Communication:
/20 Application:
/13 Knowledge:
Name: ______________________________________________
SBI3U 11 UNIVERSITY BIOLOGY PREP
SPECIATION ASSIGNMENT
Question One
(Communication/5)
Design a creature. Describe at least 5 unique traits this organism has and a draw a
picture of a population (a whole bunch!) of these creatures. The traits are up to you. Be
creative.
Question Two
(Communication/5)
Have your population undergo isolation from one of the following events, so that it’s
separated into 2 groups: by flood, volcanic eruption, mountain formation, earthquake,
storm, forest fire, etc. Draw a picture and describe what is happening in the picture.
/4
Question Three
(Communication/5)
Have your population of organisms go through adaptation. Choose a way for the
environment to change so that the population undergoes natural selection, and each
separated population becomes adapted to their different environment. Describe the
change in environment and draw a picture.
Question Four
(Communication/5)
Now your population of organisms will go through differentiation, where the isolated
populations become so different that they cannot interbreed anymore. The isolated
populations become genetically different from each other. Draw a picture of your
different populations and describe how they are different.
Question Five
(Application/10)
Classify each of the following situations as either a prezygotic or postzygotic isolating
mechanism, and then specify which type of prezygotic or postzygotic isolating
mechanism is being used.
a. In flowering plants, the pollen is often transferred from the pistil of one plant to
the stigma of another by some type of animal vector (e.g. bee or hummingbird).
As a result, there are times when the pollen of one species ends up on the
stigma of another. But for fertilization to occur, a pollen tube must form to allow
the pollen to reach and fertilize the ovum. In most cases, this will not occur when
the wrong pollen reaches the stigma due to differences in the structure of the
pollen.
b. A short hike through the Sandia Mountains from early spring to late summer will
often reveal several different species of penstemon. The Rocky Mountain
penstemon blooms in the spring while the very similar inflated penstemon blooms
in late summer. As a result, hybrids are rarely encountered.
c. Ligers are the result of a cross between a male lion and a female tiger. Almost all
known male offspring of these crosses have been infertile.
d. Norway rats and black rats are very similar. Attempts to cross the two species
have led to pups being born, but they die within hours.
e. When male fruit flies of one species (Drosophila melanogaster) attempt to mate
with females of another (D. pseudoobscura), the act generally leads to severe
injury or even death to both flies.
Question Six
(Application/3)
Thinking in terms of natural selection, which isolating mechanism, prezygotic or
postzygotic, would you expect to be most common in nature and why?
Question Seven
(Knowledge/4)
Ever since Darwin published his book, On the Origins of Species, there has been
significant debate about the relative importance of the two main patterns of speciation:
allopatric and sympatric speciation. Darwin actually believed, with little evidence to
support his position, that sympatric speciation was probably most important, while most
biologists since the early 1900’s favored allopatric speciation.
a. Distinguish between allopatric and sympatric speciation.
b. Why do you think it has been so difficult to establish which pattern of speciation
is most important in nature?