Chapter 1

1. Chapter 1 Themes in the Study of 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. Themes of Biology: • Evolution • Ecosystems • Biological organization • Cells • DNA • Feedback mechanisms

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

6. The study of life extends from molecules and cells to the entire living planet • Biological organization is based on a hierarchy of structural levels

7. 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

8. 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

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

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

11. 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

12. 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

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

14. 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

15. LE 1-5 25 µm

16. 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

17. 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

18. 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

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

20. 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

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

22. 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

23. 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

24. 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

25. 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

26. 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

28. 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

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

30. 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

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

32. 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

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

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

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

37. The evolutionary view of life came into sharp focus in 1859, when Charles Darwin published On the Origin of Species by Natural Selection

38. 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

40. 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

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

42. An example is the effect of birds preying on a beetle population

43. LE 1-21 Population with varied inherited traits Elimination of individuals with certain traits Reproduction of survivors Increasing frequency of traits that enhance survival and reproductive success

44. Natural selection is often evident in adaptations of organisms to their way of life and environment • Bat wings are an example of adaptation Video: Soaring Hawk

46. Hypothesis-Based Science • In science, inquiry usually involves proposing and testing hypotheses • Hypotheses are hypothetical explanations

47. The Role of Hypotheses in Inquiry • In science, a hypothesis is a tentative answer to a well-framed question • A hypothesis is an explanation on trial, making a prediction that can be tested

48. LE 1-25a Observations Question Hypothesis #1: Dead batteries Hypothesis #2: Burnt-out bulb

49. LE 1-25b Hypothesis #2: Burnt-out bulb Hypothesis #1: Dead batteries Prediction: Replacing batteries will fix problem Prediction: Replacing bulb will fix problem Test prediction Test prediction Test falsifies hypothesis Test does not falsify hypothesis

50. A Closer Look at Hypotheses in Scientific Inquiry • A scientific hypothesis must have two important qualities: • It must be testable • It must be falsifiable