Life Cycles Grade 3

ENGAGEMENT

Students may know about butterfly development. You can introduce or refresh their awareness by showing the 4.5 minute life cycle of the Monarch:

EXPLORATION

Part I

Depending on the age group you might be dealing with, select any of the following organisms for exploration:

• Mealworms mix with all stages

• Roach nymph mix

• Wax Moth or soldier fly Larvae

1. Provide students with a petri plate and a few organisms and a hand lens. Ask students to observe their insect/bug.

2. Have students observe the mealworm. Is it an insect (3 pairs of legs and head, thorax and abdomen?) Examine these and discuss the relationship of each form of the mealworm.

3. Introduce the Life Cycle chart of the mealworm and invite students to re-examine the organism.

4.Have students examine each stage and rehearse the life cycle by placing the plated insect in the appropriate place on the chart.

5. Have students inspect roaches, fly larvae and wax moths. Use the data sheets below to have students identify the stage of the insect. Students should see a difference in how roaches develop--incomplete metamorphosis. No larvae or pupae in the roaches.

Incomplete Roach Metamorphosis Fly metamorphosis

Moth Complete Metamorphosis

6. For each insect and stage, students can research where the egg, larvae, pupae, and adult live and what they eat. For the insects with incomplete metamorphosis they can research any changes in how young insects differ from adults.

7. Discuss with students the reason why insects developed these complicated life cycles. Consider the following:

For complete metamorphosis:

• Larvae are specially designed for one feature--eating! A larvae can burrow in soil, inside a plant, in compost, or on a special host plant like the Monarch. The larvae has much more ability to get food and grow in size than an adult would.

• Adults are highly specialized to move with wings. This allows them to spread out and populate wider regions and find mates to diversify the gene pool. Adults are generally poorer eaters only taking in nutrients enough to feed their muscles, egg laying apparatus, and nervous system. Some adults have very small mouthparts and some even do not feed at all. Their only job is to find a mate.

• The pupae is the resting/changing stage. Inside a protective barrier the amazing changes from larvae to adult take place. The pupae does not eat, but it still breathes!

For incomplete metamorphosis:

• Since nymphs look very much like adults and eat the same thing and move in the same way, there is no real differentiation. The advantage of incomplete metamorphosis is for insects who have ample space and food and where staying in one place is an advantage--like in a house where there is plenty of crumbs and spills, or . in a garbage dump where there is always food, or even under a log where there is little change over time.

• No energy is spent in metamorphosis, so nymphs are just like mini adults. They can grow quickly and when they do mature, they can breed.

An amazing spider that feeds its young milk

Project Learning Tree/Project Wild Extensions

PLT, p. 23. Peppermint Beetle

PLT, p. 105. The Fallen Log

PLT, p. 108 Nature's Recyclers

PLT, p. 194. Web of Life

PLT, p. 197. School Yard Safari

PLT, p. 200, Are Vacant Lots Vacant?

PLT, p. 263, The Closer You Look.

PW, p. 4, Grasshopper Gravity

PW, p. 12, Interview a spider

PW, p. 34, Spider web Geometry

PW, p. 88, Ants on a Twig

RETURN TO INVERTEBRATE EXPLORATIONS