Classification and Cladistics

Question 1

Molecular Clock Zbd

Answer 1

The less differences in base sequence, the more recently they mutated and diverged and the opposite is applied

Question 2

Cladogram Definitions

Answer 2

Root: The bottom part of the cladogram representing the most recent common ancestor of all the groups in the diagram

Node: A branching point in the cladogram which represents a hypothetical common ancestor

Terminal Branch (Tip): End points of the cladogram which represents currently living groups of organisms being studied

Question 3

Archaea VS Eubacteria VS Eukaryote

Answer 3

No mb bound
No mb bound
Mb bound

Circular DNA
Circular DNA
Linear DNA

Present Histones
Absent Histones
Present Histones

No Introns
No Introns
Introns

Cell Wall not made of peptidoglycan
Cell Wall made of peptidoglycan
Sometimes Cell Wall not made of peptidoglycan

Question 4

Why rRNA is Used

Answer 4

All living organisms have rRNA

rRNA sequences evolve slowly which makes them good for studying ancient divergences

rRNA has regions that are highly conserved which makes it easier to align sequences and compare them

Question 5

Definitions of Terms A3.2.3

Answer 5

Phylogeny: Study of evolutionary past of a species

Cladistics: Method of classification that groups organism based on evolutionary history

Cladogram: Diagram that shows evolutionary relationships between species and indicates common ancestry

Clade: Group of species that share a common ancestor

Question 6

Evidence for Clades

Answer 6

Molecular Evidence: Base sequence of genes can be compared to reveal how closely related organisms are with the more similar the base sequences the more recent the common ancestor. Amino acid sequences can also be compared to provide evidence of evolutionary relationships

Morphological Traits: Shared characteristics that evolved in a common ancestor that are shared by its descendants can be analyzed to group organisms into clades

Question 7

Clade VS Taxon

Answer 7

A group of organisms that include a common ancestor and all of its descendants and based on evolutionary relationships

A named group of organisms at any level of the hierarchal classification system and based on shared characteristics

Question 9

Factors affecting Molecular Clock

Answer 9

Species with short generation times would have mutations faster than other species

Smaller populations can have more genetic drift which affects evolution

Question 10

Advantage of Classifying Organisms Based on Evolution

Answer 10

Predictability of Characteristics
Understanding Evolutionary History
Accuracy

Question 11

Limitations of the Hierarchy

Answer 11

Subjectivity: Pyramid relies on physical traits which can be subjective and the choice of traits are arbitrary

Rank-Based Limitations: The hierarchy is arbitrary and doesn’t reflect gradual variation in nature, where changing a classification at one level can disrupt the system

New Discovery Challenges: Hybridization and cloning blur species boundaries which makes the pattern more of a network than a tree