What is the definition of active transport

What were the main components of earth’s earliest atmosphere? oxygen and ammonia hydrogen and helium oxygen and nitrogen hydrogen and nitrogen

Which of the following happened during the precambrian era? the first prokaryotic cells the first eukaryotic cells development of photosynthesis all of the above

Which of these would most likely be a stimulus that would cause the body to initiate feedback mechanisms a.) normal body temperature in an arctic environment b.) normal boy temperature in a tropical environment c.)light physical activity d.)low blood sugar