Can anyone help with this Natural Selection Question? I am a bit confused?
Not all heritable characteristics which contribute to longer life become more common in the population. Some characteristics contribute to long life, but not more offspring. For example, a female cat which is sterile and cannot have any offspring may live longer because she will not experience the biological stresses of repeated pregnancies. Explain why a characteristic like this which contributes to a long life, but with few or no offspring, would not become more common as a result of evolution by natural selection.
This is an interpretation but correct me if this is wrong in any way:
fitness has to do with the ability to leave large number of viable offspring that will pass down the favorable adaptation for survival to the next generation. living longer does not pass down traits that are influenced by natural selection and therefore evolution happens?
- MollyLv 41 year agoFavorite Answer
You've pretty much got it. I might tweak it a little to mention the condition that there would be few/no offspring produced. For example, the second sentence could be, "Living a long time doesn't matter if you don't have children to carry on your genes," or "The only reason living longer may lead to a trait becoming more common in the gene pool is that a longer life means you can have more children. If the cat isn't having children, she's not passing on her genes."
- MARKLv 71 year ago
What you are talking about is not heritable. If it cannot be inherited then it is not natural selection.
Many sensible owners have their pet female cats sterilised. A female cat may live longer because she has never had kittens. However, I would argue that alone is unlikely to be the only factor that leads a cat to live a long life. It is all too easy to fall into the trap of making the false argument that because B followed A then A must have been the cause of B. So if a she-cat is sterilised so she never has any kittens and lives a long life you cannot simply assume the fact she had no kittens was the reason she lived so long.
Let us say, however, for the sake of argument that not having kittens was the reason she lived longer. First, if it was as simple as having no kittens she cannot pass on that benefit because it is a surgical procedure and not something in her genome she can pass on. But, as I said it is not likely to be the reason. A complex combination of her genes and her environment will have contributed to her living longer. However, if she has no kittens she passes on none of her favourable genes.
So if she does not leave any offspring she does not pass on what made her live longer. The argument about the sterilisation is futile because by being sterilised she cannot pass on to her offspring that benefit, but it could not be passed on anyway because it was a surgical procedure and not in her genes.
- Cal KingLv 71 year ago
Living a long life is not adaptive. Fitness is measured by how many descendants are able to reach adulthood and reproduce. It does not matter how long someone lives, if he/she has no descendant, then the genes that are responsible for a long life would be lost forever. In contrast, if genes code for maximum reproduction at an early age, then those genes would be preserved. Of course sometimes longer life can be adaptive if it allows an organism to produce more young or higher qualify offspring (that have an increased chance of survival) during its life time. Maximizing fecundity is not always the most successful strategy. What good is it to lay a million eggs if none of them survive long enough to reproduce, and there is nothing wrong with having only a single offspring if the chance of survival and reproduction is virtually guaranteed.
- JazSincLv 71 year ago
I think you and Molly have the right idea...
...and in your next class your teacher is going to ask you why human women have long lives post-menopause. D' y' all have a good answer ready for that?
Hint: group selection