Brain death occurs when: all electrical activity of the brain has ceased for a specified period of time. a person remains unconscious for a specified period of time. only the lower regions of the brain stop functioning. the body loses the ability to breathe on its own.

The organelle pictured is found in cells of and is theorized to have once been an independent organism.

How can antibodies "remember" a particular bacterial invader or "antigen" on that invader?

Nephrons, the functional unit of kidneys, are responsible for formation of urine. the sentences describe situations that are the result of problems in the urine formation process. for the nephron shown below, match each situation to the step in the urine formation process where the problem lies.