BIO1130 Part 2: Systematics Quiz

BIO1130 Part 2

• Lectures are in-person
• No lecture videos pre-class
• Learning activities in class
• Lectures recorded and posted on BrightSpace
• Additional Wooclap quizzes for topics 8-16 (ungraded)
• Midterm 2 covers topics 8-12 (by Pr. Delcourt)
• Pr. Delcourt's office hours:
  • Monday 1:00 pm - 2:00 pm
  • Tuesday 10:00 am - 11:00 am
  • Location: BSC 108

Topic 7: Systematics

• Systematics combines taxonomy and phylogenetics
• Write genus & species names using Linnaean nomenclature
• Distinguish between homologous and analogous traits (importance of this distinction)
• Explain how analogous traits evolve
• Interpret phylogenetic trees, relating branching patterns to evolutionary relationships
• Define common phylogenetic tree terms (root, branch, tip, common ancestor, clade, mono-/para-/polyphyletic, taxon/taxa, sister taxa, ingroup/outgroup)
• Explain basic principles of cladistics
• Explain use of morphology/molecular data in phylogenetic tree construction
• Distinguish ingroups and outgroups
• Distinguish shared derived and shared ancestral characters
• Define parsimony and its use in phylogenetic tree construction
• Reconstruct simple phylogenetic trees using molecular data and parsimony
• Compare/contrast cladogram and phylogram
• Explain methods for adding dates to phylogenetic trees

7.1 - Definitions and Taxonomy

• Systematics is the science of classifying organisms & determining evolutionary relationships
• Two components:
  • Taxonomy: scientific discipline of naming & classifying organisms
  • Phylogenetics: study of evolutionary relationships
• Phylogenetic tree: diagrammatic hypothesis of evolutionary relationships; resulting from phylogenetic analysis

7.2 - Phylogenetic Trees

• Phylogenetics: study of evolutionary relationships
• Originally based on morphological similarities (still used for fossils)
• Modern approaches use molecular sequences (DNA, RNA, proteins) for more accurate analyses.
• Phylogenetic analyses result in phylogenetic trees, hypotheses of evolutionary relationships among a set of taxa

7.3 - Constructing Phylogenies

• Cladistics: An approach to systematics where common ancestry is the primary basis for classification. This approach uses homologies to define clades or monophyletic groups.
• Implications: Taxonomy should reflect evolutionary history and organisms should be categorized into nested monophyletic groups for phylogenetic studies.
• Evidence for common ancestry comes from shared derived characters (unique traits present in a group due to common ancestry).

Cladistics

• A clade includes a common ancestor and all its descendants (living and extinct).
• By definition, clades are monophyletic
• Clades are nested within one another
• Many existing taxonomic groups are not monophyletic (e.g., class Reptilia is paraphyletic; clade Dinosauria is only monophyletic if birds are included).

Constructing Phylogenies

• Phylogenies can be built using morphological and molecular data.
• Evidence for common ancestry comes from homologous traits (shared characters from common descent).
• Analogous traits are misleading, as they can result from convergent evolution.
• Homologous traits are further categorized into ancestral and derived types.

Adding Time to Trees

• Cladogram: Shows branching patterns only (branch lengths are arbitrary).
• Phylogram: Shows branching patterns where branch lengths are proportional to either genetic change or time.

Dating Branching Points (Nodes)

• Can be done using:
  • Fossils (in combination with radiometric or stratigraphic dating)
  • Molecular clock (assumes rate of nucleotide substitutions constant over time for a gene).

Molecular Clock

• Molecular clocks are calibrated using known fossil dates.
• Different genes have varying rates of molecular change due to differing selective pressures.

Convergent Evolution

• Independent evolution of similar traits in different lineages.
• Creates analogies (similarities not due to shared ancestry, but rather by shared environment or independent mutations).

Constructing Phylogenies

• Shared derived characteristics are unique to a group, resulting from a common ancestor
• Using an outgroup (species outside of the group of interest) can help infer evolutionary relationships between the ingroup (the group of interest)
• Systematists compare members of the ingroup with the outgroup to identify shared derived vs ancestral traits
• This process ultimately helps to group members of the ingroup based on shared derived traits and determine branching points

Test your knowledge on systematics, covering taxonomy, phylogenetics, and cladistics principles. This quiz will help you distinguish between homologous and analogous traits, interpret phylogenetic trees, and understand important terminology in evolutionary biology. Get ready to apply what you've learned in class!