1 Science, Matter, Energy, and Systems2 Science, Matter, Energy, and Systems

2 2-1 What Do Scientists Do? Science is a search for order in natureThe scientific method Identify a problem Find out what is known about the problem Ask a question to investigate Collect data to answer the question Propose a scientific hypothesis

3 Science Is a Search for Order in Nature (cont’d.)The scientific method (cont’d.) Make testable projections Test the projections with further experiments, models, or observations Accept or reject the hypothesis Scientific theory: well-tested and widely accepted hypothesis Scientific law (law of nature)

4 The Results of Science Can Be Tentative, Reliable, or UnreliableTentative science (frontier science) Reliable science Scientific consensus Unreliable science

5 Science Has Some LimitationsScientists cannot prove or disprove anything absolutely Scientists are not totally bias free Many natural world systems involve a huge number of variables with complex interactions Statistical methods are necessary when direct measures are not possible

6 Science Focus: Statistics and ProbabilityCollect, organize, and interpret numerical data Probability The chance that something will happen or be valid Need large enough sample size

7 2-2 What Is Matter and What Happens When It Undergoes Change?Matter consists of elements and compounds Matter: has mass and takes up space Elements: fundamental type of matter Cannot be broken down chemically into other substances Compounds: two or more different elements bonded together in fixed proportions

8 Matter Consists of Elements and Compounds (cont’d.)Has mass and takes up space Elements Unique properties Cannot be broken down chemically into other substances Compounds Two or more different elements bonded together in fixed proportions

9 Atoms, Molecules, and Ions Are the Building Blocks of MatterAtomic theory: all elements are made of atoms Subatomic particles Neutrons: no electrical charge Protons: positive electrical charge Electrons: negative electrical charge Atom Nucleus and an electron probability cloud

10 Atoms, Molecules, and Ions Are the Building Blocks of Matter (cont’d.)Atomic number Number of protons in the atom’s nucleus Mass number Total number of neutrons and protons in the atom’s nucleus Isotopes Forms of an element having the same atomic number but different mass numbers

11 Atoms, Molecules, and Ions Are the Building Blocks of Matter (cont’d.)Two or more atoms of the same or different elements held together by chemical bonds Ions An atom or a group of atoms with one or more net positive or negative electrical charges pH Measure of acidity based on comparative amounts of H+ and OH-

12 Organic Compounds Are the Chemicals of LifeHydrocarbons Chlorinated hydrocarbons Simple carbohydrates (simple sugars) Macromolecules: complex organic molecules Major types of organic polymers: complex carbohydrates, proteins, and nucleic acids Lipids Inorganic compounds

13 Matter Comes to Life through Genes, Chromosomes, and CellsGenes: certain sequences of nucleotides Traits Chromosome: consists of thousands of genes Cells: fundamental units of life

14 A human body contains trillions of cells, each with an identical set of genes. Each human cell (except for red blood cells) contains a nucleus. Each cell nucleus has an identical set of chromosomes, which are found in pairs. A specific pair of chromosomes contains one chromosome from each parent. Each chromosome contains a long DNA molecule in the form of a coiled double helix. Figure 2-4 The relationships among cells, nuclei, chromosomes, DNA, and genes. Genes are segments of DNA on chromosomes that contain instructions to make proteins—the building blocks of life. Stepped Art Fig. 2-4

15 Some Forms of Matter Are More Useful than OthersMatter quality High-quality matter Highly concentrated Near earth’s surface High potential as a resource Low-quality matter Not highly concentrated Deep underground or widely dispersed Low potential as a resource

16 Matter Can Undergo Change but Cannot Be Created or DestroyedPhysical change No change in chemical composition Chemical change (chemical reaction) Change in chemical composition Reactants and products Law of conservation of matter

17 2-3 What is Energy and What Happens When It Undergoes Change?Energy comes in many forms and some are more useful than others Kinetic energy Energy associated with motion Heat Electromagnetic radiation Potential energy: stored energy Can be changed into kinetic energy

18 Gamma rays UV radiation Infrared radiation TV, Radio wavesVisible light Shorter wavelengths and higher energy Gamma rays UV radiation Infrared radiation Longer wavelengths and lower energy TV, Radio waves X rays Microwaves Wavelengths (not to scale) Nanometers Micrometers Centimeters Meters Figure 2-6 The electromagnetic spectrum consists of a range of electromagnetic waves, which differ in wavelength (the distance between successive peaks or troughs) and energy content. Fig. 2-6

