**** me ********** im over this class
Consider a molecular replicator in which mutations incur a fitness cost of 0.8. What is the maximum sequence length of that replicator if a mutation occurs:
(i) once every 10 base pairs? s=1/0.8=1.25 ln(s)(1-q)=ln(1.25))(1/10)=2.23 Max seq. Is 2 nucleotides. (ii) once every 100 base pairs? ln(s)(1-q)=ln(1.25))(1/100)=22.31 Maximum seq is 22 nucleotides. (iii) once every 500 base pairs? ln(s)(1-q)=ln(1.25))(1/500)=111.57 Maximum sequence is 111 nucleotides.
Suppose A possesses a gene that imposes a fitness cost of 0.5. However, carrying the gene causes a fitness increase of C by 0.5, D by 1 and G by 0.6, will this behavior be selected for or against, according to Hamilton? (NOTE: I don't expect the exam to throw you a question calculating this across different relatives, but if this question makes sense, then you should be alright on the exam -- if you can calculate the fitness benefit of saving n siblings or n cousins, etc, you're probably good)
-C+rB > 0 In terms of A and C. r for A and C is 0.50. B in this case says 0.5, while C is 0.5. Since (0.5)(0.5) > 0.5 is not a true statement, not selected for. In terms of A and D. r for A and D is 0.50. B in this case is 1, while C is 0.5. Since 1(.5) > 0.5 is not a true statement, not selected for. G does not matter since not family, does not have any genes of A. Overall, this will be selected against, according to Hamilton.
ETI NOT an ETI Formation of earth X Evolution of eukaryotes from prokaryotes X Great oxidation event X Evolution of metazoans (e.g. sponges) from unicellular eukaryotes X Evolution of terrestrial animals from vertebrate fishes X Evolution of multicellular plants from unicellular eukaryotes X Evolution of multicellular bacteria ~3byp from unicellular bacteria X Evolution of Homo sapiens (modern humans) from Australopithecus afarensis X Evolution of Homo sapiens (modern humans) from rodent-like ancestors X
1- not 2-is 3-not 4- is 5-not 6-is 7-is 8-not 9-not
Outline the five hypothesized stages during evolution of the eukaryotic cell. Consortium of Cells Phagocytosis Stable coexistence Genomic reduction of endosymbiont to avoid conflict and create new individual: Functional specialization of endosymbiont
1-coupled metabolic pathway; mutual cooperation, cheating is not possible- without either nothing 2- engulfed cell retained in cytoplasm of host; the original phagocytosis that initiated the evolution of the eukaryotic cell resulted in the engulfed cell with two membranes: an inner one that was the original membrane of the engulfed cell and the membrane that results from the host cell wrapping the engulfed cell in a membrane 3-multilevel selection occuring at both levels; multiple small bacterial cells living within a larger bacterial cell in the gut of a mealybug. Endosymbiosis within an endosymbiosis 4-Individuality starting to emerge at the group level; don't want 'too many cooks in the kitchen'. To avoid conflict, genome reduction of endosymbiont occurs after the emergence of coordinated replication 5-selection is now almost entirely at the group level → emergence of an organelle
What is endosymbiotic theory? What is the evidence for it?
A theory stating that the eukaryotes evolved through a process whereby different types of free-living prokaryotes became incorporated inside larger prokaryotic cells and eventually developed into mitochondria, chloroplasts, and possibly other organelles. Evidence for this is their are similarities of bacteria and organelles. Ribosomal genes are present in all cells and in genomes of organelles and nucleus. Genes in organelles are distantly related to the genes in the nucleus of their host cell. Mitochondrial genes cluster with alpha proteobacteria genes. Chloroplast genes cluster with cyanobacteria genes. Eukaryotic nuclear genome is chimeric with genes from archaea and bacteria.
What are the advantages and costs of multicellularity?
Advantages: Internal environment buffered from external environment; division of labor; avoid predation (Big things eat small things); swim faster Costs: compete with neighbors for resources; waste products; death of nearby cells; longer generation time compared to single cells
What is altruism?
Altruism is a behavior that benefits the group at a cost to the individual. This means that an individual sacrifices or exports its fitness to the overall group.
