Science- Biology

Living things have certain life processes in common. There are seven things that they need to do to count as being alive. The phrase MRS GREN is a way to remember them:

M Movement All living things move, even plants R Respiration Getting energy from food S Sensitivity Detecting changes in the surroundings G Growth All living things grow R Reproduction Making more living things of the same type E Excretion Getting rid of waste N Nutrition Taking in and using food

It can be easy to tell if something is living or not. A teddy bear might look like a bear, but it can't do any of the seven things it needs to be able to do to count as being alive.

What about a car? A car can move, it gets energy from petrol (like nutrition), it might have a car alarm (sensitivity), and it gets rid of waste gases through its exhaust pipe (excretion). But it can't grow or make baby cars. So a car is not alive.

imal cells usually have an irregular shape, and plant cells usually have a regular shape

Cells are made up of different parts. It is easier to explain what these parts are by using diagrams like the ones below.

Animal cells and plant cells both contain:

• cell membrane, cytoplasm, nucleus

Plant cells also contain these parts, not found in animal cells:

• chloroplasts, vacuole, cell wall

The table summarises the functions of these parts.

The male reproductive system contains these parts:

• testes (pronounced "test-eez")

• glands

• sperm ducts

• urethra

• penis.

Testes

The two testes (one of them is called a testis) are contained in a bag of skin called the scrotum. They have two functions:

• to produce millions of male sex cells called sperm

• to make male sex hormones, which affect the way a man's body develops.

he female reproductive system contains these parts:

• ovaries

• egg tubes

• uterus (pronounced "yoo-ter-russ")

• cervix

• vagina.

Ovaries

The two ovaries contain hundreds of undeveloped female sex cells called egg cells or ova. Women have these cells in their bodies from birth - whereas men produce new sperm continually.

Egg tubes

Each ovary is connected to the uterus by an egg tube. This is sometimes called an oviduct or Fallopian tube. The egg tube is lined with cilia, which are tiny hairs on cells. Every month, an egg develops and becomes mature, and is released from an ovary. The cilia waft the egg along inside the egg tube and into the uterus.

Uterus and cervix

The uterus is also called the womb. It is a muscular bag with a soft lining. The uterus is where a baby develops until its birth.

The cervix is a ring of muscle at the lower end of the uterus. It keeps the baby in place while the woman is pregnant.

Vagina

The vagina is a muscular tube that leads from the cervix to the outside of the woman's body. A man's penis goes into the woman's vagina during sexual intercourse. The opening to the vagina has folds of skin called labia that meet to form a *****. The urethra also opens into the *****, but it is separate from the vagina, and is used for passing urine from the body.

When you eat a piece of bread, you don't wake up next day to discover it growing out of your arm! The food we eat has to be broken down into other substances that our bodies can use. This is called digestion. Without digestion, we could not absorb food into our bodies and use it.

Digestion happens in the digestive system, which begins at the mouth and ends at the anus.

After we swallow, our food passes through these organs in turn:

any living things are so small that they can only be seen through a microscope. These living things are called microorganisms or microbes. There are three main types of microbe:

• fungi

• bacteria

• viruses

Animals eat food to get their energy. But green plants don't. Instead they make their own food, glucose, in a process called photosynthesis. We say that plants can photosynthesise.

These are the things that plants need for photosynthesis:

• carbon dioxide

• water

• light

These are the things that plants make by photosynthesis:

• glucose

• oxygen