EvolutionLesson 3 of 3 in the course Phylogenies and the History of Life

Horizontal Gene Transfer, Endosymbiosis, and Phylogenetic Models

5 flashcards · 5 quiz questions · 5 match pairs · 4 fill-in sentences · English

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Summary

This lesson introduces the classic phylogenetic tree and explains why horizontal gene transfer complicates the traditional picture of evolutionary relationships.

A phylogenetic tree is a model of evolutionary relationships. Its trunk represents shared ancestry, while its branches represent lineages that diverged over time. Charles Darwin sketched an early version in 1837, and the tree analogy became a useful way to visualize how species may be related.

All flashcards

Horizontal gene transfer (HGT)
Movement of genetic material between organisms by routes other than parent-to-offspring transmission.
Transformation
Uptake of naked DNA from the surroundings by a bacterium.
Gene transfer agent (GTA)
A virus-like particle that carries random genomic segments between prokaryotes.
Endosymbiosis
An interaction in which one organism lives inside another.
Web of life
A model emphasizing gene exchange among multiple prokaryotic lineages.

Quiz questions

  1. A bacterium takes up naked DNA from its surroundings. Which mechanism does this describe?Answer: Transformation: uptake of environmental DNA
  2. A bacteriophage carries genes from one bacterium to another. Which mechanism is involved?Answer: Transduction
  3. In prokaryotes, DNA passes between organisms through a connecting pilus. What is this mechanism called?Answer: Conjugation
  4. According to the endosymbiont theory, how did mitochondria and plant chloroplasts originate?Answer: They descended from free-living prokaryotes that became established inside ancestral cells.
  5. What does the ring of life model propose about the origins of Archaea, Bacteria, and Eukarya?Answer: They arose from a shared pool of primitive prokaryotes that exchanged genes.

Based on Biology 2e by Mary Ann Clark, Matthew Douglas, Jung Choi (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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