Transcript Q5 Evolution of exagerrated traits

5.) Link between evolution
of exaggerated traits and
mate selection
Jun ha, Zaina, Ruman
Evolutionary success
 Passing of genes to future generations
 Natural selection
 Has led to evolution of differences between males and
females
 ‘sexual dimorphism’
 Sexual dimorphism = the change in phenotypic
differences between males and females of the same
species
(males and females are physically different in ways other than
their sexual organs)
Plays a role in indicating which is a stronger mate
 Darwin found that species where males and females that
were similar were more likely to be monogamous
 Polygamous species have differences to allow males to
mate with more females
 Differences are indicative of stronger characteristics
Secondary Sexual
Characteristic
•Traits that appear to be peculiar to one sex but are not
part of the reproductive organs
•When you consider peacocks, they have special
extravagant traits that can act as an advantage when
mating
•Through modification, traits can become attractive
overtime as seen in peacock feathers. The peacock
flares out his feathers when he is trying to get the
peahen's attention for the purpose of mating to continue
reproducing as means for survival.
 In some peacocks,
males show
exaggerated traits.
 Colourful tail feathers
 Advertises their
reproductive worth to
peahens
Downsides
 Tail feathers are an encumbrance
 Hinders rapid movement, e.g. during attacks by predators
Evidence
 Studies have shown
 Peahens prefer to reproduce with more colourful
peacocks
 Colourful peacocks are often the strongest, healthiest and
least-parasitised males
Counterclaim
 But some research has shown
 No link between the colourfulness and parasitism
 Peahens select males with the loudest vocalisation
 Thus peacock’s colour may not indicate health
Runaway evolution
 Colourful peacock feathers may be an example of
 Runaway evolution
There are other examples
like...
The lyre bird is able to imitate sounds of at least
20 different species to scare their rivals (males)
When male deer fight with their strong antlers to
show superiority
Singing (sense: sound) of
Blackbirds
 Reverse dimorphism = when females develop the
dominant traits
 Blue whales- females
are larger as they’re
easier to find
 Black myotis- females
are larger to facilitate
egg formation (which
need more energy)
Sources
 Antigrandiose. File:Peacock Milwaukee County Zoo.jpg. Digital
image.En.wikipedia.org/. 24 June 2010. Wikipedia. 20 Feb. 2012
<http://en.wikipedia.org/wiki/File:Peacock_Milwaukee_County_Zoo.jpg>.
 Boultont. "Explain how mate selection can lead to exaggerated
traits."Ibbiology.wetpaint.com. 29 May 2009. Wetpaint. 20 Feb. 2012
<http://ibbiology.wetpaint.com/page/Explain+how+mate+selection+can+lead+t
o+exaggerated+traits>.
 Pape, Dave. File:Golden tiger 1 - Buffalo Zoo.jpg. Digital
image. En.wikipedia.org/. 16 Dec. 2006. Wikipedia. 20 Feb. 2012
<http://en.wikipedia.org/wiki/File:Golden_tiger_1_-_Buffalo_Zoo.jpg>.
 http://animal-unique.blogspot.com/2011/10/blue-whale.html
 http://en.wikipedia.org/wiki/Sexual_dimorphism
 http://animals.about.com/od/zoology12/f/sexualdimorphis.htm