Why do living things stop growing? Not all living things stop growing, but those that do stop for a number of different reasons. Mammals, birds, fish, reptiles, insects, and plants all follow different growth programs, and those programs reflect different body plans and different trade-offs. Not all living organisms stop growing. Plants and fungi often […]
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Why does an octopus have three hearts? An octopus has three hearts because getting oxygen from gills is hard work, and its copper-based blood does not carry oxygen as efficiently as human blood. Using three pumps keeps oxygen moving through the gills and around the body. The job of a heart is to keep blood
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Can birds sleep while they fly? Not all species can, but there are some birds that can sleep while they are flying. Most birds land to sleep. They perch on branches or buildings, balanced so well that they can stand on two legs without toppling over. Many species also have tendons that lock their feet
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How do salt flats form? Salt flats form when water with a high mineral content gets trapped and evaporates more quickly than it can be replenished. Salt flats are sometimes called salt pans. They are a large expanse of land that used to be a lakebed but is now covered in a hard crust of
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Do submarines still use periscopes? Yes, submarines do still use periscopes, although they now combine them with many other high-tech sensors as well. At its simplest, a periscope uses two angled reflectors to send light down a long tube. A basic periscope looks a bit like a straightened “S.” The top opening faces whatever is
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How does bleach kill microbes? Bleach sterilizes by oxidizing molecules in the cells of germs, viruses, and bacteria, killing them. When something is oxidized, electrons are taken away, which disrupts the function of important molecules. Rust is a familiar example of the kind of damage oxidation can do. There are two main types of bleach.
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What is Monosodium Glutamate? Monosodium Glutamate (MSG) is a salt used to add flavor to food. MSG is the sodium salt of glutamic acid. Glutamic acid is an amino acid that occurs naturally in lots of foods, such as tomatoes, cheese, mushrooms, and seaweed. In foods, glutamic acid often loses a hydrogen ion and becomes
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How does a tunnel ventilation system work? A tunnel ventilation system either uses evenly spaced air vents to pull in air or powerful fans to push it along. They also use extractor fans to remove the car emissions, and they rely on the piston effect of vehicles entering the tunnel. As tunnels get longer, designers
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Do all animals have imprinting? No, not all animals have imprinting, but a lot do. Imprinting is where a newborn animal learns to follow its protector as soon as it is born. When the animal is born, it imprints the closest animal, usually its mother, into its brain and then follows that animal exclusively. The
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What does E = mc² mean? E = mc² means that mass and energy are two ways of describing the same physical thing. In everyday life, mass feels like “stuff” and energy feels like “activity,” but Einstein showed that they are connected. If a system loses energy, it also loses mass. If it gains energy,
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