Cooperation & Conflict/ Kin Selection / Relatedness
Define R, S, T, and P in the Prisoner's dilemma, and rank them in order of payoff.
R = reward for mutual cooperation (both you and opponent cooperate)
S = sucker's payoff (you cooperate, but opponent defects)
T = temptation to cheat (you cheat against an opponent that cooperates)
P = punishment for mutual defection (both you and opponent defect)
T > R > P > S
Define "Ribozyme", and give two examples of ribozymes seen today
Ribozyme = RNA with catalytic enzyme properties
Examples: modern ribosomes, self-splicing introns, viroids
Rank these terms in order of increasing biological complexity:
multicellular organism without specialized cells; single celled prokaryote; template replicator; multicellular organism with two cell types; single celled eukaryote
template replicator -> single celled prokaryote -> single celled eukaryote -> multicellular organism without specialized cells -> multicellular organism with two cell types
What are the two components of inclusive fitness?
direct fitness (your reproduction) and indirect fitness (relatives' reproduction)
What is the "Catch-22" / paradox regarding the origin of life?
Long genetic sequences are required to produce enzymes, but enzymes are required to have long genetic sequences
Compare and contrast the soma and germ cells of Volvox algae with regards to the following features:
size, presence of flagella, regA expression, fitness component, costs/benefits to cell
Soma: small, have flagella, express regA, contribute to survival rather than reproduction, cost: no reproduction, benefit: increased inclusive fitness by enhancing germ cell viability
Germ cells: larger, no flagella, no regA expression, contribute to reproduction, cost: can't survive without soma, benefit: able to reproduce
Vampire bats roost in large colonies in caves across Central and South America. Each night, the bats leave and forage for blood meals before returning to roost in the same cave. Despite most individuals within a cave being unrelated, vampire bats have been observed sharing food with other bats in the cave who were unsuccessful at foraging.
What is a potential explanation for this observed cooperative behavior?
Vampire bats could be demonstrating reciprocal altruism / reciprocity. Since the bats roost in the same place each night, they will have multiple chances to interact with the same individuals. Therefore, the bats could be sharing food with hungry individuals with the anticipation that those individuals would help them in return on a future night.
According to Eigen's threshold equation, the maximum sequence length (N) of a molecular replicator is determined by what two values?
The selective advantage (s) and the mutation/error rate (1-q).
In volvocine algae, the evolution of multicellularity was initiated by two traits: the development of the extracellular matrix (ECM), and genetic control of cell numbers.
Explain how these two traits promote cooperation in multicellular organisms.
ECM connects cells together, facilitating the sharing of resources and creating a sort of "commons" where cells can cooperate.
Genetically controlling cell numbers can prevent the spread of selfish cells that exploit the shared resources
Describe the "Tragedy of the Commons" and how it relates to multi-level selection
Multi-level selection = selection happening on individuals as well as groups.
Even though individuals who cheat have higher fitness within their group, the high cost of losing shared resource will decrease fitness of group overall. Groups who fully cooperate will have higher fitness in the long run.
A _______ is a group of cooperating molecular replicators.
What condition must be met to allow for selection at the level described above? Explain your answer.
A hypercycle is a group of cooperating molecular replicators.
For selection to happen at the level of a hypercycle, the group must be contained in a compartment such as a cell / protocell. If the group is not bound together in some way, selfish replicators will have a higher fitness and will increase in frequency, leading to the dissolution of the cycle.
Human zygotes inherit mitochondria from maternal egg cells; therefore, mitochondrial DNA (mtDNA) is inherited exclusively from the maternal parent.
Considering only mtDNA, calculate the relatedness between a human male and his following relatives:
1) full brother
2) male cousin (son of mother's full sister)
3) maternal grandfather
1) 1 (received all mtDNA from the same mother)
2) 1 (focal male's mother and her sister received the same mtDNA from their mother, and cousin would have received that from his mom)
3) 0 (males don't pass on their mtDNA)