The Science of Biology. Chapter 1

Transcription

1 The Science of Biology Chapter 1 1

2 The Science of Life Biology unifies much of natural science Life defies simple definition Living systems are the most complex chemical systems on Earth Life is constrained by the properties of chemistry and physics Science is becoming more interdisciplinary Combining multiple fields 2

3 7 characteristics of all living organisms 1. Cellular organization 2. Ordered complexity 3. Sensitivity 4. Growth, development, and reproduction 5. Energy utilization 6. Homeostasis 7. Evolutionary adaptation 3

4 Living systems show hierarchical organization Cellular level Atoms, molecules, organelles, cells Cell is the basic unit of life Organismal level Tissues, organs, organ systems 4

5 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. CELLULAR LEVEL Atoms Molecule Macromolecule Organelle Cell O H N C O H N C O 0.2 µm (organelle): Dr. Donald Fawcett & Porter/Visuals Unlimited; (cell): Steve Gschmeissner/Getty Images 5

6 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ORGANISMAL LEVEL Tissue Organ Organ system Organism 100 µm (tissue): Ed Reschke; (organism): Russell Illig/Getty Images RF 6

7 Populational level Population, community Ecosystem level Biosphere Earth is an ecosystem we call the biosphere Each level has emergent properties Result from interaction of components Cannot be deduced by looking at parts themselves Life is an emergent property 7

8 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. POPULATIONAL LEVEL Population Species Community Ecosystem Biosphere (population): George Ostertag/agefotostock; (species): PhotoDisc/Volume 44 RF; (community): Ryan McGinnis/Alamy; (ecosystem): Robert and Jean Pollock; (biosphere): NASA 8

9 The Nature of Science Science aims to understand the natural world through observation and reasoning Science begins with observations, therefore, much of science is purely descriptive Classification of all life on Earth Human genome sequencing 9

10 Science uses both deductive and inductive reasoning Deductive reasoning uses general principles to make specific predictions Inductive reasoning uses specific observations to develop general conclusions 10

11 Scientists use a systematic approach to gain understanding of the natural world Observation Hypothesis formation Prediction Experimentation Conclusion 11

12 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Observation Question Hypothesis 1 Potential hypotheses Hypothesis 2 Hypothesis 3 Hypothesis 4 Experiment Reject hypotheses 1 and 4 Hypothesis 5 Remaining possible hypotheses Hypothesis 2 Hypothesis 3 Hypothesis 5 Experiment Reject hypotheses 2 and 3 Last remaining possible hypothesis Hypothesis 5 Modify hypothesis Predictions Experiment 1 Experiment 2 Experiment 3 Experiment 4 Predictions confirmed 12

13 A hypothesis is a possible explanation for an observation A hypothesis Must be tested to determine its validity Is often tested in many different ways Allows for predictions to be made Iterative Hypotheses can be changed and refined with new data 13

14 Experiment Tests the hypothesis Must be carefully designed to test only one variable at a time Consists of a test experiment and a control experiment 14

15 Predictions Hypotheses should make predictions Predictions provide a way to test the validity of hypotheses Hypothesis must be rejected if the experiment produces results inconsistent with the predictions The more experimentally supported predictions a hypothesis makes, the more valid the hypothesis 15

16 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. SCIENTIFIC THINKING Question: broth left exposed to the air? What is the source of contamination that occurs in a flask of nutrient Germ Hypothesis: Preexisting microorganisms present in the air contaminate nutrient broth. Prediction: Sterilized broth will remain sterile if microorganisms are prevented from entering flask. Spontaneous Generation Hypothesis: Living organisms will spontaneously generate from nonliving organic molecules in broth. Prediction: Organisms will spontaneously generate from organic molecules in broth after sterilization. Test: Use swan-necked flasks to prevent entry of microorganisms. To ensure that broth can still support life, break swan-neck after sterilization. Broken neck of flask Flask is sterilized by boiling the broth. Unbroken flask remains sterile. Broken flask becomes contaminated after exposure to germ-laden air. Result: No growth occurs in sterile swan-necked flasks. When the neck is broken off, and the broth is exposed to air, growth occurs. Conclusion: Growth in broth is of preexisting microorganisms. 16

17 Philosophical approaches to science Reductionism To break a complex process down to its simpler parts Systems biology Focus on emergent properties that can t be understood by looking at simpler parts 17

18 Models in science Way to organize thought Parts provided by reductionist approach Model shows how they fit together Suggest experiments to test the model 18

19 Scientific theory Is a body of interconnected concepts Is supported by much experimental evidence and scientific reasoning Expresses ideas of which we are most certain Compare to general meaning of theory Implies a lack of knowledge or a guess 19

