EvolutionLesson 2 of 2 in the course Diversity of Life

Evidence, Cladistics, and Parsimony in Phylogenetic Inference

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Scientists reconstruct the evolutionary history of organisms by examining evidence, much as detectives piece together clues. This lesson introduces the main kinds of evidence used to infer relatedness and explains why appearance alone can sometimes mislead.

Morphological evidence concerns an organism’s form and structure, including how body parts are arranged and what they do. Organisms with similar physical features may share an evolutionary history, but scientists must ask whether the similarities reflect common ancestry or similar adaptations.

All flashcards

Homologous structures
Features that share an evolutionary origin, even if their forms or functions differ.
Analogous structures
Features with similar functions or appearances that arose from different ancestral structures.
Molecular systematics
The use of molecular information, such as DNA sequences, to study evolutionary relationships.
Shared derived character
A changed trait shared by members of a group that can help identify a clade.
Maximum parsimony
A principle that favors the tree requiring the fewest evolutionary changes to explain the data.

Quiz questions

  1. What defines a clade in cladistic classification?Answer: A common ancestor and all of its descendants
  2. In cladistic analysis, what is an outgroup used for?Answer: To help infer which character state is ancestral in the comparison
  3. What does maximum parsimony favor when comparing phylogenetic trees?Answer: The tree requiring the fewest character changes to explain the observations
  4. What is a character reversal in phylogenetic analysis?Answer: A lineage changes back from a character state found in its ancestor
  5. Why can scientists revise a proposed phylogenetic tree?Answer: New evidence can support a different explanation of evolutionary relationships

Based on Concepts of Biology by Samantha Fowler, Rebecca Roush, James Wise (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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