They are all compounds. This means that several elements make them up. H2O, or water for example, is a mix of two Hydrogen (H) and one Oxygen (O).
I'd say more effective.
"Insects have a more efficient respiratory system than humans. "
But at the same time insects don't have any lungs they breathe through the help of trachea/tubes/and or holes along their abdomen area.
You need to think about how small, compared to us humans, and insect is. They can take in a lot more oxygen than we can (for their size)
If we were to be able to shrink until we're the same size as an insect, they would be the ones taking in way more oxygen because of the way their system is constructed.
Answer:
I'm almost certain that it's mucus. (been a hot sec since I took a bio or anatomy class)
Explanation:
Here's a quote: "The colon secretes mucus to bind and lubricate the food waste to help it pass through smoothly as it is dehydrated." -the Cleveland Clinic
1. Early earth had no ozone layer, which means it was most likely extremely hot.
2. Young earth had no oxygen and life needs oxygen in order to survive.
3. There where so many natural disasters happening all the time, like volcanic eruptions and constant impact with meteorites and asteroids.
-Extra one (4. Earth originally had no ocean and water. Oceans eventually formed from the water vapor released from the volcanic eruptions, but before that there was nothing.)
Physical change as no new substance is created
