Why couldn't there be a real single-celled organism as large as the blob in the movie?

Answer 1

Because it is too big to be single celled. Multicelluar is a different question.

The monster in The Blob is never determined to be single celled or mulitcelled; the film just doesn't address it. The original story, before the film, actually described it as a mineral.

Answer 2

The largest single cell organism so far discovered is a Mediterranean seaweed about one meter (3 feet) across. It looks like an ordinary plant with many branches. It has many nucleases. It also has a number of provisions for repairing broken off parts. Since there are many branches, respiration is not a problem. It would be possible to have a single celled organism as large as the blob. It would be much easier underwater with a multi branched organism. That way oxygen could get to all parts of the organism. Insects using spiracles are restricted to about 2 cm maximum diameter. Animals with lungs can pump blood to all parts of their bodies and can get oxygen to all parts and therefore have no such restriction. It would be quite difficult to create a circulatory system within a single cell. Many millions of different species of insects exist in the world today. They are unable to evolve past a certain body size due to their inability to get air past a certain point. Your blob could not breathe on land.

Answer 3

There is a possibility of a single celled organism getting as large as the blob in the movie. However, it would be easier for it to grow and live underwater due to possible respiration issues.

Answer 4

There could not be a single-celled organism that big on this planet... something extraterrestrial that is unknown to us at this time may or may not exist... but there are multi-celled fungus, such as mushrooms, that may actually be hundreds of square miles large, and still only be a single organism.