1.5: The Origin of cells
Teaching time: 2 hours Practical time : 0 hours
key vocabulary
prior learning
Review 1.1 introduction to cells
Review 5.1 evidence for evolution
Louis Pasteur's experiments
A1: Evidence from Pasteur’s experiments that spontaneous generation of cells and organisms does not now occur on Earth.
U1: Cells can only be formed by division of pre-existing cells.
Exercise 1: Outline Louis Pasteur's experiments that falsified spontaneous generation.
The Origin of cells
Essential idea: There is an unbroken chain of life from the first cells on Earth to all cells in organisms alive today.
NoS: Testing the general principles that underlie the natural world—the principle that cells only come from pre-existing cells needs to be verified. (1.9)
U2: The first cells must have arisen from non-living material.
Exercise 2: If cells do not arise spontaneously i.e. out of thin air, how did the first cell come into existence?
There must have been a time before cells because the earth is approximately years old and our oldest fossils are years old.
During this gap in time the following processes must have occurred to allow living cells to emerge:
1. The formation of organic compounds or from other simple molecules like ______, ________, methane and _______ gas.
2. The formation of from these monomers.
3. The formation of -replicating molecules that would have allowed inheritance of information to begin.
4. The formation of that would enclose and package these molecules. This would provide an internal chemistry that was from the surroundings.
Out of a harsh hostile world article.pdfThe Endosymbiotic Theory: Explaining the origin of eukaryotes
U3: The origin of eukaryotic cells can be explained by the endosymbiotic theory.
Guidance from the syllabus: Evidence for the endosymbiotic theory is expected. The origin of eukaryote cilia and flagella does not need to be included. Students should be aware that the 64 codons in the genetic code have the same meanings in nearly all organisms, but that there are some minor variations that are likely to have accrued since the common origin of life on Earth.
Exercise 3: Discuss the evidence for the endosymbiotic theory.
