Life comes from life
Pasteur and the cell theory.
Mould on bread
A slice of bread left on a damp kitchen counter grows fuzzy patches. The bread was fresh and clean a few days ago.
Where do you think the mould came from?
What this lesson covers
The idea
Living things never arise spontaneously from non-living matter: new life always comes from pre-existing life, and all cells arise from pre-existing cells (cell theory).
Mould on bread
A slice of bread left on a damp kitchen counter grows fuzzy patches. The bread was fresh and clean a few days ago.
Where do you think the mould came from?
- From living things that were already there, such as spores
- From the bread itself changing into living matter
- From nothing, by chance
From belief to proof
Press Next step through the four pictures.
New life from old life
For long, people thought living things could arise spontaneously from non-living matter. Louis Pasteur showed this was wrong. He also found the germ theory of disease, and his work led to practices like sterilising food and instruments.
Living things never arise spontaneously from non-living matter. New life always comes from pre-existing life, and all cells arise from pre-existing cells (cell theory).
Notes
New life always comes from pre-existing life; all cells arise from pre-existing cells (cell theory). Living things never arise spontaneously from non-living matter.
Check yourself
Whose experiments proved that new life always comes from pre-existing life?
For long, people thought living things…
According to the cell theory, all cells arise from…
The mould on a slice of bread grew from…
- P. Maheshwari. P. Maheshwari is known as the Father of Indian Embryology, the study of plant reproductive organs.
- Louis Pasteur — correct. Yes!
- Subhash Mukhopadhyay. He pioneered India's first test tube baby through experimental IVF work. He is not the scientist of this idea.
- always came from pre-existing life. That is what Pasteur's experiments proved. People had long thought otherwise.
- could grow only from seeds. People believed living things arose from non-living matter. Pasteur showed new life comes from pre-existing life.
- arose spontaneously from non-living matter — correct. Yes!
- pre-existing cells — correct. Yes!
- non-living matter. Living things do not arise spontaneously from non-living matter.
- water alone. Cells arise from pre-existing cells, not from water.
- fresh bread, where mould was already present. The mould was not present when the bread was fresh.
- spores already present in the air, which settled on the moist bread — correct. Yes!
- a part of the bread that changed into living matter. Living things do not arise from non-living matter. The mould grew from spores in the air.