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Lecture 3

BIOL 1202 Lecture Notes - Lecture 3: Stabilizing Selection, Directional Selection, Punctuated Equilibrium


Department
Biological Sciences
Course Code
BIOL 1202
Professor
Pomarico
Lecture
3

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MASTERING BIOLOGY CH 24
1. Three of the most prominent definitions of species are the biological species concept, the
phylogenetic species concept, and the morphological species (morphospecies) concept.
Drag each characteristic to the appropriate bin based on the species concept(s) to
which it applies.
a. Biological: not applicable for extinct species
b. Morphological: relies on similarities in structure
c. Phylogenetic: based on evolutionary history
d. Morphological and phylogenetic: accommodates asexual reporuction and
species acceptance criteria can be subjective.
e. Morphological, phylogenetic, and biological: used by scientists in
classification.
2. (screenshot of part B)
3. The researchers discovered that the 12 populations could be organized into 3 distinct
species. Populations A, B, and C each belong to a different species.
Use the data in the grid to sort each population to the species to which it belongs.
a. Species 1: a,k,d,f,h,i
b. Species 2: b,l,e
c. Species 3: c,g,j
4. What is the most important factor that holds a gene pool of a species together and
prevents speciation?
a. gene flow: as long as populations are exchanging alleles, specification is
unlikely.
5. According to the phylogenetic species concept, what is a species?
a. A set of organisms with a unique genetic history
6. Which of the following statements about species, as defined by the biological species
concept, is (are) correct?
I. Biological species are defined by reproductive isolation.
II. Biological species are the model used for grouping extinct forms of life.
III. The biological species is the largest unit of population in which successful
interbreeding is possible.
a. I and II
7. You are confronted with a box of preserved grasshoppers of various species that are new
to science and have not been described. Your assignment is to separate them into species.
There is no accompanying information as to where or when they were collected. Which
species concept will you have to use?
a. Morphological
8. Two species of frogs belonging to the same genus occasionally mate, but the offspring
fail to develop and hatch. What is the mechanism for keeping the two frog species
separate?
a. The postzygotic barrier called hybrid inviability
9. Rocky Mountain juniper (Juniperus scopulorum) and one-seeded juniper (J.
monosperma) have overlapping ranges. If pollen grains (which contain sperm cells) from
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one species are unable to germinate and make pollen tubes on female ovules (which
contain egg cells) of the other species, then which of these terms is applicable?
a. Mechanical isolation
10. On the volcanic, equatorial West African island of Sao Tomé, two species of fruit fly
exist. Drosophila yakuba inhabits the island's lowlands, and is also found on the African
mainland, located about 200 miles away. At higher elevations, and only on Sao Tomé, is
found the very closely related Drosophila santomea. The two species can hybridize,
though male hybrids are sterile. A hybrid zone exists at middle elevations, though hybrids
there are greatly outnumbered by D. santomea. Studies of the two species' nuclear
genomes reveal that D. yakuba on the island is more closely related to mainland D.
yakuba than to D. santomea (2n = 4 in both species). Sao Tomé rose from the Atlantic
Ocean about 14 million years ago.
Which of the following reduces gene flow between the gene pools of the two species on
Sao Tome, despite the existence of hybrids?
a. Hybrid sterility
11. Which of these is an example of temporal isolation?
a. One species is nocturnal, and the other species is not.
12. Rocky Mountain juniper (Juniperus scopulorum) and one-seeded juniper (J.
monosperma) have overlapping ranges. If pollen grains (which contain sperm cells) from
one species are unable to germinate and make pollen tubes on female ovules (which
contain egg cells) of the other species, then which of these terms are applicable?
1. sympatric species
2. prezygotic isolation
3. postzygotic isolation
4. allopatric species
5. habitat isolation
6. reduced hybrid fertility
a. 1 and 2
13. Among known plant species, which of these have been the two most commonly occurring
phenomena that have led to the origin of new species?
1. allopatric speciation
2. sympatric speciation
3. sexual selection
4. Polyploidy
a. 2 and 4
14. On the Bahamian island of Andros, mosquitofish populations live in various, now-
isolated, freshwater ponds that were once united. Currently, some predator-rich ponds
have mosquitofish that can swim in short, fast bursts; other predator-poor ponds have
mosquitofish that can swim continuously for a long time. When placed together in the
same body of water, the two kinds of female mosquitofish exhibit exclusive breeding
preferences.
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