A cell is needed

The idea

Viruses are microscopic and acellular; they multiply only after entering a living cell and may infect plants, animals or bacteria and cause disease.

Does a virus multiply on its own?

A virus is microscopic. It is also acellular: it is not made of cells. Bacteria and Amoeba can multiply by themselves because they are living cells.

Where do you think a virus can multiply?

• Anywhere, on its own
• Only after it enters a living cell
• Only in water

Test the virus

Wait with the virus outside any cell. Then put it inside a plant cell, an animal cell and a bacterial cell, and wait each time.

Only inside a living cell

Viruses are microscopic and acellular. They multiply only after entering a living cell. They may infect plants, animals or bacteria and may cause disease.

• Question | Answer
• How big? | Microscopic
• Made of cells? | No, acellular
• Where does it multiply? | Only inside a living cell
• What can it infect? | Plants, animals or bacteria
• What may it cause? | Disease

Notes

Viruses are microscopic and acellular. They multiply only after entering a living cell, may infect plants, animals or bacteria, and may cause disease.

Check yourself

What does acellular mean?

A virus is left on a clean plate with plenty of food but no living cell. What happens?

Which can a virus infect?

• Not made of cells — correct. Yes. A virus has no cells.
• Made of one cell. That is unicellular, like bacteria and Amoeba.
• Made of many cells. That is multicellular.
• It does not multiply — correct. Yes. A virus multiplies only after it enters a living cell.
• It multiplies quickly. Food alone is not enough. A virus needs a living cell.
• It becomes a cell. A virus does not become a cell. It stays acellular.
• Plants, animals or bacteria — correct. Yes. A virus may infect plants, animals or bacterial cells.
• Only animals. Viruses may infect plants and bacteria as well.
• Only plants. Viruses may infect animals and bacteria as well.