🔬 ScienceGrade 4Lesson 4
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Life Cycles of Amphibians and Insects
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Learning Objectives
- 1Describe the stages of a frog's life cycle
- 2Describe the stages of a butterfly's life cycle
- 3Compare complete and incomplete metamorphosis
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Mini Lesson
A life cycle shows the stages an organism passes through from birth to death and reproduction. Each stage has a purpose and prepares the organism for the next stage.
Frog Life Cycle (Amphibian)
- Egg — laid in water, protected by a jelly-like coating.
- Tadpole — hatches from the egg; lives in water, breathes through gills, has a tail.
- Tadpole with legs — legs begin to grow while the tail is still present.
- Froglet — transitional stage; has legs, still has a small tail, developing lungs.
- Adult Frog — fully developed; breathes air through lungs, lives on land and in water.
Butterfly Life Cycle (Complete Metamorphosis)
- Egg — tiny egg laid on a leaf; the starting point.
- Larva (caterpillar) — hatches from the egg; feeds and grows rapidly.
- Pupa (chrysalis) — the caterpillar forms a protective case; transformation happens inside.
- Adult butterfly — fully formed; emerges from the chrysalis, can fly and reproduce.
Complete vs Incomplete Metamorphosis
- Complete metamorphosis (insects like butterflies): 4 stages — egg, larva, pupa, adult.
- Incomplete metamorphosis (e.g. grasshoppers): 3 stages — egg, nymph, adult.
- In incomplete metamorphosis there is no pupal stage; the nymph looks like a small adult.
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Tip: butterflies have COMPLETE metamorphosis (egg, larva, pupa, adult — 4 stages). Grasshoppers have INCOMPLETE metamorphosis (egg, nymph, adult — 3 stages). No pupa in incomplete!
Vocabulary
life cycle
The series of stages an organism passes through from birth to reproduction.
metamorphosis
A process of transformation that an insect or amphibian undergoes during its life cycle.
complete metamorphosis
A 4-stage life cycle: egg, larva, pupa, adult (e.g. butterfly).
incomplete metamorphosis
A 3-stage life cycle: egg, nymph, adult (e.g. grasshopper).
tadpole
The aquatic larval stage of a frog; breathes through gills and has a tail.
chrysalis
The protective case in which a caterpillar transforms into a butterfly (pupal stage).
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