Biology Notes Chapter 2 Outline

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The Chemical Context of Life - biology is a multidisciplinary science - living organisms are subject basic laws of physics and chemistry - one example is the use of formic acid by ants to maintain "devil's gardens," stands of Duroia trees - ants keep all other plants and trees and shrubs out of the area so that the Duroia trees can grow there by "sticking" other plants with formic acid bite that makes them shrivel up and die - in return, trees provide shelter for the ants - Fig. 2.1 - Duroia trees in Amazon forest - Fig. 2.2 - D. Gordon and M. Green did experiment: took a tree, planted it inside, sprayed insecticide around the tree so ants wouldn't bother it, the unsprayed tree grew, the sprayed one died - organisms are composed of matter - matter is anything that takes up space and has mass - matter is made up of elements - an element is a substance that cannot be broken down into other substances by ordinary means - a compound is a substance consisting of 2 or more elements in a fixed ratio - a compound has characteristics different from those of its elements - emergent properties - when a mixture has properties that do not belong to its components (i.e. sodium chloride) - Fig. 2.3 - sodium chloride (salt) - about 25 of the 92 natural elements are essential to life - carbon, hydrogen, oxygen, and nitrogen make up 96% of living matter - most of the remaining 4% consists of calcium, phosphorus, potassium, and sulfur - trace elements are those required by an organism in minute quantities - Table 2.1 - necessary elements and trace elements in the human body - Fig. 2.4 - iodine deficiency that has lead to a goitre (inflamed and swollen thyroid gland) - each element consists of unique atoms - an atom is the smallest unit of matter that still retains the properties of an element - atoms are ecomposed of subatomic particles (protons - positive

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