Theme 5A/B: Evolutionary patterns

Question 1

What’s an extant species?

Answer 1

• A living species

Question 2

What’s a phylogenetic tree?

Answer 2

• A branching diagram that shows the relationships between species, often according to the time since a common ancestor
• Acts as a hypothesis for evolutionary relationships

Question 3

What’s the difference between a phylogram and a cladogram?

Answer 3

• Phylogram - a tree where the branch lengths represent the amount of inferred evolutionary change/time
• Cladogram - a tree where all branches are of equal length

Question 4

What’s a sister group?

Answer 4

• Two species that share a unique common ancestor not shared by any other species or group

Question 5

What’s the difference between a character and its character states?

Answer 5

• A character describes a specific trait, while a character state describes the variation within that trait.
• Ex. A character being a flower, while the character states including blue flowers or yellow flowers

Question 6

What are homologous characters?

Answer 6

• Characteristics that are shared because of common ancestry
• Ex. the four limbs of tetrapods

Question 7

What are analogous characters?

Answer 7

• Similarity in appearance but not in origin
• Shared because of convergent evolution

Question 8

What are synapomorphies?

Answer 8

• Homologies shared by some, but not all species. Help build phylogenetic trees

Question 9

What does the principle of parsimony describe?

Answer 9

• The phylogeny requiring the fewest evolutionary changes is the best estimate of the true phylogeny (most parsimonious)

Question 10

What are the different kinds of phylogenetic groups?

Answer 10

• Monophyletic - includes a CA and all of its descendants
• Paraphyletic - includes a CA and some, but not all of its descendants
• Polyphyletic - Does not include the CA

Question 11

What’s the difference between anagenesis and cladogenesis?

Answer 11

• Anagenesis - speciation where the ancestor species is wholly replaced by new species
• Cladogenesis - Parent species splits into two new species

Question 12

What’s the difference between graduated evolution and punctuated evolution?

Answer 12

• Graduated - Slow and steady gradual evolution
• Punctuated - Rare and rapid events of branching speciation
  *seems to be a combination of the two
  *fossil record shows the idea of punctuated evolution