sexual selection 1

• selection mainly acts on individual organism
• its genes that actually survive - 'selfish gene'
• the gene is the unit of selection - things competing to get into next gen. are different versions (alleles)
• bodies are disposable vehicles built by the genes to make it to next gen.

• many animals have a sex and a gaudy sex
• secondary sexual characters may be subtle
• examples = peacock, widow bird, zebra finch
• gaudiness may apply to behaviour too

• combination of physical + behavioural displays used to attract mating decisions 
• males aggregate at a 'lek' site to strut
• each claims small territory + defends it

• 2 forms
• polygyny = males seek many mates + don't care
• polyandry = females seek many mates

males + females pair and both help raise offspring

• few offspring vs many offspring
• become mature slowly or develop quickly

• an animal group consisting of 1 or 2 males, number of females + their offspring
• dominant male drives off other males + mates, 2nd male is subservient to dominant
• primary benefit for male is exclusive access to group of mature females

• recognised by darwin in his 1871 book
• realised that in diploid, sexually reproducing organisms natural selection works by acting on individuals on both survival + reproductive access

evolution is for the good of genes, not individuals, groups or species

• an allele that acts to limit male reproductive effort cant spread
• an allele that acts to limit current reproduction in females could spread if it increased 'lifetime reproductive success' (LRS)
• an alleles that acts to increase investment in offspring in females could spread if it increasive survival + reproductive success

• in species with dominant hierarchies, alleles leading to alternative strategies for acquiring a mate can become common:
• sneaky males
• game theory