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Name: Alvis
Status: student
Age: 16
Location: N/A
Country: N/A
Date: 12/7/2004


Question:
This is about natrual selection/evolution, Im not very clear on this subject so please clear this up for me,

If I was to take animals from nature (lions for example), and took care of them (fed them by hand, food predigested and full of nutrients for it to grow) will they lose certain attributes they had gain over thousands of years of evolution?


Replies:
If you take one lion, and do these things, no. Organisms don't evolve in their own lifetime. And traits don't just fade away without use. Look at housecats, which are relatives of lions. When we speak of evolution, we are talking about populations evolving over time. There would have to be a random mutation that took place in say the tooth length gene in one lion, and because that lion didn't hunt anymore, that random mutation wouldn't matter. It wouldn't affect whether that lion reproduced or not. Perhaps that lion would pass the mutated gene on to a few of its offspring, and then there would be more like him-and if they didn't hunt either, the mutation wouldn't matter. Organisms don't evolve because they NEED to or because they don't NEED a trait. When mutations happen, if the environment is such that they can survive with the mutated trait there will be more offspring with that trait. Now if somet ime down the road, the offspring of this original lion were suddenly set free and had to hunt again, they would probably be at a disadvantage and wouldn't survive long in the wild.

vanhoeck


This is an interesting question.

If you're talking about individual animals during one generation, then no, you won't see any inherited traits lost or gained. There may be other characteristics that change during an individual's lifetime. A lion's claws may grow long if it is kept in captivity, for example, or its muscles may atrophy if it doesn't get much exercise. However, an individual's genetic makeup will not change. It's offspring will have all the normal traits of lions living in the wild.

On the other hand, if you're talking about keeping a population of animals in captivity for many generations, then the situation is different. The most important thing to think about is how these animals reproduce. Do they have free choice of mates or do you control their breeding? Do all individuals have an equal chance of reproducing or will some have more offspring than others? Also, it is important to ask questions about the population being kept. How large is the population? Does the population accurately reflect the natural population?

If you control the breeding, then the population absolutely can change over the course of a few generations. Indeed, this has happened with dogs and cats (and sheep and camels and wheat and broccoli and apples and yeast and all other domesticated organisms). In this case, evolution can be strikingly rapid.

If your animals are allowed to have free choice of mates, then the story may be different. Some may end up reproducing more than others. If there is some inherited trait that helps them reproduce, then their offspring may inherit that trait, and those offspring will also reproduce more, etc. This is called natural selection. The key is this: future generations will most closely resemble those individuals who reproduce most successfully. Notice we are talking about whole populations. Populations evolve; individuals do not.

There is a common misconception that if some trait is not used, then it will go away ("use it or lose it"). But evolution doesn't work that way. It doesn't really matter if a trait is used or not; all that matters is whether that trait helps the individual reproduce. Harmful traits tend to disappear from populations. Helpful traits tend to become more common in populations. Neutral traits will tend to stick around, but they typically won't become any more common than they already are.

In the case of the lions, if the animals are kept reasonably healthy and they reproduce normally, then we should not expect them to lose their sharp teeth or their muscular physiques. If you control their breeding, though, you could probably breed those kinds of traits out of them.

Christopher P.


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