Exam 2 Flashcards
What is a constraint of selection
Can only act on what is there, especially since development is a careful process
Genetic Redundancy
Extra gene copy that can undergo change without much consequence
What are the postulates of evolutionary development
- Concentration dependent response by control genes
- TFs interact with genes that repress transcription to define areas where only certain genes are expressed
- Many genes are regulated by a combination of activators and repressors
- TF hierarchy allows signal in both early and late development
- Developmental genes are activated in a sequence so that one control gene triggers another, ensuring correct temporal sequence fo events
Homeotic genes
Genes that encode for proteins that control the switching off/on of a cascade of other genes affecting cell size, shape, division, and the positioning of the cells within an organism’s body plan
Explain how the hox genes in drosophila work
Hox genes repress other developmental genes leading to the body plan and certain appendages. If hox genes are inserted in new areas it could lead to appendages in area they are not typically found
What causes differences in species
Changes in developmental genes that give rise to the body plan and tweaks in timing and rate of development
heterochrony
Tweaking in timing/rate of developmental events (changing when and where genes are turned on)
What are the two types of heterochrony
Paedomorphosis: reduction in the rate of change of development (descendants resemble juvenile stages of ancestor) and Peramorphosis: increase in the rate of change of development (descendants experience growth stages beyond those of the ancestor)
Heterotopy
Tweaking the location of expression of developmental genes; generally refers to changes in the cells/tissues in which gene activation or other developmental events occur
What is an example of heterotopy
Squid light organs which have a protein in their eyes to be able to perceive light. This protein is also used in the light organ so that bacteria can use quorum sensing to light up to protect the squid
Ontogeny
stages of growth throughout development
What are the types of ontogeny
Isometric: linear change in size of features (relationship between 2 features/traits stay the same) and Allometric: differential growth in different parts of organisms (relationship between 2 features/traits is negative or positive)
What is an example of allometry
Human babies’ legs grow faster than torso (positive) and heads grow slower than torso (negative)
What are the traits that affect reproductive success and how do they do so?
Survival (more energy dedicated to reproduction than body maintenance), age (mature younger=lower chances of survival into later years), size at maturity (larger= ability to have more offspring), fecundity (can only have so many offspring; more offspring at a time = less energy to dedicate to each one)
What are the main things done with energy
Growth, reproduction, and body maintenance
What do the fundamentals of life history variation boil down to
Resource allocation trade-offs and genetic trade off
Reproductive value
expected contribution of organisms in that stage of life to lifetime reproductive success
Residual reproductive success
remaining contribution to lifetime reproductive success after that current activity has made its contribution
Explain how guppies reproduction rates were affected by predation rates
When guppies experienced high predation rates they produced more but smaller offspring and when they experienced low predation rates they produced less but bigger offspring. High predation rates led to quicker maturity
Senescence
late-life decline to fertility and probability of survival; despite having mostly the same cellular make-up some organisms are able to survive much longer than others
What are the 2 explanations of senescence
Rate of living theory: aging is due to genetic and physiological constraints (accumulation of irrepable damage to cells) and Evolutionary theories: aging is a result of evolutionary trade-offs between reproductin and repair
Explain how the accumulation of deleterious mutations happens
If the mutations don’t affect an organism until later in life then there affect on reproductive succes thus they get passed on and are not selected agaisnt
What is an example of antagonisitic pleiotropy
mutation found in C. elegans that lead to an 80% increase in adult life span but decreased in frequency when elegans were under starving conditions since non-mutants laid eggs immediately while mutants delayed reproduction due to expected long life
Antagonistic pleiotropy
mutations that are beneficial in early life often have costs later in life
Behavior
internally generated response to external stimuli
What evidence is there that behavior can be selected for
Scientist was able to domesticate foxes by breeding those that had a gentler temperament and select for foxes that were more aggressive by breeding foxes that were more mean
What is optimal foraging behavior
energy gained from a food item is independent of what others are eating; when graphed, will level out once food in the area is gone
What is an example of optimal foraging behavior
Starlings that feed young by finding as many mealworms in one trip as possible but the more worms they collect, the harder it is to get more. Optimal forgaing model took into account energetic costs to the parent for foraging and chicks for begging and was able to predict when the parents would return yielding a step-wise graph
ESS
Evolutionary stable strategy: strategy in which, if adopted by most individuals, cannot be invaded by another strategy that is initially rare
What is the tit-for-tat strategy
Start out cooperating and copy what the other player did in the previous round. Actor is never the first to defect, retaliates immediately, and is willing to cooperate after just one act of retaliation. Retaliation discourages the other side from defecting and forgiving allowed cooperation to be restored
What are the four types of social interactions two individuals can have
Altruistic, reciprocity, selfish, spiteful
Altruism
Acting to increase another individual’s lifetime number of offspring at a cost to one’s own survival and reproduction (AKA kin selection)
When is altruism likely to happen
benefits to the recipient are great, costs to the actor are low, and participiatns are closely related
Why are altruism and reciprocity (AKA cooperative behaviors) difficult to explain
Chance of cheaters and actor is taking a cost to them to help someone else. Recipient is related to them for the most part so they are helping to pass on genes but not all the time as seen with blood bats
What is an example of manipulation
Cuckoo eggs are laid in the nests of other birds and when they hatch they push the other eggs out. Hatchling mimics a whole brood of young manipulating the nesting bird to feed it despite it looking so different. Is not selected agaisnt since it does not happen at high enough rates
Mutualism
two or more individuals cooperate because each gains a net survival or reproductive benefit from doing so (kin selection and mutualism do not have to be mutually exclusive)
Reciprocity
When actor and recipient are not related and the benefits are not immediate.
