Life Cycles of Animals
Grade 3 · Science · Study Guide
Explore how animals grow and change from birth to adulthood.
Every animal goes through a life cycle — a series of stages from birth to grown-up. Some life cycles are simple, and some involve big transformations called metamorphosis.
A frog starts life as a tiny egg in a pond. The egg hatches into a tadpole that breathes underwater using gills. Over weeks, the tadpole grows legs, loses its tail, and becomes a frog that can live on land and in water. That's a dramatic change!
Butterflies go through four stages: egg, larva (caterpillar), pupa (chrysalis), and adult. Inside the chrysalis, the caterpillar's body completely rebuilds itself into a butterfly. This is called complete metamorphosis. Moths, beetles, and flies also go through complete metamorphosis.
Not all animals change so dramatically. A dog is born as a puppy, grows into an adult dog, and the cycle continues. Humans, birds, and lizards also have simple life cycles with no metamorphosis. Understanding life cycles helps scientists protect endangered animals and helps farmers and gardeners work with nature.
| Type | Stages | Example Animals |
|---|---|---|
| Complete metamorphosis | Egg → Larva → Pupa → Adult | Butterfly, beetle, fly |
| Incomplete metamorphosis | Egg → Nymph → Adult | Grasshopper, dragonfly, cricket |
| No metamorphosis | Birth → Juvenile → Adult | Dog, bird, human |
Key terms
- life cycle
- The stages an animal goes through from birth to death and reproduction
- metamorphosis
- A big change in body shape and function during an animal's life cycle
- larva
- The worm-like stage of an insect after hatching from an egg
- pupa
- The resting stage where a larva transforms into an adult insect
- tadpole
- The young form of a frog or toad that lives in water and breathes through gills
Flashcards
- life cycle
- The stages from birth through growth to reproduction and death
- metamorphosis
- A major change in body form during an animal's development
- complete metamorphosis
- Life cycle with four stages: egg, larva, pupa, adult
- incomplete metamorphosis
- Life cycle with three stages: egg, nymph, adult
- larva
- The eating and growing stage after an insect hatches from an egg
- pupa
- The transformation stage inside a chrysalis or cocoon
Practice questions
What are the four stages of complete metamorphosis in order?
- Egg, nymph, pupa, adult
- Egg, larva, pupa, adult
- Larva, egg, pupa, adult
- Egg, larva, adult, pupa
Show answer
Answer: Egg, larva, pupa, adult
Complete metamorphosis always goes egg → larva → pupa → adult. The larva (caterpillar) eats and grows, then forms a pupa (chrysalis) where it transforms.
A tadpole is the young form of a frog.
Show answer
Answer: True
Tadpoles hatch from frog eggs and live in water. They breathe with gills and gradually grow legs before becoming adult frogs.
Which animal goes through complete metamorphosis?
- Grasshopper
- Dog
- Butterfly
- Robin
Show answer
Answer: Butterfly
Butterflies are a classic example of complete metamorphosis. Grasshoppers use incomplete metamorphosis; dogs and robins have simple life cycles.
The resting stage where a caterpillar transforms into a butterfly is called a ___.
Show answer
Answer: pupa
Inside the pupa (chrysalis for butterflies), the caterpillar's body breaks down and rebuilds into an entirely new adult form.
All animals go through metamorphosis.
Show answer
Answer: False
Many animals like dogs, birds, and humans grow and change size but don't go through metamorphosis — their basic body form stays the same.
Fun facts
- A monarch butterfly migrates up to 3,000 miles during its adult life!
- Some cicada nymphs stay underground for 17 years before becoming adults.
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