How are altruistic cooperation and mutual cooperation different?
Altruism, is costly to the actor, beneficial to recipient. Mutual and synergistic cooperation may not involve distinct costs.
What is an individual?
An individual is a unit of selection and adaptation.
Darwinian approach to complexity?
Darwinian principle explain a large jump in level of complexity and the evolution of new kinds of individuals
The case of altruism illustrates an important principle, namely that what is advantageous at one hierarchical level may be disadvantageous at another level, leading to a conflict. Various features of modern organisms suggest the importance of such inter-level conflicts. Mammalian cancer is an example. Cancerous cells increase in frequency relative to other cell lineages within the organism's body. So a maladaptive feature of individual organisms is explained by selection at a lower hierarchical level, in the case the cellular level.
Cancer: is explained by selection at the cellular level being stronger than selection at the organism level.
Fitness of Volvox vs. Gonium
Cell level fitness Fitness in the context of the group In Volvox somatic cells have NO individual fitness In Gonium cells can reproduce and have individual fitness Thought experiment: What would a cell's fitness be if ti were taken out of the group? Volvox germ cells and somatic cells would have 0 fitness outside of the group, while Gonium cells will have fitness if outside or inside the group since they all have the ability to reproduce. Group level fitness Aggregative property Average of cell ftines E.g. non-differentiated volvocine algae like Gonium Non-aggregative or 'emergent.' Decouple from cell level fitness Function of cell interactions, e.g. Volvox
Why is cooperation hard to evolve within the hypercycle? What is required of the hypercycle to prevent selfish replicators from outcompeting altruistic or wild-type replicators?
Cooperation is hard to evolve within the hypercycle because when one individual conducts altruistic acts, it is least likely to see a return later in the cycle, since there is no barrier controlling whether another individual can just leave. Selfish mutants can also spread, with no individuality at the level of cycle. Therefore, there is a NEED for conflict mediation. This is where enclosing/encapsulating hypercycles come into play. When the components of the hypercycle are enclosed in a membrane and share a common reproductive fate, all of the benefits that one individual confers onto another come back around to benefit that individual. This overall prevents selfish replicators from outcompeting altruistic or wt replicators.
Choose one event that is an ETI and one that is not an ETI. Compare and contrast what features of each major event determine whether or not there has been an evolutionary transition in individuality.
ETI: Evolution of multicellular plants from unicellular eukaryotes Not an ETI: Evolution of terrestrial animals from vertebrate fishes The difference here is that the evolution of multicellular plants from unicellular eukaryotes goes from a single type of individual, unicellular, to a whole new individual, multicellular. There has been a change on the unit of selection or adaptation. This is fundamental because although the terrestrial animals may have speciated from vertebrate fishes, the type of individual has NOT changed, it is still a multicellular animal. There has also not been a change in the unit of selection or adaptation.
What is the paradox of enzymatic replication that Eigen identified (catch-22 of prebiotic evolution)? What does Eigen's error threshold describe? What are each of the variables of Eigen's equation?
Eigen identified the catch-22 of prebiotic evolution: no enzymes without large genome and no large genomes without enzymes. Eigen's error threshold: N < ln(s)(1-q), where N is the sequence length, S is the intensity of selection, q is fidelity of replication, 1-q is the error rate. This describes how the relationship between the error rate, 1-q, and the sequence length, N, depends on selection.
Why did it take so long in the history of life on earth for eukaryotic cells to evolve? (First life appeared ~500 million years after earth formed, but eukaryotic cell evolution took another ~1.5 billion years.)
Eukaryotic organisms have higher metabolic needs, so it needs oxygen for aerobic respiration. This couldn't happen until the atmosphere accumulated enough oxygen (great oxidation event).
What is an evolutionary transition in individuality? How is it different from speciation? Are all major evolutionary events also ETIs?
Evolutionary transition in individuality is a change in the unit of selection and adaptation. This typically occurs when individuals come together to form a whole kind of new individual at a higher level of organization. Speciation is the formation of a whole new, different species, but not individual. For an ETI to occur, there would need to be a whole new individual. Not all major evolutionary events are ETI's. This is because although major events, like the great oxidation event or the formation Earth may have been important for evolution purposes, it did not take create a whole new individual.
