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  1. Splash

  2. An insect from the order Heteroptera feeding on a white fly (Trialeurodes vaporariorum). Transport Systems • How does this scene demonstrate the relationship between life, energy, and the biosphere? • What is the source of energy that maintains these organisms? Chapter Introduction 1

  3. An insect from the order Heteroptera feeding on a white fly (Trialeurodes vaporariorum). Transport Systems • Biologists agree that the ability to absorb and convert energy is a basic characteristic of life. Chapter Introduction 2

  4. End of the Introduction

  5. Organisms and Energy 2.1 Characteristics of Organisms • Living organisms have the following characteristics: • Take in and convert materials and energy from the environment; release wastes • Have a high degree of chemical organization compared to nonliving objects • Have complex structural organization that is responsible for their appearance and activities • Contain coded instructions (such as DNA) for maintaining their organization and activities 2.1 Characteristics of Organisms 1

  6. Organisms and Energy 2.1 Characteristics of Organisms (cont.) • Living organisms have the following characteristics: • Sense and react to changes in their environment • Grow and develop during some part of their lives • Reproduce others like themselves • Communicate with similar organisms • Move under their own power 2.1 Characteristics of Organisms 2

  7. Organisms and Energy 2.2 Energy and Nutrients • Energy, the capacity to do work or to cause change, is needed by all living things. Organisms store chemical energy in the organic molecules from which the organisms are made. The portion of this chemical energy that is available to do work is called free energy. 2.2 Energy and Nutrients 1

  8. Organisms and Energy 2.2 Energy and Nutrients (cont.) • Living cells need a constant source of free energy for chemical and mechanical work and for transport. Heterotrophs are organisms that obtain energy and nutrients from other organisms, either living or dead. Autotrophs are organisms that obtain energy and nutrients from nonliving sources such as the Sun, minerals, and the air. 2.2 Energy and Nutrients 2

  9. Organisms and Energy 2.2 Energy and Nutrients (cont.) • Photoautotrophs are autotrophs that capture energy from sunlight and use it to synthesize organic compounds from carbon dioxide and water in a process called photosynthesis. Chemoautotrophs are autotrophs, all of which are bacteria, that use chemosynthesis to capture energy, which is stored as chemical energy and used for cellular work. Autotrophs use the organic compounds they make as building blocks for maintenance, growth, and reproduction. 2.2 Energy and Nutrients 3

  10. Organisms and Energy 2.2 Energy and Nutrients (cont.) • Heterotrophs consume autotrophs and other heterotrophs as food. Autotrophs directly or indirectly supply the energy and organic nutrients needed for the maintenance, growth, and reproduction of all heterotrophs. Both autotrophs and heterotrophs carry out chemical reactions, known as cell respiration, that release the free energy of organic compounds. 2.2 Energy and Nutrients 4

  11. Organisms and Energy 2.2 Energy and Nutrients (cont.) In the relationship between autotrophs and heterotrophs, energy passes from autotrophs to heterotrophs. Oxygen and carbon dioxide cycle repeatedly between them. 2.2 Energy and Nutrients 5

  12. Organisms and Energy 2.3 Energy and Ecosystems • The need for energy and nutrients links organisms in many complex ways. • Autotrophs, which produce food other organisms use, are the producers in a community of living organisms, such as a forest or an ocean. • Heterotrophs consume plants and other organisms for food; they are the consumers. • Bacteria, fungi, and other heterotrophs that break down and use dead plants and animals for food are decomposers. 2.3 Energy and Ecosystems 1

  13. Organisms and Energy 2.3 Energy and Ecosystems (cont.) • Producers, consumers, and decomposers form a food web in which energy and nutrients flow from the environment through the producers to the consumers and finally to the decomposers. 2.3 Energy and Ecosystems 2

  14. End of Section 1

  15. Energy Flow 2.4 Energy Conversions • Energy conversions are described by principles called the laws of thermodynamics. The first law of thermodynamics states that energy cannot be created or destroyed, but it can change form. On a broader scale, the first law is called the law of conservation of energy and it states that the total energy of the universe is constant. 2.4 Energy Conversions 1

  16. An important difference between living and nonliving systems is the ability of living systems to conserve and use some of the energy released in chemical reactions. Energy Flow 2.4 Energy Conversions (cont.) • The first law of thermodynamics means that organisms cannot create their own energy, but must obtain it from an outside source. 2.4 Energy Conversions 2

  17. Energy Flow 2.5 Energy and Entropy • The second law of thermodynamics states that systems tend to change in a way that increases the disorder, or entropy, of the system plus its surroundings. Because energy tends to spread out into the surroundings, the free energy in a system is slightly less after each energy conversion than before. The world becomes increasingly disordered as free energy is released. 2.5 Energy and Entropy 1

