Overview & Lesson Sequence

Focus on Standards & Assessment

Materials Needed, Preparation & Planning, Management Strategies

Background Info

Intro Activity
Why Study Predator - Prey interactions?

Activity 1
Observation of a predator-prey interaction

Activity 2
What makes a predator successful?

Research Project
Designing a predator - prey experiment

Optional Activity
Biological Control vs. Pesticides

Case Study
Rabbits in Australia

References

Glossary

Suppliers

Resource Sheets

Enforcers Home

CISEO Home

Activity 2: What makes a Predator successful?

In order to better understand predator success, they need a background of the predator anatomy…In this activity, students learn how the differences in predator and prey morphology contribute to a predator or prey’s success. You may want to conduct this activity as an interactive whole class discussion or in individual or small student groups.

Class time required
Approximately 30 minutes

Materials needed
Overhead transparencies of each of the following:

• Chewing Mouthparts
• Piercing-Sucking Mouthparts
• Modified Piercing-Sucking Mouthparts
• Aphid Anatomy
• Ladybird Anatomy (both larva and adult)
• Lacewing Larva Anatomy
• Big-eyed Bug Anatomy
• Mantid Anatomy

Live predators

Dissecting microscope and/or hand lenses

Activity
Start a general discussion about predator and prey adaptations using the following prompts:

What makes a predator or other animal “successful”? (survives long enough to reproduce.)

What are some morphological or behavioral attributes that could help an organism succeed? (camouflage, swiftness, keen vision, good hearing, aposomatic or warning coloration, can produce large numbers of offspring in a short period of time, generalist feeder, etc….)

Refer back to the observations the students made while initially witnessing predation during Activity 1. What body parts did the predators use to catch their prey? (mouthparts, claws, legs, etc…) What features did the prey have that helped them escape? (legs, defensive secretions from siphunculi)

Have the students draw the insects including some of the specific structures they observed the predators and prey using during their observations.  A dissecting microscope, TriLens or other magnifier will help the students create more detailed drawings.

Display the three different Mouthpart overheads.  How did each of the insects use their mouthparts to feed?  (biting, chewing, piercing, sucking.)

Note
Below are the roots of the words for each of the mouth parts: hypopharynx, labium, labrum, mandibles, and maxillae.

• hypo - Greek root meaning under, underneath
• pharynx - Greek root meaning throat
• labi, labr - Latin roots meaning lip
• mandib - Latin root meaning chew or jaw
• maxilla - Latin root meaning jaw or jawbone

Display the External Anatomy overheads for each of the predators and the aphid.  Use the following questions to help students explore the different mouthpart and other anatomical structures:

Do the ladybird beetle and lacewing larva use their mouths the same way?  How are their mouthparts different?

Why do you think so many different mouthpart types evolved? (each structure allows the predator to exploit a different type of prey or live in a different microhabitat, thus reducing competition between predator species.)

Do predators have any anatomical features or behaviors in common? (large eyes or large mouthparts). How might these unrelated predators come up with the same method for subduing or eating their prey? (each adapted to a similar ecological or environmental problem in the same way, i.e. convergent evolution.)

Ask the students to think about the idea that “form follows function” where the design of a structure is optimized for a particular function.  How might a structure become optimized? (adaptation through evolution).

If you were going to control an insect population using one of these insect predators, which one would you choose? What characteristics would you want it to have? In what ways would it be adapted for its job? (students should be able to relate specific behaviors from Activity 1 and morphological characteristics from Activity 2.)

Insect Note
Lacewing larvae have unusual piercing-sucking mouthparts. After piercing the aphid, and injecting a paralyzing saliva, the mouth parts are moved around, scrambling the inside of the prey.  The mandibles and maxillae work in concert by sliding against one another to form a tiny tube whereby pulverized aphid tissue and hemolymph (insect blood) can be sucked up using capillary action.  Students are easily engaged by this particularly gruesome method of feeding, so be prepared for some squeals and other expressions of disgust.

Note
A video microscope (if you are lucky enough to have access to one) is an excellent tool for watching the drama as each predator feeds on aphids.

Language Arts Tie-in
Annie Dillard has a wonderful description of a frog being sucked dry like a balloon losing air in "Pilgrim at Tinker Creek". Other chapters of this book are dedicated to a celebration of insect biology and ecology and would also make great tie-ins to the lesson.  In addition, the newer version of the movie "The Fly" shows a particularly graphic example of how a different insect, a fly, uses its saliva to liquefy food and then slurp up the liquid with its sponge-like mouthparts.

Assessment
Over the course of the introductory activities use the Observation Check sheet to record students’ attainment of the learning objectives listed at the beginning of the lesson.  Review students’ journal entries and/or charts to determine what levels of conceptual understanding they are developing.  Students should be able to make a generalized statement about what makes a predator or prey successful (including predator behavior and morphology).  They should also be able to begin describing how a predator population might impact a prey population.