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Sexual selection
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True or false? Natural selection is about the individual animal's ability to survive.
All living creatures have developed characteristics that are adapted to their natural habitat. This fur protects the reindeer from cold... And the reindeer has antlers which it can use to shovel snow when searching for food. And if a predator shows up, the reindeer can defend itself with the antlers. The antlers are a tool which the reindeer uses to find food, and protect itself.
If an individual has extra good characteristics, like if they endure cold somewhat better than the others of the same species, or if it can protect itself better, then this individual has a somewhat better chance of survival. Therefore, that individual also has a larger chance of reproduction. The offspring can then inherit the traits, and get the same characteristics. Characteristics that are beneficial in the habitat, tend to become more common with every new generation. This is called natural selection.
But the antlers of the reindeer are beneficial also in another way. This male reindeer has the largest antlers in the neighbourhood. With them, he can fight other males. But for the most part, he doesn't even have to fight. It's the signal transmitted that matters.
It is as if the reindeer shows off his antlers to say: "I'm big, and I'm strong. You don't want to pick a fight with me. And my kids will also become big and strong." The antlers, and the signal, gives a high rank in the group. And they make him popular among the females. So, males with large antlers have a larger chance of mating with females.
This increases the chances of having many offspring. And the offspring inherit the trait of large antlers. This is sexual selection. It is as if nature selects who will get to mate, and pass their genes on to the next generation. Here is a peacock, with large beautiful tail feathers.
They can't be used for anything in particular. The long feathers don't help the peacock to fight, or flee or find food. They don't help him to survive. But the feathers still increase his chances of finding a mate. Long feathers...
make the male more popular among the females ... so that he can have more young ... who will also have the trait of long feathers. How can this be? Feathers that can't be used for anything, and just seem to be a nuisance?
It takes a lot of food and nutrients to develop the feathers. They are heavy and make the bird a lot slower, which ought to be a problem when there are predators nearby. How can such a thing be beneficial in sexual selection? The answer is found in the signal the feathers send. The feathers are impractical, but they send the signal that the male is healthy and strong.
The male, and the feathers, say: "Look at me! I am so strong I am able to carry this heavy but noble feathering. A weak male could never do that." The female receives the signal "healthy and strong", and chooses this male to mate. In order to have offspring, and spread their characteristics, their genes, an animal has to survive. Survival isn't enough.
You also have to find a partner to mate. Natural selection, selects and benefits characteristics that help the individual to survive. The sexual selection selects and benefits characteristics that help animals to find a mate. Even when the characteristics occasionally appear to be rather uncomfortable to live with.