- Over time, more sediment piles on top - The resulting heat and pressure transforms the organic layer into a dark and waxy substance known as kerogen - Left alone, the kerogen molecules eventually crack - The molecules break up into shorter and lighter molecules composed almost solely of carbon and hydrogen atoms - It will turn into either petroleum or natural gas - What might be the first step of the process?
Ans: Dead organic material accumulates on the bottom of oceans, riverbeds or swamps, mixing with mud and sand

- Animals gain weight - The season changes to one with bad (cold, snowy) weather - Animals find a place to hibernate - Animals enter a type of 'sleep' (hibernation) - Body processes slow down - The animal's heart rate and breathing rate slow - The animal loses weight more slowly than usual - The animal is able to survive not eating or drinking without hurting itself - What might be the first step of the process?
Ans: Animals eat a lot during good (warm, clear) weather

- Bacteria enters through the wound - The bacteria reproduces and spreads - Causes symptoms - The bacteria is either fought off or becomes a disease. What might be the first step of the process?
Ans: Skin is cut or damaged

- Passes through the lungs - And into the bronchial tissue - The carbon dioxide is removed - The lungs bring the oxygen to the rest of the body. What might be the first step of the process?
Ans: Air is brought in through the mouth