Salutations!
<span>Scientists have arranged all of the different types of material or elements we can find into groups known as what?
</span><span>Scientists have arranged all of the different types of material or elements we can find into groups known as periods. Period is the horizontal row in the periodic table. All of the known elements can be found in the periodic table.
Hope I helped :)</span>
The mechanism is Natural Selection
Answer: The blood vessels farthest from the heart must have valves.<span><span>
Blood
flow through the body system by the action of the pumping heart and it is
usually pushed under high velocity and pressure away from the heart, toward the
main artery and the aorta. The flow of
blood through the capillary beds is usually regulated by the body needs which
is directed by the nerves and hormone signals. However, </span>for
blood to always flow unidirectionally through a closed circulatory system, the blood vessels farthest from the heart must
have valves.</span>
Because two inedible insects share common colors they may be warning a predator and this type of defense is called Mullerian mimicry because two or more species are presenting themselves as harmful.