In synthetic cell biology, how do fatty-acid bilayers form and replicate? How does selection promote the formation of phospholipid bilayers?
Fatty acid bilayers form based on hydrophobic and phobic regions. A bilayer consist of polar heads of fatty-acids pointing out towards the extracellular matrix and outside the cell, while the hydrophobic region is pointing into the middle of the layer. This forms this way because hydrophobic molecules do not like interacting with polar molecules. Formation: A synthetic cell grows by adding more micelles-As micelles are added, the surface area of the synthetic cell grows faster than the cell volume --> a tail of extra fatty acid bilayer grows, which is fragile. Replication: Then the cell agitates and divides into two synthetic cells, and the cell repeats.
What happens to cells that express the gene rls1? When is it expressed?
Found in chlamydomonas, cells that express the gene rls1 inhibits cell reproduction.-inhibits chloroplast biosynthesis, starves the cells so that it remains small, doesn't lose flagella (staying small and keeping flagella is relevant to the evolution of regA) This is typically expressed as a function of environmental cues-ie., rls1 is a stress response gene, such as resource depletion or stressful factors
Describe and contrast egalitarian vs fraternal transitions.
Fraternal transitions is when like (ie. genetically similar) units stay together and enjoy economies of scale and division of labor, which just means that when both like units interact they interact with splitting the 'labor.' An example of this is multicellularity (having multiple cells for division of labor compared to being unicellular) or even eusocial societies (which is a prime example of division of labor in that everyone has a certain role). Lower level units of individuals that arise by fraternal transitions are genetically similar (eg. Gonium or multicellular yeast are multicellular because daughter cells don't disperse) Egalitarian is when unlike (genetically dissimilar) units come together and complement each other's functions in the higher unit, which just means different individuals interact with each other and complement each other. Prime examples of these are hypercycles and eukaryotic cells. Lower level units of individuals that arise by egalitarian transitions are not genetically similar (eg. ancestral prokaryotes that engulfed ancestral alpha-proteobacteria or cyanobacteria were from different evolutionary lineages)
Which of the following is/are correct concerning the multi-level selection model discussed in class? More than one answer can be correct and all or no answers may be correct.
Frequence of defect D never decreases within groups Groups with more cooperators C are more productive Groups with more defectors D are less productive Cooperators C never increase in frequency within a group Frequency of cooperators C increases overall, if between group selection overpowers within group selection.
What makes Gonium an individual? What is makes it not an individual?
Gonium is an individual (pros) because: Genetic homogeneity, all the cells are genetically identical. Indivisible: does not remain the same if split apart spatial/temporal boundaries Group level adaptations (cellular adaptations to stay stuck together) Functional integration (cells within multicellular gonium point flagella outward for motility) Gonium is not an individual (cons) because: Group state is plastic response to the environment Fitness is based on average of individuals in group: this goes against the fitness of the group all together
What are the steps in multi-level selection?
Group formation: How? Daughter cells fail to separate due to homeostasis in the group or predation. Groups increase in size Cooperation altruism Conflict and conflict mediation Germ soma specialization (division of labor) Fitness transfer ALtruism: costs reduce fitness of cells and benefits increase fitness of the group Fitness decoupling: Fitness of group not average of fitness of cells Group becomes indivisible, an individual
Which group composition is most conducive to enhanced between-group selection? C and D refer to cooperate and defect, respectively.
Groups are composed of either all C or all D. No mixed groups.
Charles Darwin was initially puzzled by the observation that worker honeybees die when they sting an intruder to their hive (the bee's stinger is ripped from the bee's abdomen, causing a fatal injury). Based on what you know about natural selection, why did this observation complicate Darwin's theory?
He found it hard to imagine how such behavior could evolve, since a defending worker's chance of survival is zero.
Hypercycle
Hypercycles are Eigen's proposed solution to Eigen's paradox --> if you can't get large genomes without proteins and no proteins without large genomes, then maybe molecular replicators can interact/cooperate to catalyze each other. these are groups of molecular replicators, a cycle of connected, self-replicating macromolecules.
