Question

figure 1. models of a prokaryote, first eukaryotic common ancestor, and last eukaryotic common ancestor. based on the information provided in the figure, which of the following best predicts how membrane - bound organelles provided unique evolutionary advantages to the last eukaryotic common ancestor? a cells with nuclear membranes were better able to protect their genetic material against damage. b cells with flagella were better able to find food and escape predators. c cells with ribosomes were better able to produce proteins needed for a variety of metabolic functions. d cells with mitochondria were able to utilize metabolic energy more efficiently.

Explanation:

• Option A: The nuclear membrane (a membrane - bound organelle) in eukaryotes encloses the genetic material (DNA) within the nucleus. This provides a physical barrier that protects the genetic material from various damaging factors in the cytoplasm, such as reactive molecules or enzymes that could potentially degrade or mutate the DNA. This protection is a significant evolutionary advantage as it helps in the accurate transmission of genetic information and the proper functioning of the cell.
• Option B: Flagella are not membrane - bound organelles, and the question is about membrane - bound organelles, so this option is not relevant.
• Option C: Ribosomes are not membrane - bound organelles (they are either free in the cytoplasm or attached to the endoplasmic reticulum but are not surrounded by a membrane of their own in the same way as other organelles like the nucleus or mitochondria). So this option does not address the role of membrane - bound organelles.
• Option D: While mitochondria are membrane - bound organelles and are important for energy production, the figure (which shows the last eukaryotic common ancestor with mitochondria - like structures) - but the key here is that the question is about the unique advantage of membrane - bound organelles in general. The protection of genetic material by the nuclear membrane (a membrane - bound organelle) is a more fundamental and unique advantage related to the organization of the eukaryotic cell, especially in terms of protecting the genome. Also, prokaryotes can have mechanisms for energy production, but the nuclear membrane is a defining feature of eukaryotes related to genetic protection.

Answer:

A. Cells with nuclear membranes were better able to protect their genetic material against damage.