Chapter 6 - Phylogeny and Tree of Life

Question 1

Linnaean system (Linnaeus)

Answer 1

• Binomial nomenclature
• Hierarchical system
• Taxon

Question 2

Binomial nomenclature

Answer 2

using 2 names to identify a particular organism
(Homo sapiens or H. sapiens)

Question 3

Taxon

Answer 3

is a taxonomic unit at any level of the hierarchy

Question 4

Classification

Answer 4

grouping species into broader taxonomic categories

Question 5

Taxonomy

Answer 5

hierarchical classification, the identification, naming, and classification of species

Question 6

Taxonomic Hierarchy:

Answer 6

Domain – Kingdom – Phylum – Class – Order – Family – Genus – Species

Question 7

Systematics

Answer 7

the study of past and present biological diversity
But now we try to group/classify organisms based on evolutionary relationships

Question 8

Phylogenies

Answer 8

evolutionary trees
- Hypotheses about which species are closely related and in what order they evolved
- But cannot base your hypotheses just on similarities between species:
 Degree of similarity not an accurate reflection of amount of time since species diverged from a common ancestor
 Convergent evolution may create similar looking species that are not closely related
 Some species may evolve to look like a more distant ancestor

Question 9

Node or branch point

Answer 9

where lineages split; the most recent common ancestor of the taxa it connects

Question 10

Clade

Answer 10

a taxon that includes a common ancestor and ALL of its descendants. is another term for a monophyletic group.

Question 11

Sister taxa

Answer 11

are each other’s closest relatives

Question 12

Interpreting Phylogenies

Answer 12

To identify a taxon’s closest relative, find the closest node, and follow that branch out

Question 13

Three kinds of groupings:

Answer 13

1. Monophyletic group
2. Paraphyletic group
3. Polyphyletic group

Question 14

Monophyletic group

Answer 14

common ancestor and all of its descendants (a clade) GOOD. One in which all species share a common ancestor, and the group includes all descendants of that common ancestor. Clade is another term for a monophyletic group.

Question 15

Paraphyletic group

Answer 15

common ancestor and only some of its descendants BAD. All species share a common ancestor, but not all descendants from that common ancestor are included, e.g., class Reptilia does not include birds.

Question 16

Polyphyletic group

Answer 16

does not include the most recent common ancestor BAD. Species that do not share a recent common ancestor are lumped together.

Question 17

Constructing Phylogenies

Answer 17

Use CLADISTIC analysis
Objective is to determine which characteristics reveal common ancestry between two or more groups
- Emphasizes COMMON ANCESTRY as the basis of classification.
- Reflects evolutionary history
- Use of fossil record, molecular biology, morphology, comparative embryology
- Steps in creating a phylogeny:
 Select the organisms to be studied
 Select the characteristics to be used to separate the organisms
 Select an outgroup (similar to the common ancestor)
 Look at shared characteristics: used to place organisms into taxa

Question 18

Shared Characteristics

Answer 18

ancestral (primitive)
derived

Question 19

Ancestral (primitive)

Answer 19

(symplesiomorphies)
 Traits originating in a distant ancestor and also shared by organisms outside the taxon you are studying

Question 20

Derived

Answer 20

(synapomorphies)
 Present only in the descendants of one branch of the tree (taxon) – arose within the group

Question 21

Choose the best tree based on “parsimony”

Answer 21

• the principle that, out of all possible explanations for a phenomenon, the simplest of the set is most likely to be correct.
  he simplest tree is best
• i.e., the one that requires the fewest evolutionary major evolutionary events e.g., loss of a tail/evolution of fur/ etc.

Question 22

Cladistics

Answer 22

• concentrates on order of evolution only
   does not show amount of divergence over time
   adjacent groups may actually be distantly related
• Note that
   derived characteristics may have evolved independently
   derived characteristics may be lost in related groups

Question 23

Homology

Answer 23

structures that have the same embryonic origin but may have a different function.
- E.g., parental care in birds, crocodiles, and dinosaurs = homologous

Question 24

Analogy

Answer 24

resemblance of structures but different origin
- Saber teeth in various mammals = analogous

Question 25

Exaptation

Answer 25

• when some biological function takes novel advantage of another function
• Features that were selected for as adaptations for one function, but that now serve a different function. (e.g., feathers and other adaptations for flight)