AP Biology Practice Quiz: Common Ancestry
Written by AP Content Team, Verified for 2026 AP Exams, Last updated: May 2026
Test your understanding with short quizzes. This quiz has 7 questions to check your progress.
Question 1 of 7
All Questions (7)
A) Presence of a cell wall
B) Presence of ribosomes
C) Presence of membrane-bound organelles
D) Presence of a circular chromosome
Correct Answer: C
The presence of complex, membrane-bound organelles like the nucleus, mitochondria, and endoplasmic reticulum is a defining characteristic shared by all eukaryotes, supporting the theory that they descended from a common ancestor possessing these structures. Ribosomes are found in all life (prokaryotes and eukaryotes), a cell wall is not present in all eukaryotes, and a circular chromosome is characteristic of prokaryotes.
A) A single, circular chromosome
B) Genes containing introns
C) The presence of plasmids
D) An operon system for gene regulation
Correct Answer: B
The presence of non-coding sequences called introns within genes is a complex feature shared across the eukaryotic domain. This indicates that the machinery to process introns was likely present in the last common eukaryotic ancestor. Circular chromosomes, plasmids, and operons are characteristic of prokaryotes.
A) The organization of DNA into linear chromosomes.
B) The presence of a nucleus and other organelles enclosed by membranes.
C) The presence of ribosomes for protein synthesis.
D) The inclusion of introns within gene sequences.
Correct Answer: C
While eukaryotes do have ribosomes, their presence is not unique evidence for eukaryotic common ancestry, as all known life (including prokaryotes) has ribosomes. Therefore, ribosomes are evidence for a more ancient, universal common ancestor of all life, not specifically eukaryotes. The other options are distinct features shared among eukaryotes.
A) Fossil and biogeographical evidence
B) Structural and functional evidence at the molecular level
C) Behavioral evidence at the organismal level
D) Anatomical evidence at the tissue level
Correct Answer: B
Linear chromosomes and genes with introns are physical structures of the genetic material (structural evidence). The processes of managing linear chromosomes (e.g., telomeres) and splicing introns are complex functions. Both are observed at the molecular level and provide strong evidence for a common ancestor.
A) The organism has a cell membrane and cytoplasm.
B) The organism's DNA is organized into several linear chromosomes.
C) The organism uses DNA to store its genetic information.
D) The organism is capable of reproducing asexually.
Correct Answer: B
The organization of DNA into linear chromosomes is a defining characteristic of eukaryotes and a key piece of evidence for their common ancestry. A cell membrane, cytoplasm, and the use of DNA are features common to all life, while asexual reproduction occurs in both prokaryotes and eukaryotes.
A) The common ancestor of all eukaryotes likely possessed genes with introns.
B) Prokaryotes are more evolutionarily advanced because they lack introns.
C) Introns evolved independently in multiple eukaryotic lineages.
D) Linear chromosomes are a direct result of the splicing process.
Correct Answer: A
The conservation of a complex molecular process like splicing implies it was inherited from a common ancestor. It is far more parsimonious to assume this system evolved once in a common ancestor that had introns than to assume it evolved convergently in every eukaryotic lineage. This supports the idea that introns are an ancestral eukaryotic trait.
A) Genes containing introns
B) A single, circular chromosome
C) Membrane-bound organelles
D) A cell wall composed of peptidoglycan
Correct Answer: C
Membrane-bound organelles, such as the nucleus and mitochondria, are structures found within the cell (cellular level) that are common to all eukaryotes and serve as evidence for their shared ancestry. Genes with introns are evidence at the molecular level, while circular chromosomes and peptidoglycan cell walls are features of prokaryotes.