Building on the life cycle concept introduced in Lesson 24, learners investigate the remarkable variety of ways different organisms develop. The lesson focuses on metamorphosis, the dramatic physical transformation that many animals undergo, and distinguishes between complete metamorphosis, with four distinct stages, and incomplete metamorphosis, with three. Students also examine variation within a species, discovering that individuals of the same kind can look and behave very differently at different life stages, and explore how environmental conditions can influence life cycle timing.

Key Ideas

• Metamorphosis is a dramatic change in body form that occurs during an organism's life cycle. It allows the same species to occupy different ecological roles at different stages.
• Complete metamorphosis has four stages: egg, larva, pupa, and adult. The larva and adult look and behave very differently from each other.
• Incomplete metamorphosis has three stages: egg, nymph, and adult. The nymph resembles the adult but is smaller and lacks fully developed wings.
• Variation within a species means individuals of the same kind can look very different depending on their life stage, sex, or environment.
• Life cycle timing is not always fixed. Temperature, day length, and food availability can speed up or slow down development in many organisms.

Vocabulary

• Metamorphosis: A dramatic change in body form that some animals undergo during their life cycle.
• Complete Metamorphosis: A four-stage life cycle (egg, larva, pupa, adult) in which the organism changes dramatically in form.
• Incomplete Metamorphosis: A three-stage life cycle (egg, nymph, adult) in which the organism gradually develops into its adult form.
• Larva: The immature, worm-like stage of an insect that undergoes complete metamorphosis. Examples include caterpillars and grubs.
• Pupa: The resting, transformation stage of complete metamorphosis, during which the larva reorganizes into the adult form.
• Nymph: The immature stage in incomplete metamorphosis. Nymphs resemble small adults without fully developed wings.
• Variation: Differences among individuals of the same species in appearance, behavior, or development.

Hands-On Activity: Complete vs. Incomplete Metamorphosis Sort and Compare

Supply List

• Paper and pencil
• Optional: printed or drawn images of insect life stages (butterfly, grasshopper, dragonfly, beetle)

Instructions

• Draw two columns on your paper. Label one "Complete Metamorphosis" and the other "Incomplete Metamorphosis."
• Under each heading, write the stages in order and draw a simple picture of each stage. (Complete: egg, caterpillar/larva, chrysalis/pupa, adult butterfly. Incomplete: egg, nymph, adult grasshopper.)
• Write one sentence under each stage describing what the organism is doing or what is happening to its body.
• Now add a second example to each column. Choose from: a beetle (complete), a dragonfly (complete), a cockroach (incomplete), or a cricket (incomplete). Look up or recall what each stage looks like and add it to your column.
• At the bottom of each column, write one advantage that type of metamorphosis gives the insect. (Complete: larva and adult do not compete for the same food. Incomplete: nymphs can begin competing for resources much sooner.)