Which of these is a body fossil 1. dinosaurs nest 2. shrimp burrow 3. leaf imprint 4. claw print

The negative change found inside the plasma membrane is created by potassium ions sodium ions hydrogen ions chlorine ions

Which of the following statements is true about the relationship between genetic variation and natural selection? a. genetic variation must be present in a population before natural selection can act on it. b. genetic variation arises in a population as a result of natural selection. c. natural selection can act on a population whether there is genetic variation within the population or not. d. after natural selection acts on a population, the amount of genetic variation in the population always increases.

If a cell is placed into a hypertonic environment,what will happen to it ? a)it will shrink or shrivel b)nothing c)it will burst d) it will expand or enlarge