Why am I always answering people questions when they should answer mine
Single-celled organisms exchange gases directly across their cell membrane. However, the slow diffusion rate of oxygen relative to carbon dioxide limits the size of single-celled organisms. Simple animals that lack specialized exchange surfaces have flattened, tubular, or thin shaped body plans, which are the most efficient for gas exchange. However, these simple animals are rather small in size.
Low amounts of adrenaline, secreted within 30 seconds of learning, have a role in the consolidation of memory. Emotions that produce adrenaline therefore have an effect on the strength of a newly forming memory. The memories that are formed under circumstances of emotional arousal are often vital to survival.
