Viruses and the Speed of Evolution
Subject: Science/Biology; Science-Fiction;
Ages: 14+: High School;
Length: Snippet: 3 minutes (in two segments); Lesson: 30 minutes; Homework: Research and Essay Assignment.
These film clips and the ensuing discussion and assignment will provide students with an interesting change of pace in studying virology and the speed of evolution.
Different aspects of life sciences are used in movies like The Relic to give events in the story a scientific framework and increased credibility. In The Relic, scientists put the existence of a monstrous creature into the context of DNA alterations through a virus, the ingestion of genetically modified nutrients, and a new wrinkle in the theory of evolution. Their hypotheses are completely fictitious, but the errors provide a context for learning the real scientific understanding of virus and the pace of evolution.
DESCRIPTION OF SNIPPET
A monster runs amok in the Natural History Museum of Chicago when the museum is about to open a new exhibition. The creature seems to be connected to some crates sent to the museum by a scientist doing field work in a remote South American jungle. The crates are crammed with leaves containing a parasitic fungus. Even the ship that carried the crates from South America has become the scene of vicious attacks by the monster. But the monster is too big to have arrived in the crates and scientists at the museum are looking for an explanation.
The scientists in the movie hypothesize that the creature started as a normal being but was changed into this monstrous state by eating infested leaves from the crates. They claim that the virus would have inserted its own DNA to the cells of the plant and that in turn take over the DNA of any animal that eats it. However this altered DNA seems to be coding reptilian hormones and, in fact, turns out to be reptilian DNA altogether.
As confirmation of their theory, the scientists point to the case of a small beetle that accidentally ate from the same leaves and in matter of days became a bug the size of a small cat. Segment 1 shows the scientists, Margo and Dr. Frock, commenting on this after a DNA analysis reveals that the giant bug has reptilian DNA in it.
In the second film clip, the scientists describe their thoughts to a detective who is investigating the case. Dr. Frock relates their theory on the monster to a hypothesis about evolution called the Callisto Effect, for which he is seeking proof. The Callisto Effect is entirely fictitious and postulates that evolution can lead to a predator with extraordinary powers that is so strong and voracious that it causes the extinction of other species before dying out itself.
Viruses and DNA Rewriting
It is true that some viruses have developed the ability to replace DNA segments of the infected cells in their effort to use the host cell for their own reproduction. In fact, this ability of viruses is being studied for its therapeutic uses by medical researchers in what is called “gene therapy”: What is Gene Therapy from Wisegeek.com.
However, viruses would not sporadically insert DNA of a third kind of organism; they use their ability to rewrite DNA to introduce their own genetic information, to have the cells build replicas of the virus. So, unless someone deliberately programmed some viruses to rewrite the plant’s DNA with reptilian features as is done in gene therapy, the first part of the theory of the scientists in The Relic is not realistic at all.
The hijacking of the replicating mechanism of other organisms in order to reproduce is the very essence of a virus. This is why viruses are considered to be on the borderline between living and non-living things: if the ability to reproduce is part of what we understand as life, can something be considered life if it only is able to reproduce through the cells of others? Learn more about this debate at Are Viruses Alive from Microbial Life Educational Resources.
Acquiring New Genetic Information Through DNA Ingestion
Second, even if reptilian features somehow found their way into the plant’s DNA, there is no way that an animal eating these leaves with altered DNA could evolve into a reptile-like-creature: DNA is not acquired and replaced by eating cells with different DNA. If that were so, we would end up becoming what we eat. However, Dr. Frock in The Relic clearly states in the second film clip that by ingesting such leaves any animal would experience a DNA alteration. He believes that the tribe of the Zanzera used this in order to create monstrous creatures to fight their enemies.
The belief that DNA, or parts of it can be acquired by eating it is behind some of the objections against the use of genetically altered foods. People making this objection assumed that our normal DNA is somehow related to eating food as provided by nature and that ingesting altered DNA could alter our own genetic code.
But there is a justified concern about genetically altered food: if some DNA segments have been altered to improve the plant, the change may cause some other unforeseen effects in the plants. Our still limited knowledge of genetics does not allow us to be sure before the change has been tried. However, genetically altered food is not allowed into the market unless it has been thoroughly tested for unexpected side effects. Regulations are strict and regulators tend to stay on the safe side when in doubt.
