Rain worms.

Date: 2015-10-07; view: 430.

D. The text below has been jumbled. Arrange the paragraphs in the correct order to make a full story.

C. Read the text again and answer the following questions in your own words.

1. Why are Caenorhabditis elegans considered to be the best-understood multicellular organism on the planet?

2. How does the worms' genome evolve?

3. What kinds of worms are mentioned in the reading? Basing on the text, give as much information about them as possible.

4. How are worms connected with humans in the reading?

5. What are the reasons of the fact that the worms' genomes are evolving faster than mammalian ones?

6. What is the use of C.elegans in science?

7. What is the evidence of fast progress of the worms' genomes?
8. Why do the scientists study the genomes of C. briggsae and C. elegans simultaneously?

9. Why is it important to find out the way the worms' genomes work?

10. Why do two kinds of worms differ from each other more than human and mice do?

11. What is silent mutation according to the reading?
12. What is the mechanism of spotting genes?

(1) A further theory is that, as there are many other organisms in the ground as well, and their respiration increases carbon dioxide, this gas may dissolve into the rainwater to form carbonic acid. As the soil becomes too acidic for the worms, they seek a more neutral environment on the surface.

(2) An alternative theory concerning this behaviour is that as some species (notably Lumbricus terrestris) come to the surface to mate they may become stranded. However, as this behaviour is limited to only a few species and L. terrestris is rarely, if ever, one of those found stranded on impermeable surfaces, this theory does not seem a very likely explanation.

(3) Earthworms are seen on the surface after large rain storms flood the soil because, despite needing a moist environment to allow the diffusion of gases across their skin membrane, where the soil becomes saturated they begin to drown. To protect themselves they escape to the surface but if the ground is unnaturally hard they may become stranded and die from exposure. This is why they are seen in places like driveways after a storm. However, this theory is not applicable to certain earthworm species that can survive immersion for several days in oxygenated water.

(4) Another theory is that the worms may be using the moist conditions on the surface to travel more quickly than they can underground, thus colonizing new areas more quickly. Since the relative humidity is higher during and after rain, they do not become dehydrated. This is a dangerous activity in the daytime, since earthworms die quickly when exposed to direct sunlight with its strong UV content, and are more vulnerable to predators such as birds.