Unit 1
Cells and life.
What makes something alive: the cell and what is inside it, plant, animal and bacterial cells, and life in a drop of pond water.
Before this unit
- Ratio and scale Mathematics
The unit, lesson by lesson
Lessons
7 lessons · 38 practice questions · about 3 hours
The signs of life
What makes something alive: seven signs a living thing shows all at once, a flame that imitates life, a virus on the border, and one bacterium that becomes thousands.
Inside a cell
Cell theory, and what is inside an animal cell: membrane, cytoplasm, nucleus, mitochondria and ribosomes, and the job of each.
Plant and animal cells
What a plant cell has that an animal cell lacks: a wall, chloroplasts and a large vacuole. And why a plant has mitochondria too.
A bacterial cell
A cell with no nucleus: how a bacterium is built, splitting in two, growth that doubles itself, and the effect of temperature.
Magnification and scale
How a microscope magnifies, how to work out true size from a magnified picture, and why magnification alone shows no detail smaller than light's wavelength.
Life in a drop
One drop of pond water under a microscope: what the eye alone can make out, which magnification suits each creature, single cells bigger than whole animals, and three ways to get food: hunting, grazing and making it from light.
The hidden fungus
What comes up above the ground is only the fruit: the web of threads below digests leaves outside its body, works faster in warmth and slower when the soil is too dry or too wet, and trades sugar for water with the tree’s roots.