I am the outermost layer of an animal cell , but not a plant cell. What am I?

What was dr. willem johan kolff’s first step in using the scientific process to invent the hemodialysis machine? he built the machine and tried it with various patients, collecting data about its effectiveness. when a patient’s kidneys failed, he wondered if it would be possible to perform kidney functions with an external machine. he researched and collected data about numerous patients who exhibited symptoms of kidney failure. he drew conclusions from studies of various symptoms of kidney failure, and drew a design for the ideal external blood-processing machine.

Body systems are not completely independent they integrate and work together describe one example of the integration between body systems

Give an example of a trait that is controlled by more than one gene.