a drug that speeds up the action of the nervous system.
the volume of air that is inhaled and exhaled during normal breathing.
mass extinction event of 250 million years ago, in which about 90% of all species on Earth died...
a blood vessel that returns oxygenated blood from the lungs to the left atrium of the heart.
the immunity an organism develops during its lifetime.
a watery fluid in which organelles are suspended.