BIOL1001 Lecture Notes - Lecture 3: Homeostasis, Smallest Organisms
Document Summary
All living organisms share several key characteristics or functions: order, sensitivity or response to the environment, reproduction, growth and development, regulation, homeostasis, and energy processing. When viewed together, these eight characteristics serve to define life. Organisms are highly organized, coordinated structures that consist of one or more cells. Even very simple, single-celled organisms are remarkably complex: inside each cell, atoms make up molecules; these in turn make up cell organelles and other cellular inclusions. In multicellular organisms , similar cells form tissues. A toad represents a highly organized structure consisting of cells, tissues, organs, and organ systems. Plants can grow toward a source of light, climb on fences and walls, or respond to touch. Even tiny bacteria can move toward or away from chemicals or light. Movement toward a stimulus is considered a positive response, while movement away from a stimulus is considered a negative response. The leaves of this sensitive plant will instantly droop and fold when touched.