For the same set of populations as above, suppose individuals are also capable of remembering the whether an individual cooperated or defected. How do you expect the group compositions to change?
I would expect the frequencies to change substantially. In fact, within group and between group selection would increase frequency for Cooperation and decrease the frequency of defect. Typically, the frequency of defectors increase within populations if already present, but in this case I would expect it to drop significantly. Is there within group variation? Yes --> there is within group selection. Is there between group variation? No --> no between group selection, all groups are equally productive Within group selection causes cooperator frequencies to decline, while between group selection causes global increases in cooperator frequency. --> selection increases frequencies of defectors, cooperators go down.
Genomic reduction of endosymbiont to avoid conflict and create new individual:
Individuality starting to emerge at the group level; don't want 'too many cooks in the kitchen'. To avoid conflict, genome reduction of endosymbiont occurs after the emergence of coordinated replication
What processes characterize major transitions in individuality? Choose all that apply.
Individuals join together to form a larger grouping that shares reproduction. The evolution of cooperation Groups of individuals become a new kind of individual. Higher-level groupings can take advantage of economies of scale and efficiencies of specialization.
Criteria for individuality are:
Indivisibility: unable to remain the same individual if parts are removed/split Genetic homogeneity: all the cells within the individual/group are genetically identical Genetic uniqueness: is the individual genetically different than other individuals Spatial/temporal boundaries: is everything held together in one space, are things unable to leave; individuals are localized in time and space Physiological unit and integration: the individual interacts as a whole with the external environment Division of labor especially germ and soma: are there germ and somatic cells, in other words do some cells specialize in one thing with others specializing in others Group-specific adaptations (adaptations at group level) Darwin's conditions: Heritable variation in fitness at group level Lineages at group level or just at cell level Fitness of group not average fitness of individuals in group: is the fitness of the group considered the whole group together, or is it the fitness of all the individuals summed together and then divided by the amount of individuals Fitness decoupling. Fitness at group level decouple from fitness of lower level
How is information different from most physical resources?
Information does not become depleted by sharing.
The origin of multicellularity is what?
It is a prime example of premiere example of the integration of lower level individuals in the hierarchy of life (cells) into a new evolutionary unit (the multicellular organism).
What characteristics make the gene for small-subunit ribosomal RNA particularly well suited for studies of the phylogeny of all living things?
It is present in all extant living organisms, it has always been under very strong stabilizing selection, such that very few differences accumulate per year, and the gene performs the same function in all living things.
What is the hypothesized origin of the regA gene?
Life history genes are natural candidates to be co-opted for fitness reorganization as they already have the capacity to regulate fitness components RegA evolved from a rls1-like common ancestor of regA and rls1 with rls1 functions. Evolves via co-option of a previously existing gene that was expressed in stressful environments and instead is expressed in a developmental context Some evidence for the origin of regA: One prediction would be that these genes are homologous from a common ancestor gene similar to fls1 in function. Traits are homologous if they are similar because they are inherited from a common ancestor.
The process of reorganizing fitness involves cell specialization for different components of fitness (ie. reproduction, and viability/survival). What kinds of genes are likely to be responsible for fitness reorganization? Why?
Life history traits are traits related directly to fitness, e.g., if and when to reproduce. In stressful environments, many organisms do not reproduce (to maximize survival). Hence, we expect life history genes (traits) to exist in most organisms, including unicellular organisms. Definition of fitness reorganization: Transfer of fitness from lower to higher level. Lower levels specialize in fitness components of higher level. Mechanisms of fitness reorganization: Evolution of cooperation → Conflict mediation → Co-option of stress-responses life history genes → Germ-soma specialization → Evolution of group specific adaptations. Consequences of fitness reorganization: Transfer fitness from lower to higher level. Fitness at higher level decoupled from fitness of lower level. Individuality at the new higher level. Increased functionality and complexity. Evolvability at new level. why-rls1, as a life history gene, already downregulates components of fitness (ie. reproduction) in favour of other components of fitness (survival)
Multi-level selection theory predicts what?
Multi-level selection theory predicts that within-group selection must be restricted and between-group selection enhanced for fitness to be transferred from the level of the cell to the level of the group. This process of fitness transfer involves the evolution of reproductive altruism and germ soma division of labor.
