Unit 7: Topic 7 - Common Ancestry

Question 1

What types of structural evidence help show common ancestry (in eukaryotes)?

Answer 1

Linear chromosomes, introns, and membrane-bound organelles.

Question 2

How do linear chromosomes help show common ancestry?

Answer 2

Linear chromosomes exist in all eukaryotic cells alongside other complex structures, such as histones, compared to prokaryotes which contain circular chromosomes and not much further complexity. If any prokaryotic cell was compared to a eukaryotic cell, the chromosome would be a very clear identification.

Question 3

How do genes containing introns help show common ancestry?

Answer 3

Introns and exons in eukaryotic genes are removed before the protein can be made (during RNA splicing). Introns are not present in prokaryotes and are unique to all eukaryotic cells.

Question 4

How do membrane-bound organelles help show common ancestry?

Answer 4

Membrane-bound organelles are only found in eukaryotic cells, and they are found in each one. Endosymbiotic theory states a large prokaryotic cell took in prokaryotic mitochondria, and this first eukaryotic cell would be (in theory) the latest ancestor of all eukaryotic cells.