Lecture 6 - Systematics

Question 1

systematics

Answer 1

the study of the diversification of life on planet Earth, both past and present, and the relationships among living things through time

• > discovering, organizing, classifying, and interpreting biological diversity
• > uses features to classify organisms and infer evolutionary relationships (i.e. binomial naming system)

Question 2

Phylogenetics

Answer 2

the study of evolutionary relationships among biological entities

• > pylogenies are shown as trees of relatedness

Question 3

anatomy of a phylogenetic tree

Answer 3

1. Ancestral lineage (common ancestor)
2. is a common ancestor for 3,4,5

Question 4

Branch Points/internal Node

Answer 4

where lineages diverge (speciation event)

• > forms a polytomy, which is a term for an internal node of a cladogram that has more than two immediate descendents (i.e, sister taxa)

Question 5

Homology vs Analogy

Answer 5

Homology

• > similar features (morphological or molecular, i.e. arm structure or DNA) due to shared ancestry

Analogy

• > similar features due to convergent evolution but DO NOT share recent common ancestors

Question 6

how can Convergent Evolution mislead our classification of organisms

Answer 6

analogous characteristics can confusion in the interpretations of similarities (i.e. flight) and can mask true relatedness

Question 7

Homologous vs Analogous characteristics

Answer 7

Homologous

• > derived from common ancestor (hair)
• > morphological or molecular

Analogous

• > evolved independently (flight)

Question 8

What are some challenges of determining phylogeny

Answer 8

• > hard to compare vastly different organisms
• > unicellular and simple organisms have few features to compare
• > many lineages lack good fossil records
• > relationships are easily confounded by convergent evolution

Question 9

what kind of characteristics are used to contruct phylogenetic trees

Answer 9

homologous characteristics (morphological or molecular)

Question 10

Monophyletic vs Paraphyletic vs Polyphyletic

Answer 10

1. Mono

• > ancestral species and all descendents

2. Para

• > some but not all descendents
  3. poly
• > includesspecies from different ancestors

Question 11

cladistics

Answer 11

• > a method of classification of animals and plants according to the proportion of measurable characteristics that they have in common.
  (i. e. monophyicl, paraphylic, polyphylic / bacteria, eukaryota, archaea)
• > It is assumed that the higher the proportion of characteristics that two organisms share, the more recently they diverged from a common ancestor.

Question 12

Maximum parsimony

Answer 12

states that the simplest tree (one with fewer volutionary changes/steps) is the best tree

Question 13

Maximum likelihood

Answer 13

Maximum likelihood is a character-based method that incorporates the lengths of branches into the tree that has the highest likelihood of being the correct representation of the phylogenetic relationships among the sequences