Consider the following points:
a) All excavates live in environments where oxygen availability is low; b) all excavates lack mitochondria; and c) all excavates have some mitochondrial genes. Based on this information, which of the following statements is true of the excavate lineage?
A) Their ancestors were not able to metabolize glucose.
B) Their ancestors were eukaryotes that existed prior to the origin of mitochondria.
C) Their ancestors had mitochondria, but the mitochondria were lost over time.
D) Excavates are in the process of acquiring mitochondria through evolutionary adaptation.

Question

Consider the following points: 
a) All excavates live in environments where oxygen availability is low; b) all excavates lack mitochondria; and c) all excavates have some mitochondrial genes. Based on this information, which of the following statements is true of the excavate lineage?
A) Their ancestors were not able to metabolize glucose.
B) Their ancestors were eukaryotes that existed prior to the origin of mitochondria.
C) Their ancestors had mitochondria, but the mitochondria were lost over time.
D) Excavates are in the process of acquiring mitochondria through evolutionary adaptation.

Quizplus · Accepted Answer

This is the most likely explanation based on the given information. The fact that excavates have some mitochondrial genes suggests that they once had mitochondria, but for some reason lost them over time. The lack of mitochondria in modern excavates may be due to adaptations to low oxygen environments or other factors that made mitochondria less necessary for energy production. Option A is incorrect because the presence of mitochondrial genes indicates that excavates have the potential to metabolize glucose. Option B is unlikely because all known eukaryotes have mitochondria or descended from eukaryotes that had mitochondria. Option D is also unlikely because if excavates were evolving to acquire mitochondria, they would not have mitochondrial genes already present in their genomes.

Consider the Following Points