Chapter 1

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. Some Properties of Life

5. Themes Connect Biological Concepts • 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

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

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

14. 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

15. 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

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

17. 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

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

19. 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

20. Discovery Science • Discovery science describes nature through careful observation and data analysis • Examples of discovery science: • understanding cell structure • expanding databases of genomes

21. Types of Data • Data are recorded observations • Two types of data: • Quantitative data: numerical measurements • Qualitative data: recorded descriptions

22. Induction in Discovery Science • Inductive reasoning involves generalizing based on many specific observations Hypothesis-Based Science In science, inquiry usually involves proposing and testing hypotheses Hypotheses are hypothetical explanations

23. 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 Observations Question Hypothesis #1: Dead batteries Hypothesis #2: Burnt-out bulb

24. 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

25. Deduction: The “If…then” Logic of Hypothesis-Based Science • In deductive reasoning, the logic flows from the general to the specific • If a hypothesis is correct, then we can expect a particular outcome

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

27. The Myth of the Scientific Method • The scientific method is an idealized process of inquiry • Very few scientific inquiries adhere rigidly to the “textbook” scientific method

28. A Case Study in Scientific Inquiry: Investigating Mimicry in Snake Populations • In mimicry, a harmless species resembles a harmful species • An example of mimicry is a stinging honeybee and a nonstinging mimic, a flower fly Flower fly (nonstinging) Honeybee (stinging)

29. This case study examines king snakes’ mimicry of poisonous coral snakes • The hypothesis states that mimics benefit when predators mistake them for harmful species • The mimicry hypothesis predicts that predators in non–coral snake areas will attack king snakes more frequently than will predators that live where coral snakes are present

30. LE 1-27 Scarlet king snake Key Range of scarlet king snake Range of eastern coral snake Eastern coral snake North Carolina South Carolina Scarlet king snake

31. Field Experiments with Artificial Snakes • To test this mimicry hypothesis, researchers made hundreds of artificial snakes: • An experimental group resembling king snakes • A control group resembling plain brown snakes • Equal numbers of both types were placed at field sites, including areas without coral snakes • After four weeks, the scientists retrieved the artificial snakes and counted bite or claw marks • The data fit the predictions of the mimicry hypothesis

32. LE 1-28 (a) Artificial king snake (b) Artificial brown snake that has been attacked

33. LE 1-29 17% In areas where coral snakes were absent, most attacks were on artificial king snakes. 83% Key North Carolina % of attacks on artificial king snakes % of attacks on brown artificial snakes South Carolina Field site with artificial snakes 16% 84% In areas where coral snakes were present, most attacks were on brown artificial snakes.

34. Designing Controlled Experiments • Scientists do not control the experimental environment by keeping all variables constant • Researchers usually “control” unwanted variables by using control groups to cancel their effects

35. Limitations of Science • The limitations of science are set by its naturalism • Science seeks natural causes for natural phenomena • Science cannot support or falsify supernatural explanations, which are outside the bounds of science

36. Theories in Science • A scientific theory is much broader than a hypothesis and has been rigorously investigated. • A scientific theory is: • broad in scope • general enough to generate new hypotheses • supported by a large body of evidence

37. Science, Technology, and Society • The goal of science is to understand natural phenomena • Technology applies scientific knowledge for some specific purpose