1.5 Flashcards
Discuss how cells can only be formed by a division of pre-existing cells.
Cells are very complex and impossible to build from basic subunits. No cell has ever been created in a lab, and there is no known example of cells that haven’t come from pre-existing cells division
What must the first cells have arisen from?
They must have arisen from non-living material.
Miller & Urey’s experiment showed this in that they put steam through a mixture of methane, hydrogen & ammonia (simulates pre-biotic earth atmosphere). They then simulated a lightning storm and found that this produced amino acids and carbon compounds that are needed for life.
Discuss the endosymbiotic theory for the origin of eukaryotes
Endosymbiotic theory states that:
Mitochondria were once free living bacteria
Then larger cells engulfed them (endocytosis) and allowed them to stay in their cytoplasm
The bacteria supplied energy for the cell and the cell provided protection for the bacteria
The bacteria eventually evolved into mitochondria
Outline evidence from Pasteur’s experiments showing that spontaneous generation of cells and organisms does not occur on Earth now:
Pasteur put broth in swan necked flasks and sealed them
He then boiled the broths to purify/sterilise them
After a year, the broth mixture was clear
When Pasteur snapped the swan neck, within a day the mixture turned cloudy
This disproved spontaneous generation, as Pasteur proved that microbes in the broth needed contamination to grow.
