16. Parent offspring conflict Flashcards
Explain why natural selection plays a role in reproduction?
All genes are selfish - want to be passed on to next generation but not all can because:
Natural selection acts on traits - if the randomly chosen trait survives into the next generation - the offspring which survive further carry the trait - produce more fit offspring - have higher fitness and chance of survival
=> changes gene frequency in the population
but Natural selection is NOT = Evolution - only a single component contributing to evolution
Why are genes selfish?
Because selection favours behaviour which increases chances of the genes to be passed on to the next generation despite other concerns
It is not that genes can ‘decide’ to become selfish, but rather that natural selection preserves genes that are more selfish
What are the phenomena to be considered in parent-offspring conflict?
- Natural selection
- Fitness
- Altruism
- Parent-offspring arms race: in pregnancy / care although genes are passed on - survive - parents’ altruism is at their own expense - parents and offspring in competition for resources
Explain why fitness is considered in reproduction?
Because of natural selection only fittest offspring survive - goal of reproduction is to produce most fit possible offspring, so that your genes survive in future generations
Explain why altruism is considered in reproduction?
Altruism is considered in reproduction because although genes are selfish - individuals are not: family groups form which practice altruism - beneficial to care for others who carry your genes - higher chance of survival into next generation
Explain what is inclusive fitness
Inclusive fitness - evolutionary biology theory in which an organism’s genetic success is believed to be derived from cooperation and altruistic behaviour
How related / how much of genes success into next generation from parents to offspring?
The more genes are shared - the more beneficial to be altruistic and gain from inclusive fitness
Explain the Hamilton’s rule
Hamilton’s rule - a central theorem of inclusive fitness (kin selection) theory and predicts that **social behaviour evolves **under specific combinations of relatedness + benefit + cost
In mammals:
rb > c
In humans benefits outweight the costs to initiate altruistic behaviour / parental care - but not in all animals - ex: frogs don’t look after their children but release thousands of eggs into the environment - balance between nr of possible offspring and parental care - they experience rb < c per single offpring
What is relatedness assymmetry?
Ex: relatedness assymmetry in bees - varying inclusive fitness for different players
What are the interactions between mother and fetus in pregnancy which could provide basis for parent-offspring conflict?
Mother-fetal interactions:
- placenta - most obvious location of conflict - transfer of nutrients and waste (a parasite inside of mother) - there’s evidence for arms race between mother and fetus
What is the evidence of arms race between mother and fetus?
Evidence for competition between mother and fetus:
- protease activity
- endocrine competition
Explain protease activity as evidence for arms race between mother and fetus
Evidence for competition between mother and fetus:
- protease activity - fetal TE invasiveness: fetus secretes protease - mother secretes protease inhibitors
Explain endocrine comeptition as evidence for arms race between mother and fetus
Endocrine competition between mother and fetus:
- fetal hormones released by TE + human placental alctogen (hPL) released by placenta - binds prolactin receptor in mothers causing insulin resistance -> increase in blood sugar levels - allows fetus to source sugar more easily - parasite
What could be the hypothesis disproving the evidence for the maternal-fetal arms race?
Mutual advantage hypothesis - maybe both protease activity and endocrine competition are beneficial making pregnancy more efficient:
- protease inhibitors in the mother protect from preeclampsia
Explain what is preeclampsia
Preeclampsia is one high blood pressure (hypertension) disorder that can occur during pregnancy
What other conflict could occur in pregnancy besides parent-offspring conflict?
Parent-parent conflict:
- in humans no relatedness assymmetry but asymmetrical reproductive costs in mothers vs fathers
- genomic imprinting
Why is genomic imprinting a basis for parental-parental conflict?
Genes in developing offspring undergo complimentary paternal / maternal gene imprinting - silencing via methylation - not all genes which are passed on to offspring will be active in offspring - the partner ‘robs’ of the potential
Even though genomic imprinting is not beneficial to parents what are the reasons why it might have persisted in evolution?
Maternally silenced genes - protect the mother - the genes affect embryonic growth, metabolism, placental development, suckling -> increases maternal survival to silences these genes
Paternally silenced genes: ??
What is an example of a syndrome caused by faulty paternal genomic imprinting?
Angleman syndrome
What is an example of a syndrome caused by faulty both paternal and maternal genomic imprinting?
Beckwith-Wiedemann syndrome
Lecture summary
