Chapter 3 - Sexual Selection Flashcards
Sexual Selection
Darwin’s second mechanism of
evolutionary change. Sexual selection ‘selects for’ characteristics that help an individual gain access to mates. May be divided into intersexual
and intrasexual selection.
Female Choice
The theory that females should be more selective than males when it comes to choosing a sexual partner because they invest more heavily in offspring.
Parental Investment + assymetry
The time, effort and resources
expended by a parent on one offspring that might
otherwise be expended on other offspring
Females often invest additional energy in raising the
offspring»_space; leads to female choosiness
Handicap hypothesis
The theory that males develop
an impediment such as elaborate tail feathers
in order to demonstrate to potential mates their
ability to survive despite having such a handicap.
First proposed by Amotz Zahavi in 1975
Parasite Hypothesis
Propose: Male adornments arose to display lack of parasites to females. Male features signify genetic superiority, i.e. ‘healthy offspring’
Predicts: females choose male features that demonstrate a lack of parasites and hence genetic quality
Muller’s Ratchet
The notion that, in an asexual
population, due to mutations over a number of generations, deleterious genes will build up
(i.e. due to a lack of sex it is difficult to remove such genes from a population – rather like a
ratchet that only allows a cog to turn in one direction).
Tangled Bank
Under predictable conditions you will encounter the greatest competition from those closest to you, that is, other members of your own species. This means it may pay you to be a bit different
Due to the competition that individuals within a species have with each other, we would expect to see continual change over a geological time scale (wrong)
The Red Queen hypothesis
The notion that evolutionary
‘improvements’ to members of a species counteracting changes in members of other species, which may for example be parasites of that species, lead members of the first species
back to where they started.
Arms race
The phenomenon of a change or
improvement on one side of a competition leading to change or improvement in the other.
Applied particularly, but not exclusively, to predator/prey and host/parasite relationships.
Androphilia
The term used, both for men and women, to describe those who are attracted to males.
Gynephilia
The term used, both for men and women, to describe those who are attracted to females
What are the 2 types of sexual selection
intersexual selection- Competition to attract members of the opposite sex for the purposes of mating
intrasexual - selection Competition between
members of one sex for sexual access to members
of the other sex
Runaway selection theory
Propose: Male adornments driven beyond original function by female preference for attractive features. Male features not direct indicators of genetic superiority, i.e. ‘sexy sons’
Predicts: Females will choose males purely on grounds of attractiveness
Handicap theory
Proposes: Male adornments are chosen by females for their conspicuous and costly nature. Male features signify genetic
superiority, i.e. ‘healthy offspring’
predicts: Females choose males which show conspicuous and costly adornments as a sign of genetic quality
Sexual production happen in what ways?
Sex: two parents, recombination of DNA
Asex: cloning, most offspring is identical
