Answer:
Mechanical digestion begins in the mouth as the food is chewed. Chemical digestion involves breaking down the food into simpler nutrients that can be used by the cells.
Explanation:
Chemical digestion begins in the mouth when food mixes with saliva. Saliva contains an enzyme (amylase) that begins the breakdown of carbohydrates.
Answer: The literal reason would be because our ancestors did. The ancestors of all modern mammals had five digits on each limb up to 360 million years ago.
Explanation:
The three types of chemical bonds are Ionic, Covalent, and Metallic
False, the ozone layer protects Earth from UV radiation.
<u>ANSWER:</u>
Cosmic background radiation is leftover thermal energy from the Big Bang best describes the origin and expansion of the universe.
<u>EXPLANATION:</u>
- The "Big Bang Theory" is used to describe how the universe has begun.
- The theory basically states that the "universe" began as a "single point" and then "expanded and stretched" and is expanding even today.
- When the universe began, it was "hot tiny particles" mixed with heat and light and as it "expanded" and took up "more space", it cooled down and formed atoms.
- The "best evidence of the big bang" is the radiation of cosmic background that was leftover when the first big bang explosion took place and began the universe.
