---
title: "Born, Growing, Dying"
book: "Primary & Middle School Biology"
subject: biology
language: en
chapter: 7
exercises: 10
source: https://one-course.com/books/biology/1/en/chapter/7-born-growing-dying
---

# Chapter 7 — Born, Growing, Dying

In the spring, the cherry tree by the gate is covered in blossom; under it, a cat nurses her newborn kittens; and Grandpa shows a photograph of himself when he was your age — small, gap-toothed, and already fond of cherries. Every [living thing](https://one-course.com/books/biology/1/en/chapter/1-living-or-not-living#def-g1-living-or-not-living) travels the same road: it begins, it grows, and one day it ends. That road is called the [life cycle](#def-g2-born-grow-die-cycle).

## 7.1 The stages of a life

**Definition 7.1 (Life cycle).**

The *life cycle* of a [living thing](https://one-course.com/books/biology/1/en/chapter/1-living-or-not-living#def-g1-living-or-not-living) is the row of *stages* its life goes through:

1. it is *born* — the beginning;
2. it is *young* — it grows and changes fast;
3. it is an *adult* — fully grown; adults can have young of their own;
4. it grows *old* , and at the end it *dies* .

**Example 7.2 (Three lives, same road).**

A kitten is born, plays and grows into a cat, who may have kittens herself, and grows old. A cherry seed sprouts, the young tree grows taller for years, the [adult](#def-g2-born-grow-die-cycle) tree makes blossom and cherries, and after many tens of years it dies. And you: baby, child, then one day a grown-up. Kitten, cherry tree, child — the same four [stages](#def-g2-born-grow-die-cycle).

![The beginning of three life cycles at once: newborn kittens at their mother’s milk.](https://one-course.com/images/onecourse/chapters/biology-1/g2-born-grow-die/img-627e030ba3b5.jpg)

*The beginning of three [life cycles](#def-g2-born-grow-die-cycle) at once: newborn kittens at their mother’s milk.*

![The stages of a life — and the arrow that starts the road again with the next generation.](https://one-course.com/images/onecourse/chapters/biology-1/g2-born-grow-die/fig-48dc4c82d0de.svg)

*The [stages](#def-g2-born-grow-die-cycle) of a life — and the arrow that starts the road again with the next generation.*

**Remark 7.3 (Why it is called a cycle).**

Each single life runs from [birth](#def-g2-born-grow-die-cycle) to death, like a road with two ends. But before the end, [adults](#def-g2-born-grow-die-cycle) have young, and those young start the road again. Seen over many generations, life turns like a wheel — that is why we say life *cycle*.

## 7.2 Growing and changing

**Proposition 7.4 (Growing up is more than getting bigger).**

While it grows, a young [living thing](https://one-course.com/books/biology/1/en/chapter/1-living-or-not-living#def-g1-living-or-not-living) also *changes*: a baby gets teeth, loses them, and gets stronger ones; a chick’s yellow fluff becomes real [feathers](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-covering); a young tree’s soft green [stem](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) turns to hard wood. Growing is getting bigger *and* becoming different.

**Proof.** *Admitted at this level.* ∎

**Example 7.5 (The photograph test).**

On Grandpa’s old photographs you can follow one person through every [stage](#def-g2-born-grow-die-cycle): baby, schoolchild, young man, father, grandfather. Same person, changing body. Photographs are little time machines for watching a [life cycle](#def-g2-born-grow-die-cycle).

**Method 7.6 (Putting life stages in order).**

Given pictures of a [living thing](https://one-course.com/books/biology/1/en/chapter/1-living-or-not-living#def-g1-living-or-not-living)’s life, mixed up:

1. find the [birth](#def-g2-born-grow-die-cycle) picture — egg, seed or newborn baby;
2. find the [adult](#def-g2-born-grow-die-cycle) — fully grown, able to have young;
3. place the young in between, from smaller to bigger;
4. check your row: does each picture lead to the next?

## 7.3 Every life ends — and life goes on

**Proposition 7.7 (Lifespans).**

Different [living things](https://one-course.com/books/biology/1/en/chapter/1-living-or-not-living#def-g1-living-or-not-living) live different lengths of time — a *lifespan*. A butterfly may live a few weeks; a cat, and a dog, ten to twenty years; a person often more than eighty years; some trees, hundreds of years. Long or short, every life has an end.

**Proof.** *Admitted at this level.* ∎

**Example 7.8 (The old apple tree).**

The bent old apple tree at the end of the garden gives fewer apples each year — it is in its [old age](#def-g2-born-grow-die-cycle). But its apples have pips, and one pip, planted, is already a young apple tree beginning the road. When the old tree dies, apple trees will not be gone: its young carry on.

**Remark 7.9 (Talking about death).**

Dying belongs to every [life cycle](#def-g2-born-grow-die-cycle), and it is all right to feel sad about it — people do, especially about pets and about people we love. [Biology](https://one-course.com/books/biology/1/en/chapter/1-living-or-not-living#def-g1-living-or-not-living) adds one comfort: because [adults](#def-g2-born-grow-die-cycle) have young before they die, life itself continues, cycle after cycle.

