The document discusses the origin of cells. It states that cells can only arise through the division of pre-existing cells, as there is no natural mechanism for cells to form from simpler subunits. The first cells must have originated from non-living material. The origin of eukaryotic cells can be explained by the endosymbiotic theory, where mitochondria and chloroplasts were once free-living protists that were taken in by larger protists, establishing a mutualistic relationship where the smaller cell supplied food/resources and the larger cell supplied energy.

1. Topic 1.5 The Origin of Cells
IB Biology
R. Price
v. 1 2015

2. Allott 45

3. Cells can only be formed by division of pre-existing cells
Evidence:
• No natural mechanism to
produce cells from simpler
subunits
• No example of cell number
increasing without cell division
• Viruses are produced from
simpler subunits but not made
of cells and can only reproduce
inside host cells

4. Allott 47

5. Allott 48

6. The first cells must have arisen from non-living material
Where did the first cells come
from?
Hypothesis:
• A series of stages over long
periods of time
• Evolved over a period of
hundreds of millions of years

7. Allot 48

8. Allott 49

9. The origin of eukaryotic cells can be explained by the endosymbiotic theory
• Explanation for mitochondria,
chloroplasts, and mDNA &
ctDNA
• Mitochondria & chloroplasts
were once free-living protists
• Taken in by larger protists
• Mutualistic relationship
 Smaller cell supplied w/food or
resources
 Larger cell supplied w/ energy

10. Allott 50

12. Sources
Content
Allott, Andrew, and David Mindorff. Biology: Course Companion. 2014
ed. Oxford: Oxford UP, 2014. Print. Oxford IB Diploma Programme.
Walpole, Brenda. Biology for the IB Diploma. 2nd ed. Cambridge:
Cambridge UP, 2014. Print.
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