Because it is direct contact of the molecules in the air and the land that are touching.
Answer:
b. a person has an emotional need for a drug
<span>A hydrophillic amino acid will have it's functional group positioned where the water is. Generally this will be outside of the polypeptide, and the amino acid will interact with polar entities, this will include other amino acids that match it's polarity.</span>
A horseshoe crab has been around for almost 500 million years. They are classified as arthropods and not actual crabs. However, There are many reasons that have helped them survive this long including, they can eat almost any organic matter. There blood is different from normal, in fact it’s blue. This blood helps them heal any wounds right away. They can also live in areas with very low levels of oxygen, meaning habitat is not a big issue for them. Evolution has also helped them grow and adapt seeing as they’ve survived this long.
Hope that helps:)
<span>Certainly. Every organism has a variety of different characteristics. One person writing a key might choose to use different characteristics than another person would use.
For example: Here's a key for separating fish, snake, frog and mouse
1.
A. Has scales on its skin ... 2
B. Has no scales on its skin ... 3
2.
A. Breathes with gills - fish
B. Breathes with lungs - snake
3.
A. Has hair or fur - mouse
B. Has no hair or fur - frog
Here's a different key for the same four animals:
1.
A. Has four legs ... 2
B. Does not have 4 legs ... 3
2.
A. is warm-blooded - mouse
B. is cold-blooded - frog
3.
A. has fins - fish
B. has no fins - snake</span>