## 7.4 Exercises

**Exercise 7.1 ★.**

Name the four [stages](#def-g2-born-grow-die-cycle) of a [life cycle](#def-g2-born-grow-die-cycle), in order.

**Solution of Exercise 7.1.**

Born, young, [adult](#def-g2-born-grow-die-cycle), [old age](#def-g2-born-grow-die-cycle) (ending in death).

**Exercise 7.2 ★.**

At which [stage](#def-g2-born-grow-die-cycle) can a [living thing](https://one-course.com/books/biology/1/en/chapter/1-living-or-not-living#def-g1-living-or-not-living) have young of its own?

**Solution of Exercise 7.2.**

At the [adult](#def-g2-born-grow-die-cycle) [stage](#def-g2-born-grow-die-cycle).

**Exercise 7.3 ★.**

Put in order, oldest to youngest: a schoolchild, a baby, a grandmother, a mother.

**Solution of Exercise 7.3.**

Oldest to youngest: the grandmother, the mother, the schoolchild, the baby.

**Exercise 7.4 ★.**

Give the [life cycle](#def-g2-born-grow-die-cycle) of the cherry tree of [Example 7.2](#ex-g2-born-grow-die-three), [stage](#def-g2-born-grow-die-cycle) by [stage](#def-g2-born-grow-die-cycle).

**Solution of Exercise 7.4.**

A cherry seed sprouts ([birth](#def-g2-born-grow-die-cycle)); the young tree grows taller for years; the [adult](#def-g2-born-grow-die-cycle) tree makes blossom and cherries — and so new seeds; then it grows old and dies.

**Exercise 7.5 ★.**

Give two examples from [Proposition 7.4](#prop-g2-born-grow-die-change) of a young [living thing](https://one-course.com/books/biology/1/en/chapter/1-living-or-not-living#def-g1-living-or-not-living) *changing* while it grows, not just getting bigger.

**Solution of Exercise 7.5.**

For example: a baby gets teeth, loses them and gets stronger ones; a chick’s yellow fluff becomes real [feathers](https://one-course.com/books/biology/1/en/chapter/2-animals-around-us#def-g1-animals-around-us-covering); a young tree’s soft green [stem](https://one-course.com/books/biology/1/en/chapter/3-plants-around-us#def-g1-plants-around-us-parts) turns to hard wood.

**Exercise 7.6 ★.**

Who usually lives longer: a butterfly, a cat, or an oak tree? Put the three in order of [lifespan](#prop-g2-born-grow-die-lifespan).

**Solution of Exercise 7.6.**

Shortest to longest: the butterfly (a few weeks), the cat (ten to twenty years), the oak tree (hundreds of years).

**Exercise 7.7 ★.**

Why is the word *cycle* used, when each single life runs from [birth](#def-g2-born-grow-die-cycle) to death like a road? Use the figure’s purple arrow.

**Solution of Exercise 7.7.**

Because before the road ends, [adults](#def-g2-born-grow-die-cycle) have young, and the young begin the road again — that is the purple arrow looping back. One life is a road; life over the generations turns like a wheel.

**Exercise 7.8 ★.**

Try it: ask your family for photographs of one grown-up at different ages, and put them in life-cycle order with [Method 7.6](#met-g2-born-grow-die-order). Which [stages](#def-g2-born-grow-die-cycle) do the photographs show? Which [stage](#def-g2-born-grow-die-cycle) is still to come?

**Solution of Exercise 7.8.**

Open answer. The photographs usually show baby, child, [adult](#def-g2-born-grow-die-cycle) — [old age](#def-g2-born-grow-die-cycle) may be the [stage](#def-g2-born-grow-die-cycle) still to come.

**Exercise 7.9 ★★.**

The old apple tree of [Example 7.8](#ex-g2-born-grow-die-oldtree) will die one day, yet the garden need not lose its apple trees. Explain why, with the word *generation* or the purple arrow of the figure.

**Solution of Exercise 7.9.**

The old tree’s apples carry pips — seeds — and each planted pip is a young apple tree: the next generation. When the old tree dies, its young continue the cycle, so the garden keeps its apple trees.

**Exercise 7.10 ★★.**

A pebble never dies. Is that because it is very strong? Use [Chapter 1](https://one-course.com/books/biology/1/en/chapter/1-living-or-not-living#ch-g1-living-or-not)’s idea of living and non-living to explain.

**Solution of Exercise 7.10.**

No — it is because the pebble was [never alive](https://one-course.com/books/biology/1/en/chapter/1-living-or-not-living#def-g1-living-or-not-nonliving). Only [living things](https://one-course.com/books/biology/1/en/chapter/1-living-or-not-living#def-g1-living-or-not-living) are born, grow and die; a pebble has no [life cycle](#def-g2-born-grow-die-cycle) at all, so “never dying” is not strength, it is not living.