L17: Parent - Offspring Conflict Flashcards
What is natural selection?
- Acts on traits, inherited via genes or acts on traits that change gene frequency over time.
- Organisms that are more adapted to their environment are more likely to survive and pass on the genes that aided their success
What is fitness in terms of natural selection?
Ability to produce more offspring
How is natural selection beneficial?
If a gene improves the fitness of the individual, it is more likely to survive to the next generation
What if selection acts on the individual? What is ‘Selfish gene hypothesis’?
Selection will favour behaviour which increases an individual’s genetic representation in the next generation, therefore expect individuals to act ‘selfishly’, also known as ‘selfish gene hypothesis’
What is Hamilton’s theory of inclusive fitness?
Inclusive fitness theory can be summarized by Hamilton’s rule, which states that a gene for any social behaviour is favoured by natural selection if the sum of rb and c exceeds zero, where c and b are the lifetime changes in the direct fitnesses (offspring numbers) brought about as a result of the behaviour being performed in, respectively, the performer (actor) and recipient of the behaviour and r is their genetic relatedness at the locus for the social behaviour.
rb>c
r - relatedness coefficient
b - benefit to recipient
c - cost to actor
if r=0.5 altruism will occur if benefit to recipient is more than twice the cost to the actor
rb<c
if r=0.5 selfishness will occur if benefit to actor is more than twice the cost to the victim
What is relatedness asymmetry?
Relatedness asymmetry in biology refers to the unequal genetic relatedness between individuals within a social group. This concept is particularly relevant in the context of kin selection theory, which explains the evolution of altruistic behaviors based on the genetic relatedness between individuals.
In many social species, individuals may exhibit altruistic behaviors, such as helping others or sacrificing their own reproductive opportunities, to benefit their relatives. The key idea is that by helping relatives, individuals can still pass on their genes indirectly, as relatives share a portion of their genetic makeup.
Relatedness asymmetry arises when there is variation in the degree of relatedness among individuals within a group. For example, in some animal societies, such as those of social insects like ants, bees, and termites, there is often a high degree of relatedness among individuals due to the reproductive division of labor and the presence of closely related family members within the colony. In these cases, individuals may be more inclined to sacrifice their own reproductive potential to benefit the group because the recipients of their altruistic acts are likely to share a significant portion of their genes.
However, relatedness asymmetry can also occur when there are differences in relatedness between individuals within a group. For instance, in certain mammalian societies where there is a mix of related and unrelated individuals, such as some primate groups, individuals may be less inclined to exhibit altruistic behaviors towards unrelated group members compared to their own relatives. This is because the genetic benefits of altruism are greater when directed towards close relatives who share more genes.
What is the most likely location of conflict between mother and fetus?
placenta, transfer of nutrients and waster, humans special because lack of maternal barrier, has hemochorial placenta, the only individual
What is the arms race between mother and fetus?
- protease activity ~ invasiveness
- breaks down protein of maternal wall
- mother releases protein inhibitor
- this makes into a balance
- ectopic pregnancy might occur when offspring might want more invasiveness, more nutrients
What is ectopic pregnancy?
When blastocyst implants outside of the womb, for example, could be in the Fallopian tube
What is hPL? what is its function? what does it cause to the mother?
- fetal hormones, released by trophoblast
- hPL - human placental lactogen
- binds to prolactin receptors, causing insulin resistance <– in some cases can cause gestational diabetes
What is the mutual advantage hypothesis regarding invasiveness of offspring?
might be evidence that invasiveness is useful for both sides, not just for fetus, maybe mother would not survive without this invasiveness
What is parent-parent conflict?
- no relatedness asymmetry
- but asymmetrical reproductive costs (between sperm and egg production)
What is maternal/paternal genomic imprinting?
- certain genes on maternal/paternal chromosomes are methylated
- methylation prevents transcription
- these genes not expressed in offspring
Why does maternal/paternal genomic imprinting occur?
- think back to natural selection
- preventing a gene being expressed must benefit the donating parent and not the other
- but it can’t benfit both, otherwise gene would be selected to always be expressed
Example: mother might have a gene for gigantic babies, while father might have a gene for normal babies, then mother’s gene is silenced, saves mother’s life
Why might it be beneficial for one parent to control genome imprinting outcomes more?
Example: mother might have a gene for gigantic babies, while father might have a gene for normal babies, then mother’s gene is silenced, saves mother’s life
