- Define and explain Animal Life Cycles in your own words
- Use key terms such as metamorphosis accurately
- Apply what you have learned to new examples and questions
- Avoid the common mistakes learners make with this topic
This lesson focuses on Animal Life Cycles: compare the life cycles of mammals, birds, amphibians and insects, including metamorphosis.
Compare the life cycles of mammals, birds, amphibians and insects, including metamorphosis.
Key ideas
Animal life cycles
Mammals give birth to live young that grow steadily into adults. Birds lay eggs that hatch into chicks. Amphibians such as frogs lay eggs in water that hatch into tadpoles, which gradually change into froglets. Insects such as butterflies undergo complete metamorphosis: egg → larva (caterpillar) → pupa (chrysalis) → adult. Each strategy suits the animal's habitat.
Puberty and the human life cycle
Humans pass through infancy, childhood, adolescence, adulthood and old age. During puberty, usually between about 10 and 16, hormones trigger physical changes: growth spurts, development of reproductive organs, and secondary sexual characteristics such as facial hair or breast development. Emotional changes are normal too, as the brain continues developing into the mid-twenties.
Key term — metamorphosis: A complete change in body form during an animal's life cycle, such as a caterpillar becoming a butterfly.
How does a frog's life cycle differ from a human's?
Frogs lay eggs in water that hatch into tadpoles, which live in water and undergo metamorphosis into air-breathing froglets. Human babies are born live and grow steadily without metamorphosis.
Answer: Frogs lay eggs in water that hatch into tadpoles, which live in water and undergo metamorphosis into air-breathing froglets. Human babies are born live and grow steadily without metamorphosis.
- Thinking metamorphosis means simply growing bigger Metamorphosis is a complete rebuilding of the body form, not just growth. A tadpole does not simply inflate into a frog; it grows legs, loses its tail and changes how it breathes.
- Confusing pollination with fertilisation Pollination is the transfer of pollen to the stigma; fertilisation is the later fusion of gametes inside the ovary. One is delivery, the other is joining.
Practice
Egg → larva (caterpillar) → pupa (chrysalis) → adult.
Insects carry pollen between flowers when visiting for nectar; bright petals and scent attract them, and sticky or spiky pollen clings to their bodies.
Pollination is the transfer of pollen from anther to stigma. Fertilisation is the fusion of male and female gametes to form a zygote.
Any two of: a growth spurt; development of reproductive organs; growth of underarm and pubic hair; deepening of the voice or breast development; skin becomes oilier.
Quick check
Which of these best defines "metamorphosis"?
Why do plants produce so many seeds when most will never grow?
- Animal Life Cycles: compare the life cycles of mammals, birds, amphibians and insects, including metamorphosis.
- Animal life cycles: Mammals give birth to live young that grow steadily into adults.
- pollination: The transfer of pollen from the anther to the stigma of a flower, carried out by insects, wind or other agents.
- Watch out for: thinking metamorphosis means simply growing bigger