The days are getting shorter and colder. these trees are responding to the change. their leaves change color and will soon fall off. losing leaves during the winter is the response to the external environment called
a) dormancy.
b) hibernation.
c) hydrotropism.
d) phototropism.

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation:

the dna molecules have a negative charge because of the phosphate groups in their sugar-phosphate backbone, so they start moving through the matrix of the gel towards the positive pole. power is turned on and dna fragments migrate through gel (towards the positive electrode).

explanation:

acceleration = 18/3 = 6 m/s per second.

hope i

-lavira: )