19 Energy Comes in Many Forms (cont’d.)Solar energy principle of sustainability Energy quality High-quality energy Concentrated Great capacity to do useful work Low-quality energy Dispersed Little capacity to do useful work

20 Energy Changes Are Governed by Two Scientific LawsFirst law of thermodynamics (law of conservation of energy) Energy is neither created nor destroyed in physical and chemical changes Second law of thermodynamics When energy is changed from one form to another, it always goes from a more useful to a less useful form

21 2-4 What Keeps Us and Other Organisms Alive?Ecology is the study of connections in nature Organism: any form of life Species: set organisms Resemble one another in appearance, behavior, chemistry, and genetic makeup

22 Science Focus: Have You Thanked the Insects Today?Insects’ vital roles in helping to sustain life on earth Pollinating Eating other insects Helping control pests Loosening and renewing the soil

23 Life Is Organized Within Populations, Communities, and EcosystemsGenetic diversity Habitat Biological community (community) Ecosystem Biosphere

24 Biosphere Ecosystem Community Population Organism Cell Molecule AtomParts of the earth's air, water, and soil where life is found Ecosystem A community of different species interacting with one another and with their nonliving environment of matter and energy Community Populations of different species living in a particular place, and potentially interacting with each other Population A group of individuals of the same species living in a particular place Organism An individual living being Cell The fundamental structural and functional unit of life Figure 2-8 Some levels of organization of matter in nature are shown here. Ecology focuses on the top five of these levels. Molecule Chemical combination of two or more atoms of the same or different elements Water Smallest unit of a chemical element that exhibits its chemical properties Atom Stepped Art Hydrogen Oxygen Fig. 2-8

25 Earth’s Life-Support System Has Four Major ComponentsAtmosphere Troposphere: inner layer Stratosphere: contains ozone layer Hydrosphere Geosphere Biosphere Biomes Aquatic life zones

26 Atmosphere Biosphere (living organisms) Soil Rock Crust MantleGeosphere (crust, mantle, core) Mantle Figure 2-9 Natural capital: General structure of the earth, showing that it consists of a land sphere, an air sphere, a water sphere, and a life sphere. Core Atmosphere (air) Hydrosphere (water) Fig. 2-9

27 Three Factors Sustain the Earth’s LifeOne-way flow of high-quality energy Two laws of thermodynamics Cycling of nutrients through parts of the biosphere Fixed supply Gravity holds earths atmosphere

28 Sun, Earth, Life, and ClimateSun’s energy Reaches the earth as electromagnetic waves UV radiation, visible light, and heat Absorbed or reflected back into space by the earth’s atmosphere and surface Natural greenhouse effect

29 2-5 What Are the Major Components of an Ecosystem?Ecosystems have living and nonliving components Biotic: living components Abiotic: nonliving components Range of tolerance Optimum level or range Limiting factor principle Impact of too much/little of any abiotic factor

30 Secondary consumer (fox)Oxygen (O2) Precipitation Carbon dioxide (CO2) Producer Secondary consumer (fox) Primary consumer (rabbit) Figure 2-11 Key living and nonliving components of an ecosystem in a field. Producers Water Decomposers Soluble mineral nutrients Fig. 2-11

31 Producers and Consumers Are the Living Components of EcosystemsProducers (autotrophs) Photosynthesis: CO2 + H2O + solar energy → glucose + oxygen Consumers (heterotrophs) Primary consumers (herbivores) Secondary consumers Tertiary (higher) consumers Omnivores

32 Producers and Consumers Are the Living Components of Ecosystems (cont’d.)Decomposers Consumers that release nutrients Bacteria and fungi Detritus feeders (detritivores) Feed on dead bodies of other organisms Earthworms, some insects, and vultures Aerobic respiration glucose + oxygen → CO2 + H2O + energy

33 Termite and carpenter ant workDetritus feeders Decomposers Carpenter ant galleries Termite and carpenter ant work Bark beetle engraving Long-horned beetle holes Dry rot fungus Wood reduced to powder Figure 2-13 Various detritivores and decomposers (mostly fungi and bacteria) can “feed on” or digest parts of a log and eventually convert its complex organic chemicals into simpler inorganic nutrients that can be taken up by producers. Mushroom Time progression Powder broken down by decomposers into plant nutrients in soil Fig. 2-13

