Most of the concentration of which gas results from the activity of producer organisms?

Spring tides, when the high tides are at their highest and low tides at their lowest. what is it about these positions that causes these high and low tides?

About how many years does it take for one cycle of surface water to become deep water and then surface water again in the oceans? 101001,000

Can happen anywhere along the spine if the neural tube does not close all the way. the backbone that protects the spinal cord does not form and close as it should. this often results in damage to the spinal cord and nerves. a) cleft palate b) spina bifida c) encephalocele d) down's syndrome