Defenses

... ability to take in food through phagocytosis. Perhaps because digestive machinery was not yet particularly efficient, or the prey had developed defenses against the predator's enzymes, some of the ingested organisms survived and continued living within the predator. This was absolutely mind ...

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It does work, it just doesn't eliminate it. HIV isn't a superbug, it's just a virus that can eliminate your natural defenses against it.

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... effect. An organism is born with a set of genes to combat disease, parasites, predators, etc. (DPP). The DPP evolve to counteract these defenses. So its a genetic arms race, and the older an organism is, the more subject it is to newly evolved DPP.The organism species must keep evolving ...

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... have helped them to endure for so long on earth? Basic body plan and rapid asexual reproduction are the biggest factors. Physical and chemical defenses also help.

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... - back when they were birds? Yes cactus are plants. They live in the desert, and there are quite a lot of plant eaters there, so yes they need defenses against grazing. Bird do not have teeth, they have a beak and I wonder how you would compare teeth that would be located in the mouth and spikes ...

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