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An introduction to the idea that all living things are born, grow, and change over time.
Did you know that a giant oak tree was once a tiny acorn that could fit in your pocket? How does something so small turn into something so big?
Every living thing on Earth goes through changes. A life cycle is the set of changes a living thing goes through from the beginning of its life until it is an adult. It is called a cycle because it happens over and over again, like a circle! Just like a wheel spins around, the life cycle starts with a new life, moves through growing up, and then starts again with new babies or seeds.
Quick Check
Why do we call the changes in a living thing a 'cycle'?
Answer
Because it repeats over and over again like a circle.
Most life cycles have three main parts that we can easily see. First is birth, which is when a living thing starts its life (like a chick hatching from an egg). Second is growth, where the living thing eats and gets bigger. Third is adulthood. When a living thing is an adult, it is fully grown and can have babies or make seeds of its own to start the cycle over!
Humans follow a simple path: 1. Birth: A tiny baby is born. 2. Growth: The baby grows into a toddler, then a child, then a teenager. 3. Adulthood: The person becomes a grown-up. Eventually, they might have a baby of their own, starting the cycle at step again.
Quick Check
What are the three main stages of a life cycle?
Answer
Birth, growth, and adulthood.
It doesn't matter if it is a tiny ant, a huge whale, or a blade of grass—all living things have a life cycle. Some cycles are very fast, like a fly that lives for only a few weeks. Other cycles are very slow, like a turtle that can live for over years! Even though they take different amounts of time, they all follow the same pattern of starting, growing, and becoming an adult.
A frog's cycle has a few extra steps, but follows the same pattern: 1. Birth: It starts as an egg in the water. 2. Growth: It hatches into a tadpole with a tail. Then it grows legs! 3. Adulthood: It becomes a frog. The adult frog lays more eggs, and the cycle continues.
Some insects change their whole shape! 1. Egg: The tiny start. 2. Larva: A caterpillar that eats and grows. 3. Pupa: A hard shell where the body changes. 4. Adult: A butterfly comes out! Even though it looks different, it still follows the rule: .
What is a life cycle most like?
Which of these is the stage where a living thing is fully grown?
Only animals have life cycles. Plants do not have them.
Review Tomorrow
Tomorrow, try to remember the three main stages of a life cycle. Can you name them while you eat breakfast?
Practice Activity
Go outside and look for a plant or an insect. Can you guess which stage of its life cycle it is in right now? Is it a baby, is it growing, or is it an adult?