Question

4. When building a phylogenetic tree, why is it important to select as a molecular marker a gene involved in an essential process? [1 point] 5. Methanogens, the only type of Archaea known in 1977, are organisms that use CO2 as a carbon source and do not rely on sunlight as a source of energy. Which nutritional class do they belong to? [1 point] 6. Methanogens do not tolerate oxygen and can thus be referred to as? [1 point]

Answer 1

4.
To construct a phylogenetic tree, DNA or protein sequence of an important gene must be taken. This is because the evolutionary modifications (mutations) that occur in an important gene might reflect the evolutionary diversification of a species.
If we consider an unimportant gene, the changes in such a gene may not provide a selective advantage and hence not necessarily involve speciation/diversification of an organism.

5.
Methanogens are chemoautotrophs.
Inorganic energy source = H₂S, S, NH₃, H₂, and Fe⁺²
Carbon source = CO₂

6.
Methanogens are obligate anaerobic organisms.