|| home ||| units ||||| help

Analysis

1. Think of some other examples of mutations, besides getting more energy from grass, which might be favored to become more common in this sheep population.

   Mutation	Why it might become more common

   
   
2. Suppose the environment changes:
   1. The rainfall decreases.
   2. A competing species (goats) moves in that eats the same kind of grass.
   3. Small coyotes arrive with a fondness for baby sheep.

   Think of some small mutations that might help the sheep population survive in these new circumstances.

   Mutation	Why it might help

   
   
3. Male peacocks have very large tails, and they can hardly fly because their tails are so big! How could you explain the evolution of such large tails?
   
   
4. One way that two different species develop from one is that two populations become geographically separated. Mutations occur in each group, and they gradually become distinct -- especially if environmental pressures are different.
   Invent a story of deer that become separated by a large desert that they don't like to cross. They live separately in two somewhat different habitats. One is mainly forest and the other is mainly grasslands. How might the two groups be different after 10,000 years?
   
   
5. Instead of a rancher removing some sheep each year, imagine natural predators, such as wolves. How would this have the same or a different effect on the genetic features of the sheep, compared to selection by a rancher? (Hint: what are the features of a sheep that a rancher or a wolf is most likely to remove?)
   
   
6. Think about these two theories about how giraffes acquired long necks.

   Theory 1: As they grew up, giraffes stretched out their necks to reach higher in trees for leaves. The babies inherited their parents' longer necks. This was repeated every generation until all giraffes had longer necks.

   Theory 2: There were different neck lengths in the giraffe population, due to natural variations and mutations. The giraffes with longer necks were more successful getting food because they could reach higher into the trees. They were more likely to reproduce, and their babies inherited their longer neck feature. Gradually there were more giraffes with long necks than short necks. Over many generations, the average neck length of giraffes increased.

   Which theory do you think is more correct, and why?