Cycle 9: Evolutionary Relationships

Question 1

Taxonomic Hierarchy of Living Things

Answer 1

Does - Domain
Katy - Kingdom
Perry - Phylum
Come - Class
Over - Order
For - Family
Grape - Genus
Soda - Species
Classifies organisms based on similarities, most general fit into 3 domains, down to the very specific species

Question 2

Phylogenetic trees

Answer 2

• Used to show evolutionary relationships
• To find a most recent common ancestor (MRCA) find the branching point of the two species
• The more recent the branching points are, the more closely related the two species are

Question 3

Derived

Answer 3

Evolved after the MRCA

Question 4

Ancestral

Answer 4

Evolved before the MRCA

Question 5

Outgroup

Answer 5

An outgroup consists of species related to a clade, but not included in it
Outgroup Comparison is used to:
- Identify ancestral and derived traits
- Identify the root (common ancestor of the ingroup and outgroup)

Question 6

Parsimony

Answer 6

A particular trait is unlikely to evolve independently in separate evolutionary lineages. The simplest possible approach is the best. Minimize the number of homoplasies. Count the number of evolutionary changes. The evolutionary tree with fewer evolutionary changes will be the one that is most parsimonious.

Question 7

Homology

Answer 7

trait that is shared between two or more organisms (or species) due to common ancestry.

similarity that reflects common ancestry
Ex. Pterodactyl limbs in bats, dinosaurs

Question 8

Homoplasy

Answer 8

A homoplasy is a trait that is shared between two or more organisms due to convergent evolution. IT HAS NOTHING to do with common ancestry.
misleading similarities or dissimilarities
Ex. Trait missing/gained for separate lineages

Question 9

Monophyletic

Answer 9

Include MRCA and all the descendants

Question 10

Cladistics

Answer 10

Autapomorphy:
- Unique to a single taxon
- Derived trait
(uniquely derived character)

Symplesiomorphy:
- Shared by 2 or more taxa
- Ancestral trait
(shared ancestral character)

Synapomorphy:
- Shared by 2 or more taxa
- Derived trait
- USEFUL FOR MAKING PHYLOGENIES
(shared derived character)

Goal: Make a phylogeny
Method: Compared shared and different traits to guess which organisms are closely vs. more further related
- Outgroup comparison
Shortcoming: homoplasy (creating cladistics using physical traits can sometimes be misleading, hence we have molecular sequences)

Question 11

Node

Answer 11

representing a common ancestor (speciation event) - branching point

Question 12

Root

Answer 12

common ancestor of all the organisms included in the tree

Question 13

Clade

Answer 13

Feature of a Phylogenetic tree
Clade: all descendants of an ancestor, i.e. monophyletic group

Question 14

Sister clade

Answer 14

Feature of a Phylogenetic tree
Sister Clade: clades that share a most recent common ancestor (closest relatives)

Question 15

Non-monophyletic

Answer 15

doesn’t include MRCA/all the descendants

Question 16

Traditional Groupings

Answer 16

Many groupings we know today are non-monophyletic. This is because we started grouping organisms before we really understood their evolutionary history!

Question 17

Convergence

Answer 17

OPPOSITE of homology
not closely related organisms develop similar features through evolution

Question 18

How do you build a phylogenetic tree?

Answer 18

1) Use parsimony
2) Group organisms based on relevant traits
3) Determine the outgroup
4) Determine the organism with the fewest 5) differences from the outgroup
5) Repeat