Ecological Relationships
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Summary:
There are many ecological interactions that occur in the natural world. Population
dynamics is the pattern of any process or interrelationship that affects growth or change
in a population of organisms. This lesson goes through some of the ecological
relationships dealing with population dynamics, including producer-consumer systems,
predator-prey relationships, parasite-host relationships, competition between organisms
for resources, and the flow of energy and nutrients in a food web.
Subject:
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Science TEKS 8.11 A-Describe producer/consumer, predator/prey, and
parasite/host relationships as they occur in food webs within marine, freshwater,
and terrestrial ecosystems.
Science TEKS 8.11 B- investigate how organisms and populations in an
ecosystem depend on and may compete for biotic and abiotic factors such as
quantity of light, water, range of temperatures, or soil composition.
Grade Level:
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Target Grade: 8
Upper Bound: high school
Lower Bound: 6
© Partnership for Environmental Education and Rural Health at
College of Veterinary Medicine & Biomedical Sciences, Texas A&M University
Funding support from the National Institutes of Health Office of Research Infrastructure Programs (ORIP)
Time Required: each section of the PowerPoint can be covered in ~20 minutes; time
requirements are listed for each activity
Activity Team/Group Size: for the lesson introduction, the whole class participates as
one large group; for the competition activity, groups of 4-5 are optimal
Materials:
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“Food tokens” – 5 per student
Timer or stopwatch
Reusable Activity Cost Per Group [in dollars]: ~$10
Expendable Activity Cost Per Group [in dollars]: $0
Learning Objectives:
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Understand the relationships or interactions between predators and prey,
producers and consumers, parasites and their hosts
Understand food webs of marine, freshwater, and terrestrial ecosystems and the
interactions of the above relationships in these food webs
Understand that there are requirements for organisms to live, and that these
requirements are not always readily available
Understand the concept of competition between organisms for these resources to
meet requirements
Lesson Introduction / Motivation:
Habitat Lap Sit (found in TPWD’s Project WILD):
Every habitat needs to have four things to make it successful: food, water, shelter, and
space. In this short activity, students will represent these four things in a ‘habitat’ circle;
then see what happens when a certain requirement is removed from the ‘habitat’. First,
have students stand shoulder-to-shoulder in a circle. Going around the circle, assign each
student to represent food, water, shelter, or space until all students have a requirement to
represent. Next, have everyone turn to the right so that they are looking at the back of
someone else’s head, and take one big step towards the middle of the circle. Students
should be standing close together. Now, have everyone place their hands on the shoulders
of the person in front of them and, on the count of three, sit down slowly on the knees of
the person behind them, keeping their own knees together for support for the person in
front of them. As the students are sitting, explain how food, water, shelter and space are
needed in a proper arrangement for a suitable habitat (suitable habitat is represented by
the intact lap-sit circle). Have students stand up again and offer them an ecological event
that would remove a requirement from the ‘habitat’, such as a drought. The students
representing that requirement step out of the circle, and the remaining students try the
lap-sit again, without moving the circle closer together. At this point, the circle should
© Partnership for Environmental Education and Rural Health at
College of Veterinary Medicine & Biomedical Sciences, Texas A&M University
Funding support from the National Institutes of Health Office of Research Infrastructure Programs (ORIP)
collapse or suffer some sort of disruption without the missing habitat requirement. Ask
students what this means to them in terms of habitats and varying resources or conditions.
Lesson Plan:
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Habitat Lap Sit (this should take ~10-15 minutes)
PowerPoint presentation – this can be broken down into four segments/lessons,
each ~20 minutes long, accompanied by activities listed below
Predator/Prey activity: included in the slideshow section ‘Predator-prey
Relationships’. Handout included with the lesson. Go through the activity with
students as a discussion; use handout questions as discussion points. ~10-15
minutes
Competition Activity: after going through the ‘Competition’ section of the
slideshow, proceed with the competition activity ~30+ minutes
Adapted from Project WILD activity, “Carrying Capacity”
o Spread tokens out on a table or the floor in the middle of an open room.
