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Chapter 6

BIO120H1 Chapter Notes - Chapter 6: Pipefish, Anaphrodisiac, Wiman Of Gojoseon

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June Larkin

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Coyne chapter 6 how sex drives evolution for lec 6 and 7
- Peacock with its blue tail violates every aspect of Darwin because the traits
that make him beautiful is making him maladaptive for survival because the
tail produces a problem in it not being able to fly to escape predators
especially when their tail so wet it’s hard to drag. The sparkling colours also
make it attract praetors especially compared to the females who are short
tailed and camolfauged to have a more drab greenish colour and a lot of
the energy is gone into to the male’s tail which must be re-grown each year
- How could the peacocks feathers be an adaptation when it is a barrier?
Also if the males evolved by natural selection why the females aren’t as
bright as the males are?
- These unique traits and behaviours are only seen in one sex
- Another example would be the frog of central America where the male sing
at night time to attract the attention of the females but also in doing so
they are attracting predators like flies that prey on these frogs and get their
attention more than the intended no calling females they are after
- These examples shows us that just as Darwin thought these traits do
reduce survival
- Let’s take a look at the red colored widowbird who have long talk feathers
longer than their bodies and so a university group captured them as they
would see them flying in struggle so what they did was cut an inch in one
group and another 4 inch in another and recapturing them in the breeding
season they found that: longer tailed males lost more weight than shorter
ones making te longer tailed ones a disability for them
- Another example would be the footlong lizard where the males and females
look different meaning the males are bright colours having yellow head
while the females were grayish colour and lightly spotted. An experiment
was done to test a hypothesis to see that the males bright colours attracts
more predators and after the experiment the male models showed bite
marks by birds and snakes while none were on the female models
-Sexual dimorphismstraits that differ between males and females of a
species such as colour, and songs
- biologists have found that sexual dimorphic traits that are found in males
seem to violate the evolutionary theory because they waste time and
energy and reduce survival look at the colours of the species in males we
have seen in experiments that they are eaten more than the plain females
- If selection is responsible for these traits we need to explain how?
- Before Darwin sexual dimorphism was a mystery that not even creationist
could explain how one sex should produce features that are harmful for
their survival

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- Darwin finally noted an explanation- if traits he said differed between males
and females such as their behaviours, ornaments, or structures only being
done to the males these costly traits have evolved for a reason and it is not
for survival
- selection we have to remember is not only for survival but it is also for
successful reproduction and by having fancy tail or singing doesn’t help you
to survive but it does enhance your chances to have offspring’s which
answers why these traits have Rosen
- Darwin was the first to recognize this trade off and said that this type of
selection responsible for sexually dimorphic features are called sexual
-Sexual selection- it’s a selection that increases an individual’s chance of
getting a mate which is a division of natural selection but has a unique way
of operating and is also nonadaptive adaptation that it produces
-Sexually selected traits evolve more when there is a increase in
reproduction like the widowbird noted before have long tails because the
females prefer the longer tailed males as mates even though it is hard for
the males to run from predators or look at deers with big antlers where they
too might struggle with a burden but the win contests more to create more
-Sexual selection comes in 2 forms:
-1)direct competition between males for access to females (huge
-2) female choiceness – widowbird long tail among possible mates
- Male-male completion is the easiest to understand with almost all animals
between the males for the possession of the female and when the males
battle directly it is usually clashing antlers of the deer, the stabbing horns of
stag beetle , head butting of stalk eyed flies
- Selection will favour any trait that promotes victories so getting more mates
for pffsprings producing armaments- stronger weapons, larger body size or
anything that helps the male win physical contest
- Whereas bright colours, ornaments are more for mate choice
- To female eyes not all males are the same because they find that some
male traits and
- behaviours more attractive so genes that produce those favourites are
accumulated in the population
- Another indirect completion among males is that they have the loudest
voice, brightest colours and then the winner is decided by the female in
contrast to the male- male competition
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