34 Chemical nutrients (carbon dioxide, oxygen, nitrogen, minerals) HeatSolar energy Chemical nutrients (carbon dioxide, oxygen, nitrogen, minerals) Heat Heat Heat Decomposers (bacteria, fungi) Producers (plants) Figure 2-15 Natural capital: The main structural components of an ecosystem (energy, chemicals, and organisms). Nutrient cycling and the flow of energy—first from the sun, then through organisms, and finally into the environment as low-quality heat—link these components. Consumers (plant eaters, meat eaters) Heat Heat Fig. 2-14

35 Science Focus: Many of the World’s Most Important Species Are Invisible to UsMicrobes (microorganisms) Bacteria Protozoa Fungi Floating phytoplankton

36 Natural Systems Have Tipping PointsThreshold level (ecological tipping point) Tipping points currently being faced Collapse of certain populations of fish Overfishing Premature extinction of thousands of species Overhunting and habitat destruction Long-term climate disruption Gas emissions

37 2-6 What Happens to Energy in an Ecosystem?Energy flows through ecosystems in food chains and food webs Food chain Movement of energy and nutrients from one trophic level to the next Photosynthesis → feeding → decomposition Food web Network of interconnected food chains

38 Primary consumers (herbivores) Secondary consumers (carnivores) First Trophic Level Second Trophic Level Third Trophic Level Fourth Trophic Level Producers (plants) Primary consumers (herbivores) Secondary consumers (carnivores) Tertiary consumers (top carnivores) Heat Heat Heat Heat Solar energy Heat Figure 2-16 A food chain. Arrows show how the chemical energy in nutrients flows through various trophic levels in energy transfers; most of the energy is degraded to heat, in accordance with the second law of thermodynamics (Concept 2-3B). Question: Think about what you ate for breakfast. At what level or levels on a food chain were you eating? Heat Heat Decomposers and detritus feeders Fig. 2-16

39 Carnivorous zooplankton Herbivorous zooplankton KrillHumans Blue whale Sperm whale Elephant seal Crabeater seal Killer whale Leopard seal Adelie penguin Emperor penguin Petrel Squid Figure 2-17 Greatly simplified food web in the southern hemisphere. The shaded middle area shows a simple food chain. Many more participants in the web, including an array of decomposer and detritus feeder organisms, are not shown here. Question: Can you imagine a food web of which you are a part? Try drawing a simple diagram of it. Fish Carnivorous zooplankton Herbivorous zooplankton Krill Phytoplankton Fig. 2-17

40 Usable Energy Decreases with Each Link in a Food Chain or WebBiomass Dry weight of all organic matter of a given trophic level in a food chain or food web Decreases at each higher trophic level due to heat loss Ecological efficiency Pyramid of energy flow Ninety percent energy loss with each transfer Less chemical energy at higher trophic levels

41 Usable energy available10 Heat Tertiary consumers (human) Usable energy available at each trophic level (in kilocalories) Heat Decomposers Heat Secondary consumers (perch) 100 Heat Primary consumers (zooplankton) 1,000 Heat Producers (phytoplankton) 10,000 Figure 2-18 This model of a generalized pyramid of energy flow shows the decrease in usable chemical energy available at each succeeding trophic level in a food chain or web. The model assumes that with each transfer from one trophic level to another there is a 90% loss in usable energy to the environment in the form of low-quality heat. Question: Why is a vegetarian diet more energy efficient than a meat-based diet? Stepped Art Fig. 2-18

42 Some Ecosystems Produce Plant Matter Faster Than Others DoGross primary productivity (GPP) Conversion rate of solar energy to chemical energy Net primary productivity (NPP) Measure of how fast producers can make the chemical energy that is stored in their tissues Ecosystems and life zones differ in their NPP

43 Figure 2-19 The estimated annual average net primary productivity in major life zones and ecosystems is expressed in this graph as kilocalories of energy produced per square meter per year (kcal/m2/yr). Question: What are nature’s three most productive and three least productive systems? (Data from R. H. Whittaker, Communities and Ecosystems, 2nd ed., New York: Macmillan, 1975) Fig. 2-19

44 2-7 What Happens to Matter in an Ecosystem?Nutrients cycle in the biosphere Biogeochemical cycles (nutrient cycles) Cycles Driven directly or indirectly by incoming solar energy and the earth’s gravity Include hydrologic (water), carbon, nitrogen, phosphorus, and sulfur cycles

45 The Water Cycle Major processes Natural renewal of water qualityEvaporation Precipitation Transpiration Natural renewal of water quality

46 Human Activities Have Major Effects on the Water CycleWithdrawing large amounts of freshwater at rates faster than nature can replace it Clearing vegetation Increases runoff and reduces amount of water seeping into the ground Draining wetlands Increases flooding