Why are phospholipid bilayers favoured by natural selection over simple fatty acid bilayers?
Natural selection actually favors phospholipid bilayers over simply fatty acid bilayers because of the dissociation rate of fatty acid bilayers. Phospholipids have an extra carbon chain and a phosphate group to help stabilize interactions with other phospholipids-Biologically, this means that more stable cell structures grow faster and divide more often than ones that only have simple fatty acid bilayers, and the more phospholipids, the more stable the cellular structure. The result is an increase in the frequency of phospholipid bilayer membranes in the population, because they survive better and reproduce faster than cells that have fewer or no phospholipids.. Thus, phospholipid bilayers will stabilize and will degrade/dissociate as faster as a fatty acid one.
Is a hypercycle an evolutionary individual? Why or why not?
No the hypercycle is not an evolutionary individual. It is a just a group of individuals interacting with one another. In fact, encapsulating the hypercycle into a cell (protocell)-No the hypercycle is not an evolutionary individual. It is a just a group of individuals interacting with one another. In fact, encapsulating the hypercycle into a cell (protocell) is considered the individual. is considered the individual.
Can there be selection at the group level, at the level of the whole hypercycle, if the hypercycle is not in a compartment like a cell?
No there can not be selection at the group level (level of whole hypercycle) if the hypercycle is not in a compartment like a cell because there is no between group selection. Selection can act within the hypercycle to increase the frequencies of mutants that are selfish and/or mutants that are better targets Selection cannot act to increase the frequency of cooperators (ie. replicators with improved enzymatic activity), so conflict mediation doesn't occur without the cell
Suppose that an allele is present in blue-footed booby offspring that causes a nestling to share its food with its nestmate if it is not particularly hungry during times of adequate food availability. This gene imposes a fitness cost of 0.3 on those who carry it, while conferring a benefit of 0.4 on the sibling who receives the additional food. Will this gene increase in frequency if the two nestmates are always half siblings (with the same mother but different fathers)? Why or why not?
No, because rb-c<0
What are the benefits of protein-aided replication over template replication?
One of the benefits of protein-aided replication is that one molecule is not reliant on both genotype and phenotype proteins specialize in phenotype, DNA specializes in fidelity of information/genotype → phenotype is more free to vary while genotype specializes information storage.- why is this beneficial? template replicators where the same molecule is genotype and phenotype is constrained --> folded 3d structure is more stable, but replication is harder because it requires a more open structure
Evolution of regA gene Family
The origin of the altruistic gene regA has been traced back to an undifferentiated unicellular ancestor. The ancestor gene was a life history gene and likely functioned to reduce reproduction of the unicellular organism in stressful environments. This ancestor gene was co-opted and expressed developmentally in a group context where it gives rise to somatic cells
ECM (extracellular matrix):
Shared space between the cells. Provides structural and biochemical support for surrounding cells. A kind of commons for storage of resources.
Two fundamental aspects of the prisoner's dilemma are that (1) no matter what your partner does, defection has a greater payoff than cooperation and (2) mutual cooperation is better than mutual defection. (NOTE: I suspect Dr. Michod will want you to know these two things...) With respect to the payoff matrix, what condition must be met for a true Prisoner's dilemma? cc "Reward" for mutual cooperation cd "Sucker's" payoff dc "Temptation" to defect dd "Punishment" for mutual defection
T > R > P > S T is the temptation to defect (You defect, partner cooperates) R is the reward for mutual cooperation (both cooperate) P is the punishment for mutual defection (both defect) S is the sucker pay off. (you cooperate, partner defects)
Describe the so-called "hierarchy of life" and what process is hypothesized to be responsible?
The "hierarchy of life" basically shows that life exists as a hierarchy of nested levels. Life's hierarchical organization suggests a hypothesis for the evolutionary origin of a new kind of individual. New kinds of individuals evolve from groups of previously existing individuals. Some of the levels are Darwinian individuals, while some are parts of individuals. To reach a higher level of organization within the hierarchy of life, lower level units must undergo a cycle of cooperation → conflict → conflict mediation.
