Sex conflict and cooperation Flashcards
What is sex?
Any genetic exchange between individuals, the occurence of meoisis
What does meoisis involve
Initiated by the fusion of two haploid gametes to form a diploid zygote. Process of recombination of paternal and maternal genomes
What are the costs of sex
Physiological costs of meiosis
Risk of producing maladapted offspring
Cost of mating
Cost of producing males
What does asexual reproduction produce
Its a copying process, produces genetically identical clones
What does recombination allow
Favourable mutations to be integrated more qucikly into the population
What is mullers rachet
Random loss of mutation free chromosomes, population gets worse every generation
What is genetic hitchhiking
Deleterious mutations linked to beneifical ones, beneficial under positive selection, increasing in frequency, deleterious mutation is dragged along
What is ruby in the rubbish
Linkage between strong deleterious mutation and a weakly beneficial one, weak beneficial one will be lost so process of adaptation is slower
What is the Hill Robertson effect
Asexual population, 3 genes, when these beneficial alleles arise, they arise in different individuals. The only way to get the fittest genotype is to wait overtime
What is the benifit of sex
Shuffles the genome to produce new combinations of genes
What are the other hypothesises to why sex is maintained
Advantageous in variable environments, more likely to be an advantage if the environment changes rapidly
What is the co-evolutionary arms race aka red queen hypothesis and what does it lead to
Between parasite and the host. Leads to cycles of adaption and counter adaption
List of evidence for the red queen hypothesis
Sex of new zealand snails, parasite has large fitness consequences
High levels of parasitism favours sexual reproduction
Gibson reviewed that theres a strong correlation between parasitism and outcrossing
What determines sex in male in American alligators
Incubation of eggs, 33 degrees produces males and lower produces females
Who discorred sex chromosomes in the early 1900s
Nettie Stevens
What are the new type of chromosomes
Females have ZW, males have ZZ. Occurs in birds, fish and geckos
What happens when recombination is lost
Deleterious mutations start to accumulate
What does the X chromosome in humans contain compared to Y
1000 genes, Y only encodes 45 proteins
What does gene conversion involve
The transfer of genes from the donor sequence to the acceptor sequence facilitated by the amplionic regions
What are palindrome regions
Mirror image repeat structures
How many palindrome repeats does the Y chromosome have
9
Whats the cycle of sex chromosome evolution
Sex chromosomes -> supression -> divergence -> degeneration -> loss of Y/W -> autosomes ->
What are the two different strategies for gamete production
One really big gamete, or lots of smaller gametes
What is zygote size determined by
The sum of gametes that fuse from it
Which gametes are more likely to survive
The bigger gametes
What does disrputive selection of gamete size act against
Medium gametes as they are mediocre at both functions. Disruptive selection leads to unequal gamete sizes
Balanced polymorphism/ anisogamy of gametes
Males and females produce different sized gametes. Females produce less, larger gametes, males produce smaller gametes
Whats the bateman principle
Matin success should be more variable than female success. Females are the limiting factor for reproduction
What does female limitation lead to
Competition between males and the evolution of choosiness among females
Direct benifits of choosiness examples
Mottled sculpin, females come to breeding patches then lay eggs and males fertilise their eggs and defend terriory- positive correlation between size and the egfs
Female scorpianflies copulations for nuptial gifts- fmeales get nutritional benifits
What is fisherian runaway selection and example
Females choose males that are attractive because they produce attractive sons
Traits become more exaggerated.
Molly schumer, sword tail fish with elongated fins
What do male sexual ornaments tend to be
Conditon dependant
Costs of sexual selection
Favours costly males
How can sexual dimorphisms differ
In secondary characteristics, in reproductive traits and in physiology
What is intra locus conflict
When conflict arises in males and females with a shared genetic basis
Whats inter-locus conflict
A trait in one sex interacts with a trait in another sex, different genomic loci are involved
How does intralocus conflict arise
When there is contradictory selection pressures between males and females acting on the same gene with the same trait
What does intralocys conflict promote
Genetic diversity within populations, which is key for adaptions
What does concordant mean
Operates in the same direction
Example of interlocus conflict
Sex peptide protein is expressed by males, transferred to females in the mating interaction, reducing female receptivity, ramping up egg production
Where are sex biased genes more common in
The gonad and are more common in animals
What are selfish genes
Elemements within the genome that replicate themselves at a higher rate than the normal duplication of DNA
What are transposable elements
Made up of 3 protein coding components, these are transcribed by normal cellular machinery and translated
What can lead to an increase in genome size
Transposable elements
An example of a meiotic driver in drospophila
A gene called sr found in the x chromosome
What is altruism
Sacrificing their own fitness or reproductive output is beneficial for others to evolve
What is the kin selection theory
A theory put forward by Hamiltion to explain the problem of altruism
Whats inclusive fitness
The combination of direct fitness and indirect fitness
Whats the hamiltons rule equation
rB - C > 0
B = benifit to recipient
C = cost to the actor for an altruistic behaviour
r = degree of relatedness
Whats an example of altruism
Euosociality
Whats hapodiploidy and where does it occur
Males come from unfertilised eggs and females are diploid
Happens within ants, wasps and bees
Coevolution definiton
Reciprocal genetic change in interacting species, owing to natural selection imposed by each on the other
What are examples of inerspecific interactions that aren’t coevolution
Neutralism, commensalism, amensalism
What are examples of inter specific interactions that lead to coevolution
Antagonism, competition, mutalism
Whats the parasite evolution equation
R0 = bN/ v + d + r
What does R stand for
The fitness of the parasite, the higher the R, the fitter
What does bN stand for
rate of new infection
What does v + d + r stand for
rate at which hosts are lost
What are parastitoids
Parasites where a part of their life cycle means they have to kill their hosts to be passed on to the next generation
What are some examples of vertical transmission
Mitochondria, aphids and their symbiotic bacteria
What are passifloras main adaption
Secondary metabolites in the form of cyanogenic compounds
What is the counter adaption for the heliconius butterflies
The cyanogenic compounds dont effect them
Counter adaptions in passiflora
Egg mimicry
Another counter adaption in the butterflies
The butterflies learn leaf shape
What are the competition end points
One species can out compete the other and drive it to extinction
Could result in adaptations that reduce competition, helping the species to coesxit
An example of mutalism
Pollinators and flowering plants
