Natural variation provided the phenotypes that natural selection then acted on, over time causing evolution
A group of people are building a house. They have a large package of building materials that needs to be moved. A block and tackle, a type of pulley, is used to pull the material up so it can be set in the back of a truck.
Light is a form of EM radiation.
EM radiation has no mass (it's just energy packets called photons).
EM radiation can travel through a vacuum. (The speed of light in a vacuum is called c and is around 300,000 m/s).
Hope this helps!
Answer:
Muscles contract rapidly to produce heat on a cold day.
Explanation:
