Section 2: Living things depend on the function of cells.

Key Ideas     Unit Checklist 

  Unit B: Section 2 – Introduction


Figure B.S.2.1 – Red blood cells are about 20 times smaller than the width of a hair.

Figure B.S.2.2 – 10 000 viruses could fit into a millimetre.
 

Figure B.S.2.3 – If a red blood cell was the size of a baseball stadium, a bacterium would be the size of the pitcher’s mound, and a virus would be the size of a baseball.
Tiny Things

There are billions of living things surrounding us that we can’t see with our unaided eyes. The smallest thing we can see is a single strand of hair. A piece of hair is about 10 times smaller than one millimeter on a ruler. That means you could fit 10 hairs side by side into 1 millimetre.

In Canada, we measure objects with the metric system. Length in the metric system is based on the metre. We use prefixes, or tiny words, before metre, for smaller or bigger measurements. You probably know the prefixes centi- and milli-. 100 centimetres (cm) fit into 1 metre. 1000 millimetres (mm) fit into 1 metre. There are additional prefixes to describe objects smaller than a millimetre.

1 000 000, or 1 million, micrometres fit into 1 metre. The symbol for micrometres is μm. μ is a letter in the Greek alphabet called mu. Cells and bacteria can be measured in micrometres. Red blood cells are about 6 μm wide. Many bacteria are about 2 μm long. A piece of hair is about 100 μm wide.

1 000 000 000, or 1 billion, nanometres fit into 1 metre. The symbol for nanometre is nm. Viruses can be measured in nanometres. For example, the flu virus is about 100 nm long.

 Watch More

Tiny is a Relative Thing

Nano and micro-sized objects can be hard to visualize. This cartoon shrinks down a human to get a different perspective of nano-sized objects.

 
 
 
 
Watch this video to understand the relative sizes of tiny objects.

 
 

  Words to Think About:

Check out the word cloud below. It pictures the important words that you are going to learn in this section. Watch for these words, and combinations of these words, as you read. When you see them highlighted, you can click on them to learn more about what the word means. You can also visit the course glossary and read definitions for all of these words.


Lessons in This Section

Lesson B4: Looking at Cells
Key Question – What technologies do we use to observe tiny cells?

Lesson B5: Studying Cells
Key Question – What structures are found inside living cells?
Lesson B6: Unicellular and Multicellular Organisms
Key Question – What are the differences between organisms with one cell and organisms with many cells?

Lesson B7: Specialized Cells and Tissues
Key Question – What are the special roles of different body cells?

Lesson B8: The Effect of Diffusion and Osmosis on Cells
Key Question – How do substances move in and out of cells?
Reading and Materials for This Section

Science in Action 8
Reading: Pages 98–125

Materials Lists for Unit:
Master List of all materials
Materials organized by lesson and activity

  Try It!


How Small Can You Cut?

Try this activity to visualize just how small cells and bacteria are.

Materials: 

  • Sheet of paper
  • Scissors
  • Ruler
  • Pencil
 
Take care with scissors; don't cut yourself or anyone else!
Instructions: 
    1. Measure a strip of paper that is 1 cm wide and 28 cm long.

    2. Cut out the strip of paper.

    3. Cut the strip of paper in half along its length. It should now be 1 cm by 14 cm.

    4. Cut the strip of paper in half again. It should now be 1 cm by 7 cm.

    5. Keep cutting the strip of paper in half. Count how many times you are able to cut the paper in half, before it is too small to cut.

Questions: 

Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.

Most people can cut the strip of paper in half 8 or 9 times, before it is too small to cut.
You would have to cut the paper in half 15 times to get to the size of a red blood cell, 18 times to get to the size of a bacteria, and 22 times to get to the size of a virus. That’s pretty tiny!