BIOL-2116 - Tree Thinking
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The beginning of an exploration into evolutionary biology
Mention of trees in the context of evolutionary thought
Possible metaphorical representation of branching evolution
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Information Sources- Introduction to Chapter 11: Vertebrate Life
Book Description
"A compelling scientific adventure story that will change forever how you understand what it means to be human."
Author: Neil Shubin, F. Harvey Pough, Christine M. Janis
Focus:
History of the human body from a 3.5 Billion-year perspective
Explores human evolution and connection to ancestors
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Key Topics
Organizing Organisms
Reading Cladograms
Ancestral vs. Derived characteristics
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Taxonomy
Definition: Hierarchical classification system created by Carolus Linnaeus.
Incorporates binomial nomenclature for creating common names.
Based on morphological features
Initial assumption: species were fixed entities.
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Morphology-based Classification
Relying just on morphology has limitations.
Introduction of Cladistics
New method categorizing organisms based on evolutionary relationships, beyond morphology.
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The Biological Law of Everything
Ancestry traces back to a common ancestor for all life.
Suggests that life evolved once!
All organisms have parental genetic material.
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Cladograms
Represent evolutionary history of taxonomic groups visually.
Differentiates from a phylogenetic tree, which provides an evolutionary time scale.
Cladograms are hypotheses about relationships.
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Focus on Key Topics Again
Organizing Organisms
Reading Cladograms
Ancestral vs. Derived characteristics
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Parts of a Tree:
Root: Base of the tree
Node: Points in phylogeny where a lineage branches.
Preceded by a speciation event.
Branch: Lineage evolving over time.
Tip: Terminal end of a phylogenetic branch, representing a species or group.
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Different Forms: Visual representations comparing ancestral and derived traits.
Time depicted along the evolutionary timeline.
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Rotation of Branches
Groups around a node can be rotated without changing relational information.
Rotation possibilities depend on the form of the cladogram.
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Extant ≠ Ancestor
Current species are not direct ancestors of others.
Tracing back through ancestry reveals evolutionary paths.
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Monophyletic Groups
Definition: A clade is a group with a last common ancestor and all its descendants.
Identification of monophyletic groups varies with perspectives considered in classification.
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Characteristics of Monophyletic Groups:
Key features such as skull, spine, limbs, and evolutionary milestones (e.g. amniotic egg, hair, milk).
Illustrations of relationships between vertebrates, tetrapods, and amniotes included.
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Overview of Key Topics
Organizing Organisms
Reading Cladograms
Ancestral vs. Derived characteristics
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Ingroup vs. Outgroup
Ingroup: Organisms that are the focus of the study.
Outgroup: Organisms less related to the ingroup, included for comparative purposes.
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Ancestral Characters
Definition: Traits that are considered ancestral.
When these traits are shared by group members, they are termed shared ancestral characteristics.
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Derived Characters
Clades are defined by specific derived traits.
These traits differentiate members of a clade from the outgroup.
Example: Difference in characteristics of tetrapods compared to all vertebrates.