The seminar will concentrate on the evolutionary theory of conflict and cooperation and the deductions derived from this theory with special reference to problems concerning social behavior, origin of the major levels of selection (gene, bacteria-like cells, eukaryotic-like cells, multicellular organisms, societies) and the evolution of sex. Population genetics and game theory approaches will be covered. Some possible topics are listed below. Student input into topics covered is welcome.
About
2 billion years ago, archaebacteria-like cells (destined to be the ancestors of
all eukaryotes) began alliances with other bacteria (the mitochondrion-to-be
or mtb for short). Most workers agree
that the mtb was a purple
eubacteria-like cell, but it could have been a bacterium of the mycoplasma group or an
archaebacterium like Sulfolobus. There is less agreement on whether the initial
association between the host and the mtb
was relatively benign, like predators engulfing prey, like parasites and
pathogens infecting hosts, or like farming. What is clear is that this association, along with
other associations involving cyanobacteria (leading to plastids), spirochetes
(leading to centrioles) and possibly eocytes (leading to the nucleus and
endoplasmic reticulum), eventually led from independent bacteria-like cells
through conflictual and then cooperative associations to a new level of
selection—the eukaryotic cell (Table
1). Our focus will concern the host cell and the mtb, however, I believe the approach we will follow is applicable
to the other associations.
|
Hypothesis |
Initial Association |
Conflict Stage |
Mediation Stage |
Cooperation |
|
Predator-prey |
Predator-prey: host engulfs mtb for food |
mtb is engulfed and digested
for food |
mtb escapes digestion by host
(reside in vacuole) |
host gives organic carbon and protection mtb gives O2
metabolism (ATPs) and protection from ROS |
|
Parasitic |
Parasitic: mtb infects host for reduced
carbon |
mtb infects host for reduced
organic compounds and weakens or kills host |
host escapes mtb’s lytic
mechanisms and ROS and uses ATP from mtb |
|
|
Hydrogen |
Benign: host uses mtb’s H2 waste
product |
host engulfs mtb and mtb starves for organic carbon; mtb trapped inside host |
exchange of carbon import and glycolysis genes from mtb to host |
|
|
ROS |
Mutualistic: mtb uses
host’s excreted carbon compounds for energy and recycles NADH for host |
mtb inside host and releases
ROS which harmed or manipulated host’s transmission of mtb |
in order to escape ROS, host keeps mtb active and steals ATP from mtb |
|
Table 1. Conflict, mediation and
cooperation in the origin of eukaryotes for different hypotheses about the
initial association. mtb =
mitochondria to be. ROS = reactive oxygen species. For all hypotheses, the
mediation stage could result in a dissolution of the association by reverting
to free living state. In these cases, the association could not pass into the
cooperation stage. Alternatively, conflict mediation could stabilize the
association as indicated during the mediation stage, so that the association
could pass into the cooperation stage which, of course, was the same in all
cases. In other words the end point of the evolutionary transition is the
same for all hypotheses. |
Grading
will depend on class participation, presentation, and question and thought
cards handed in at each meeting. Graduate students must give a class
presentation, whereas this is not required of undergraduates .