4.2.3 Evolutionary Relationships

• What are phylogenetic trees used to represent?

  Evolutionary relationships among organisms
• The common ancestor of all organisms in a phylogenetic tree is called the root
• Branches in a phylogenetic tree represent evolutionary paths.
• What do nodes in a phylogenetic tree represent?

  Speciation events
• Groups of organisms that share a common ancestor are called clades
• The branching structure of a phylogenetic tree indicates the timeline of speciation events.
• What is the root of a phylogenetic tree?

  The common ancestor
• Order the following events as represented in a phylogenetic tree showing the relationships between species X, Y, and Z.

  1️⃣ Common ancestor A exists

  2️⃣ Speciation of X and Y occurs

  3️⃣ Speciation of Y and Z occurs
• What is the primary difference between homologous and analogous structures?

  Origin and ancestry
• Homologous structures evolve from a common ancestor
• Analogous structures are similar due to convergent evolution.
• What is the origin of homologous structures?

  A common ancestor
• Homologous structures may or may not have the same function
• The human arm and whale flipper are examples of homologous structures.
• What is an example of analogous structures?

  Wings of birds and insects
• What are homologous structures in related organisms evidence of?

  Common ancestor
• Homologous structures evolve independently in unrelated organisms.

  False
• Homologous structures may or may not have the same function
• Why are the forelimbs of vertebrates considered homologous structures?

  Common ancestral origin
• What makes the wings of birds and insects analogous structures?

  Evolved separately for flight
• What three sources provide molecular evidence for evolution?

  DNA, amino acids, pseudogenes
• DNA sequences are compared to identify shared genetic regions indicating common ancestry
• Similar amino acid sequences in different species suggest a common ancestor.
• Why are pseudogenes useful in studying evolutionary relationships?

  Shared non-functional genes
• Match the molecular evidence with its interpretation:

  DNA Sequences ↔️ Shared genetic regions indicate common ancestry

  Amino Acid Sequences ↔️ Similar arrangements reveal common ancestry

  Pseudogenes ↔️ Shared non-functional genes confirm ancestry
• What is speciation, and what are its two primary mechanisms?

  New species arise; allopatric and sympatric
• Allopatric speciation occurs when populations become geographically isolated
• What is an example of allopatric speciation?

  Darwin's finches
• Sympatric speciation requires physical isolation between populations.

  False
• Steps for sympatric speciation

  1️⃣ No physical barrier

  2️⃣ Strong disruptive selection

  3️⃣ Reproductive isolation develops
• What is an example of sympatric speciation?

  Apple maggot fly
• What is the purpose of a phylogenetic tree?

  Shows evolutionary relationships
• The root of a phylogenetic tree represents the common ancestor
• Clades in a phylogenetic tree share a common ancestor.
• What are phylogenetic trees used to understand?

  Evolutionary relationships
• The root of a phylogenetic tree represents the common ancestor
• Match the components of a phylogenetic tree with their descriptions:

  Branches ↔️ Show evolutionary paths

  Nodes ↔️ Represent speciation events

  Clades ↔️ Groups sharing a common ancestor

  Root ↔️ Common ancestor of all organisms
• In the example tree, species X, Y, and Z are related through common ancestor A.
• In the example tree, node B represents the speciation of species X and Y
• What are homologous structures in related organisms?

  Shared ancestral origin