it has been hypothesized that chloroplasts originated from photosynthetic cyanobacteria that became symbiotic inside a host cell. Which of the following observations provides the strongest evidence for this suggestion?
A) microscopically, chloroplast appear similar to cyanobacteria
B) chloroplast DNA shows clear similarities to cyanobacterial DNA
C) both chloroplast and cyanobacteria are green and perform photosynthesis
D) Photosynthetic cyanobacteria and fungi form a mutualistic association in lichen
The answer is B
B) chloroplast DNA shows clear similarities to cyanobacterial DNA
To determine which observation provides the strongest evidence for the suggestion that chloroplasts originated from photosynthetic cyanobacteria that became symbiotic inside a host cell, we need to consider the information provided in each option.
Option A suggests that chloroplasts appear similar to cyanobacteria when observed under a microscope. This observation alone does not necessarily provide strong evidence for the suggestion, as there could be other reasons why chloroplasts and cyanobacteria appear similar microscopically.
Option B suggests that the DNA of chloroplasts shows clear similarities to cyanobacterial DNA. This observation provides more substantial evidence for the suggestion, as DNA similarities indicate a common genetic origin between chloroplasts and cyanobacteria.
Option C suggests that both chloroplasts and cyanobacteria are green and perform photosynthesis. While this observation is relevant to the topic, it does not directly provide evidence for the suggestion of a symbiotic relationship between chloroplasts and cyanobacteria.
Option D mentions a mutualistic association between photosynthetic cyanobacteria and fungi in lichen. Although this observation is interesting and may provide insight into mutualistic relationships, it does not particularly support the suggestion of cyanobacteria becoming symbiotic with a host cell to form chloroplasts.
Based on these considerations, option B - chloroplast DNA showing clear similarities to cyanobacterial DNA - provides the strongest evidence for the suggestion that chloroplasts originated from photosynthetic cyanobacteria that became symbiotic inside a host cell.