Subject: Science/Biology (Symbiosis & Predation; Ants, Aphids, & Ladybugs)
Length: Snippet: about 25 minutes; Lesson: one 45-55 minute class period.
DESCRIPTION OF SNIPPET
This snippet contains four examples of symbiosis and predation in the insect world: (1) bees pollinating plants; the stamens of the flowers actually move to deposit pollen onto the bees; (2) a ladybug that is eating aphids is driven away by the ant which tends the aphids; the ant then strokes the aphids and harvests their honeydew; (3) grasshoppers are caught and eaten by a spider; (4) flying insects are caught by carnivorous plants.
“Microcosmos” consists of many extraordinary and beautiful shots of insects. There is almost no narration.
HOW TO USE THIS GUIDE
TWM suggests that teachers keep a pre-selected film in their classroom along with any handouts, readings, and other materials that a substitute will need. If required, get permission from school administrators to allow this snippet to be shown.
As you adapt this lesson to the needs and abilities of your classes, modify the Instructions to the Substitute to take account of any changes you make. Pay special attention to the following points:
- If the class already knows the definition of symbiosis and predation, eliminate all but the first sentence of Instruction #1.
- If Instruction #4 is retained, tell the substitute whether the quick write is to be in the students’ notebooks or on loose notebook paper to be handed in.
INSTRUCTIONS TO THE SUBSTITUTE
1. Tell students that this class will be about symbiosis and predation. If necessary, define those terms. Symbiosis occurs when two living organisms of different species depend on one another and both derive benefit from their relationship. Tell students or elicit from class discussion the facts that bees pollinate more than flowers and that much of our food depends upon bees pollinating fruit trees, vegetable plants, and beans. Ask students to think about what the world would be like without oranges, apples, tomatoes and other fruits and vegetables. Predation occurs when one species feeds upon another, like in Africa when the lions feed on the zebra and antelope or when people hunt deer.
1. Segment #1: Start playing the film from DVD Scene 1. Play the film to the end of Segment #3 with brief stops for the introductions and closings set out below or for class discussion. Playing the movie to the end of Segment #3 takes about 22 minutes. You can also talk over this film; it has very little narration.
2. Segment #2: As the segment begins, ask students if they’ve ever seen a plant move on its own power in response to some stimulus from the environment.
This segment starts with time-lapse photography showing flowers opening. It lasts for a little more than two minutes and ends with a scene of a large tree surrounded by grass.
Tell students that the powdery material being placed onto the bees by the plants is pollen. At the end of this segment run the DVD back for a few seconds to show this remarkable footage again.
Introduction to Segment #2:
Tell students that aphids are small insects that eat plants and emit a sweet sticky substance called honeydew. Some species of ants use honeydew for food. Ants will tend the aphids and stroke them to encourage the aphids to produce honeydew. Chemicals on the feet of the ants tranquilize and subdue the aphids. Ants will take aphids into their nests during cold weather, returning them to food plants when the weather warms. Ants will also transfer aphids to new feeding sites. Ants store excess honeydew in a separate stomach and regurgitate it for other ants when needed. Ladybugs eat aphids and many gardeners buy ladybugs to release into their gardens to kill aphids.
Segment #2 starts with a ladybug climbing up a plant stalk to clicking sounds and lasts about 2.5 minutes. It ends with ladybugs mating.
Closing for Segment #2:
Ask students to write a paragraph identifying the predatory or symbiotic relationships between aphids, ladybugs, and ants. They should describe what the insects get, give or lose in each relationship. Allow five minutes for this activity. Then diagram the flow of benefits on the board (or have a student do it). Ask students to describe what the activity engaged in by the ants would be called if it was performed by a human being. Good responses will include farming, ranching, herding, or nurturing.
3. Introduction to Segment #3:
Tell students that spiders keep the populations of other insects in check.
This segment starts as soon as the grasshoppers appear. They will soon fly into the spider’s web. Segment #3 lasts about two minutes. It ends when the film shows a hole which turns out to be an exit for winged ants.
Closing for Segment #3:
Tell younger classes, if they don’t already know, that spiders eat by sucking the fluids from their prey.
4. Introduction to Segment #4:
Tell the class that there are some plants that eat insects.
This segment begins at DVD Scene 9 and lasts for about three minutes. It ends with a Sundew enveloping a wasp.
Closing for Segment #4:
Tell students that the second plant is called a Sundew. It has sticky glands on hairs which trap insects. The edges of the leaf then slowly roll over the prey as shown in the segment. These plants get their name from the glands on top of the hairs; they glisten like dew. Sundews are common in bogs and can occur on sandy banks and other mineral soils that are poor in organic nitrogen and phosphorus. The prey of the Sundew is used to supplement the nutrition that the plant gets through its roots. The glands at the end of the hairs produce digestive juices that decompose the prey. This process takes days and the maximum concentration of digestive enzymes is reached by the fourth day.
After Segment #4, as time allows, describe the additional examples of symbiosis found in the Supplemental Materials below.
Almost every animal constantly interacts with other animals and with plants. Symbiosis occurs when two living organisms of different species depend on one another and both derive benefit from their relationship. Here are a few examples.
1. Clownfish live within the stinging tentacles of anemones. The anemone provides protection and food for the clownfish who in turn cleans the anemone of debris. Clownfish may even swim out onto the reef and, with their bright colors, lure other fish to their host anemone to be stung and trapped in the tentacles.
2. People have symbiotic relationships with their pets. The pets get love, food, protection and veterinary care. The people get companionship and an object for their affection. Studies have shown that people, especially people who live alone, enjoy health benefits from having pets as objects of their love. People also have symbiotic relationships with many species of plants, such as wheat, corn, fruits and vegetables. People sow, water and care for the plants, which in turn provide food for people to eat.
3. Algae and coral polyps also serve one another. Zooxanthellae, a type of algae that use photosynthesis, live within coral polyps. Zooxanthellae are nourished by gasses (carbon dioxide, nitrogen, and phosphorus) produced as waste products by the coral. The presence of algae increases the speed with which these waste products are removed from the coral polyp as well as the rate at which the hard outer skeleton of the polyp is created. Corals consume the oxygen and nutrients produced by their zooxanthellae. In fact, coral reefs are built only where there are plentiful zooxanthellae in the living tissues of stony corals.