1. Discuss and decide upon characteristics that define each of the following broad groups
(domains, kingdoms) of organisms in order to attempt to define these major groups of life
on the planet. Although many characteristics may overlap from one group to the next,
attempt to define some traits that could be used to definitively (exclusively) place an
organism into a specific group. Finally, for each, what would the small subunit ribosomal
rRNA gene sequence tell us?
Viruses
Bacteria
Archaea
Protists (algae, protozoa)
Fungi
Animals
Plants
2. For the previous groups, which include representatives of ones that live as part of the
âhuman ecosystemâ? Provide some examples of each and where they can be found,
including both those that are part of our normal microbiota (i.e., not pathogens) and some
that are.
3. Considering the above and what weâve covered about these groups of organisms,
identify some structures/processes that hypothetically could be used to inhibit or kill
different types of pathogens without (hypothetically, at least) harming the human host.
4. Consider the microbial world. Which has a greater impact or importance â pathogens,
or benign microbes? Explain, giving examples.
5. A number of antibiotics target the bacterial 70S ribosome, exploiting structural
differences from the 80S ribosome found in humans and other eukaryotes. Although
effective at killing bacteria, these drugs can still have some toxicity to humans. In the
context of the endosymbiotic theory of evolution, provide a hypothesis as to why this
might be.
