lab exam 3

As animals get larger, their volume——————- than their surface area.

High SA:V ratio Can rely more on diffusion for gas exchange Less need for complex circulatory/respiratory systems

Low SA:V ratio Diffusion alone is too slow to meet oxygen and nutrient demands Require: Well-developed circulatory systems to transport materials Specialized respiratory systems (lungs, gills) to increase surface area for gas exchange

Fluid is not always in vessels Found in insects, many invertebrates

Blood stays inside vessels Found in vertebrates (like humans)

pumps fluid

carries materials

tubes that transport blood

top chambers (receive blood)

bottom chambers (pump blood out)

– wall that separates left and right sides

carry oxygen

fight infection

help blood clot

liquid that carries everything

carry blood away from heart

tiny vessels where exchange happens

carry blood back to heart

force of blood against vessel walls

heartbeat you can feel in arteries

brain and spinal cord

all nerves outside CNS (connects body to brain/spinal cord)

a fast, automatic response: Stimulus (touch something hot) Sensory neuron → spinal cord Interneuron processes it Motor neuron → response (pull hand away)

receive signals