Lecture 6 P2

Question 1

What are phylogenetic systematics? When were they developed?

Answer 1

They were developed in the mid 1900’s are evolutionary trees used to classify animals into groups and to understand how these groups relate to one another.

Question 2

What do phylogentic systematics represent? What does it depict about organisms?

Answer 2

They represent a hypothesis of inner relationships, we can use them to depict the change in organisms over time

Question 3

What do we need to understand to reconstruct phylogeny, what do we use to understand this?

Answer 3

we need to understand how closely related two creatures are and we do this using characters.

Question 4

What are characters?

Answer 4

These are observable features of anatomy

Question 5

What kind of characters do we want to use to reconstruct phylogeny? Homologous or analogous?

Answer 5

Homologous, we don’t want to group animals base don purely physical similarities as that could lead to misinterpretations of their phylogeny

Question 6

Are all homologous characters useful in reconstructing phylogeny? Why or why not?

Answer 6

No, this is because for ex, all living animals with feathers are birds but we can’t use the characteristic of feathers to distinguish between types of birds.

Question 7

What are diagnostic characters? What does a character being diagnostic depend on?

Answer 7

These are the characters used to reconstruct phylogeny, are homologous distinct and unique characters which define a taxon. This depend son the groups ur comparing for ex: fur is diagnostic of mammals, but not dogs (all dogs have fur not distinct or unique)

Question 8

What are cladograms?

Answer 8

These are branching diagrams that show hierarchies of diagnostic characters, they depict a hypothesis of how two organisms are related to each other and are key to understanding who’s related to whom

Question 9

What are shared derive characteristics?

Answer 9

these characteristics allow us to assess relationships which we use to form cladograms

Question 10

What is a node on a cladogram?

Answer 10

it’s a common ancestor, where we get the separate evolution history for each lineage. Has point below it which has the characters they share listed.

Question 11

Does the order in which animals are presented on a node matter?

Answer 11

No

Question 12

When a third animals is added to a cladogram what must we consider and why?

Answer 12

We must consider which animal is more closely related to another because the cladogram is supposed to hypothesize who’s more closely related to whom

Question 13

If a character has developed before a node, the animals branching after that node all share that character and are therefore ________ for that character? Why?

Answer 13

positive, because the character evolved prior to those lineages

Question 14

If a character has developed after a node, the animals branching after that node all share that character and are therefore ________ for that character? The animals that branched before that node are _______ for that character? Why?

Answer 14

positive, 0, because the character evolved before the node (common ancestor) so therefor all branches after have it, but all branche sbefore it the character ddin’t evolve yet so it’s negative

Question 15

What character tells us that cats and dogs are more closely related to eachother than monkeys?

Answer 15

carnissial teeth

Question 16

Do the characters you choose in cladograms produce diff ones?

Answer 16

yes for example if you chose shortened snout as a diagnostic character which is analogous it might give you a more imporbable cladogram (says cats and monkeys more closely related)

Question 17

Which cladogram is closest to the truth?

Answer 17

The one that does not change and is robust to adding more characters

Question 18

What is the principle of parsimony?

Answer 18

That the simplest expanation is often the best

Question 19

How is the principle of parsimony related to cladograms?

Answer 19

The most robust cladogram is often the one with the fewest evolutionary steps

Question 20

What is an evolutionary step?

Answer 20

the loss of a character

Question 21

What are primitive characters? What are derived characters?

Answer 21

characters that appear low on the cladogram- these are passed up the cladogram, derived characters are new characters which are evolved and are further up the cladogram- is relative when describing a character as derived or primitive

Question 22

Does primitive or derived mean better or worse?

Answer 22

no

Question 23

What does the term plesiomorphic mean? anomorphic?

Answer 23

primitive, anomorphic means derived

Question 24

The lineage of a taxon is represented by what in cladograms?

Answer 24

branches

Question 25

What are nodes used for in cladograms?

Answer 25

are common ancestors, organisms that share a recent node are more closely related.

Question 26

What three things can be seen in a cladogram?

Answer 26

distinct lineage
shared lineage
common ancestors