47 Precipitation to oceanCondensation Ice and snow Condensation Transpiration from plants Precipitation to land Evaporation of surface water Runoff Evaporation from ocean Lakes and reservoirs Runoff Precipitation to ocean Increased runoff on land covered with crops, buildings and pavement Infiltration and percolation into aquifer Increased runoff from cutting forests and filling wetlands Runoff Groundwater in aquifers Figure 2-20 Natural capital: Simplified model of the water cycle, or hydrologic cycle, in which water circulates in various forms within the biosphere. Major harmful impacts of human activities are shown by the white arrows. Question: What are three ways in which your lifestyle directly or indirectly affects the hydrologic cycle? Overpumping of aquifers Water pollution Runoff Ocean Natural process Natural reservoir Human impacts Natural pathway Pathway affected by human activities Fig. 2-20

48 The Carbon Cycle Link between photosynthesis in producers and aerobic respiration in producers, consumers, and decomposers Circulates carbon in the biosphere

49 Carbon dioxide in atmosphereRespiration Photosynthesis Animals (consumers) Burning fossil fuels Diffusion Forest fires Plants (producers) Deforestation Transportation Respiration Carbon in plants (producers) Carbon in animals (consumers) Carbon dioxide dissolved in ocean Marine food webs Producers, consumers, decomposers Carbon in fossil fuels Decomposition Figure 2-21 Natural capital: Simplified model illustrating the circulation of various chemical forms of carbon in the global carbon cycle, with major harmful impacts of human activities shown by the white arrows. Question: What are three ways in which you directly or indirectly affect the carbon cycle? Carbon in limestone or dolomite sediments Compaction Process Reservoir Pathway affected by humans Natural pathway Fig. 2-21

50 Human Activities Affect the Carbon CycleAdditional CO2 added to the atmosphere Tree clearing Burning of fossil fuels Increased atmospheric CO2 and other greenhouse gases Could lead to climate disruption

51 The Nitrogen Cycle: Bacteria in ActionNitrogen-fixing Lightning Nitrogen-fixing bacteria Major parts of the cycle Nitrogen fixation Nitrification Ammonification Denitrification

52 Human Activities Affect the Nitrogen CycleBurning fossil fuels Acid rain Adding N2O to the atmosphere through Bacteria acting on fertilizers and manure Destroying forests, grasslands, and wetlands Releases stored nitrogen

53 Human Activities Affect the Nitrogen Cycle (cont’d.)Increasing nitrates in bodies of water Agricultural runoff and sewage discharges Removing nitrogen from topsoil Harvesting crops and clearing grasslands and forests

54 The Phosphorus Cycle and Human Interference with ItCycles through water, the earth’s crust, and living organisms Limiting factor for plant growth Impact of human activities Removing large amounts of phosphate from the earth to make fertilizers and detergents Clearing tropical forests Erosion leaches phosphates into streams

55 Runoff Runoff Runoff Erosion BacteriaProcess Reservoir Pathway affected by humans Natural pathway Phosphates in sewage Phosphates in fertilizer Plate tectonics Phosphates in mining waste Runoff Runoff Sea birds Runoff Phosphate in rock (fossil bones, guano) Erosion Ocean food webs Animals (consumers) Phosphate dissolved in water Phosphate in shallow ocean sediments Figure 2-23 Natural capital: Simplified model of the circulation of various chemical forms of phosphorus in the phosphorus cycle, with major harmful human impacts shown by the white arrows. Question: What are three ways in which you directly or indirectly affect the phosphorus cycle? Phosphate in deep ocean sediments Plants (producers) Bacteria Fig. 2-23

56 Earth’s Rocks Are Recycled Very SlowlyIgneous rock Form below or at earth’s surface from molten material Sedimentary rock Created from sediments under pressure Metamorphic rock Existing rocks subjected to high temperatures, high pressures, and/or chemically active fluids

57 Three Big Ideas According to the law of conservation of matter, no atoms are created or destroyed whenever matter undergoes a physical or chemical change.

58 Three Big Ideas (cont’d.)According to the laws of thermodynamics, whenever energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed, and we always end up with lower-quality or less usable energy than we started with.

59 Three Big Ideas (cont’d.)Life is sustained by the flow of energy from the sun through the biosphere, the cycling of nutrients within the biosphere, and gravity.

60 The second law of thermodynamics holds, I think, the supreme position among laws of nature. . . .If your theory is found to be against the second law of thermodynamics, I can give you no hope. Henry David Thoreau