- Define and explain The Human Life Cycle in your own words
- Use key terms such as adolescence accurately
- Apply what you have learned to new examples and questions
- Avoid the common mistakes learners make with this topic
This lesson focuses on The Human Life Cycle: follow the stages from baby to adult to older age and what changes at each stage.
Follow the stages from baby to adult to older age and what changes at each stage.
Key ideas
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.
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.
Key term — adolescence: The stage of life between childhood and adulthood when puberty occurs and the body becomes capable of reproduction.
List the four stages of a butterfly's life cycle in order.
Egg → larva (caterpillar) → pupa (chrysalis) → adult.
Answer: Egg → larva (caterpillar) → pupa (chrysalis) → adult.
- 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
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.
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.
Pollination is the transfer of pollen from anther to stigma. Fertilisation is the fusion of male and female gametes to form a zygote.
Insects carry pollen between flowers when visiting for nectar; bright petals and scent attract them, and sticky or spiky pollen clings to their bodies.
Quick check
Which of these best defines "adolescence"?
Why do plants produce so many seeds when most will never grow?
- The Human Life Cycle: follow the stages from baby to adult to older age and what changes at each stage.
- Puberty and the human life cycle: Humans pass through infancy, childhood, adolescence, adulthood and old age.
- metamorphosis: A complete change in body form during an animal's life cycle, such as a caterpillar becoming a butterfly.
- Watch out for: thinking metamorphosis means simply growing bigger