Question

The endosymbiotic theory hypothesizes that mitochondria and plastids evolved from prokaryotic cells. What evidence supports the hypothesis?

A. They are autotrophic and have parasitic relationships
B. They have circular chromosomes similar to bacterial chromosomes
C. They have chromosomes and ribosomes that are similar to prokaryotes
D. They have flagella similar to prokaryotes

Answer 1

Mitochondria and plastids are thought to have evolved from prokaryotic cells based on their circular chromosomes similar to those of bacteria, the similarity of their ribosomes to bacterial ribosomes, and the resemblance of their binary fission reproduction to that of bacteria.

Step-by-step explanation:

The endosymbiotic theory suggests that mitochondria and plastids developed from prokaryotic cells that established a symbiotic relationship within a eukaryotic host. A key piece of evidence supporting this hypothesis is that mitochondria and chloroplasts have circular chromosomes that are similar to bacterial chromosomes, which is option B in the student's question. Further evidence includes:

• The DNA sequence of mitochondrial DNA and chloroplast DNA is highly related to their bacterial counterparts.
• The structure of mitochondrial and chloroplast ribosomes is similar to that of bacterial ribosomes, rather than the eukaryotic ribosomes of their hosts.
• These organelles replicate through binary fission, which is characteristic of bacteria, and not through the mitosis used by eukaryotes.

Additionally, the genetic material within these organelles has been integrated with the host eukaryotic cell's nucleus over millions of years of evolution.