Humans have eyes composed of three layers?
The three layers are the retina, sclera, and the choroid.
How is vision in humans different from vision in animals whose eyes are on opposite sides of the head?
How is sunlight composed of energy that is visble to humans and energy that is not visble to humans?
Electromagnetic waves have a wide range of frequencies; some of those are visible for human eyes (visible light), some are not (radio waves, infrared, ultraviolet, x-rays, ...). Our eyes are simply designed to detect only part of this range. And it so happens that the energy emitted by the Sun has a wider range - including infrared and ultraviolet light.
Botanically the coconut (meaning the fruit) is a drupe, not a true nut. Like other fruits it has three layers: exocarp, mesocarp, and endocarp. The exocarp and mesocarp together make up the husk, and the mesocarp is composed of fibers called coir. Coconuts sold in the shops of non-tropical countries often have had the husk removed. The endocarp or shell is the hardest part of the coconut. The shell has three germination pores (stoma) or…
The bulb of an onion is that round or roundish vegetable that is composed of many concentric layers, that causes a burning sensation in your eyes when you chop it up, and that is usually what people cook when they use onion in their recipes - although the green leaves of the onion, also called scallions, can be eaten too.