1.5 Origin of Cells

Question 1

Spontaneous Generation

Answer 1

The formation of living organisms from non living matter.

Question 2

Origin of the first cells.

Cells are only formed by division of pre-existing cells. Repeated cell division.

Answer 2

However, if we trace back then the first cells must have evolved from non-living material.
Why could spontaneous generation take place then but not now?

Question 3

The Endosymbiosis Theory.

• Helps explain the evolution of eukaryotic cells
• Chloroplasts (photosynthesis eukaryotic cells) and mitochondria

Answer 3

• A larger cell takes in a smaller cell by endocytosis. Stay in a vesicle in the cytoplasm.
• Instead of being digested it performs a useful function for the larger cell.
• Smaller cell divides as frequently as the large cell

Question 4

Symbiosis
Two organisms living together.
The two cells are in a symbiotic relationship.

Answer 4

• Both organisms are benefited. Know as a mutualistic relationship.
• Large cell supplies food and smaller cell carries out aerobic respiration to supply efficient energy.
• Natural selection favoured cells that developed this endosymbiotic relationship.

Question 5

Mitochondria

Answer 5

And anaerobic respiring cell took in a bacterium that respired aerobically which supplies both of them energy in the form of ATP.
This aerobic bacterium evolved into mitochondria and the larger cell evolved into heterotrophic eukaryotes alive today such as animals.

Question 6

Chloroplast

Answer 6

A heterotrophic cell took in a smaller photosynthetic bacterium, which supplied it with organic compounds, thus making it an autotroph. Evolved into chloroplasts