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Midterm

BIOL 1001 Study Guide - Midterm Guide: Species Problem, Ring Species, Reproductive Isolation


Department
Biology
Course Code
BIOL 1001
Professor
Tamara Kelly
Study Guide
Midterm

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Learning Objectives: Second Midterm Content
Section E. – Phylogenetic
E.1 – Using the Linnaean system of classification, list from most inclusive to least inclusive
and most similarities to least similarities with the following terms: phyla, family, genus,
species and domain.
To remember the order of the taxonomic hierarchy, use the acronym:
Did King Philip Come Over for Good Soup?
Domain, Kingdom, Phyla, Class, Order, Family, Genus, Species.
Domain (most inclusive, least similarities – relatively speaking) and
Species (least inclusive, most similarities – relatively speaking)
E.2 – Be able to read a phylogenetic tree. Identify where speciation events occurred (node),
common ancestor and identify outgroups
Do this manually, you should know.
b. Explain the link between phylogenies and descent with modification.
Phylogenies are well-reasoned and educated hypothesis. They portray the evolutionary
diversification of lineages as a hierarchy that reflects the branching pattern of evolution. Each
branch represents the descendants of a single ancestral species. Don’t forget that once a lineage
branches off, the species will continue to evolve. As lineages branch off and differ from each
other, descent with modification occurs as new phenotypic traits are favoured and gene
frequencies change over time.
E.3 – Identify a tree as monophyletic, paraphyletic or polyphyletic.
When systematists convert the phylogenetic tree into a classification, they use the principle of
monophyly. It consists of three parts.
A. Monophyletic taxa - those derived from a single ancestral species.
B. Paraphyletic taxon - it includes an ancestor and some, but not all of its descendants.
C. Polyphytic taxa - includes species from separate evolutionary lineages (this is not what
you want to do in a real classification system).
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E.4 – Describe how the principle of parsimony and maximum likelihood are used in the
construction of cladograms and phylogenetic trees.
The method of including the fewest possible evolutionary changes to account for diversity within
a lineage are called parsimonious phylogenetic hypotheses. This approach is called the
assumption of parsimony, which states that the simplest explanation should be the most accurate.
It works by saying that any given particular evolutionary change is an unlikely event and hence if
it did occur, it would only happen once, not twice.
b. Utilize the principle of parsimony to construct a phylogenetic tree.
In the simplest number of evolutionary steps, show a group of species evolving with descent with
modification based on how many species share a similar phenotypic trait. The very last species
off the branch should be the least similar to the rest because it has undergone the most changes,
especially if it is a cladogram.
E.5 – Construct a cladogram
Construct a cladogram based on the following information. Indicate which nucleotide base
changed and the change that occurred.
Out-group T T G C C C A A A
X T G G C C C A C A
Y T G G T T C A C A
Z T G G C C C A A A
Eliminate vertical columns that are similar, you should be left with the following.
Out-group T C C A
X G C C C
Y G T T C
Z G C C A
Use species x, y and z and compare them to how many changes deviate from the out-group.
Species X has two changes - T~G and A~C
Species Y has four changes - T~G, C~T, C~T, A~C
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Species Z has one change - T~G
Species Z comes first after the out-group with one change, with T-G being the determining trait.
Species X comes second with two changes, with A-C being the determining trait (since T~G is
already used)
Species Y is the last one in the cladogram with C-T being the determining trait.
E.6 – Describe attributes of a reliable molecular clock
1. Uses DNA sequences that have regular rates of mutation or change
2. These DNA sequences have little to no selection. This means it undergoes no selective
pressure from the environment.
3. Does look at the DNA sequences in relation to the evolutionary history (uses context of
the DNA sequences)
4. Does not underestimate the time of the molecular clock
5. Uses the concept of molecular clocks between two living species (in the attempt to trace
any signs of recent common ancestry or homology)
Bad molecular clocks do the following:
1. They try to sequence living species today in the hopes of identifying past reversions. This
does not work because trying to do DNA sequencing on a living species will not tell you
how long ago a fossilized organism had adapted with a new phenotypic trait.
2. Use DNA sequences with mutations that don’t move at the same rate of change with the
organism they want to compare it to.
3. Consider net mutations
a. This means (a to A) changes ARE NOT EQUIVALENT to (A to a) but they still
use it anyways.
Section F. – Speciation
F.1 – Explain how the term ‘species can vary between groups of organisms. Compare and
contrast the 4 species concept addressing their limitations and uses.
Biological Species Concept
A species is a group of organisms that can successfully interbreed and produce fertile
offspring.
Advantages
oIt refers to the genetic cohesiveness of species
oPopulations of the same species are said to experience gene flow that mixes their
genetic material and could be the “glue” that holds a species together
oIt clearly differentiates the genetic differences of each species.
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