MOLLUSCS: THE SURVIVAL GAME (shapeoflife.org)

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Their basic body plan includes a foot for mobility; a mantle that secretes a shell and a radula for eating. Molluscs today show many variations on this original body plan. An abalone escapes a sea star predator using its foot; and a moon snail hunts a cockle using its foot as a weapon. The radula has even evolved in an astonishing variety of ways to serve as a tool for feeding. The ancient nautilus was the first mollusc to leave the sea floor. Their ancestors evolved a way to swim using jet propulsion and evolved a way to maintain buoyancy. The evolution of speedy fishes drove the next step in the survival game: speed and loss of the shell, as seen in squid. Octopuses returned to live on the bottom and evolved intelligence and an ability to instantly camouflage itself in order to survive.

openstax | Psychology | 3.2 Cells of the Nervous System Psychologists striving to understand the human mind may study the nervous system. Learning how the cells and organs (like the brain) function, help us understand the biological basis behind human psychology. The nervous system is composed of two basic cell types: glial cells (also known as glia) and neurons. Glial cells, which outnumber neurons ten to one, are traditionally thought to play a supportive role to neurons, both physically and metabolically. Glial cells provide scaffolding on which the nervous system is built, help neurons line up closely with each other to allow neuronal communication, provide insulation to neurons, transport nutrients and waste products, and mediate immune responses. Neurons, on the other hand, serve as interconnected information processors that are essential for all of the tasks of the nervous system. This section briefly describes the structure and function of neurons.