Why do you call cell membrane as selectively permeable membrane?

Which statement describes compounds a. compounds are made of one type of atom. b. compounds cannot be represented by models. c. compounds are represented by chemical formulas. d. compounds cannot be broken down into simpler forms.

Explain what a zygote is. use the terms egg cell, sperm cell, and fertilization in your explanation.

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.