In what ways does reciprocity prevent cheaters
If using the tit-for-tat strategy, cheaters should not be able to get away without retaliation, cooperators should be able to recognize each other, probability of two cooperating individuals interacting repeatedly must be high
What is an example of reciprocity
Blood bats which, if an individual fails to obtain a mean throughout the night might be able to get one from a well-fed individual durind the day. Found to only occur between close relatives or unrelated individuals who were frequent roost mates (companions for years thus, likelihood of encountering one another is high)
Direct fitness
component of fitness gained through personal reproduction
Indirect fitness
Component of fitness gained through aiding the survival and reproduction of non-descendant kin (siblings)
inclusive fitness
fitness gain through both direct and indirect measures
Explain how helpers in white-fronted bee eaters works
males stay around nest while females leave to join mates, low rates of divorce and males help to rear young. Males often recruit young to help rather than allowing them to mate (more beneficial to father to have more offspring than to have grandchildren while son is equally benefited since he is equally related to siblings and offspring). Females that were going to mate with sons that were then recruited often stay with mate and sneak eggs into nests
What is Hamilton’s rule
Br- C > 0 B is benefit, r is coefficient of relatedness, and C is cost of action
What is the r for full siblings
(½ x ½) + (½ x ½) = ½
Actor to parent 1 to recipient and actor to parent 2 to recipient
What is r for half siblings
½ x ½ = ¼
Actor to shared parent to recipient
What is r for cousins
½ x ½ x ½ = ⅛
Actor to parent to aunt/uncle to cousin (recipient)
Eusociality and why does it happen
When worker ants and bees are permanent helpers- do not reproduce themselves. Happens because of haplodiploidy: males develop from unfertilized eggs (related only to mother) and females develop from fertilized eggs (diploid: half of mom’s genes and all of dad’s genes).
What is the evolutionary explanation for eusociality
Eusociality is associated with extreme conditions, having complex nests, and extended parental care. May be favored for in the beginning of its evolution but then species is stuck due to an evolutionary constraint
Sex
Coming together of different genomes in one individual
What are the different ways sex can happen in eukaryotes vs bacteria and archaea
In eukaryotes, gametes come together to make a zygote while in bacteria and archaeal genomes it happens by incorporating fragments of other genomes via conjugation, transduction, and transformation
recombination
production of new combinations of genes
What are the disadvantages of sex
Takes time to find and convince mate, offspring are only 1/2 related, energy needed to mate, and danger in announcing position and competing for mate
What is the two-fold cost of sex
If females produce two offspring every generation then an asexual female can give rise to two females (clones) but a sexual female will likely give rise to a sexual male and female thus, the sexual female does not benefit as much compared to the asexual female
isogamy
gametes of the same size
Anisogamy
gametes of different sizes
How did mating types evolve
To avoid mating with close relatives (outcrossing) which gives rise to variation
How did anisogamy evolve
trade-off between producing large numbers of small gametes to increase the probability of a mating and producing fewer, larger gametes that will produce larger zygotes with a better chance of survival
What is Muller’s Ratchet
Every generation, drift eliminates individuals with the lest mutations; most powerful in small populations
What is Kondrashov’s hatchet
Sex is beneficial because it compartmentalized deleterious mutations and removed them from the populations. Asexual individuals can only produce their own gentypes while sexual individuals can produce offspring fitter than themselves
What are the conditions that must hold in order for Kondrashov’s hatcher
Deleterious mutations affect fitness but when multiple occur they have a larger combined effect and there have to be enough mutations
What is the Fisher-Muller hypothesis
Sex speeds up the rate of adaptation; asexual individuals have to wait for the first beneficial mutation while in sexual individuals, the mutations could appear in indivuals and through sex end up in offspring together
What is the red queen hypothesis
Sexual organisms are likely to fare better in continual coevolutionary arms races than asexual organisms
What is the ancient asexual scandal
Bdelloid rotifers reproduce asexually yet are able to resist parasites and mutations very well. Likely because they have adapted very well to double stranded breaks in DNA by copying homologous genes and are able to take up DNA from the environment. When they encounter a parasite they are able to dessicate themselves for up to 9 years which kills the parasite and then they can reanimate themselves. Not traditional form of sex but still able to incorporate novel DNA into their genomes
