simplified Chap 2

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Slide 1:

Homeostasis = tendency to remain more or less stable and unchanging over time. Negative feedback = maintain stability in a system by counteracting change Positive feedback = change becomes amplified 2- 1

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Disturbances = events that destabilize the system Can cause dramatic and persistent change. Resilience = ability to return to their previous condition after disturbance. State shift = conditions do not return to “normal .” 2- 2

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2.2 Elements of Life Matter anything that takes up space and has mass . makes up everything in the universe 3 states of Matter: solid, liquid, and gas Principle of conservation of matter: Under ordinary circumstances, matter is neither created nor destroyed, but rather is recycled over and over again. Your body probably contains atoms that once made up the body of a dinosaur. 2- 3

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Matter is made of Elements Pure substances that cannot be broken down into simpler forms by ordinary chemical reactions. Found on Periodic Table Examples: P (phosphorus) or N (nitrogen). Each has distinct chemical characteristics. 115 known 4 elements make up 96% percent of the mass of most living organisms: oxygen, carbon, hydrogen, and nitrogen (CHON) Made up of ATOMS 2- 4

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09/22/10 Atoms Smallest part of an element Has characteristics of the element Each atom is made of Protons (+) Neutrons (0 charge) Electrons (-) Different elements vary in the number of these particles Neutral = NO charge

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Ions Charged particle (no longer an atom) Formed by atoms gaining or losing electrons Anions: Negatively charged ions one or more extra electrons Cations : Positively charged ions One or more less electrons Changes the properties of the substance!!!!! Examples: Sodium (Na) and Chlorine (Cl) are highly toxic in elemental form When they become ions Na+ or Cl-; they are components necessary for life!!!! NaCl is table salt! 2- 6

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Bonding Atoms of elements joining Molecule: 2 or more atoms bonded Compounds: 2 or more atoms of different elements bonded. 2- 7 Common Molecules

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pH Based on hydrogen ions in a aqueous (water based) solution Water has 0.0000001g of H+/Liter Water has a pH of 7 and is considered neutral Acids More hydrogen ions pH is < 7 Bases Less hydrogen ions pH is >7 2- 8

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Organic Compounds Contain Carbon Compose living organisms 4 major categories lipids carbohydrates proteins nucleic acids 2- 9

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4 Categories of Organic Molecules Lipids fats and oils store energy for cells, and they provide the core of cell membranes and other structures. Carbohydrates sugars and starches store energy and provide structure to cells. Example: Glucose . 2- 10

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Proteins composed of chains of amino acids folded into complex 3-D shapes. provide structure to cell s and are used for countless cell functions , including enzymes. Nucleotides complex molecules ATP : energy within cells DNA and RNA : store and express genetic information. 2- 11

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2.3 Energy ability to do work many different forms light , electricity, and chemical energy Heat = low quality energy formed in energy conversion 1 st law of thermodynamics : energy is conserved; neither created nor destroyed 2 nd law of thermodynamics : with each energy transfer, l ess energy is available to do work. Entropy: disorder tends to increase in all natural systems. 2- 12

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Kinetic energy energy of movement Examples rock rolling down a hill water flowing over a dam electrons speeding around the nucleus of an atom. Potential energy stored energy Examples water stored behind a dam Chemical energy : stored in the food that you eat and the gasoline that you put into your car 2- 13

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2.4 Energy for Life SOLAR ENERGY Nearly all organisms on the earth depend on solar radiation for life-sustaining energy Some organisms use chemical energy such as sulfur bacteria in the thermal vents of the ocean Primary producers Green plants , algae, some bacteria Photosynthesis: converts solar energy into chemical energy Occurs in chloroplasts 2- 14

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PHOTOSYNTHESIS In chloroplasts, Solar energy is converted into the Carbohydrate, Glucose C 6 H 12 O 6 , using Carbon dioxide, CO 2 , and Water, H 2 O 2- 15 6CO 2 + 6H 2 O + sunlight = C 6 H 12 O 6 + 120 2

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RESPIRATION Animals eat plants—or other animals that have eaten plants— Break down the organic molecules (C 6 H 12 O 6 ) in their food through cellular respiration to obtain energy. 2- 16

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2.5: Basics of Ecology Population = same species; same place; same time Community = All the populations; same place; same time Ecosystem = community + physical environment Biotic : living part Abiotic : non-living part: soil, water, air, etc. 2- 17

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In ecosystem: Flow of energy = what eats what Food Chain = shows what eats what Food Web: interconnected food chains Trophic Level = an organism’s feeding status in an ecosystem. 2- 18

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Producers Photosynthetic autotroph Primary Consumers = heterotroph Herbivores = Plant eaters Omnivores = plant or flesh eaters Secondary Consumer Carnivore = flesh eaters Decomposers —feed on all levels Scavengers: clean up dead carcasses of larger animals. Detritivores : consume litter, debris, and dung. Fungi and bacteria: complete the final breakdown and recycling of organic materials. 2- 19

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Ecological Pyramids Describe Trophic Levels often form a pyramid with a broad base of primary producers and only a few individuals in the highest trophic levels. pyramid idea helps us describe generally how energy and matter move through ecosystems. Only about 10% of energy is retained from one level to another. 2- 21

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2.6 Biogeochemical Cycles Elements and compounds are cycled endlessly through abiotic and biotic components of the environment. Human activity can (and has) altered some of these cycles! 2- 22

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The Carbon Cycle 2- 23

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The Carbon Cycle Photosynthetic organisms take up carbon dioxide and convert it to sugar. This is a process called carbon-fixation . Sugar molecules are consumed by animals and absorbed into their bloodstream, where it is made available to the cells for cellular respiration or the production of more complex biomolecules. If it is used in respiration, it may be exhaled as CO2 in an hour or less, and a plant could take up that exhaled CO2 the same afternoon. The carbon atoms from the sugar molecule could remain a part of the body until it decays after d eath. carbon in the wood of a thousand-year-old tree will be released only when fungi and bacteria digest the wood and release carbon dioxide as a by-product of their respiration. Recycling may take a very long time. Fossil fuels like coal and oil are the remains of organisms that lived millions of years ago. Their carbon atoms are not released until the coal and oil are burned. 2- 24

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The Hydrologic Cycle 2- 25

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The Nitrogen Cycle Plants acquire nitrogen from nitrogen-fixing bacteria that live in and around their roots. These bacteria combine gaseous N2 with hydrogen to make ammonia (NH3) and ammonium (NH4+). Other bacteria then combine ammonia with oxygen to form nitrites (NO2–). A third group of bacteria converts nitrites to nitrates (NO3–), which green plants can absorb and use. Plant cells absorb nitrates, and use them to build amino acids and eventually proteins. Plant proteins are consumed by animals and incorporated into their own protein molecules. Nitrogen reenters the environment through the death of organisms. Fungi and bacteria decompose dead organisms, releasing ammonia and ammonium ions for nitrate formation. Denitrifying bacteria break down nitrates (NO3-) into N2 and nitrous oxide (N2O), gases that return to the atmosphere. 2- 26

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The Nitrogen Cycle 2- 27

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The Phosphorus Cycle 2- 28

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The Sulfur Cycle 2- 29

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