BIOL3046 Lecture Notes - Lecture 8: Egg Rolling, Traumatic Insemination, Ejaculation
5 Jul 2018
School
Department
Course
Professor
Animal Behaviour BIOL3046 460381099
Lecture 8: Sexual selection and mate choice.
• Males need to attract females, whereas females need to choose the best mate.
Sexual dimorphism: Differences in females and males, can be extreme in some cases.
Example: this is seen in ducks.
Male ornaments: Used to attract females and gain reproductive advantages. These
traits are selected for even if they hinder the organisms’ survival. This
shows females that the fitness of the male is so high that the
ornament doesn’t lessen his reproductive success.
Males compete in 2 ways
Direct competition: Males can compete with each other over direct access to females,
territory for resources that females need, so often bigger males are
selected for (intrasexual selection).
Indirect competition: Males display in order to attract a female (intersexual selection).
Greater male variability hypothesis
• Intellectual abilities are more variable in males than in females. There is both an excess
of males among the mentally defective and very few female geniuses. Human males
have been selected to be witty, clever and creative through sexual selection. Selection
stronger on males than on females; hence large variance among males because of linked
mental disorders.
Females can compete for males
• This can happen when the male is required for the survival of young. Example:
polyandrous birds that get males to incubate their eggs; Seahorses in which the male is
pregnant.
Intrasexual selection
Harems: Males fight over access to females, or over the resources the females will
need. Most successful will have lots of females, living life as a group.
Example: Elephant seal. If you are not big enough you would start life off as a
male, or become a ‘sneaker’.
Leks: Males display together, while females choose which male to mate with.
Female choice
Sexy sons hypothesis: Females prefer males with long tails, so males with long tails
are selected for. This creates an even greater preference for males
Document Summary
Lecture 8: sexual selection and mate choice: males need to attract females, whereas females need to choose the best mate. Sexual dimorphism: differences in females and males, can be extreme in some cases. Used to attract females and gain reproductive advantages. These traits are sele(cid:272)ted for e(cid:448)e(cid:374) if they hi(cid:374)der the orga(cid:374)is(cid:373)s(cid:859) sur(cid:448)i(cid:448)al. This shows females that the fitness of the male is so high that the or(cid:374)a(cid:373)e(cid:374)t does(cid:374)(cid:859)t lesse(cid:374) his reproductive success. Direct competition: males can compete with each other over direct access to females, territory for resources that females need, so often bigger males are selected for (intrasexual selection). Indirect competition: males display in order to attract a female (intersexual selection). Intellectual abilities are more variable in males than in females. There is both an excess of males among the mentally defective and very few female geniuses. Human males have been selected to be witty, clever and creative through sexual selection.
