Ch. 14 Review Questions

Defining Species

1. 
Distinguish between microevolution and
speciation.

                    Speciation is
different from microevolution in a very certain way. Microevolution is the
changing of a species gradually based on alleles in the gene pool. Speciation
completely divides the original into two new daughter species. The alterations
are so immense that the new generation is classified as a completely different
species. Speciation occurs usually with an isolation aspect of some sort.

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2. 
Compare the definitions, advantages, and
disadvantages of the different species concepts.

                    A species is a
body of populations whose components can mate and have offspring that can
reproduce. The biological concept is advantageous because it is broad enough
that even organisms far away from each other are considered part of the same
species. It is deleterious because it can sometimes cause conflicts because it
is solely based off reproductive success. Sometimes, scientist can’t determine
the mating process of some organisms and fossils don’t provide much
information. However, the morphological species concept can be used without
sexual relations knowledge but it is very subjective and opinionated. The
ecological species concept can be used based on diet instead of appearance. It
all depends on the situation.

3. 
Describe five types of prezygotic barriers and
three types of postzygotic barriers that prevent populations of closely related
species from interbreeding.

                    Prezygotic
barriers are those that halt reproduction or fertilization through organisms. For
example, habitats sometimes interfere with animals’ chances of ending up
together. Some garter snakes are aquatic while some live on land. Also,
temperature can be considered a barrier. Some organisms only breed during
certain seasons and if the seasons don’t match up with their counterpart then
they cannot mate. Mechanical issues may also pose a clash. Some flowers have to
be fertilized with a certain beak shape. It’s like putting puzzle pieces
together. Just like humans, behavior can also cause problems. Actions and
awkwardness can be a blockage to the chemistry to mate. Last but not least, on
the smaller level, gametes can be incompatible and not able to conceive an
embryo. Postzygotic barriers occur after birth. Sometimes the hybrid genes do
not fully develop or function causing the organism to have a low survival rate
and not make it to reproduce. Hybrids may survive, but be sterile. For example,
a mule is sterile. If a hybrid does survive and produce offspring, the
offspring might be weak and unable to reproduce.

   

Mechanisms of Speciation

4.  Explain how geologic processes can fragment
populations and lead to speciation.

                    The act of geologic processes
separating species is called allopatric speciation. If a geographic barrier
develops, it can divide a population to where on certain alleles are present in
certain areas. This is more impactful on animals that are limited in mobility.

For example, if fish are separated because a lake is subsidized, they cannot
travel to reconnect with the rest of their population. That gene pool must
continue to reproduce without the alleles that were lost in the division. This
and environmental factors lead to the development of two or more new species.

5. 
Explain how reproductive barriers might evolve
in isolated populations of organisms. Refer to studies of laboratory-raised
fruit flies and monkey flowers.

                    Reproductive
barriers, like attraction and ability to mate, may evolve when organisms are in
certain conditions. For example, fruit flies were experimented on and two
groups were isolated. One group was fed maltose, while the other was fed
starch. They both started digested the substance they were fed more easily.

When time to mate, they preferred a mate that grew up in the same environment. This
is an example of a prezygotic barrier. This not only leads to evolution, but it
could also lead to speciation. Preference is a huge factor in the development
of reproductive barriers in organisms, especially pollinators. Flowers, wanting
to be pollinated, gradually changed their shape and color to make them more
simple and desirable to pollinators. Monkey flowers practiced this and the two
colors never interbreed now.

6. 
Explain how sympatric speciation can occur,
noting examples in plants and animals.

                    Sympatric
speciation can happen creating a new species even when the parent species and
new species are cohabitating an area. This can happen when a discrepancy
happens during cell division. An additional set of chromosomes creates an
organism considered polypoid. A tetraploid plant has four sets of chromosomes.

Because it creates diploid daughter cells, it cannot mate with the already
existing plants. Therefore, since interbreeding is not an option, it is
considered a new species. Every once in a while, sympatric speciation occurs in
animals.  If it does, it would most
likely be a byproduct of isolation of habitats and sexual preference.

7. 
Describe the circumstances that led to the
adaptive radiation of the Galápagos finches.

                    The Galapagos
islands match the characteristics of a habitat that encourages adaptive radiation.

It has a diverse body of organisms and the islands are far enough apart so that
isolated reproduction car occur. After arriving to the island, the founder
population probably evolved from environmental driven adaptations. Reproductive
barriers contributed to the allelic difference in the now 14 different species
of finches. The beaks altered to match the birds’ diet to the best of its
ability.

8. 
Explain how coloration and properties of light
transmission in water has led to speciation in Lake Victoria.

                    Female cichlids
were more attracted to males that possessed brighter colors. This is a
considered a reproductive barrier, and the gene is limited. This creates a new
gene pool, which continues to become a new species. The amount of light
transmitted affects the diet of certain cichlids. Because of different diet, these
two species separate themselves in the interbreeding processes.

9. 
Explain how hybrid zones affect speciation.

Describe examples of reinforcement and fusion in hybrid zones.

                    Hybrid zones
are areas where two different species reproduce together. Gene flow permits the
hybrid zone to exist by knocking down reproductive barriers. Hybrids are born.

Reinforcement is natural selection adding more physical support to the
offspring of hybrids. This is because they sometimes aren’t as fit as their
parents, so reinforcement eliminates less strong hybrids. Therefore,
eliminating barriers that could cause problems when reproducing. Fusion is two
species coming together as one. It is also known as “reverse speciation”
because they are opposites. Reproductive barriers aren’t stable and two species
mate with each other so much, they merge into one.

 

 

10. 
Compare the gradual model and the punctuated
equilibrium model of evolution. Explain how each model applies to the fossil
record.

                    Punctuated
equilibrium is the really really long process of evolution. Speciation is all
of a sudden visible in the species after a long time of little alteration. It
is a big jump in the appearance in spurts of time. The gradual model of
evolution is like a stair case. You see a small amount of change until you
reach the new species. Change is constantly happening slowly. It creates
uncertainty in the fossil record because it cannot be distinguished in the
strata. Speciation has created many dramatic alterations in the fossil record.

 

 

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