Bottom-up model and bottom-down model??

Question

what are they? i tried looking them up and couldn't find anything. i need to compare and contrast them.

Answer 1

It sounds like bottom up meaning hands, face, torso, back models. Then bottom down would be foot, legs, butt models.  

Answer 2

Bottom-up and top-down refer to different mechanisms of population regulation in ecosystems.

Top-down regulation is where the ecosystem is regulated by predation from the top of the food chain (i.e. There is enough food available to support a large population of rabbits, but carnivores keep rabbit population low).

Bottom-up regulation is where primary producers (plants) regulate the trophic levels above them by the amount of food they produce (i.e. plants only producing enough food to support a small population of rabbits.  The small population of rabbits only supports a tiny population of carnivores).

Answer 3

I think you're thinking of top-down and bottom up models.

This is taken right from a webpage, but I think it explains it okay.

"These terms are also employed in neuroscience and psychology. The study of visual attention provides an example. If your attention is drawn to a flower in a field, it may be simply that the flower is more visually salient than the surrounding field. The information that caused you to attend to the flower came to you in a bottom-up fashion — your attention was not contingent upon knowledge of the flower; the outside stimulus was sufficient on its own.

Contrast this situation with one in which you are looking for a flower. You have a representation of what you are looking for. When you see the object you are looking for, it is salient. This is an example of the use of top-down information.

In cognitive terms, two thinking approaches are distinguished. "Top down" (or "big chunk") is stereotypically the visionary, or the person who sees the larger picture and overview. Such people focus on the big picture and from that derive the details to support it. "Bottom up" (or "small chunk") cognition is akin to focusing on the detail primarily, rather than the landscape. The expression "seeing the wood for the trees" references the two styles of cognition."