Title: How Do Predators Locate Their Prey?
Time: 2 hours (1.5 h for introduction, experiment and data analysis; 0.5 h for presentation of results)
Objectives:
Students will formulate a hypothesis based on observations and scientific information
Students will learn the elements of a well-designed experiment before creating and conducting
their own small research project
Data will be collected and analyzed by students, demonstrating good scientific inferences and
logical conclusions in their discussion
Biology Inquiry standards covered in this lesson:
B-1: The student will demonstrate an understanding of how scientific inquiry and
technological design, including mathematical analysis, can be used appropriately to pose
questions, seek answers, and develop solutions.
1.1, Generate hypotheses on the basis of credible, accurate, and relevant sources of
scientific information;
1.2, Use appropriate laboratory apparatuses, technology, and techniques safely and
accurately when conducting a scientific investigation;
1.4, Design a scientific investigation with appropriate methods of control to test a
hypothesis (including independent and dependent variables), and evaluate the designs
of sample investigations;
1.5, Organize and interpret the data from a controlled scientific investigation by using
mathematics, graphs, models, and/or technology;
1.6, Evaluate the results of a controlled scientific investigation in terms of whether they
refute or verify the hypothesis;
1.9, Use appropriate safety procedures when conducting investigations.
Materials:
3 – 5 medium sized, native toads or frogs (e.g. southern toad or leopard frog)
One large plastic tote with high sides
1 cup of red wigglers (obtained from any bait shop)
Common craft materials: tape, construction paper, paper and plastic cups, scissors
Procedure:
Introduction of this classroom exercise will cover the basics of prey location by predators. A brief
discussion featuring selected native species and the senses and adaptation they use to locate prey will
serve to acquaint students with the subject. For example, what are the senses used by these three
animals to locate their prey:
Point out the large eyes and concave shape around them on the barred owl. This shape funnels sound to their ears.
This animal hunts by sight and sound.
Notice both prominent and also apparently absent features on the face of the eastern mole. This animal hunts by
smell and touch.
An American alligator can see, smell and hear above water with most of its body still submerged.
Research application (and a second good example for students about the topic of today’s activity):
Diamondback terrapin are aquatic turtles that live in brackish water and lay eggs on land.
The nests are created in dry, open, sandy areas. Females crawl across sand and mud to dig a
nest in dry sand where they lay eggs, they then cover the nest with sand (and scratch marks)
and return to the water. Nests are raided, often at rates exceeding 90% and usually within the
first two nights. Raccoons are prime suspects. Question for students:
If the female terrapin lays eggs, buries them and leaves, and the nest is raided later that night,
how are raccoons locating the nests?
Good discussion would include recognition of the visual clues left by females covering
completed nests (e.g. scratches and crawl marks) as well as inferences about scent left from
both females and their eggs.
This is a great opportunity to review the scientific method with students before proceeding to the
activity and experiment. What are the elements of the scientific method?
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Identify a testable question
Research information about the topic
State the hypothesis
Design an experiment
Conduct experiment and record data in tables, graphs, or charts
Analyze data from tables, graphs, or charts
Does the data support the hypothesis?
Communicate the results to others
Share conclusions and make recommendations for further study
Students will now be introduced to their test subjects for the day: a few frogs and a cup of worms. These
frogs (whether leopard frogs or southern toads) eat worms and other insects. Crickets and worms are
both easy to get at bait shops but we are using worms because crickets make a lot of noise and move
around too much. We need to limit our variables during the experiment on how predators locate prey.
The first trial will be an observational study for the students. A frog will be introduced to the tub at one
end and a worm will be left at the other. Once the frog has had its meal students will be asked to explain
the first few steps of the scientific method and give a testable hypothesis:
What is our question?
How do frogs locate prey?
How did we research the topic
We observed the frog catch his prey.
What is our hypothesis?
Does the frog use sight, touch, taste or smell?
Students will be divided into four groups, two for each of the most popular hypotheses. Students will be
allowed to design an experiment that the instructors will execute upon completion. For example:
Students may elect to place worms in two cups, one clear and one paper, at the same end of the tub to
test whether frogs use sight to locate prey. Before experiments are conducted students will be
encouraged to make observations and they will be instructed to record the results for all four
experiments. At the end of the experiments each group will be expected to present their data analysis
and conclusions to the class; paying attention and making notes during the experiments will be critical.
Once all experiments are constructed the instructor will place the tub at the front of the class and
introduce a frog, running each experiment in turn.
Evaluation:
After each experiment has been completed our test subjects will be placed out of sight so that data
analysis can begin. Students are expected to learn the difference between qualitative and quantitative
data. What type of data will we have for this experiment? Groups will be allowed time to create a visual
representation of the class data (table, chart or graph) and prepare a brief presentation of their
interpretation of the day’s experiments. Key points for groups to address in presentations will be
explained to the students before they begin.
Key points to a successful evaluation will include:
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Brief introduction to the day’s topic
What was the group hypothesis and how was it formulated?
Why the experiment was designed the way it was
Detail of data and observations
Verbal and visual presentation of the data
Did the results support the class hypotheses?
Conclusions and discussion of improvements to future experiments
All students are expected to participate in the group presentation. A summary discussion at the end of
the day’s exercise will reinforce the scientific method and our class conclusions regarding how our
amphibian predator located its prey.
How do frogs locate their prey?
Do predators have specific adaptations to help them locate their prey? What are some examples
of this that you learned today?
What could we do better to test how frogs locate prey? Were worms in a cup just too weird for a
wild frog to accept?
Do frogs and toads hunt at night? How could we test their hunting ability in the dark?
If it rains hard after a terrapin lays her eggs will a raccoon still be able to find the nest?