(these tokens represent a food supply that has been fixed by the end of a
growing season)
o Divide students into groups (“herds”) of about 5 students each
o Act as a timekeeper, and set the timer to ring every minute (you can use
shorter intervals, too)
o During the time intervals, students gather food tokens, relay-style. One
student from each herd comes and takes one food token before tagging the
next person in their herd and so on, until the timer sounds.
o Record the students who did not get a food token that round. Repeat the
process until all food tokens are gone. Any herd member that has less
than 4 tokens to last them through the winter ‘dies’.
o Record the number of survivors from each herd. Ask the students what
happened to the competition level between herds as the number of food
tokens decreased.
Lesson Closure:
Discuss with the students the concept of competition and carrying capacity – how
are they related to the number of ‘survivors’ in this activity? What are other factors that
contribute to competition that could affect the numbers in an animal population? A plant
population?
Assessment:
Provided is a quiz with questions that cover the information in the PowerPoint.
© Partnership for Environmental Education and Rural Health at
College of Veterinary Medicine & Biomedical Sciences, Texas A&M University
Funding support from the National Institutes of Health Office of Research Infrastructure Programs (ORIP)
You can also do the following homework assignment or mini-project:
Have the students choose one of the systems from the PowerPoint and pick two
specific organisms that are a part of that system. For example, for producer-consumer
systems, they would choose algae and marine iguanas; for predator-prey systems, they
would choose bobcats and snowshoe hares; for parasite-host systems, they would choose
heartworms and dogs. Have the students research their chosen organisms’ relationship
and write up a short 1-2 page paper using ideas from the PowerPoint, discussing the
relationship, and how that relationship could be affected by competition.
Vocabulary / Definitions:
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Population dynamics – pattern of any process or interrelationship that affects
growth or change in a population of organisms
Producer – organism capable of producing organic compounds from inorganic
molecules through the process of photosynthesis or chemosynthesis; autotroph
Consumer – organism that obtains food by feeding on other organisms or organic
matter; heterotroph
Herbivore – organism that eats plants and other photosynthesizing organisms
Carnivore – organism that eats other animals; predator
Omnivore – organism that eats both plant and animal matter
Decomposer – organism that eats and recycles dead animal and plan matter and
releases chemical nutrients back into the environment
Prey- animal that is eaten by another animal
Parasite – organism that grows, feeds, and is sheltered in or on a different
organism while contributing nothing to the survival of that organism
Host – organism where a parasite takes residence
Competition – when organisms compete for resources in times of resource
scarcity
Background and Concepts for Teachers:
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Food webs/food chains
Population dynamics
Competition
Lesson Scaling:
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This lesson can be simplified by cutting out the predator-prey activity, and
simplifying the competition activity with just one factor (food). The lesson can be
taken up a notch for older or more advanced students by taking out much of the
vocabulary slides (students should already know what a food web/chain is, etc.),
discussing the topic of competition to higher detail, and including both of the
assessment activities provided.
© Partnership for Environmental Education and Rural Health at
College of Veterinary Medicine & Biomedical Sciences, Texas A&M University
Funding support from the National Institutes of Health Office of Research Infrastructure Programs (ORIP)
Safety Issues:
 The habitat lap sit can cause some slight injuries if done improperly – students
need to be careful with physical contact activities.
 The competition activity is a kinetic activity – there should be no jostling or
roughhousing during the course of the relay for food tokens.
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References:
 http://www.cumauriceriver.org/downjersey/natural/n-lesson5.html
 http://www.blueplanetbiomes.org/animals.htm
 http://necsi.edu/projects/evolution/co-evolution/parasites/coevolution_parasite.html
 http://www.chs.k12.nf.ca/science/b3201/WebCT-Copy/units/unit1-05.htm
 http://www.sheppardsoftware.com/content/animals/kidscorner/games/produce
rsconsumersgame.htm
 http://www.ecokids.ca/pub/eco_info/topics/frogs/chain_reaction/play_chainre
action.cfm
Keywords:
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Population dynamics
Relationship
Competition
Habitat
Authors:
Undergraduate Fellow: Katelyn Wilson
Graduate Fellow: Jennifer Graham
Please email us your comments on this lesson:
E-mail to ljohnson@cvm.tamu.edu
Please include the title of the lesson, whether you are a teacher, resident scientist or
college faculty and what grade you used it for.
© Partnership for Environmental Education and Rural Health at
College of Veterinary Medicine & Biomedical Sciences, Texas A&M University
Funding support from the National Institutes of Health Office of Research Infrastructure Programs (ORIP)