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Japan is made up of four large islands: Honshu, Hokkaido, Kyushu, and Shikoku. In addition, there are more than 6,000 smaller islands, including Okinawa. Japan is an island nation with many islands, and because it is surrounded by the sea, it is characterized by abundant fish catches and differences in climate and culture from region to region.

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About 70% of Earth’s surface is covered by water, such as oceans and lakes. The remaining 30% is land. So, the oceans cover a larger area than the parts of the world where humans live.

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A squid has 10 legs, and an octopus has 8. A squid has eight short legs called “arms” and two long legs called “tentacles.” These long legs are used to catch prey.

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Penguins don’t live in the Arctic. In fact, penguins live in the southern parts of the Earth, such as Antarctica and the nearby islands. Animals like polar bears live in the Arctic. Penguins are very good at swimming in cold oceans, and their thick layer of fat and water-repellent feathers protect their bodies. They can’t fly, but in the water they can move as quickly as fish. Living things survive by adapting their bodies and behavior to the places where they live.

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The Earth takes one year to orbit around the Sun. This is called revolution. The Earth's rotation creates day and night.

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One characteristic of insects is that their bodies are divided into three parts—the head, thorax, and abdomen—and they have six legs on the thorax. It’s also fun to check which creatures among the bugs are actually insects.

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Crows are very intelligent birds. They can remember people’s faces and even use tools to get food. For example, some crows drop walnuts onto roads so cars will run over them and crack them open.

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Deserts receive little rain and are dry, but that doesn’t mean there’s no water at all. There are oases where water accumulates underground, and some plants and animals contain moisture. Cacti have stems that store water instead of leaves, and desert animals survive without wasting the water in their bodies.

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The speed of electric flow varies depending on the material, but it doesn’t reach the speed of light (about 300,000 km/s). In other words, the flow of electricity is fast, but it’s a bit slower than light speed. Both happen in a realm so fast that they’re invisible to the human eye.

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Ordinary liquids shrink in volume as their temperature drops, but water is a bit special. Water’s volume decreases as it cools down to 4°C, but if it gets colder than that, its volume actually increases. That’s why ice floats on water.