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Chapter 1

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  1. Chapter 1 Exploring Life

  2. Overview: Biology’s Most Exciting Era • Biology is the scientific study of life • Biologists are moving closer to understanding: • How a single cell develops into an organism • How plants convert sunlight to chemical energy • How the human mind works • How living things interact in communities • How life’s diversity evolved from the first microbes

  3. Life’s basic characteristic is a high degree of order • Each level of biological organization has emergent properties Video: Seahorse Camouflage

  4. Concept 1.1: Biologists explore life from the microscopic to the global scale • The study of life extends from molecules and cells to the entire living planet • Biological organization is based on a hierarchy of structural levels

  5. A Hierarchy of Biological Organization • Biosphere: all environments on Earth • Ecosystem: all living and nonliving things in a particular area • Community: all organisms in an ecosystem • Population: all individuals of a species in a particular area • Organism: an individual living thing

  6. A Hierarchy of Biological Organization (continued) • Organ and organ systems: specialized body parts made up of tissues • Tissue: a group of similar cells • Cell: life’s fundamental unit of structure and function • Organelle: a structural component of a cell • Molecule: a chemical structure consisting of atoms

  7. The biosphere Organelles 1 µm Cell Ecosystems Cells Atoms Molecules 10 µm Communities Tissues 50 µm Populations Organs and organ systems Organisms

  8. A Closer Look at Ecosystems • Each organism interacts with its environment • Both organism and environment affect each other

  9. Ecosystem Dynamics • The dynamics of an ecosystem include two major processes: • Cycling of nutrients, in which materials acquired by plants eventually return to the soil • The flow of energy from sunlight to producers to consumers

  10. Energy Conversion • Activities of life require work • Work depends on sources of energy • Energy exchange between an organism and environment often involves energy transformations • In transformations, some energy is lost as heat • Energy flows through an ecosystem, usually entering as light and exiting as heat

  11. LE 1-4 Sunlight Ecosystem Producers (plants and other photosynthetic organisms) Heat Chemical energy Consumers (including animals) Heat

  12. A Closer Look at Cells • The cell is the lowest level of organization that can perform all activities of life • The ability of cells to divide is the basis of all reproduction, growth, and repair of multicellular organisms

  13. LE 1-5 25 µm

  14. The Cell’s Heritable Information • Cells contain DNA, the heritable information that directs the cell’s activities • DNA is the substance of genes • Genes are the units of inheritance that transmit information from parents to offspring

  15. LE 1-6 Sperm cell Nuclei containing DNA Fertilized egg with DNA from both parents Embryo’s cells With copies of inherited DNA Egg cell Offspring with traits inherited from both parents

  16. Each DNA molecule is made up of two long chains arranged in a double helix • Each link of a chain is one of four kinds of chemical building blocks called nucleotides

  17. LE 1-7 Nucleus DNA Nucleotide Cell DNA double helix Single strand of DNA

  18. Two Main Forms of Cells • Characteristics shared by all cells: • Enclosed by a membrane • Use DNA as genetic information • Two main forms of cells: • Eukaryotic: divided into organelles; DNA in nucleus • Prokaryotic: lack organelles; DNA not separated in a nucleus

  19. LE 1-8 PROKARYOTIC CELL EUKARYOTIC CELL DNA (no nucleus) Membrane Membrane Cytoplasm Organelles Nucleus (contains DNA) 1 µm

  20. Concept 1.2: Biological systems are much more than the sum of their parts • A system is a combination of components that form a more complex organization • Cells, organisms, and ecosystems are some examples of biological systems

  21. The Emergent Properties of Systems • Emergent properties result from arrangements and interactions within systems • New properties emerge with each step upward in the hierarchy of biological order

  22. The Power and Limitations of Reductionism • Reductionism is reducing complex systems to simpler components that are easier to study • The studies of DNA structure and the Human Genome Project are examples of reductionism

  23. Systems Biology • Systems biology seeks to create models of the dynamic behavior of whole biological systems • An example is a systems map of interactions between proteins in a fruit fly cell • Such models may predict how a change in one part of a system will affect the rest of the system

  24. LE 1-10 Outer membrane and cell surface CELL Cytoplasm Nucleus

  25. Systems biology uses three key research developments: • High-throughput technology: methods to generate large data sets rapidly • Bioinformatics: using computers and software to process and integrate large data sets • Interdisciplinary research teams

  26. Feedback Regulation in Biological Systems • Regulatory systems ensure a dynamic balance in living systems • Chemical processes are catalyzed (accelerated) by enzymes • Many biological processes are self-regulating: the product regulates the process itself

  27. In negative feedback, the accumulation of a product slows down the process itself • In positive feedback (less common), the product speeds up its own production Animation: Negative Feedback Animation: Positive Feedback

  28. LE 1-11 A A Negative feedback Enzyme 1 Enzyme 1 B B Enzyme 2 C C Enzyme 3 D D D D D D D D D D D

  29. LE 1-12 W W Enzyme 4 Enzyme 4 X X Positive feedback Enzyme 5 Enzyme 5 Y Y Enzyme 6 Enzyme 6 Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z Z

  30. Concept 1.3: Biologists explore life across its great diversity of species • Biologists have named about 1.8 million species • Estimates of total species range from 10 million to over 200 million

  31. Grouping Species: The Basic Idea • Taxonomy is the branch of biology that names and classifies species into a hierarchical order • Kingdoms and domains are the broadest units of classification

  32. LE 1-14 Family Phylum Order Kingdom Domain Species Genus Class Ursus americanus (American black bear) Ursus Ursidae Carnivora Mammalia Chordata Animalia Eukarya

  33. The Three Domains of Life • At the highest level, life is classified into three domains: • Bacteria (prokaryotes) • Archaea (prokaryotes) • Eukarya (eukaryotes)Eukaryotes include protists and the kingdoms Plantae, Fungi, and Animalia

  34. LE 1-15 Protists Kingdom Plantae Bacteria 4 µm 100 µm Archaea Kingdom Animalia Kingdom Fungi 0.5 µm

  35. Unity in the Diversity of Life • Underlying life’s diversity is a striking unity, especially at lower levels of organization • In eukaryotes, unity is evident in details of cell structure

  36. LE 1-16a 5 µm 15 µm Cilia of Paramecium Cilia of windpipe cells

  37. LE 1-16b 0.1 µm Cross section of cilium, as viewed with an electron microscope Cilia of windpipe cells Cilia of Paramecium

  38. Concept 1.4: Evolution accounts for life’s unity and diversity • The history of life is a saga of a changing Earth billions of years old

  39. The evolutionary view of life came into sharp focus in 1859, when Charles Darwin published On the Origin of Species by Natural Selection • “Darwinism” became almost synonymous with the concept of evolution

  40. The Origin of Species articulated two main points: • Descent with modification (the view that contemporary species arose from a succession of ancestors) • Natural selection (a proposed mechanism for descent with modification) • Some examples of descent with modification are unity and diversity in the orchid family

  41. Natural Selection • Darwin inferred natural selection by connecting two observations: • Observation: Individual variation in heritable traits • Observation: Overpopulation and competition • Inference: Unequal reproductive success • Inference: Evolutionary adaptation

  42. LE 1-20 Population of organisms Overproduction and competition Hereditary variations Differences in reproductive success Evolution of adaptations in the population

  43. Natural selection can “edit” a population’s heritable variations • An example is the effect of birds preying on a beetle population