What is the RNA world hypothesis and what is the evidence for it?
The RNA World hypothesis is a period of time in primitive Earth's history (4 bya) when the primary living substance was RNA molecules. Evidence for this is surrounded by the fact that (1) RNA has both genotype and phenotype abilities, meaning it can store information by using sequences of nucleotides, but can at the same time form a 3D folded structure. (2) RNA can also function as an enzyme through ribozymes. (3) It is also important to include the fact that protein enzymes have cofactors made of RNA. Other important evidence: In modern organisms, DNA is synthesized by first making RNA and modifying it to be DNA. The ribosome is a ribozyme. Viroids are also evidence in that they are small, circular, noncoding RNAs (infects plants).
How is the life of a single cell?
The advantages of being a single cell is surface/volume, immediate and effective interaction with the environment, and faster generation time. The problem is the single cell has to do everything, and has to deal with trade-offs, i.e. can not swim and divide at the same time. The answer to this problem is division of labor, cells specialize in tasks for the benefit of the group. In Chlamydomonas, selection acts at the level of the cell but in Volvox, selection acts at the level of multicellular organisms. In Gonium, it IS NOT clear if selection is only acting on the multicellular organisms.
What is the benefit of cellular life over hypercycles?
The cell aligns the interests of its members. Cells with selfish mutants do worse than cells with cooperative genes. Cells with altruistic mutants do better than ones without.
Why is life cellular?
The cell aligns the interests of its members. Cells with selfish mutants do worse than cells with cooperative genes. Cells with altruistic mutants do better than ones without.
The coming together model vs the staying together model for the evolution of multicellularity:
The coming together model posits that independent cells came together during the early stages of the evolution of multicellularity, producing unicellular non clonal propagules, while the staying together model hypothesizes that cells of a single lineage remained together after cell replication, producing unicellular clonal propagules.
What is the evolutionary origin of mitochondria in eukaryotic cells? Describe the evidence for this origin.
The evolutionary origin of mitochondria in eukaryotic cells is a cell conducting phagocytosis on a proteobacteria. It is thought that endosymbiosis theory explains this occurrence. Evidence for this is that mitochondrial genes cluster with proteobacteria genes. Also, mitochondrial DNA is single and circular, which is the same as proteobacteria. They also both conduct replication through binary fission.
Would the small subunit RNA gene discussed above be useful for comparing groups of mammals to each other?
The gene evolves very slowly because it is under strong stabilizing selection (ie mutations in the gene cause a lot of problems for individuals that carry it, so mutants have few/no descendents). This means that closely related lineages that haven't been evolving independently for very long, like mammals, will have nucleotide sequences that are almost exactly the same.
What are the genotypes and phenotypes of molecular replicators that replicate via (i) template and (ii) protein aided replication?
The genotypes of molecular replicators are sequences of nucleotides. The phenotype of molecular replicators are folded 3D structures.
What are three mechanisms to explain the evolution of cooperation (ie. mechanisms of conflict mediation)?
The three paths to cooperation are kin selection, multilevel selection, and reciprocity. Kin selection is more geared towards relatedness and inclusive fitness, which may be used to understand natural selection when interactions occur between genetic relatives. Basically, although being altruistic decreases the overall fitness of an individual, it can potentially increase the fitness of genetic relatives, since they also consist of your genes. Kin selection is well described by Hamilton's rule through its condition for spread of such an altruistic gene. Hamilton's rule for spread of allele is -C+rB>0, with C being direct fitness of the individual, r being the coefficient of relatedness, and B being sum of all indirect fitnesses to recipients of benefit (ie. this is inclusive fitness). To solve for individuals need to actually be altruistic for genetic reasons, rB must be greater than C. Multilevel selection implies that when their are groups of individuals, selection occurs both at between-groups and within-groups. Even though altruism decreases within a group it can increase in the global population because group with lots of altruists do better than groups with a few. In the examples given in discussion and lecture, how does within group selection alter frequency of cooperators? How does between group selection alter frequency of cooperators? Based in discussion and lecture, the within-group selection decreases the f(C), while between-group selection increases f(C). Reciprocity is cooperation for the benefit of your partner, with the expectation of future benefits from that cooperating partner. As described in class can be explained by Tit for Tat, which states that the only rational thing to do in a one shot, or fixed length PD game, is to defect. But however, if you are unable to determine when the interaction will end, you are better cooperating with them. Key thing is that if probability of the game continuing is high, TFT can be EVOLUTIONARILY stable.