On the other hand, mankind has been genetically altering plants since agriculture was adopted as a means of providing food. Certain types of plants were favored to obtain the seeds for the next sowing season. “Natural” wheat or corn is substantially smaller than that growing in modern fields. Also, animals have been genetically engineered since wolves were domesticated and bred to become something as different as a poodle or a Chihuahua. Chickens are bred to have enlarged meaty breasts that make them fall over if they ever get out of their tiny cages. Animal breeding has also been done by trial and error without the knowledge of possible unwanted collateral effects. See Understanding Evolution: Artificial Selection from Berkely.edu.
Mutations and Transformations
Now, even if the altered DNA could somehow be transferred to an organism that ate it, in order to change the whole structure of the animal it would need to reach every cell of the specimen. Fully developed individuals have already built their bodies according to their genetic information, which is contained in each and every cell. Every cell has the whole instruction manual in it on how to build the body, even if a particular cell only needs to know the small part of this information that instructs it to become part of a particular organ. If a cell ends up with DNA which is different from its precursor cell, either through an error during replication, or an externally induced mutation, it will only behave abnormally if the alteration affects the part of the DNA that contains information specific to its function. And even in this case, only that particular cell, and those that will originate by its replication, will deviate from healthy development. This may cause a localized problem, like cancer (which can spread to other local sites by metastasis), but it will not cause a complete change in all the cells of the whole organism.
In order to affect a whole individual, mutations would need to occur in the gametes of its parent individuals or, at most, immediately after fertilization of the egg, when there is only one cell that will be the model for all other cells.
The Pace of Evolution
In The Relic, Dr. Frock claims that the Zanzera tribe’s way of inducing the development of a monster by feeding infected leaves to a normal animal is proof that the “Callisto Effect” is possible. According to this theory, which exists only in the fiction of The Relic, random mutations should be able to induce sudden major changes in some organisms, creating short-lived creatures that are very different from their immediate ancestors.
This “Callisto Effect” is a completely fictitious theory, but it is based on an issue that is still today under debate among experts in evolution. It is the question of whether evolution tends to occur slowly and steadily or in sudden jumps. As in every field of science, to test such a question, hypotheses are formulated and their predictions compared to observation. This process is explained as applied to the question of the pace of evolution in The pace of evolution from Berkely.edu. See also the Helpful Background of the TWM Snippet Lesson Plan for Evolution Using H. G. Wells’ The Time Machine which discusses and provides links to sites relating to the speed of evolution in blue moths and fish; the ability of human adults to digest milk; and the appearance of blue eyes in human beings.
1. Read the Helpful Background section of this Guide.
2. Be familiar with the location of the segments and how to quickly get from the first to the second film clip. Minute and second calculations may differ from what is set out below.
Clip #1 runs from 50:21 to 51:49. While the opening reception for the new exhibition at the museum is beginning, the scientists Margo and Dr. Frock comment on the surprising results of the DNA analysis of the giant bug that developed from a beetle and the possible connection between the leaves it ate and the origin of the monster that is causing havoc in the basement of the museum.
Clip #2 runs from 1:13:10 to 1:14:40. After the creature has shown itself and the reception was interrupted by the alarm, the two scientists and a detective are hiding from the monster in a room of the basement of the museum. The scientists explain their theory on the monster to the detective and Dr. Frock is happy to realize that it could be related to his long sought proof of the “Callisto Effect.”
3. Cue the DVD to the first film clip.
STEP BY STEP
1. Show the film clips to the class.
2. Ask the students to identify the errors or impossible statements in the explanations of the scientists in the movie. Help them to mention that virus would not naturally insert reptilian DNA into the cells of a plant because viruses survive and multiply by inserting their own DNA into cells, that DNA is not acquired by eating, and that even if it was, the new DNA acquired by an adult could not transform it since all of its other cells already have their own DNA. During the discussion bring up any additional information from the Helpful Background section or other sources.
3. Concluding Assignment – Assessment: Ask students to research and to write a short essay on the speed of natural selection and the various theories about it, taking into account recent findings, including: blue moths, the size of ocean living fish, blue eyes in human beings, and the ability of adult humans to digest milk after reaching adulthood. Coordinate with your students’ ELA teacher for a rubric for the essay.