1.A type of ground beetle has two phenotypes: orange and yellow. This particular
ID: 10328 • Letter: 1
Question
1.A type of ground beetle has two phenotypes: orange and yellow. This particular population lives in a small flower garden and is 3/4 yellow and 1/4 orange. The following are 3 different scenarios for the reproduction of this population. Determine whether the following are examples of natural selection or genetic drift. If it is an example of genetic drift, state what process is occurring. State the reasoning for your answers.a. The gardener uproots a dozen flowers and gives them to another gardener in the next town. Randomly eight beetles, two yellow and six orange, are also transplanted. The transplanted beetles reproduce and their next generation is 3/4 orange and 1/4 yellow.
b. A storm knocks a tree into the garden crushing a majority of the beetles. Only ten beetles remain and all are yellow. The next generation of beetles is all yellow.
c.The gardener picks all of the yellow flowers and only orange tiger lilies are left. The orange beetles blend in with the flower petals while the yellow ones do not. The birds begin to eat the yellow beetles more than the orange ones. The next generation is 1/2 yellow and 1/2 orange.
Explanation / Answer
First, it's very important to understand the distinction between these terms (which will be tested by tricky multiple choice questions that mix up scenarios to confuse you!):
Genetic drift =
an 'event' occurs in the population which drastically changes gene frequencies, usually by removing a lot of members. the shift is unequal so there is also a change in the total number of individuals, making it possible for a lesser frequency to stand out more and for mutation to have a dramatic effect.
2 basic types of genetic drift are the "bottleneck effect" where a catastrophe (earthquake, hungry bird, etc.) kills off many members of the population. The "founder effect" is when several members split off to form a new group isolated from the rest (or are not isolated by choice). This new group has very different gene frequencies.
Migration =
this is usually thought of as immigration or emigration (ie new members coming/going in a population). It's also known as Gene Flow, which is distinct from Genetic Drift.
Natural Selection =
this is the biggie! Darwin postulated that animals have a wide variety of traits. Of these, some are useful for longer survival in the given environment. Longer survival or more food = more mating = more offspring have the genes with this useful trait. Pretty soon the trait is common in the population and becomes part of the normal trend. This trait has been naturally selected. Darwin said that survival of the fittest organisms is an indication that traits are naturally selected which confer survival-related benefits.
Now for the questions:
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