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Origins of the Species Answers
1. Are mutations always helpful? Explain.
Mutations are not always helpful. Most are harmful … causing the organism to die
before it is able to reproduce. Many other mutations are neutral, there is a change
but nothing that benefits or harms the organism. A mutation is only helpful if it
enables the organism to better adapt to its environment.
2. How can mutations help the evolution of a new species to occur? Use the story of the
cichlids to help explain your ideas.
A helpful mutation that allows a member of one species to better adapt to a niche in
its environment could result in that member breeding (reproducing) and passing on
the beneficial mutation to its offspring. The result would be a variation that
eventually makes the mutant’s offspring so different that they can no longer
interbreed with the original species. Example: The cichlids of Lake Victoria all
began as one species of cichlid, but some mutated to survive better in deeper waters,
others to survive better in shallow waters, and so on. Each new variation allowed the
cichlids to take advantage of different habitats in Lake Victoria. Eventually the
different variations became so different that they could not breed with other
variations of cichlids in the lake.
3. Under ideal conditions bacteria have a generation time of about 20 minutes. Humans
have a generation time of about 20 years. Which would you expect to evolve faster?
Why?
Remember with each reproduction there is a chance of beneficial mutations which
will allow the species to evolve. So, bacteria will evolve faster because in the space of
one human generation the bacteria have many, many more chances to reproduce
and pass along beneficial mutations to their offspring.
365 days in a year = 8,760 hours = 525,600 minutes/20 minutes = 26,200. So in one
year, bacteria have approximately 26,200 generations. In other words, in the 20
years of one human generation the bacteria have 525,600 generations. Even if the
human reproduces as many times as possible in that 20 year span, the bacteria
reproduce hundreds of thousands of times more often.
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