Can someone explain primary succession and secondary succession to me?

Areal dna molecule consists of thousands of these pairs of nucleotides. what is the pairing arrangement of the nitrogen bases

High blood pressure occurs when there is too much blood flowing through the blood vessels at one time. by changing the amount of water in the blood, blood pressure can change. the excretory system can to lower blood pressure.which would most likely occur in the kidney? a)more water would be transferred from the nephron.b)less water would be absorbed into the nephron.c)the amount of water in the bladder would decrease.d)the amount of water in the blood would increase.

Energy for use in cells is stored in form of 1.chemical bond energy 2.physical energy 3.heat energy 4.mechanical energy.