<span>Oxygen travels to insect tissues through tiny openings in the body walls called spiracles, and then through tiny blind-ended, air-filled tubes called tracheae. Therefore, insects obtain oxygen through the spracles, which are small abdominal holes that lead into traecheal tubes called tracheae that branch into smaller tubes called tracheoles. From there, oxygen diffuses into body cells.</span>
Scientific investigations that involve some kind of testing will make use of observations. generally speaking making observations is the first step of the scientific method.
Outer most layer of the Earth is the crust
