ENS 201 Chapter 3, Spring 2008

Matter, Energy, and Life Chapter 3 Outline: • Basic Definitions of Organic Compounds • Energy  Types  Laws of Thermodynamics  Solar energy  Photosynthesis & Respiration • From Species to Ecosystems  Food Chains, Food Webs & Trophic Level  Ecological Pyramids  Material Cycles (Carbon Cycle) Organic Compounds  Material making up biomolecules  Rings and chains of carbon backbones  Four major categories: - Lipids (e.g., fats oils) - Carbohydrates (e.g., glucose, starch, cellulose) - Proteins (structural and functional roles) - Nucleic Acids (stores of the genetic information) ENERGY • Energy: Ability to do work or to cause heat flow  Kinetic: Energy in moving objects  Potential: Stored energy - Chemical: Stored in food or fossil fuels • Heat: Useless form of energy Kinetic Energy Thermodynamics and Energy Transfers • Thermodynamics: studies how energy is transferred in natural processes • Energy  Must be supplied from an external source to keep biological processes running  Flows in a one-way path through living systems (accomplish work) & eventually into a low temperature sink (e.g., outer space)  Can be stored temporarily in the chemical bonds (chemical energy) Laws of Thermodynamics • First Law  Energy is neither created nor destroyed  Energy can be transferred or transformed but it is always conserved • Second Law  With each successive energy transfer - Less energy is available to perform work - Dissipated from a higher quality form (chemical electrical…) to a lower quality form (heat) High and Low-quality Energy Energy for Life: Warmth and light • Ultimately, most organisms depend on the sun for energy needed to carry out life processes • Solar energy is essential for 2 reasons:  Warmth  optimal temperature range for life  Photosynthesis - Radiant energy transformed into useful, high- quality chemical energy in the bonds of organic molecules Energy For Life: Radiant Energy distribution • Of all solar radiation reaching the earth’s surface, about 10% is Ultraviolet, 45% is Visible, and 45% is Infrared • More than half of the incoming energy is absorbed in the atmosphere by clouds, dust, and gases • Most of energy reaching the earth is absorbed by land or water, or reflected back • Only about 1-2% of the sunlight falling on plants is captured for photosynthesis Energy for Life: Photosynthesis • Occurs in organelles of green plant cells called chloroplasts • Water + Carbon dioxide + solar energy  Glucose (sugar) + Oxygen 6H20+6CO2 + solar energy = C6H12O6+6O2 • Water and carbon dioxide in the presence of sunlight yields glucose (sugar) and oxygen • Glucose serves as primary fuel for all metabolic processes in cells Energy for Life: Cellular Respiration • Photosynthesis captures energy, while cellular respiration releases energy.  Glucose (sugar) + Oxygen  Water + Carbon dioxide + Energy C6H12O6 + 6O2 = 6H2O +6CO2 + energy Energy exchange in ecosystems Copyright © The McGraw-Hill Companies, Inc. 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Sun Photosynthesis Respiration Producers Consumers and decomposers CO2 H2O Carbon dioxide (CO2) Water (H2O) Heat (low-quality energy) High-quality energy for work: Biosynthesis Movement Membrane transport Bioluminescence Oxygen (O2) Oxygen (O2) Sugars (high-quality energy) Nature of Ecology: from species to ecosystems • Ecosystem organization: Organisms  Populations  Communities  Ecosystems  Biosphere From Species to Ecosystems • Species – Organisms of the same kind that are genetically similar enough to breed in nature and produce live, fertile offspring • Population - All members of a species living in a given area at the same time • Community - All of the populations of organisms living and interacting in a particular area • Ecosystem - Biological community (biotic factors) and its physical environment (abiotic factors) Food Chains • Productivity  Amount of biomass (biological material) produced in a given area during a given period of time • Primary Productivity = photosynthesis  Manufacture of biomass by green plants  The basis for almost all other growth in an ecosystem • Secondary Productivity  Manufacture of biomass by organisms eating plants • Food Chain - Linked feeding series in an ecosystem  Most consumers have multiple food sources • Food Web  Interconnected food chains Each time an organism feeds, it becomes a link in a food chain 03_12 Food web Slide number: 1 Copyright © The McGraw-Hill Companies, Inc. 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Harsh environments tend to have shorter food chains Trophic Levels • Trophic Level - An organism’s feeding status in an ecosystem:  Producers (plants)  Consumers - Primary (herbivores) - Secondary (carnivores) - Tertiary (top carnivores)  Terrestrial food chains are relatively short  Aquatic food chains tend to be longer Trophic Levels • Organisms can also be identified by the type of food they consume:  Herbivores (Plants) {Deer, Bison}  Carnivores (Meat) {Wolves, Tigers}  Omnivores (Plants/Meat) {Human, Bear, Pig}  Scavengers (Carcasses) {Hyena, Vultures, Crows}  Detritivores (Debris) {Ants, beetles}  Decomposers (All) {fungi, Bacteria} Ecological Pyramids • Due to Second Law of Thermodynamics, food chains often form a pyramid • Biomass energy loss  Undigested  Used to carry out metabolic reactions necessary for life  Lost as heat 10% Rule (Energy / Biomass) - 100 kg clover  10 kg rabbits  1 kg foxes MATERIAL CYCLES • Elements of matter are recycled in the biosphere • E.g.: Carbon Cycle:  Begins with intake of CO2 during photosynthesis: Carbon atoms are incorporated into glucose and then: - Remain in plant material until death (incorporation) - Eaten by predator - Released by respiration - Secreted (excretion of plants exudates) - Returned to the environment after death via decomposers CO2 in atmosphere plus traces of CH4 and CO 03_17 Carbon cycle Slide number: 2 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Carbon Cycle CO2 in atmosphere plus traces of CH4 and CO Photosynthesis (terrestrial food chains) Photosynthesis (aquatic food chains) CO2 in water 03_17 Carbon cycle Slide number: 3 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Carbon Cycle CO2 in atmosphere plus traces of CH4 and CO Photosynthesis (terrestrial food chains) Respiration and decomposition Photosynthesis (aquatic food chains) CO2 in water 03_17 Carbon cycle Slide number: 4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Carbon Cycle CO2 in atmosphere plus traces of CH4 and CO Burning of forests, fuelwood, and organic debris Photosynthesis (terrestrial food chains) Respiration and decomposition Photosynthesis (aquatic food chains) CO2 in water 03_17 Carbon cycle Slide number: 5 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Carbon Cycle Combustion of fossil fuels for vehicles, electricity, and heat CO2 in atmosphere plus traces of CH4 and CO Burning of forests, fuelwood, and organic debris Photosynthesis (terrestrial food chains) Respiration and decomposition Photosynthesis (aquatic food chains) CO2 in water 03_17 Carbon cycle Slide number: 6 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Carbon Cycle Combustion of fossil fuels for vehicles, electricity, and heat CO2 in atmosphere plus traces of CH4 and CO Burning of forests, fuelwood, and organic debris Photosynthesis (terrestrial food chains) Respiration and decomposition Photosynthesis (aquatic food chains) CO2 in water Organic sediments Time Time Calcareous sediments Time Peat Coal Oil and gas Limestone and dolomite Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Carbon Cycle