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Unit Test Review Package
Mechanism
of
Evolution
Natural
Selection
How does it change the allele frequency?
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There are a variation of alleles in the
population
Some of these alleles give rise to traits
(e.g. longer legs/fur color) that are better
adapted for the environment than others
Members of the population with these
alleles/traits are more likely to survive
and reproduce
In the following generations, the allele
trait becomes more numerous (higher
frequency) than in the population before.
Does it tend to
increase or decrease
genetic diversity?
It tends to decrease
genetic diversity.
This is because this
mechanism tends to
favour some
traits/alleles over
others. Therefore,
these traits/alleles are
more likely to be lost
over time.
Examples.
Finches with
slightly larger beaks
are better able to
break apart the
shells and feed.
Sloths with lower
muscle mass are
better able to
survive and
reproduce, since
they do not need a
lot of energy.
Allele frequency changes because the allele that
produces that trait tends to become more
frequent.
Sexual
Selection
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
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There are a variation of alleles in the
population
Some of these alleles give rise to traits
(e.g. bright feathers) that allow the
individual to more likely reproduce
In the following generations, the allele
trait becomes more numerous (higher
frequency) than in the population before.
Allele frequency changes because the allele that
produces that trait tends to become more
frequent, since it is individuals with this trait
that are more likely to reproduce.
Gene Flow
Genetic Drift
Mutations
When individuals in two separate populations
immigrate and or/emigrate between the two
populations.
When allele frequencies change due entirely to
random chance. (e.g. natural disasters)
Bottleneck Effect: when a population is
drastically reduced
Founder effect: when individuals in a
population are removed from the main
population and founds their own.
Introduces new alleles into a population.
Happens when mistakes are made in DNA repair.
It tends to decrease
genetic diversity.
This is because this
mechanism tends to
favour some
traits/alleles over
others. Therefore,
these traits/alleles are
more likely to be lost
over time.
Tends to increase
genetic diversity
within the population.
Tends to decrease
genetic diversity
within a population.
Increase genetic
diversity by
introducing new
alleles.
Peacock’s feathers.
Birds of paradise
competing for
female’s attention.
Swedish family
moves to India and
marries into Indian
family.
e.g. Today’s
Australian people
were “founded” by
European criminals
who were shipped
to the continent.
Albinism and
Hairlessness.
Sickle celled
anemia.
The peregrine falcon was nearly wiped out when the use of DDT (an insecticide) became widespread. What impact
does this have on the genetic diversity of the population? Explain.
This is an example of the bottleneck effect. This is when a population is
drastically reduced.
Genetic drift will tend to reduce genetic diversity, as a smaller population will
generally have much lower genetic diversity than a larger one.
The Florida panthers is an endangered species of cougar. There are less than 100 Florida panthers left in the wild.
The greatest danger to the species (aside from pollution, habitat loss etc.) is the extremely low genetic diversity. In
order to increase the genetic variability of panthers, scientists are exploring ways to cross-breed the Florida
panther with closely related subspecies.
Explain how breeding with other closely related panthers could increase the genetic diversity of Florida Panthers.
This is an example of gene flow. Gene flow between the florida panthers and another
subspecies could increase new alleles into the population.
As a higher genetic diversity (more alleles in a population) tends to mean a better
chance the Florida panthers can survive change in the environment, this may increase
the Florida panther’s chance of survival.
Every few years, the pacific salmon return to their home streams from the ocean to lay their eggs. Amongst the
thousands that swim upstream, only a few will survive to reproduce.
What mechanism of evolution does this represent? How does it lead to evolution?
Natural selection. Since only the strongest salmon will be able to
reproduce, that means these traits are being selected for (and so are the
alleles that code for them). Therefore, in the next generation, there will
likely be a greater frequency of these alleles that produce stronger fish
than the last.
If genetic diversity is constantly being lost, what replenishes lost alleles/traits? How does it do so?
Mutations. Mutations occurs when errors in DNA repair produces a different allele. If the mutation occurs in a sex
cell and the sex cells produce an offspring, the mutations will be passed on to the next generation.
Three spine sticklebacks evolved from anadromous fish (fish that are born in freshwater, go to the sea, and return
to the freshwater stream to spawn). In lakes of North America, they are found at the bottom of lakes and the top.
These two populations look very different (fish that feed on the bottom are heavier bodied, with horizontal jaws
and small eyes). The two populations don’t interbreed in the wild.
What were two evolution mechanisms that lead to speciation? Explain.
Natural selection (different environmental factors at the top of the lake and the bottom of the lake means that
different traits are being selected for). The population of fish at the top and bottom of the lake will therefore evolve
different traits over multiple generations that adapts to these environments.
Genetic drift (founder effect) – the original population was separated and each “founded” their own population in
the bottom and top of the lakes.
The shark and dolphin, although from very different origins, have evolved very similar traits. What is this an
example of? Why would they have evolved such similar traits?
This is an example of convergent evolution. The traits (fins, torpedo shaped
body) developed to adapt for a similar environment (aquatic).
What are the characteristics of a good taxonomical system? How does the current system (Linnaean Taxonomy)
fulfill these characteristics?
Specific – each species has a unique taxonomical designation (e.g. Kingdom, phylum, class… genus, species). No
two species have the same name.
Objective - The groupings are based off of evolutionary history, which is specific to every organism. Instead of
using characteristics such as habitat and flying/not-flying which may be subjective.
Descriptive – based on the grouping of each species into kingdom, phylum, class etc. I know many characteristics
about the organism without really seeing it. (e.g. if it is classed under class mammalia, that means it must have fur,
be warm blooded, if it is classed under primate family, it must have opposable thumbs etc.)
There are three ways we can infer evolutionary relationships. How do we infer evolutionary relationships with
these?
1. Homologous structures If two species share homologous structures, that means the traits were derived
from a common ancestor, which means the species arose from a common ancestor as well.
2. Biochemical relationships DNA codes for some proteins, such as cytochrome C. The more similar the
cytochrome C is in two species, the more related the organisms are probably to each other.
3. Embryological relationships DNA also codes for proteins during embryological relationships.
Embryologiccal development that is more similar means that the proteins and genes being expressed are
probably also similar. As embryological development continues, genes with differences are expressed and
the embryos begin to look more different. Therefore, organisms that are more closely related will tend to
have a more similar embryological development.
Draw a prokaryotic cell and eukaryotic cell. What are the key differences between them?
Eukaryotes have a nucleus, prokaryotes do not.
Multicellular or
Unicellular?
Unicellular
Source(s) of energy?
Monera
Prokaryote or
Eukaryote?
Prokaryote
Protista
Eukaryote
Unicellular
Heterotrophy, autotrophy
Fungi
Eukaryote
Multicellular
(mostly)
Heterotrophy
Plantae
Eukaryote
Multicellular
Autotrophy
Animalia
Eukaryote
Multicellular
Heterotrophy
Other characteristics?
Heterotrophy, autotrophy,
chemotrophy
Have characteristics of
other kingdoms.
Have nucleus and
membrane bound
organelles
Have cell walls made out of
chitin
Hyphae
Cell walls made out of
cellulose
No cell walls