Science notes, unit 3

Humans

Textbook Science Year 2 (DLP), pages 23–34

What this chapter covers

You know that humans reproduce by giving birth (3.1.1)
{'You can name the stages of human growth': 'infant, child, teenager and adult (3.1.2)'}
You can describe how we change in size, height and weight as we grow (3.1.3)
You know that growth is different from one person to another, even at the same age (3.1.3)
{'You can name features that children inherit': 'iris colour, skin colour and hair type (3.1.4, 3.1.5)'}
You can find which features a child inherits from parents or ancestors (3.1.6)

Where do babies come from? How do we change as we get older? Why do you look like your mum or dad? In this unit you will find out about how humans reproduce, grow and inherit features.

3.1Humans reproduce and grow

Human reproduction

Reproduction means making more of the same kind of living thing. Humans reproduce by giving birth.

A mother gives birth to a baby. This is how humans increase their numbers. In the book, Kanang's mother gives birth to his baby brother, Kalai.

How do humans reproduce?

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By giving birth.

Stages of human growth

We grow through four stages. Look at the picture from the baby to the grown-up.

Order	Stage	Who is this?
1	Infant	A baby
2	Child	A young boy or girl
3	Teenager	A young person who is almost grown up
4	Adult	A grown-up, like a parent

Babies, then a crawling infant, then children, teenagers and adults, joined by arrows — The stages of human growth: infant, child, teenager, adult.

Did you know? You were once an infant. One day you will be an adult!

We change as we grow

Since we were born, we have changed in three ways.

Size: we become bigger. A shirt that fitted last year is now tight.
Height: we become taller.
Weight: we become heavier.

A boy buttoning a shirt before, and after one year when the shirt is tight — After one year the shirt is tight. The boy has grown bigger.

A boy measured against a wall, taller after one year; a baby on a weighing scale, heavier after one year — Taller and heavier after one year.

Your old shoes are now too small. What has changed?

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Your size (your feet) has grown bigger.

Growth is different for each person

Pupils of the same age can have different height, weight and palm size.

Four pupils standing against a height chart. Kanang is taller than Kugan. — Kanang is taller than Kugan, but Kugan is bigger than Kanang.

To compare friends, we can measure palm size with a pencil outline, weight with a weighing scale (kg) and height with a wall ruler (cm). Record the numbers in a table.

Name	Weight (kg)	Height (cm)
Nisa	Write it here	Write it here
Kugan	Write it here	Write it here

Different growth is normal. Nobody is "wrong" because they are taller or shorter than a friend.

3.2Inherited features

Inheritance means getting features from our parents or ancestors. A child is called an offspring.

Kanang's iris is the same colour as his father's iris. The iris is the coloured part of the eye.

Kanang's eye and his father's eye with the same iris colour — Kanang inherited his father's iris colour.

Offspring inherit these features:

Feature	Example
Iris colour	Brown like Mum
Skin colour	Fair like Mum
Hair type	Wavy like Dad or Grandpa

A boy, his parents and a portrait of his grandfather; the boy has his grandfather's hair type — A child can look like a grandparent too.

A girl with her mother and father, with a list of features she inherited — This girl inherited wavy hair from her father and fair skin from her mother.

Try it: Pick one feature of yours, such as iris colour or hair type. Who in your family has it too?

Features we inherit come from the family. Things we learn, such as riding a bicycle, are not inherited.

Name three features that offspring inherit.

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Iris colour, skin colour and hair type.

Pictures: Science Year 2 (DLP) textbook, pp. 25-28 and 31-33.

Summary

Idea	Remember
Reproduction	Humans give birth.
Stages of growth	Infant, child, teenager, adult
We change in	Size, height, weight
Growth	Different for each person, even at the same age
Inherited features	Iris colour, skin colour, hair type