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Honors Biology
Unit 16-18
HWK 1
Name ______________________________
Part I Chapter 16 – Speciation
The biological species concept is one of the most useful ways to define a species, but it is not foolproof. Briefly
explain why it might be difficult to apply the biological species concept to the following situations
1. Fossils of “Java Man” and “Peking Man” are both thought to represent a single species – Homo erectus.
2. One bird guide calls the flycatchers of the genus Empidonax “the bane of bird-watchers.” Several
species look so much alike that birders can distinguish them only by their songs.
Review the reproductive barriers that separate species by categorizing the following examples. State whether
each barrier is prezygotic (pre) or postzygotic (post), and then name the specific kind of barrier (such as
temporal isolation or reduced hybrid viability) it exemplifies.
Pre or Post
Kind of Barrier
Example
The salamanders Ambystoma tigrinum and A. maculatum breed in the same
area. A. tigrinum mates from late February through March. A. maculatum
does not start mating until late March or early April.
3. ___________
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4. ___________
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Two species of mice are mated in the lab and produce fertile hybrid
offspring, but offspring of the hybrids are sterile.
5. ___________
____________________
When fruit flies of two particular species are crossed in the lab, their
offspring are unable to produce eggs and sperm
6. __________
____________________
A zoologist observed two land snails of different species that were trying to
mate with little success because they apparently didn’t “fit” each other.
7. __________
____________________
Male fiddler crabs (genus Uca) wave their large claws to attract the
attention of females. Each species has a slightly different wave.
8. __________
____________________
When different species of tobacco plants are crossed in a greenhouse, the
pollen tube usually bursts before the eggs are fertilized.
9. __________
____________________
Blackjack oak (Quercus marilandica) grows in dry woodlands, and scrub
oak. (Q. ilicifolia) grows in dry, rocky, open areas. Pollen of one species
seldom pollinates the other.
10. __________
____________________
The tiglon offspring of a lion and a tiger are often weak and unhealthy.
11. What might constitute a geographic boundary, causing allopatric speciation, for the following species?
a. daisy: _______________________________________________________________________________
b. sea star: _____________________________________________________________________________
12. Analogous structures are often used to show convergent evolution. Define both terms in your own words, and
then find one example of how the italicized statement is true.
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Unit 17
Miller-Urey Experiment
The following is an illustration of the experiment conducted in the 1950’s by Stanley Miller and Harold Urey:
1)
What was the purpose of the experiment? Whose hypothesis was this trying to prove? ___________________________
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2) The apparatus above was meant to simulate the conditions of primitive Earth. What does each lettered part in the
apparatus above represent on the primitive Earth?
A) Flask with boiling water _________________________________________________________________________
B) Flask with Gasses and Electrical connections ________________________________________________________
C) Cold Water collar ______________________________________________________________________________
D) Liquid moving down inside of the collar ___________________________________________________________
E) Water trap ___________________________________________________________________________________
3) What types of materials were collected in the trap? _________________________________________________________
4) What was the conclusion of the experiment? ______________________________________________________________
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5) The above apparatus was called a closed system because it was closed to the air in the lab room. Why was this
necessary? ____________________________________________________________________________________________
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