Question

Which of these is not supported by the endosymbiosis theory concerning organelles? A) contain DNA. B) contain ribosomes. C) are capable of living independently. D) are surrounded by a double membrane.

Answer 1

The answer to this question is c) are capable of living independently.

The endosymbiotic theory is a theory regarding the origin of eukaryotic cells from prokaryotes, which states that the organelles that are specific to eukaryotes evolved from prokaryotic organisms with a single cell.

What the theory specifies is that the mitochondria and the chloroplast (as well as other plastids) are prokaryotes that used to be free-living, but have entered a eukaryotic cell about 1.5 billion years ago, and somehow managed to survive in the conditions inside it. What happened after the prokaryotic cell survived inside the eukaryotic cell is that it started relying more and more on its host, so most of the genes were tranfered to the genome of the eukaryotic cell. We can see this in today's mitochondria which has its own genome, with only genes that are completely necessary for it's survival, while most other genes it requires are a part of the nuclear DNA.

Going back to your question, both the mitochondria and the choloroplasts have two layers of phospholipids, so they have a double membrane, which suggests that they arose by entering the eukaryotic cell. The bacteria which these organelles could have originated from are bound by a vesicle when they enter a cell through the process of endocytosis, explaining how the double membrane could have appeared. Also, both of these organelles have their own DNA and ribosomes which are very similar to bacterial ones.

The only thing out of the answers you've provided that isn't supported by the endosymbiotic theory is that they aren't capable of living independently, since they have accustomed to the environment of their host cell, and need the nuclear genome to survive.

Answer 2

The endosymbiosis theory is supported by all BUT one piece of modern-day evidence. That is both organelles are capable of living independently. Although both organelles contain RNA, DNA, and ribosomes, if extracted from eukaryotic cells, they are not capable of living independently.