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1º ESO/MYTHS AND MISCONCEPTIONS ABOUT EVOLUTION - Contenido educativo
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myths and misconceptions about evolution. Let's talk about evolution. You've probably heard that
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some people consider it controversial, even though most scientists don't. But even if you aren't one
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of those people, and you think you have a pretty good understanding of evolution, chances are you
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still believe some things about it that aren't entirely right. Things like, evolution is organisms
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adapting to their environment. This was an earlier, now discredited theory of evolution.
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Almost 60 years before Darwin published his book, Jean-Baptiste Lamarck proposed that creatures
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evolve by developing certain traits over their lifetimes and then passing those on to their
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offspring. For example, he thought that because giraffes spent their lives stretching to reach
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leaves on higher branches, their children would be born with longer necks. But we know now that's
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not how genetic inheritance works. In fact, individual organisms don't evolve at all. Instead,
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random genetic mutations cause some giraffes to be born with longer necks, and that gives them a
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better chance to survive than the ones who weren't so lucky. Which brings us to survival of the
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fittest. This makes it sound like evolution always favors the biggest, strongest, or fastest
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creatures, which is not really the case. For one thing, evolutionary fitness is just a matter of
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how well-suited they are to their current environment. If all the tall trees suddenly
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died out and only short grass was left, all those long-necked giraffes would be at a disadvantage.
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percentage. Secondly, survival is not how evolution occurs. Reproduction is. And the world is full of
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creatures like the male anglerfish, which is so small and ill-suited for survival at birth that
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it has to quickly find a mate before it dies. But at least we can say that if an organism dies
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without reproducing, it's evolutionarily useless, right? Wrong. Remember, natural selection happens
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not at the organism level, but at the genetic level.
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And the same gene that exists in one organism
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will also exist in its relatives.
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So a gene that makes an animal
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altruistically sacrifice itself to help the survival
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and future reproduction of its siblings or cousins
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can become more widespread
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than one that is solely concerned with self-preservation.
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Anything that lets more copies of the gene
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pass on to the next generation will serve its purpose.
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Except...
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evolutionary purpose. One of the most difficult things to keep in mind about evolution
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is that when we say things like genes want to make more copies of themselves or even
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natural selection, we're actually using metaphors. A gene doesn't want anything and there's no
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outside mechanism that selects which genes are best to preserve. All that happens is that random
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genetic mutations cause the organisms carrying them to behave or develop in different ways.
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Some of those ways result in more copies of the mutated gene being passed on, and so forth.
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Nor is there any predetermined plan progressing towards an ideal form.
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It's not ideal for the human eye to have a blind spot where the optic nerve exits the retina,
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but that's how it developed, starting from a simple photoreceptor cell. In retrospect,
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it would have been much more advantageous for humans to crave nutrients and vitamins rather
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than just calories, but over the millennia during which our ancestors evolved, calories
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were scarce and there was nothing to anticipate that this would later change so quickly.
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So evolution proceeds blindly, step by step by step, creating all of the diversity we
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see in the natural world.
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- Subido por:
- Alicia M.
- Licencia:
- Dominio público
- Visualizaciones:
- 135
- Fecha:
- 27 de septiembre de 2020 - 19:03
- Visibilidad:
- Público
- Centro:
- IES LA SENDA
- Duración:
- 04′ 22″
- Relación de aspecto:
- 1.78:1
- Resolución:
- 1920x1080 píxeles
- Tamaño:
- 101.30 MBytes
