Lecture 6

Question 1

What is phylogeny a study of?

Answer 1

• study of the evolutionary history of related groups of organisms

Question 2

what is taxonomy

Answer 2

naming and classifying

Question 3

What is a phylogenetic tree

Answer 3

• an illustration of a hypothesis about the relationships among “taxa” (taxonomic categories: species, genera, families, etc.) based on currently available information (open to change)

Question 4

How are organisms grouped into phylogenetic taxa?

Answer 4

• based on unique shared traits that result from common ancestry (homologies)

Question 5

what are synapomorphies?

Answer 5

• a trait found in 2 or more taxa that are present in their most recent common ancestor but is missing in more distant ancestors
• unique to this group

Question 6

• What does classic taxonomy lack?

Answer 6

• useful for creating and organizing groups, but provides limited information about evolutionary relationships within and between groups

Question 7

What is modern tree-building based on?

Answer 7

• modern tree-building is based on CLADISTICS, a series of principles that define a CLADE, a group of organisms that meet the requirements of sharing evolutionary relationships: a common ancestor and all known descendants
• An evolutionary tree is technically called a CLADOGRAm

Question 8

What are sister groups on the tree?

Answer 8

• share a recent common ancestor at the node where their branches meet

Question 9

what is a branch

Answer 9

• a line representing a population through time`

Question 10

What is the root

Answer 10

the most ancestral branch in the tree

Question 11

What is the tip (terminal node)?

Answer 11

endpoint of a branch

• represents a living or extinct group of genes, species, families, phyla, or other taxa

Question 12

What is an endpoint?

Answer 12

a taxon that diverged prior to the taxa that are the focus of the study

• helps to root the tree

Question 13

What is the node (fork)?

Answer 13

a point within the tree where a branch splits into 2 or more branches

• the node represents that most recent common ancestor of the descendant groups

Question 14

what is polytomy?

Answer 14

• a node that depicts an ancestral branch dividing into 3 or more (rather than 2) descendant branches
• usually indicates that insufficient data were available to resolve which taxa are more closley related

Question 15

What is a character or trait

Answer 15

• any genetic, morphological, physiological, development, or behavioural characterisitc to be studied

Question 16

what is an ancestral trait

Answer 16

a character that existed in an ancestor

Question 17

what is a derived trait

Answer 17

one that is a modified form of the ancestral triat, found in descendant

Question 18

What is the cladistic approach based on?

Answer 18

• based on the principle that relationships among species can be reconstructed by identifying shared derived traits, called synapomorphies

Question 19

What is a monophyletic group?

Answer 19

• an evolutionary unit that includes an ancestral population and all of its descendants, but no others

Question 20

What is homology?

Answer 20

• similarity in organisms due to common ancestor
• traits inherited from a common ancestor, even though they may appear different (after descent with modification)

Question 21

What is homoplasy?

Answer 21

• similarity in organisms due to reasons other than common ancestry
• traits (analogous in function) may appear similar but are not inherited from a common ancestor
• this is the result of convergent or parallel evolution
• not helpful for tree-building

Question 22

What is a polyphyletic group?

Answer 22

• an unnatural group that does not include the most recent common ancestor

Question 23

What is a paraphyletic group?

Answer 23

• a group that includes an ancestral population and some of its descendants, but not all
• loss of trait

Question 24

What is a convergent evolution

Answer 24

• the independent evolution of similar traits in distantly related organisms due to adaptation to similar environments and lifestyles

Question 25

What are the 3 tools for creating a phylogeny and studying history?

Answer 25

• fossils are evidence for history of life on earth, extinction, and evolution
• comparative anatomy and embryology provide evidence of ancestor/descendant relationships
• DNA sequences are currently the most widely used evidence in creating phylogenies

Question 26

review flower homology in angiosperms

Answer 26

although flowers are very diverse in shape, color, and other traits, they:

• have structural similarity; petals and sepals are modified leaves
• Share a genetic similarity for flower development and overall genomics
• evidence. unites them as true monophyletic clade, derived ultimately from a common ancestor