The animals that genuinely sleep with their eyes open are snakes and fishes including sharks. These animals don’t have eyelids, rather possess a specialized membrane called the nictitating membrane that covers their eyes while they sleep. This transparent membrane allows them to rest while remaining alert to potential threats in their environment. By keeping their eyes open, these fish and snake can swiftly respond to any danger, ensuring their survival.

The attraction between the Sun and the Moon, as well as between any two objects with mass, is called gravitation. Gravitation is a force that pulls objects toward each other, and in this case, the Sun's gravity affects the Moon's orbit around the Earth. Gravitation is one of the fundamental forces of nature and is responsible for the motion of celestial bodies.

A sperm is usually a small, compact cell. Each cell is independent and effectively competitive with other sperms.

Melanin is a substance (enzyme) in human body that is responsible for hair, eye and skin pigmentation. The more melanin you produce, the darker your eyes, hair and skin will be. The amount of melanin in one’s body depends on a few different factors, including genetics and how much sun exposure your ancestral population had.

Earthworm breathes through their skin. Air dissolves on the mucus of their skin, so they must be moist in order to breathe. Again, after heavy rains earthworms surface as excess water inhibits from breathing oxygen. If they dry out and don’t surface, they suffocate and die. As fresh air is absorbed through the skin, oxygen is drawn into the worm's circulatory system, and the worm's hearts pump the oxygenated blood to the head.

Silkworms are not basically worms. They are the larval form of the silk moth broadly known as caterpillar. They spend almost a month munching on mulberry leaves. Then it ejects a single protein thread as fast as one foot per minute, then coats it in a sticky liquid to shape its cocoon. Inside the cocoon, the caterpillar pupates, changes into a moth, in about two weeks. Each cocoon may contain a single strand of silk for one mile long.

The nucleus, in the middle of the cell, contains all the cell's chromosomes, which encode the genetic material

Frog’s life depends upon the plants and insects in the swamp where it lives and on the temperature of the air and water. A combination of photoperiod, hours of daylight, and temperature tells the glands of the frog that it is summer. In summer, due to high temperatures and arid conditions, frogs go for a sleep which is known as aestivation in order to avoid high activity and lower metabolic rate.

Chlorophyll always generates green color by nature. As it is stopped it turns into red.

Shell of snail and oyster is made up of Calcium carbonate- a chemical compound with the chemical formula CaCO3. It is a common substance found in rocks in nature as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skeletons and pearls.