Under what conditions do we expect the tit-for-tat strategy to evolve in a prisoner's dilemmas games?
The tit-for-tat strategy will evolve in a prisoner's dilemma game when the game has an uncertain length, and continues with a probability p. This is expected because otherwise, it is more beneficial to defect no matter what.
Ribozyme
These are RNA with catalytic enzyme properties, having both a genotype and phenotype. Well-known Ribozymes are self-splicing introns and ribosomes.
How are multicellular groups formed?
They are formed in two main ways: by cells aggregating and by cells staying together after mitosis. All complex forms of multicellularity involve cells staying together after mitosis.
What is gene co-option?
This is when natural selection finds new uses for existing genes.
LUCA: Last Universal Common Ancestor
This refers to the point on the phylogenetic tree displaying the most recent common ancestor of all extant organisms (ie. things that are still alive today). The point LUCA is when bacteria, archaea, and eukaryotes all diverge from one another. -this is not to say that LUCA was the only living thing at that point in evolutionary history -- rather, it is the only organism that has left descendents that are still alive right now.
How do within-group and between-group selection drive changes in frequency of cooperators over time in a large set of populations that vary in their composition? What if the large set of populations are all CCDD?
Within-group selection decreases the frequency of cooperators in that as long as there is variable composition (differences in # of cooperators and defectors in each group). However, due to variable composition, between-group selection increases the frequency of cooperators over time. If you have a large set of populations of all CCDD (all groups CCDD), then you will never have between-group selection, since all the groups are the same and will ALL produce the same amount of offspring (same fitness). However, there will be within-group selection, which favors the increase in frequency of defectors and decrease in frequency of cooperators.
A unit of selection and adaptation (i.e., an evolutionary individual) must possess HERITABLE VARIATION in FITNESS. Additionally, mechanisms of RECIPROCATION conflict mediation help prevent CHEATING at the lower level. Which of the following statements regarding complexity is true?
conflict mediation (reciprocation is only one of three mechanisms of conflict mediation, the other two being kin selection and multilevel selection) During an evolutionary transition in individuality complexity increases Complexity, once gained, can be lost Complexity has increased in some lineages
Consortium of Cells
coupled metabolic pathway; mutual cooperation, cheating is not possible- without either nothing
Phagocytosis
engulfed cell retained in cytoplasm of host; the original phagocytosis that initiated the evolution of the eukaryotic cell resulted in the engulfed cell with two membranes: an inner one that was the original membrane of the engulfed cell and the membrane that results from the host cell wrapping the engulfed cell in a membrane
Protocell
in terms of a hypercycle, encapsulating a hypercycle in a cellular compartment to mediate conflict arising from cheating problems. In addition, improved catalytic activity can be selected for; is a self-organized, endogenously ordered, spherical collection of lipids proposed as a stepping-stone toward the origin of life
Stable coexistence
multilevel selection occuring at both levels; multiple small bacterial cells living within a larger bacterial cell in the gut of a mealybug. Endosymbiosis within an endosymbiosis
What happens to cells that express the gene regA? What is the phenotype of a cell that expresses it? What is the phenotype of a cell that doesn't?
regA genes regulates the differentiation of cells into germ and soma in multicellular volvox species. Overall, the cost of regA is the inability to reproduce. It keeps somatic cells small by starving them so they do not lose flagella, an altruistic gene. Phenotype of regA expression = somatic cell Phenotype of cell without regA expression = germ cell
Functional specialization of endosymbiont
selection is now almost entirely at the group level → emergence of an organelle
Reproductive Altruism:
to understand the evolution of division of labor (DOL) we need to solve the problem of altruism because somatic cells are reproductive altruists. In volvox, DOL emerges out of fitness trade-offs and altruism and cheating. The evolution of altruism is central to ETIs because altruism transfers fitness from the cell to the group level.
