Life Cycles – Grade 2

All living things go through a life cycle. Most animals have a simple life cycle which includes:

  • birth (or hatching from an egg)
  • young stage where the animal grows up
  • adulthood with reproduction
  • death

Life cycles of some animals can be different.

Category of living thing Examples Type of life cycle Links
Mammals human, owl, kangaroo, hyena, tiger, vole, bat, rabbit, racoon, meerkat, monkey, whale, dog, cat, fox, dolphin, jaguar, aye aye, seal, hedgehog, prairie dog, wombat Simple Life Cycle

  1. Born live or hatched from an egg
  2. Young mammals, look like adults but smaller. Often mothers will care for their young for some time.
  3. Adult – grown up, reproduces
Amphibians frog, newt, salamander, toad Metamorphosis (big change): Amphibians go through metamorphosis which means they completely change. Amphibians start in water, and go from underwater animals to air breathing ones.

  1. egg – not yet born
  2. tadpole (or tadpole-like) – looks like a small fish
  3. froglet (or froglet-like) – starts to grow legs
  4. adult – grown up, moves to land, reproduces
Most insects butterfly, fly, bee, beetle, hornet, mosquito Complete Metamorphosis: Most insects go through complete metamorphosis where their body changes shape completely.

  1. egg – not yet born
  2. larva – young and eats a lot. Usually looks like some kind of worm.
  3. pupa – does not eat, goes through big change, and often camouflaged
  4. adult – grown up, reproduces, can have wings
Some insects dragonfly, grasshopper, cockroach Incomplete Metamorphosis: Some insects do not have a pupa stage. The eggs hatch, and the young insect looks just like a tiny adult (called a nymph).

  1. egg – not yet born
  2. nymph – young stage, small, and most feeding is done
  3. adult – grown up, reproduces, includes wings

 
Arachnids spider, scorpion Simple Life CycleSpiders and scorpions do not go through metamorphosis. They look like little adults when they hatch, and grow bigger.

  1. egg – not yet born
  2. young (like spiderling) – looks like an adult, but smaller. Can live on mother’s back for some time.
  3. Adult – grown up, reproduces

Ticks are a little different. They go through an egg, larva, nymph, and adult life cycle.
Bird

 parrot, eagle, chicken, hawk Simple Life Cycle

  1. egg – not yet born
  2. chick – (young bird) looks like an adult but smaller and less developed. Often mothers must care for the young chicks.
  3. adult – grown up, reproduces
Fish parrot fish, trout, salmon, tuna, goldfish, few sharks Simple Life Cycle

  1. egg
  2. fry (young fish) – looks like an adult but smaller.
  3. adult – grown up, reproduces
Fish most sharks Simple Life Cycle

  1. live birth (a few lay egg cases, which later hatch)
  2. young shark looks like an adult but smaller
  3. adult – grown up, reproduces
Monotreme echidna, platypus Simple Life Cycle: Monotremes are mammals that lay eggs.

  • egg – not yet born
  • young monotreme
  • adult – grown up, reproduces
Reptile lizard, snake, crocodile, water dragon Simple Life Cycle

  1. egg – not yet born
  2. young reptile – looks like an adult but smaller
  3. adult – grown up, reproduces
crustaceans crab, lobster Simple Life Cycle

  1. egg – not yet born
  2. Larva – young, does not look like adult
  3. young/juvenile – looks like smaller adult. Growing.
  4. adult – grown up, reproduces
Echinoderms

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 Sea star (starfish), sea urchin, sea cucumber Metamorphosis (big change): Echinoderms go through metamorphosis which means they completely change. When the egg is fertilized (ready), it floats in the water, and as it changes stages, it changes shape and size.

  1. Gastrula (eggs like plankton that float)
  2. Early larva (bipinnaria – develop small arms)
  3. Older larva (brachiolaria – arms grow bigger with suckers)
  4. Juvenile – grows permanent body parts
  5. Adult – has full sized parts