The Tree of Life

Question 1

What characteristics did LUCA likely have?

Answer 1

Uses RNA
Single or double membrane
Single-celled or unicellular

Question 2

Define, recognize and describe examples of each of these terms: IDA, LUCA, ribozyme, horizontal gene transfer

Answer 2

IDA began the diversity of descendant lineages. LUCA was thought to have been a single species but evidence of lateral gene transfer suggests it may have been a community. This growing community built the tree of life through horizontal gene transfer. Ribozymes are enzymes composed of RNA; RNA has a phenotype and genotype.

Question 3

The four hypotheses for the origin of the three domains of life

Answer 3

Universal Gene Pool
Ring of Life Hypothesis
Chronocyte Hypothesis
Three viruses, three domains hypothesis

Question 4

Why was the small-subunit rRNA used for the first whole-life phylogenies and what relationships did it reveal among the three domains?

Answer 4

It was used because it grouped by genetic similarity

This relationship revealed that the previously used five-kingdom classification system had a limited resemblance to actual revolutionary relationships. Archaebacteria is more closely related to Eukaryotes than to true bacteria. So, they dropped bacteria from Archaebacteria and renamed the group Archaea giving rise to our three model systems: Bacteria, Archaea, and Eukarya.

Question 5

Last common ancestor was not a single species but rather a pool of readily and largely independent genes. eventually, the 3 cellular forms emerged with genomes stable enough to establish persistent lineages

Answer 5

Universal Gene Pool

Question 6

Eukaryotes arose by fusion of archaea and bacteria, but lacking a cytoskeleton it is difficult to see how this is possible

Answer 6

Ring of life

Question 7

Lineage called chronocyte branches deepest in the tree from bacteria and developed a cytoskeleton, then the chronocyte ate an archaea that became an endosymbiont

Answer 7

Chondrocyte hypothesis