. Poarch – 2005

Name______

Deer: Predation or Starvation

Background Information: In 1970 the deer population of an island forestreserve about 518 square kilometers in size was about 2000 animals.Although the island had excellent vegetation for feeding, the food supplyobviously had limits. Thus the forest management personnel feared thatovergrazing might lead to mass starvation. Since the area was too remotefor hunters, the wildlife service decided to bring in natural predators tocontrol the deer population. It was hoped that natural predation would keep

the deer population from becoming too large and also increase the deerquality (or health), as predators often eliminate the weaker members of theherd. In 1971, ten wolves were flown into the island.The data collected during this program are shown in the following table. ThePopulation Change is the number of deer born minus the number of deerthat died during that year.

Fill out the last column for each year (the first has been calculatedfor you).

Year / Wolf Population / Deer Population / Deer Offspring / Predation / Starvation / Deer Population
1971 / 10 / 2,000 / 800 / 400 / 100 / +300
1972 / 12 / 2,300 / 920 / 480 / 240
1973 / 16 / 2,500 / 1,000 / 640 / 500
1974 / 22 / 2,360 / 944 / 880 / 180
1975 / 28 / 2,224 / 996 / 1,120 / 26
1976 / 24 / 2,094 / 836 / 960 / 2
1977 / 21 / 1,968 / 788 / 840 / 0
1978 / 18 / 1,916 / 766 / 720 / 0
1979 / 19 / 1,952 / 780 / 760 / 0
1980 / 19 / 1,972 / 790 / 760 / 0

Adapted from an activity at M. Poarch – 2005

Graph the deer and wolf populations on the graph below. Use one color to show deer populations and another color to show wolf populations.

YEAR

Data Analysis:

1. Describe what happened to the deer and wolf populations between 1971 and 1980.

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2. What do you think would have happened to the deer on the island had the wolves NOT been introduced. ______

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Conclusion:

What do you think would have happened to the deer on the island had

wolves NOT been introduced? Explain your answer.

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Extension

Most biology textbooks describe that predators and prey exist in a balance. This "balance of nature" hypothesis has been criticized by some scientists because it suggests a relationship between predators and prey that is good and necessary. Opponents of this hypothesis propose the following questions:

Why is death by predators more natural or "right" than death by starvation? How does one determine when an ecosystem is in "balance"? Do predators really kill only the old and sick prey? What evidence is there for this statement?

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