sexual selection Flashcards
how does behaviour affect reproductive success both pre and post copulation
pre copulatory behaviour of competing to both access and attract mates and post copulatory behaviours such as nurturing
what is the sexual selection paradox and how is it explained
complex courtship displays evolve despite the fact that they reduce the chance of survival for the individual. these must have evolved as a result of sexual selection as opposed to natural
what is anisogamy
fertilisation which involves two dissimilar gametes, possible explaining differences in parental investment
what is sex ratio
the ratio of males to females. there is often more males due to females not always being available to mate eg gestation/ lactation periods
what are the results of anisogamy, other than investment differences (2)
variation in male reproductive success (some are very successful some not at all) and the creation of different territory types due to female distribution being based on resource density to support high energy cost eggs
what factors determine the intensity of sexual selection (2)
the amount of parental effort (therefore free time) and the sex ratio (ability to prevent females mating with other males)
what is intrasexual selection
the competition within a sex (usually male) for fertilisations
what is intersexual selection
the selection for traits attractive to the opposite sex eg feathers, colour
what are the two subclasses of intrasexual selection
pre copulatory which is competition based on competitor asymmetry, and post copulatory which is competition of sperm
what are the two subclasses of post copulatory competition, which is a subclass of intrasexual selection
defensive eg mate guarding, scooping sperm, penis length etc or offensive eg more efficient sperm (usually found in polygamous species)
what ae examples of pre and post copulatory traits invested in by males,, and why don’t they invest in both
pre eg size, weaponry, post eg tested mass. they usually don’t invest in both due to the energy investment
what is Fisher’s runaway effect
traits persist due to their ability to increase reproductive success despite having no real meaning. sons inherit them and daughters inherit an attraction to them
what are indirect or genetic indicator mechanisms
indicators of good traits eg health, immunocompetence, developmental stability
what are direct or non genetic indicator mechanisms
indicators of good traits which are not genetic eg ability to hold territory, gifts
when do females benefit from choosing a mate
when the ‘meaningless’ attractive traits actually have some correlation with the quality of the mate
what is the morphological result of sexual selection
females and males become different- dimorphism, dichromatism, physiological regulation etc
where do signals originate
everyday actions which were inadvertently conveyed to others and impacted their behaviour
what is sensory exploitation
exploiting existing behaviours of the receiver eg mimicking prey movement to attract a female
what is arms race of sexual selection
males to manipulate the females into mating and females to determine the deceptive males from those who are actually good quality
what are the two arms by which signals are designed
strategically (what the message conveys eg health) and tactically (efficiency of transmission, detectability, and exploitation of the receiver CNS and psychological landscape
what does receiver psychology depend on (3)
detectability, discriminability and memorability
when do signals have negative consequences
when there are eavesdroppers eg predators
what drives signal honesty
sexual selection, intrasexual by probing and punishment from other males and intersexual by females choosing dishonest males being punished by poor fitness
what is the handicap principle
high energy signals can only be borne by high quality individuals
what does the handicap model show
that high energy is needed to produce testosterone to produce high quality secondary sexual characteristics, whilst also maintaining a strong immune system
what are the different types of handicap (4)
qualifying (inhabited regardless so only quality individuals will survive), condition-dependent (will only develop if the individual can afford them), revealing (costly and developed to show an otherwise hidden quality) or strategic choice (only traits which will be ‘believed’ by the female are developed)
how do bad phenotypes survive in the population
they may reduce sexual attractiveness but increase chance of survival- it is a trade off between sexual and natural selection
