When did oxygen appear on Earth? Oxygen appeared on Earth between 2.4 and 2.2 billion years ago. The air we breathe is not made up mostly of oxygen. It is 78.084% nitrogen, 20.934% oxygen, 0.934% argon, 0.035% carbon dioxide, and then a lot of other trace elements. Our bodies need the oxygen and the carbon […]
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Why do crabs walk sideways? They walk sideways so they don’t trip over their legs. However, some crabs do walk forwards. There are many different species of crab and they can live in saltwater and in freshwater. The smallest crab is the pea crab, which is only a few millimeters across and is a parasite
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How can we catch a ball without looking at it? It is a combination of proprioception and the brain’s ability to predict. What is proprioception? It is the ability to sense your own body position. It is often called the sixth sense. All of our muscles, joints, and tendons have sensory receptors in them. When
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Why do we lose our voice when we are sick? We lose our voice because our vocal cords become inflamed. Let’s look at how the voice works to start with. We all have vocal cords inside our larynx, more commonly known as a voice box. The larynx is at the top of the trachea, the
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How big and how small can a mammal be? The Etruscan shrew is the smallest mammal and is 40 mm long and weighs 2 g. The blue whale is the largest mammal and is 29.9 m long and weighs 199 tons. The African elephant is the largest land animal and is about 4 m tall
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How does a joint replacement work? By replacing parts of the joint, or by replacing the whole joint. Joint replacement surgery is called arthroplasty. It is made from the Greek word “arthro”, which means joint and “plasty”, which means to mold or form. It is carried out when a joint is no longer usable or
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Can a tortoise live without its shell? No. Tortoises and turtles are not just inside their shells. They are the shells. The shells are part of their skeletons. Tortoises and turtles actually come from the same family. In fact, tortoises are turtles. They all come from the family testudines, which are reptiles with a shell
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What causes muscle cramps? There are several potential reasons, but nobody actually knows the real reason. Whatever the reason, all cramps happen in the same way. You may be exercising or you may be at rest, but your muscle will suddenly and involuntarily contract. This can be extremely painful and alarming. The only thing you
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Why are some animals cold-blooded? It lets them go for longer without eating, which means they can survive in more inhospitable areas. There are three types of animals: warm-blooded, cold-blooded, and those in between. Warm-blooded animals are called endotherms and they are able to maintain their body temperature by using their metabolism. We are endotherms.
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How is an addict’s brain different to a non-addict’s? They have significant changes in the reward, stress, and self-control parts of their brains. Whether or not someone becomes an addict is based on a number of things, but experiments have shown that up to 50% of that risk is genetic. One of these experiments looked
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