Ask A Scientist Zoology Archive

  
name        Alvis
status       student
age   16

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? 
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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
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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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