In previous chapters, you learned about osmotic and diffusion gradients that aid in maintaining water and ion balance and in developing resting potentials in cells, among other important biological features. how does the immune system of vertebrates exploit a chemical gradient?

In vertebrates, the immune system discharges chemical signals known as chemokines that produce a chemical gradient, which is utilized by the leukocytes in migrating towards the site of infection.  

Chemokines belong to the class of small cytokines, or signaling proteins discharged by the cells. Their name is obtained from their tendency to stimulate directed chemotaxis in the adjacent responsive cells. They are chemotactic cytokines.  

answer: - few nutrients

high pressure

low temperatures

explanation: 1. few nutrients:   open-ocean zone is located way far from the land, which is the main source of the essential nutrients.2. high pressure: pressure increases by 1 atmosphere for every 10 meters increase in depth.3. ample sunlight: a large fraction of the sunlight is reflected back to the atmosphere from the sea surface. 4. varying salinity: below the thermocline, the water is isolated from the atmosphere so the salinity remains stable over the year.5. low temperatures:   the temperature of open-ocean zone ranges from a low of -2°c to an average of 17°c

both anaerobic and aerobic respiration use glucose (or other carbohydrates), proteins and lipids to produce atp and nadh. cell uses those energy molecules, obtained from food and   breaks them down during the chemical reactions of respiration. in anaerobic respiration, nadh is regenerated to nad+ by enzymes lactate dehydrogenase (lactate is produced, e.g. in muscle cells) or by alcohol dehydrogenase where ethanol is produced (alcohol fermentation), while in aerobic respiration, electrons from nadh are deposited in the mitochondria to regenerate nad+ (electron transport chain. anaerobic respiration produces 2 atp per molecule of glucose compared to aerobic respiration where about 38 atp molecules are produced.