Lecture 18

Question 1

Taxonomy

Answer 1

• how you actually classify something

- not the same thing as systematics

Question 2

Systematics

Answer 2

• how they’re related to other organisms
• without this can’t really understand evolutionary events
• the study of phylogeny, the evolutionary relationships among organisms

Question 3

Linnaeus

Answer 3

• hierarchial classification
• left a gap in his process
• no human type?
• not evolutionary; it’s a classification-how you put them into drawers
• don’t need genetics to do this; look at anatomy
• species don’t change or transform into anything else–>they’re eternal
• based on formal structure motifs using anatomic comparisons, not genetic links
• typological-each species represents an ideal form, each species based on a type specimen

Question 4

The Origin of Species

Answer 4

• doesn’t have any pictures except for his phylogenetic tree that said all life on earth had a common ancestor
• natural selection and phylogeny were his two main points

Question 5

Monophyly

Answer 5

• single common ancestor of your clade

- all clades must be this

Question 6

Polyphyly

Answer 6

• if you actually knew evolutionary history you would know that one species that closely resembles others is actually arisen from a different clade
• the concept of the panda is this kind of solution
• no such thing as a “panda” it’s made up

Question 7

Paraphyly

Answer 7

• have a taxon that’s monophyletic but it doesn’t contain all the descendants of the common ancestor
• broke a monophyletic clade into two clades and neither one contains all the descendants from the common ancestor
• if you do this you define a grade
• ex: reptiles–>paraphyletic concept because we haven’t considered all the descendants of the common ancestor of this clade

Question 8

Phenetics

Answer 8

-take a simple list of features and classify by that

Question 9

Cladistics

Answer 9

• what you really have to do is look for monophyletic clades
• should actually reflect the branching patterns that you see when you’re setting this up
• use shared derived features–>synaptomorphies
• devised by Willi Henning
• idea that phylogeny should reflect the branching pattern among lineages by using shared, derived features

Question 10

Symplesiomorphies

Answer 10

• shared primitive features–>homologies

- helps you separate from clades below but not within clade that has feature

Question 11

Autapomorphies

Answer 11

• derived features not shared by other lineages
• not useful in making up clade diagram
• not helpful in finding out where organisms/group lies in tree at all

Question 12

Classification-Oldest

Answer 12

-based on simple similarity would put whales with fish, bats with birds

Question 13

What is a phylogenetic tree?

Answer 13

• root=base of tree; can connect to related clades outside to the clade being considred-outside clades called outgroups
• branches=connections between basal (ancestral) and terminal nodes (descendants); the higher up the branching, the closer the relationship
• nodes rotate freely

Question 14

Phylogenetic Trees

Answer 14

• present hypotheses about evolutionary relationships based on interpretations of fossils, comparative anatomy, homology, and ideas about how evolution works
• kinds of data shown: time scale, origin, divergence pattern, extinction, biogeography, environment, and hypotheses about mechanisms of evolution

Question 15

Grade vs. Clade

Answer 15

-clade: the descendants of an ancestral species; can tie to classification by assigning to an appropriate taxon

Question 16

Phylogenetic Methods

Answer 16

• phenetics
• evolutionary systematics
• paraphyly okay; thus birds put in a separate class from crocodiles on basis of similarity, not phyletic relationship. Crocs are “reptiles” based on resemblance to other members of this grade. More closely related to birds than other living reptiles
• cladistics

Question 17

Phenetics

Answer 17

-simple similarity e.g. numerical taxonomy

Question 18

Evolutionary Systematics

Answer 18

-use of all features, with stress on unique features, groups that distinguish sharply from other groups

Question 19

Aims of Phylogenetic Reconstruction by Cladistics

Answer 19

• monophyly
• recognition of homologous features that are shared and derived
• primitive features not used, even if homologous
• tabulate the data so cladogram can be inferred
• have some way to evaluate results

Question 20

Examples: Primitive Features

Answer 20

• present in entire clade, represents the unmodified condition
• ex: vertebral column (present in all vertebrates), lizard like body shape (basic to all tetrapods), cold-bloodedness and scaly body covering: primitive feature of lower tetrapods
• not informative to define relationships within a clade
• cladistics let us sort out real phylogenetic history

Question 21

Shared, Derived Features-The Critical Ones

Answer 21

• are homologous features that in modified form are shared by two or more lineages. Use unite lineages
• ex: odd number toe reduction in perissodactyls; even number toe reduction in artiodactyls; various patterns of mouthpart modification in insects

Question 22

Many examples of phylogenetic trees

Answer 22

-look at notes