20 Darwin and Evolution Example of how a scientist develops a hypothesis and a theory gains acceptance Charles Darwin served as naturalist on mapping expedition around coastal South America 30 years of observation and study before publishing On the Origin of Species by Means of Natural Selection 20

21 Voyage of the HMS Beagle Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. NORTH PACIFIC OCEAN Marquesas Society Islands NORTH AMERICA Galápagos Islands Valparaiso Straits of Magellan Cape Horn Tierra del Fuego British Isles Western Isles NORTH ATLANTIC OCEAN SOUTH AMERICA Bahia Cape Verde Islands Falkland Islands Montevideo Buenos Aires Port Desire Canary Islands Ascension St. Helena Rio de Janeiro EUROPE AFRICA Cape of Good Hope SOUTH ATLANTIC OCEAN INDIAN OCEAN Madagascar ASIA Keeling Islands Mauritius Bourbon Island King George s Sound NORTH PACIFIC OCEAN Philippine Islands AUSTRALIA Sydney Hobart Equator Friendly Islands New Zealand 21

22 Darwin was not the first to propose evolution Living things have changed over time Darwin s contribution was a mechanism Natural selection 22

23 On the Beagle, Darwin saw that characteristics of similar species varied from place to place Galápagos Finches 14 related species differ only slightly Descent with modification or evolution Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Woodpecker Finch (Cactospiza pallida) Large Ground Finch (Geospiza magnirostris) Cactus Finch (Geospiza scandens) 23

24 Darwin studied Thomas Malthus s An Essay on the Principle of Population Populations of plants and animals increase geometrically Humans can only increase their food supply arithmetically Populations of species remain constant because death limits population numbers 24

25 Darwin saw that although every organism has the potential to produce more offspring, only a limited number do survive and reproduce themselves Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. geometric progression arithmetic progression

26 Evidence supporting Darwin s theory has only grown Fossil record Transitional forms have been found at predicted positions in time Earth s age Physicists of Darwin s time were wrong Earth is very old 4.5 billion years old 26

27 Mechanism for heredity Mendel s laws of inheritance were unknown to Darwin Comparative anatomy Vertebrate forelimbs all share the same basic array of bones Homologous same evolutionary origin but now differ in structure and function Analogous structures of different origin used for the same purpose (butterfly and bird wings) 27

28 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Human Cat Porpoise Horse Bat 28

29 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Molecular Evidence Compare genomes or proteins of different organisms Phylogenetic trees based on tracing origin of particular nucleotide changes to reconstruct an evolutionary history Human Rhesus Dog Bird Frog Number of Amino Acid Differences in a Hemoglobin Polypeptide 29

30 Unifying Themes in Biology Cell theory All organisms composed of cells Cells are life s basic units All cells come from preexisting cells Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. 60 µm b. 500 µm a: Dennis Kunkel/Phototake; b: Karl E. Deckart/Phototake 30

31 Molecular basis of inheritance Deoxyribonucleic acid (DNA) Sequence of 4 nucleotides encode cell s information Gene discrete unit of information Genome entire set of DNA instructions Continuity of life depends on faithful copying of DNA into daughter cells 31

32 Structure and function Study structure to learn function Know a function look for that structure in other organisms Example Receptor on human cell for insulin known Find similar molecule in a worm Might conclude this molecule functions the same in the worm 32

33 Diversity of life arises by evolution Underlying unity of biochemistry and genetics argues for life from the same origin event Diversity due to evolutionary change over time 3 domains Bacteria single-celled prokaryote Archaea single-celled prokaryote Eukarya single-celled or multicellular eukaryote 33

34 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Plantae Fungi Eukarya Animalia Protista (plantae middle): David M. Dennis/Animals Animals; (plantae right): Corbis/Volume 46 RF; (fungi left): Royalty Free/Corbis; (fungi middle): Mediscan/Corbis; (fungi right): PhotoDisc BS/Volume 15 RF; (animalia left): Royalty-Free/Corbis; (animalia middle): Tom Brakefield/Corbis; (animalia right): PhotoDisc/Volume 44 RF; (protista left): Corbis/Volume 64 RF; (protista middle): Tom Adams/Visuals Unlimited; (protista right): Douglas P. Wilson/Frank Lane Picture Agency/Corbis 34

35 Evolutionary conservation All organisms today descended from a simple creature 3.5 BYA Some characteristics preserved use of DNA Conservation reflects that they have a fundamental role 35

36 Cells are information-processing systems Information in DNA used to direct synthesis of cellular components Control of gene expression leads to different cells/ tissue types Cells process environmental information Glucose levels, presence of hormones Cells in multicellular organisms must coordinate with each other 36

37 Nonequilibrium state Living systems are open systems Constant supply of energy needed Self-organizing properties at different levels Emergent properties from collections of molecules, cells, and individuals 37