INTRODUCTION TO PHYLOGENETICS
DEFINITIONS [KNOWLEDGE]
Systematics – the science of phylogeny+taxonomy
Common Ancestor –
Morphology – the form or shape of an organism
Paraphyletic Taxa –includes an ancestral species and
only some descendants of it
Phylogeny – science of evolutionary history
Taxonomy – the science of naming and organizing
Polyphyletic Taxa –includes species from different
lineages
Classification – arrangement of organisms into
hierarchal groups
Principle/Assumption of Parsimony –that the least
amount of evolutionary change is optimal
Taxonomic Hierarchy – organizing into increasingly
inclusive groups
Mosaic Evolution – characteristics evolve at different
rates
Taxon – a group of organisms at a taxonomic group
Ancestral Characters –traits that remain unchanged
Lineage – group related by ancestry
Derived Characters – new forms of traits
Monophyletic Taxa –includes an ancestral species and
all of its descendants
USING THE LINNAEAN SYSTEM OF CLASSIFICATION LIST FROM MOST INCLUSIVE TO LEAST EXCLUSIVE
Deadly
Domain
King
Kingdom
Penguins
Phylum
Congregate
Class
On
Order
Frozen
Family
Ground
Genus
Sometimes
Species
RELATE THE ABOVE TERMS, AND THEIR DEGREE OF INCLUSION, TO THE RELATIVE NUMBER OF ORGANISMS
(INDIVIDUALS AND TYPES OF ORGANISMS ) FOUND WITHIN EACH , EXPLAINING HOW, WITH RESPECT TO THE RELATIVE
NUMBERS OF INDIVIDUALS AT EACH LEVEL , A MAILING ADDRESS IS ANALOGOUS TO THE LINNAEAN TAXONOMIC SYSTEM .
A mailing address is analogous to Linnaean taxonomic system because like, Earth, North America, Canada, Ontario,
Toronto, York University – Domain, Kingdom, Phylum, Class, Order gets more and more inclusive. Within Earth for
example, there are 8 continents, within each continent there are several countries, within each country there are
hundreds of cities etc. With Domain, there are 8 Kingdoms, etc.
DESCRIBE WHAT IS REPRESENTED BY A PHYLOGENETIC TREE. [COMPREHENSION]
A phylogenetic tree represents the evolutionary history of life. It is used to show the unity and diversity of life.
PROVIDE ONE LIMITATION OF INTERPRETING A PHYLOGENETIC TREE.] [COMPREHENSION, ANALYSIS, APPLICATION]
One limitation is that you can’t figure out the absolute time just by the lengths.
EXPLAIN WHY SYSTEMATISTS WOULD LOOK AT CHARACTERS THAT ARE GENETICALLY INDEPENDENT.
Systematists look at genetically independent characters that is, reflecting different parts of organisms genome. It is
a precaution necessary because different organismal characters can have the same genetic basis. Otherwise
convergent evolution traits can be mixed in which are not related. It also prevents analogous traits from being
selected (different ancestors).
DEFINE: DIFFERENTIATE BETWEEN THE FOLLOWING TERMS WITH RESPECT TO THE INFORMATION THEY
PROVIDE REGARDING SHARED ANCESTRY AND THEIR USE IN CONSTRUCTING PHYLOGENIES :
Homology (homologous):
Similar ancestry with a range of
functions
Analogy (analogous):
A comparison between two things
that are similar in some way
Homoplasy (homoplasious):
Similar function with different
ancestries (convergent evo)
Homoplasious traits provide no information regarding shared ancestry because they came from different lineages
and would thus provide polyphyletic taxons. Homologous traits are used, and in particular homologous derived
characteristics.
GIVEN THE RELATIONSHIP BETWEEN SEVERAL GROUPS OF ORGANISMS , IDENTIFY STRUCTURES (E.G., FORELIMBS AND
WINGS OF TETRAPODS ) AS HOMOLOGOUS OR HOMOPLASIOUS ( ANALOGOUS ). [A NALYSIS ]
The wings of insects, birds, and bats all developed separately, which are homoplasious traits. The hands of gorillas,
chimps, and humans might be homologous. We all have a common ancestor which those winged animals do not
have a common ancestor in their lineage.
DIFFERENTIATE BETWEEN ANCESTRAL AND DERIVED CHARACTERS AND THEIR USE IN DETERMINING EVOLUTIONARY
RELATIONSHIPS . [K NOWLEDGE, ANALYSIS ]
Mosaic evolution refers to the fact that some characteristics evolve faster than others and some slower. As a result,
the characteristics that remained the same are called ancestral. And those that are new are called derived traits.
Derived characteristics are the most useful because the character is usually present in all descendants and thus,
can serve as markers for entire lineages.
DESCRIBE HOW OUTGROUP ANALYSIS (OR COMPARISON) IS USED TO IDENTIFY ANCESTRAL OR DERIVED CHARACTERS .
Out-group comparison is used to identify ancestral and derived characters. This involves comparing the study
group with an unrelated species. Example: Modern butterflies have six walking legs, but some have four. Which is
ancestral and which is derived? Out-group analysis with other insects suggests that six walking legs is ancestral
and four is derived.
IDENTIFY A PHYLOGENETIC TREE OR DESCRIPTION OF A GROUP OF ORGANISMS AS MONOPHYLETIC, PARAPHYLETIC OR
POLYPHYLETIC . [A NALYSIS , APPLICATION ] (19.6) S ECTION 19.6 B
Mammals form a monophyletic lineage because they have a unique set of derived characters, including hair,
mammary glands, reduction of bones in the lower jaw, and a four-chambered heart. The ancestral characters found
in mammals, such as an internal skeleton, vertebral column, and four legs do not distinguish them from other
tetrapod vertebrates, so these traits are excluded from analysis. If they were included, then they would form a
paraphyletic lineage since they are from different evolutionary lineages.
If a scientist ignored the principle of monophlyl, then if organisms were descendants, but had no common ancestor
within their group, it would be polyphyletic. If you left out a group because they look different, you would have
paraphyletic since you are not including all the descendants. A common example of this is birds and reptiles. They
are descendants of each other, but because they look different they were moved apart.
DEFINE CLADISTICS AND BRIEFLY DESCRIBE HOW IT PRODUCES PHYLOGENETIC HYPOTHESES.
Cladistics is a systematics approach that uses shared derived characterstics to infer phylogenetic relationships and
evolutionary history of groups of organisms. It ignores morphological divergances and follows the assumption of
parsimony. An advantage is that you can group organisms based on a single phenomenon.
DESCRIBE HOW THE PRINCIPLE/ASSUMPTION OF PARSIMONY IS USED TO CONSTRUCT PHYLOGENETIC TREES.
The principle of parsimony is used to construct phylogenetic trees. The principle does not mean that phylogenies
are now correct, but they are now the most optimal phylogeny. It is based on the fact that evolutionary change does
not happen often. It really helps out because 10 species can make 2 million trees.