Cogat Sample Questions Third Grade

a secluded retreat in the intestinal microvilli any human being, a group of bacteria produced by mitosis just gather around another, larger, plagadada cilia. Lies away from the pack. The "young" jump around, urging me to tell stories that both have heard other Gastrocomunidad bacteria.

- Come, let us know! We know things, everyone says that you know more about bacteria than anyone else! Come, come! - Cry out in unison, shaking their small cilia.

bacteria

The great sighs, resigned, and fits between the mucosa. The small stand in a circle, eager for knowledge. And they start stories.

"Okay, but I will tell you only a couple of things, right? Long time ago that you divided, and by now you will know full well that we are bodies constituted by a single cell, and that we live within a much larger bodies and complex, made up of thousands of cells, and they call themselves themselves "human beings" and we "bacteria." The wisest of human beings have for years been giving names to things and beings of their world, and therefore we have been renamed to distinguish ourselves from all other relatives who have, Escherichia coli.

Young Restless bacteria moved. The beginning history were finding it very interesting, because they knew (about) all that. He became aware of it.

- But I do not think that you may know, is that besides being a vital protagonists of the biology of these beings, who benefit from our work as we can live in its comfortable interior, our race has played a major role in the development of human science, in its ability to investigate their own physiology to combat the disease and to unravel the mysteries of other living beings who live with him in his world.

The audience was petrified, things got interesting.

- The first humans to decipher the mysteries of the genetic code and the molecular basis of life, needed a way to "play" with these molecules. Given its inability to handle the world on a microscopic scale, soon needed help. And here we come: our constitution as unicellular organisms, and our innate ability to absorb foreign DNA molecules and proteins on a large scale production, we became the ideal candidate: it took only a few years to develop techniques that allow them to enter DNA within us. Our easy to reproduce so quickly - if environment is rich enough and the right temperature - make us small protein factories, as we artificially introduced genes are translated by our own machinery. After a purification process in which our thick cell walls are broken and all content within us separately carefully, humans obtain material for their research.

general might feel a jolt similar to the description of genocide. one of the small bacteria began to tremble visibly.

- Oh, calm, fear not - calmed the old bacteria, pleased with the effect of his talk - anything can happen while we are in the interior of these beings. These bacteria are relatives I talk to us, but are themselves genetically modified, so that humans can control who grows in his hands and who is not. In fact, if any of you came by accident to one of the plates where humans grow our fellow sobreviviríais not even a division. These plates are sprayed with antibiotics, harmful substances that impede our growth. Only the genetically modified bacteria to resist those antibiotics grow there, and these bacteria are only those that have managed to introduce foreign DNA into their cellular machinery. This will ensure they are working only with the appropriate bacteria.

E. Bacteria coli transformed with a plasmid DNA which contains the gene for ampicillin resistance were seeded in separate culture plates with embedded agar ampicillin on the left, a handle was used as a seed pen, on the right, the bacteria were seeded evenly over the plate, and then wrote the word with a loop dipped in chloramphenicol, an antibiotic to which bacteria have no resistance genes (actually, the lyrics are distinguished by the mark on agar, the antibiotic released since then and can see a fairly broad halo where the bacteria do not grow).

Among the audience, suddenly, a small forward bacteria. He seemed restless, as if to say something.

- Tell me, son, what worries you - you said the old bacteria.

The little brighter, finally:

- see, is that .. I have also heard stories about bacteria that are capable of changing its resistance to antibiotics, and can grow in media they could not before.

The old bacteria was pleased. He liked his listeners to participate in their stories.

- Very good, small, that's a very astute observation. You see, that's not entirely wrong, but should be better explained. It is true that sometimes, bacteria that were resistant to some antibiotics, suddenly they are. But that does not depend on the decision itself of bacteria, nothing further. Bacterial populations are heteogéneas, is genetic variability between us, despite reproduce by mitosis. There phenomena transfer of genetic material, and some strains can incorporate genes that previously did not have. The use of antibiotics is making it artificially selected, so humans are reluctant to apply their sick too many antibiotics. In their ignorance, many fall into the same error as you, and think that bacteria on a voluntary basis "learn" to fight cocntra antibiotics in some way. None of that is something as simple as that survive only individuals who already are tough. Due to our rapid growth, any change in our genetic material (either by mutations produced spontaneously or by gene transfer between strains) can become dominant if there exists a Continuous antibiotic that kills "competitor" that do not show such resistance. We do not have free will, how we could! We are just a tiny cell, devoid of nervous system. Not to be, we have no core ...

The little bacteria still not feel satisfied. He waved a pair of flagella impatient and kept asking, without a hint of shame as any:

- But then, what we're here talking to us, and we know all these things?

This time the old bacteria took time to respond. Decided to terminate his conversation with the biggest and most worrisome of the explanation.

- Oh, small, how innocent you are. The answer is quite simple, and again we must use humans to explain. With all their accumulated knowledge and skills are still very limited, and must rely on artificial tricks to keep learning and especially to pass on their knowledge. Just as almost unconsciously assume that people around them use human qualities that they do not possess - as in the case to imagine that evolutionary processes are managed by the agencies themselves at will - very few are able to explain to his fellow phenomena its scientists discover biological. Therefore, they must resort to tricks like the one in question, whereby write stories like that I'm telling you, and endow their characters human qualities such as speech and thought. Not to mention another group of humans who prefer to go directly to the invention of superior beings of great power to explain everything for what we have not found an explanation ...

But that is another story, another day I will tell you: it's time for you to get down to work. We must do our part to work on the absorption of nutrients in this area, or being in which we stayed cease to be warm and comfortable. Stories would end forever, and do not want that, right?

All bacteria released a resounding "No!" in unison, and scattered microvilli, prepared to perform those functions as their relatives, growing comfortably in beds nutritious agar in incubators at 37 º, had almost forgotten.

This entry participates in the First Edition of the Carnival of Biology , opened by Raven in MICROGAIA .