Microorganisms

Bacteria and protozoa are single celled, fungi may be single or many celled, and algae make their own food. A virus is not fully alive on its own, becoming active only inside a living cell.

In real life: Microbes live everywhere, in soil, water, air and inside our bodies, where many help us digest food.

Worked example 1

Question. Why is a virus placed apart from other microbes?

Answer: Because a virus can reproduce only inside a living host, unlike bacteria, fungi and protozoa.

The cell

Plant, fungal and bacterial cells have an extra cell wall outside the membrane, and plant cells also have a large vacuole and green chloroplasts. Bacteria have no well-defined nucleus. A cell’s shape suits its job.

In real life: Your body is built from trillions of cells, each a tiny living unit doing its own task, just as bricks build a whole house.

Worked example 2

Question. Name two parts found in both a plant cell and an animal cell.

Answer: Both have a cell membrane, cytoplasm and a nucleus.

Worked example 3

Question. Give one part a plant cell has that an animal cell does not.

Answer: A plant cell has a cell wall (also chloroplasts and a large vacuole), which an animal cell lacks.