Phylogeny and the Tree of Life

Question 1

What is phylogeny?

Answer 1

The evolutionary history of a species or group of related species.

Question 2

How do biologists utilize systematics?

Answer 2

They use this analytical approach to understand the diversity and relationships of organisms both extant and extinct.

Question 3

What do systematists do to determine evolutionary relationships?

Answer 3

Use the data that ranges from fossils to molecules and genes to classify organisms and determine evolutionary relationships and conduct a tree of life.

More specifically:

morphological, biochemical, and molecular comparisons are used to infer relationships.

Question 4

What is taxonomy?

Answer 4

The ordered division of organisms into categories based on characteristics used to assess similarities and differences.

Question 5

Who first published a system of taxonomy based on resemblances? What is still used from his system today?

Answer 5

Carolus Linnaeus

1. The two-part name system is still used
2. hierarchical classification is still used today

Question 6

What does the first and second part of binomial nomenclature signify?

Answer 6

first: genus
second: species OR the specific epithet

Question 7

What letter is capitalized in binomial nomenclature? What part is italicized? What part is latinized? Can one part be used to name the species?

Answer 7

The first letter of the genus ONLY

All is italicized

All is latinized

Both parts together name the species ONLY

Question 8

What is a taxon?

Answer 8

A taxononomic uit AT ANY LEVEL.

SEE PICTURE

Question 9

How do systematists depict evolutionary relationships?

Answer 9

In a branching diagram called a phylogenic tree. Where each branch represents the divergence of two evolutionary lineages from a common ancestor.

Question 10

What is the order in which the evolutionary relationships between these taxa are being traced?

Answer 10

Carnivores.

Question 11

Does a phylogenic tree give us the ages of the different species within it? Can we assume that a taxon on a phylogenic tree evolved from the taxon next to it?

Answer 11

NO

NO

Question 12

What are phylogenies inferred from?

Answer 12

Morphological and molecular data.

fossils, morphology, genes, development, and biochemistry or relevant organisms.

Question 13

What are similarities that are due to a shared ancestry called?

Answer 13

homologies.

Question 14

Is it possible for related organisms to have a great morphological variance but have a small genetic divergence or vice versa?

Answer 14

YES

Question 15

What is the difference between analogy and homology and why is this important to systematists?

Answer 15

Homology is a similarity due to common ancestry

Analogy is similarity due to convergent evolution

It is important for systematists to distinguish between these two when constructing a phylogeny to ensure that relationships are properly established.

Question 16

What is convergent evolution?

Answer 16

This is when organisms from different evolutionary lineages undergo the same environmental pressures which natural selection then produces similar (analogous) adaptations.

Question 17

What is homoplasy? What is an example of this?

Answer 17

CONVERGENT EVOLUTION IS AN EXAMPLE OF THIS

Analagous structures or molecular sequences that evolved independently.

Question 18

What is a clue to help distinguish between homology and analogy? Elaborate?

Answer 18

The complexity of the characters being compared.

If two more complex character have more points of resemblance between one antoher than it is likely that they evolved from a common ancestor.

Question 19

How do systematists analyze comparable DNA segments from different organisms?

Answer 19

Picture:

• 1. identical homologous DNA from species 1 and species 2 as they diverge from common ancestor.
     
     2. Mutations to each species change the matching sequences slightly.
     3. Once matched regions no longer laign due to mutations.
     4. Computer program realigns DNA by adding gaps to show the matching sequences.

Question 20

These are 2 DNA sequences from two species that are not closely related. 25% of their bases match, what is this an example of?

Answer 20

Molecular homoplasy.

Question 21

What is cladistics?

Answer 21

This is an approach to systematics that uses common ancestry as the primary criterion to classify organisms.

Question 22

What are clades?

Answer 22

Cladstics places animals into clades which include the ancestral species and all of its descendants.

Clade can be nested into larger clades, but not all groupings of organisms qualify as clades.

Question 23

When is a taxon equivalent to a clade?

Answer 23

ONLY when it is monophyletic. Meaning it only consists of its common ancestor and all of its descendants.

Question 24

What type of group is this?

Answer 24

Monophyletic - consists of ancestral species and all descendants.

Question 25

What type of grouping is this?

Answer 25

Paraphyletic - consists of ancestral species but some and not all of its descendants.

Question 26

What type of grouping is this?

Answer 26

Polyphyletic - consists of various species that lack a common ancestor.

Question 27

What is the difference between a shared ANCESTRAL character and a shared DERIVED character? Examples?

Answer 27

Shared ancestral - character that is shared BEYOND the taxon being defined.

• A backbone is a shared ancestral character of the mammalian taxon.

Shared derived - evolutionary novelty that is unique to a particular clade.

• Hair is unique to the mammalian clade and is therefore a shared derived character.

IT ALL DEPENDS ON WHAT WE ARE COMPAING THE CHARACTER TO.

Question 28

What is an outgroup?

Answer 28

A species that comes from the same evolutionary lineage that diverged earlier than the species being studied.

REFER TO PICTURE TO FULLY UNDERSTAND

Question 29

Is the chronology represented in a phylogenic tree specific or just relative?

Answer 29

JUST RELATIVE, meaning it says if something came earlier or later

Question 30

Can varying branch length in a phylogenetic tree represent the amount of genetic change that came about in that lineage?

Answer 30

YES

Question 31

Can some trees actually give the chronological time based on the fossil record?

Answer 31

YES

Question 32

What are the two methods that are combined to determine the best way to arrange species in a phylogenetic tree?

Answer 32

Maximum parsimony - arrangement that requires fewest evolutionary events

Maximum likelihood - using DNA changes to figure the most likely sequence of evolutionary events.

Question 33

Look at this table and understand why tree #1 is more likely than tree #2.

Answer 33

DO IT.

Question 34

Are phylogenetic trees just hypothesis? Can these be used to make predicted relationships on the basis that the phylogeny is actually correct? Example?

Answer 34

YES, based on multitudes of data

YES, this is called PHYLOGENIC BRACKETING - which predicts that features shared by two groups of closely related organisms are present in their common ancestor and all of their descendants.

Such as the relationship that we know between crocs and birds between their common ancestor can be used to assume and place these dinosaurs in this phylogenic tree as well.