The energy coming from the sun to the earth's surface is called solar energy. most of it is in the form of electromagnetic radiation from the visible wavelengths. another wavelength that reaches earth's surface is responsible for sunburn, skin cancer, and is the reason why we wear cool sunglasses. what is this type of electromagnetic radiation?

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.

the menstrual cycle – higher tier. negative feedback mechanisms affect the production of hormones in the menstrual cycle. oestrogen also stimulates the release of lh (luteinising hormone) from the pituitary gland, which in turn controls the production of progesterone.

protistas excret ethanol used in the manufacture of vinegar