  18. Energy Flow 2.5 Energy and Entropy (cont.) • Organisms must be well organized to remain alive and to grow. Energy is the key to maintaining organization in all living systems. In ecosystems, light or chemical energy flows from the environment (the Sun or inorganic chemicals) to producers to consumers to decomposers. 2.5 Energy and Entropy 2

  19. Energy Flow 2.5 Energy and Entropy (cont.) • As energy flows through food webs, it eventually escapes in the form of heat energy, resulting in a one-way flow of energy. Living systems overcome the tendency toward entropy by constantly obtaining energy from their surroundings. Organisms stay organized and can function and grow only as the entropy of their surroundings increases. 2.5 Energy and Entropy 3

  20. Energy flow in an ecosystem Click the image to view an animated version. 2.5 Energy and Entropy 4

  21. End of Section 2

  22. Metabolism and Energy Transfer 2.6 Enzymes and Energy • To release chemical energy to perform work, cells must have a way to break and form chemical bonds. All living cells contain specialized proteins called enzymes that lower the activation energy required to make a reaction proceed. Chemicals, such as enzymes, that lower activation energies are called catalysts. 2.6 Enzymes and Energy 1

  23. Metabolism and Energy Transfer 2.6 Enzymes and Energy (cont.) Consider the starting molecule, S, and the product molecule, P, which can be formed from S through a chemical reaction. To achieve an activated condition S*, S must acquire considerable energy. In an enzyme-catalyzed reaction, S combines temporarily with the enzyme E, forming a complex ES*, in which S requires less energy to form P (the barrier is lower). 2.6 Enzymes and Energy 2

  24. Metabolism and Energy Transfer 2.6 Enzymes and Energy (cont.) • Each type of enzyme catalyzes only one or a few specific reactions. • The specific reaction catalyzed by an enzyme depends on a small area of its tertiary structure called the active site. • The close fit of the starting molecule, called the substrate, into the active site of the enzyme brings the enzyme and substrate close together. • The resulting interaction lowers the activation energy, which allows the chemical reaction from substrate to product to proceed. 2.6 Enzymes and Energy 3

  25. The induced-fit model of enzyme action Click the image to view an animated version. 2.6 Enzymes and Energy 4

  26. Metabolism and Energy Transfer 2.7 Chemical Reactions in Organisms • Metabolism consists of all the chemical activities and changes that take place continuously in a cell or an organism. 2.7 Chemical Reactions in Organisms 1

  27. Metabolism and Energy Transfer 2.8 Energy Transfer and ATP (cont.) • ATP is a nucleotide consisting of adenine and ribose joined to a chain of three phosphate groups. Usually when an ATP molecule is involved in a chemical reaction, the bond between the second and third phosphate groups breaks and free energy is released. 2.8 Energy Transfer and ATP 2

  28. Metabolism and Energy Transfer 2.8 Energy Transfer and ATP (cont.) • A molecule that accepts the phosphate group from ATP gains free energy and is activated; it can then react usefully with other molecules in the cell. 2.8 Energy Transfer and ATP 3

  29. Metabolism and Energy Transfer 2.8 Energy Transfer and ATP (cont.) • ATP is continually synthesized and broken down in cells, forming a cycle. ATP becomes ADP, adenosine diphosphate, when it gives up one phosphate group. ADP must combine with one phosphate group, requiring free energy from the breakdown of organic compounds to form ATP. 2.8 Energy Transfer and ATP 5

  30. End of Section 3

  31. Digestion 2.9 Digestion Inside and Outside Cells (cont.) • Digestion consists of two parts: • physical—the breakdown of large pieces of food into smaller ones to increase surface area • chemical—the breaking down of complex food molecules into simpler ones In some birds, food is temporarily stored in a sac called a crop. Farther along the digestive tract, a specialized part of the stomach—the gizzard—grinds up food to aid digestion. The walls of the gizzard are thick and muscular, an evolutionary adaptation to grinding. Some birds swallow sand and small pebbles that aid the grinding action. 2.9 Digestion Inside and Outside Cells 2

  32. Digestion 2.9 Digestion Inside and Outside Cells (cont.) • Most animals, including humans, rely on extracellular digestion—digestion that takes place outside the cells. Most animals secrete digestive enzymes into a digestive cavity, where chemical digestion yields the simpler molecules that are then absorbed by the cells. 2.9 Digestion Inside and Outside Cells 3

  33. Digestion 2.9 Digestion Inside and Outside Cells (cont.) • Most plants rely on intracellular digestion—digestion that takes place inside the cells with foods the plant has made itself. Single-celled organisms, such as Paramecium, also rely on intracellular digestion. 2.9 Digestion Inside and Outside Cells 4

  34. Venus flytrap (Dionaea muscipula) Bread mold Digestion 2.9 Digestion Inside and Outside Cells (cont.) • Many organisms, such as Venus flytraps and bread mold produce enzymes that digest food outside the organism itself and then absorb the nutrients into the cells. 2.9 Digestion Inside and Outside Cells 5

  35. End of Chapter Presentation