Sexual selection is a mechanism of evolution
and is conceptually the same as natural selection,
but those two mechanisms still remain distinct
so I’m quickly going to define and then animate a simple example of natural selection
and then do the same with an example of sexual selection
to make the rest of this video more understandable.
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Natural selection is the mechanism of evolution
where organisms within a population with certain traits
are more or less likely to survive and reproduce in a particular environment
than organisms of that population with differing traits.
Example: Say we have an isolated population of a certain species of fish in a lake.
This species specializes on eating nuts that fall into the water
from a small species of tree that grows along the shore.
One day a fire burns down all the small trees,
leaving only a bigger and different type of tree that could survive the fire.
This bigger tree produces bigger nuts.
There are a few fish in this population with mouths big enough to eat the big nuts—
—and the fish with the big mouth trait are able to eat and survive—
while the fish with the smaller mouths starve and are unable to survive.
The genes that coded for the trait of a big mouth in the survivors is likely to be passed along to future generations.
The big mouth trait has been naturally selected to be passed on
because it is better suited for the environment than the small mouth trait.
And I did add another example of natural selection within that example
and I bet you can find it. But now let’s move to sexual selection.
Sexual selection is a process where individuals within a population with certain traits
are more or less likely to obtain mates and have reproductive success
compared to other individuals within that population with differing traits.
Example: Within that same population of fish in our first example,
let’s say the males have a bright spot on the side of their body.
This spot does not help them find food or swim faster or aid in their survival in any way—
it actually increases the chance of a predator seeing them.
But females prefer males with the brightest spot.
So a male with the brightest spot in this population, able to survive to sexual maturity,
is going to have greater success mating with females.
The bright spot will be passed on, onto his and her offspring.
So his bright spot is a sexually selected trait.
So basically, natural selection determines what traits
are best suited for survivability in an environment to reach an age and opportunity to mate and have offspring
while sexual selection determines what traits
are best suited for reproductive success when those mating opportunities arise.
This short comparison clip comes from Koaw Nature’s more comprehensive examination of sexual selection.
I further explain the basics of sexual selection
with real examples as well as other examinations that are quite…interesting.
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