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Unformatted text preview: Biology 118 1. ORGANIZATION AND HOMEOSTASIS THE POWER OF TEAMWORK : consider how form affects function at every organizational level. (see pg. 6-7) Chemical atoms join to form molecules. Cellular molecules join to form organelles and other parts of cells. Tissue cells join to perform specific functions. Organ tissues join to work together. Organ system a number of organs work together. Organism many organ systems work together to keep an individual alive. INSIDE, OUTSIDE, HOMEOSTASIS : (see pg. 7, 14-16) Any organism has two environments to cope with: the external, and the internal. For the organism to survive, there must be a constant exchange between these two environments. The external environment is prone to wide fluctuations, or changes, while the organism wants to maintain its internal environment as constant as possible a steady state called homeostasis. This is why changes in the external environment are often challenges or stimuli for organisms. Organisms have homeostatic mechanisms to cope with these challenges. Negative feedback is employed to minimize flux in the internal environment: A stimulus (fluctuation) starts a chain of communication between a sensor, a control center and an effector. The effector will try to counteract, or correct for, the initial stimulus. There are also positive feedback loops. This is where the initial stimulus triggers a response that reinforces or intensifies the stimulus. Biology 118 2. ATOMS, BONDS, AND WATER WHAT ARE YOU MADE OF? (see pg. 29-30) Lifes made up of 25 naturally occurring elements. The top 13 are shown in Table 2-1, and the rest are considered trace elements (copper, for example). The prevalence of the top 4 elements (O, C, H, N about 96% of human body weight) is due in part to their availablity and abundance in the Earths crust. The top 4 can also form strong covalent bonds -- meaning reasonable stability of resulting molecules. ATOMS ARE FUN! (see pg 30-31) Basic parts of atom: protons, neutrons, electrons. Protons and neutrons cluster in a nucleus, while electrons orbit in a cloud. Atoms are neutral when the number of protons (positively charged) match the number of electrons (negatively charged). Electrons orbit the nucleus in ordered shells, which can hold only so many electrons; the first shell holds 2, the second holds 8. Look at neon: 10 protons in the nucleus, 10 orbiting electrons (2 in first shell, 8 in second shell). But what happens if an outer shell isnt completely filled? Look at carbon: 6 protons, 6 electrons, so that means But what happens if an outer shell isnt completely filled?...
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This note was uploaded on 04/07/2008 for the course BIO 118 taught by Professor Bilgen during the Spring '08 term at University of Washington.
- Spring '08