Question

How did comparisons of different rRNA sequences lead to the discovery of Archaea? Why did Woese use rRNA genes to construct molecular phylogenies? Which groups are most similar (bacteria, archaea, and eukaryotes) with respect to the following structures or processes: cellular membrane biochemistry, DNA replication, RNA transcription, mechanism of protein translation, initiation of protein translation. Explain the argument that the most fundamental divide in the Tree of Life is between Bacteria and Archaea. Why is membrane composition cited as the basis of the ‘eukaryote paradox’? Know the arguments for discontinuing use of the term “prokaryote” and be able to explain why you think (or don’t think) that prokaryote is a useful and/or accurate term. How do Lateral Gene Transfers (LGT), aka horizontal gene transfer, confound reconstruction of phylogenetic trees? Name three processes of bacteria and archaea that result in LGT. How can we overcome this difficulty in understanding the (vertical) evolutionary history of microbes? What kinds of genes seem resistant to LGT? Explain the statement “we are embedded in a microbial world” – be sure to include the production of oxygen on Earth in your answer. Remember that thermodynamics tells us that energy flows out of all systems, but matter cycles. Much of the nutrient (matter) cycling that we all depend on requires microbial activity. Name the nutrient cycles that we described in lecture that require microbial activity. When did the plant- nitrogen-fixing-bacterial symbiosis emerge in earth’s history? Chlorophylls are an innovation of which group of organisms? Why is nitrogen limiting in most ecosystems?

Answer 1

Carl Woese first discovered the relationship between the organisms with the help of rRNA sequences. Ribosomes is a important organalle present in organisms, ribosomes are made up of ribosomal RNA. Due to the mutation there is a variation and comparision of different RNA to know the evolutionary relationship which leads to the discovery of two domains under prokaryotes. There are archaea and bacteria.Between them Archea and bacteria are similar in case of cell wall peptidoglycan layer and as well as not having nuclear membrane.

Horizontal gene transfer is a method which transfer the gene from unrelated species.The three process that results in LGT are conjugation,transduction,transformation. LGT leads to the reconstruction of phylogenetic tree because there is a transfer of genes between two unrelated species which leads to the complication in constructing a tree.

Many plant nutrient cycles require microbe for activity for example nitrogen cycle and as well as organic matter decomposition.Nitrogen fixing process discovered in 1877 . Chlorophyll are present in cyanobacteria and plants mainly.Nitrogen is limiting because there are most abundant in air but form air they (plants) are not able to take up