The Krebs cycle<span> occurs right after glycolysis. The substance that begins the </span>Krebs cycle<span> is a 3-carbon molecule called pyruvic </span>acid<span>. The process breaks down the pyruvic </span>acid<span> into acetyl coenzyme A, releasing one of the carbon atoms into carbon dioxide.
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Natural Selection is when traits are "naturally" selected for, because "survival of the fitttest." Example would be a species becoming bigger over time, because the smaller animals of that species were more likely to be eaten by predators. Natural selection is when the "best" trats are passed down due to chance
Selective breeding is if an outside forece (like a dog breeder) "chooses" a triat to be passed down. Example, instead of breeding a brown dog with a white dog, the breeder breeds two black dogs together in orer for the litter to all have black fur
Living things cannot live without eachother due to the food chain, if an animal loses it's food so will his predator and so on. Soon they will end up extinct, this is why it's important to take care of animals.