Life Cycles & Reproduction

Every living thing follows a life cycle. A life cycle is the series of stages an organism passes through from the moment it begins to exist until it reproduces and the cycle starts again. Each stage has a job: some stages are for growing, others are for transforming, and the adult stage is for reproducing.

Butterfly Life Cycle (Complete Metamorphosis)

1. Egg — a tiny egg is laid on a leaf. This is the starting point of the cycle.
2. Caterpillar (larva) — the egg hatches into a hungry caterpillar that eats and grows quickly.
3. Chrysalis (pupa) — the caterpillar forms a hard case. Inside, its body completely changes shape.
4. Butterfly (adult) — a fully formed butterfly emerges, flies, and reproduces by laying new eggs.

Frog Life Cycle (Amphibian)

1. Egg — laid in water in a jelly-like cluster.
2. Tadpole — hatches with a tail and gills, lives in water.
3. Tadpole with legs, then froglet — back legs grow, then front legs; the tail shrinks and lungs develop.
4. Adult frog — breathes air, lives on land and in water, and lays new eggs.

Complete vs Incomplete Metamorphosis

• Complete metamorphosis (butterflies, beetles, bees): 4 stages — egg, larva, pupa, adult.
• Incomplete metamorphosis (grasshoppers, crickets, dragonflies): 3 stages — egg, nymph, adult.
• The nymph looks like a small wingless adult and grows by shedding its skin.
• There is NO pupa stage in incomplete metamorphosis.

Reproduction — Closing the Cycle

Reproduction is how living things make new individuals of the same kind. It is the last big step of every life cycle, and the first step of the next. Without reproduction, no species would continue.

• Most plants and animals reproduce sexually — two parents, offspring vary.
• Some living things reproduce asexually — one parent, offspring are identical (e.g. yeast budding, plant runners).
• Eggs, seeds, and live births are different ways species begin a new life cycle.