Answer: A specific chemical binding to nociceptors
Explanation:
The natural selection is the survival of the fittest, which means that o<span>nly the best adapted individuals survive and reproduce, contributing the most to the next generation</span>
According to natural selection, birds such as cardinals , eagles, and ducks have differently shaped feet due to <span>adaptation to different environments and feeding habits.
</span>
Answer:

Explanation:
In an atom, there is a dense center known as the nucleus. It is made up of two subatomic particles: <u>protons</u> and <u>neutrons</u>. The protons have a positive charge and the neutrons have no charge, so overall the nucleus is positively charged.
The third subatomic particles, negatively charged electrons, are located around the nucleus in a cloud.
The particles in the nucleus are
.
The movement in phloem is bidirectional, whereas, in xylem cells, it is unidirectional (upward).