Concepts and Methods in Biology Chapter 1 1

Biology Scientific study of life Lays the foundation for asking basic questions about life and the natural world 2

What Is Life? Capture and use of energy and raw materials Sense and respond to the environment Capacity to grow, reproduce, and develop Tendency to evolve 3

Why Study Biology? To learn how organisms are constructed, how they function, where they live, and what they do To help you develop, modify, and refine your ideas about life 4

Molecules of Life All things are made up of the same units of matter: –atoms, molecules Living things are made up of a certain subset of molecules: –nucleic acids, proteins, carbohydrates, lipids 5

DNA (Deoxyribonucleic acid) The signature molecule of life Molecule of inheritance Directs assembly of amino acids 6

Heritability of DNA Inheritance –Acquisition of traits by way of transmission of DNA from parent to offspring Reproduction –Mechanisms by which an organism produces offspring –Governed by instructions in DNA 7

DNA Guides Development Development –Transformation from fertilized egg to adult –Series of stages –Instructions for each stage in DNA 8

Nothing Lives Without Energy Energy = Capacity to do work Metabolism = Reactions by which cells acquire and use energy to grow, survive, and reproduce 9

Sensing and Responding Organisms sense changes in their environment and make responses to them Receptors detect specific forms of energy The form of energy detected by a receptor is a stimulus 10

Homeostasis Maintenance of internal environment within range suitable for cell activities Pancreas maintains level of sugar in blood by secreting hormones 11

Basic Unit of Life - The Cell Characteristics of life emerge at the level of cells A cell is the smallest unit having the capacity to live and reproduce 12

Higher Levels of Organization Cell Multicelled Organism Population Community Ecosystem Biosphere 13

Interdependencies Among Organisms Producers Make their own food Consumers Depend on energy stored in tissues of producers Decomposers Break down remains and wastes 14

Energy Flow Usually starts with energy from sun Transfer from one organism to another Energy flows in one direction Eventually, all energy flows back to the environment 15

16 Fig. 1.6, p. 7 PRODUCERS CONSUMERS,DECOMPOSERS NUTRIENT CYCLING ONE-WAY FLOW OF ENERGY Producers capture, convert, and use or store some energy from the sun. Energy gets transferred from one organism to another; in time, all flows back to the environment.

Unity of Life All organisms: –Are composed of the same substances –Engage in metabolism –Sense and respond to the environment –Have the capacity to reproduce based on instructions in DNA 17

Diversity of Life Millions of living species Additional millions of species now extinct Classification scheme attempts to organize this diversity 18

Scientific Names Two-part naming system devised by Carolus Linnaeus First name is genus (plural, genera) –Homo sapiens - genus is Homo Second name is species within genus 19

Taxa Kingdom Phylum Class Order Family Genus Species 20

The Six Kingdoms Archaebacteria or Archaea Eubacteria Protista Fungi Plantae Animalia 21

Prokaryotic Kingdoms Archaebacteria and Eubacteria Single cells No nucleus or organelles Includes producers, consumers, and decomposers 22

Eukaryotic Kingdoms Protista, Fungi, Plantae, Animalia DNA is inside a nucleus Most are larger and more complex than the prokaryotes 23

Protistans Not an easily defined group Producers and consumers Single-celled and multi-cellular species 24

Fungi Most are multicelled Consumers and decomposers Extracellular digestion and absorption 25

Plants All are multicelled Most are photosynthetic producers Make up the food base for communities, especially on land 26

Animals Multicelled consumers –Herbivores –Carnivores –Parasites –Scavengers Move about during at least some stage of their life 27

Mutation: Source of Variation Mutation = change in structure of DNA Basis for the variation in heritable traits Most are harmful 28

Adaptive Trait A trait that gives the individual an advantage in survival or reproduction, under a given set of circumstances 29

Evolution Genetically based change in a line of descent over time Population changes, not individuals 30

Artificial Selection Breeders favor some form of traits over others Individuals exhibiting favored traits are bred Favored traits increase in the population 31

Natural Selection The outcome of differences in survival and reproduction among individuals that vary in details of heritable traits This process helps explain evolution - changes in a line of descent over generations 32

Antibiotic Resistance Antibiotics are used to kill bacteria Mutations for antibiotic resistance exist or arise in bacterial population Antibiotic-resistant bacteria survive and reproduce better than non-resistant Over time, proportion of antibiotic- resistant bacteria increases 33

Scientific Method Observe phenomenon Develop hypotheses Make predictions Devise test of predictions Carry out test and analyze results 34

Inductive Logic Using observations and facts to arrive at generalizations or hypotheses Observation: Eagles, swallows, and robins have feathers Hypothesis: All birds have feathers 35

Deductive Logic Drawing a specific conclusion based on a generalization –Generalization - Birds have feathers –Example - Eagles are birds –Conclusion - Eagles have feathers 36

Role of Experiments Procedures used to study a phenomenon under known conditions Allows you to predict what will happen if a hypothesis is not wrong Can never prove a hypothesis 100% correct 37

Experimental Design Control group –A standard for comparison –Identical to experimental group except for variable being studied Sampling error –Non-representative sample skews results –Minimize by using large samples 38

39 Fig. 1.10, p. 12 CONTROL GROUP The variable being tested is absent EXPERIMENTAL GROUP The variable being tested is present Draw samples from some aspect of nature Compile results Compare and analyze the test results Report on experimental design, test results, and conclusions drawn from results

Scientific Theory A hypothesis that has been tested for its predictive power many times and has not yet been found incorrect Has wide-ranging explanatory power –Darwin’s Theory of Evolution by Natural Selection 40

Biological Therapy Experiments Can we use viruses that attack bacteria (bacteriophages) to fight infections? 41

Experiment 1 Hypothesis - Bacteriophages can protect mice against infectious bacteria Prediction - Mice injected with bacteriophages will not die as a result of bacterial injection 42

Experiment 1 - Test Experimental group Inject with bacteria and bacteriophage Control group Inject with bacteria and saline 43

Experiment 1 - Results & Conclusion Experimental group All mice lived Control group All mice died Conclusion - Bacteriophage injections protect mice against bacterial infections 44

Experiment 2 Prediction - Bacteriophage injections will be more effective treatment than single dose of the antibiotic streptomycin Test - Mice injected with bacteria, then with saline, streptomycin, or bacteriophage 45

Experiment 2 - Results When 2nd injection was: –Bacteriophage - 11 of 12 mice lived –60mg/gm streptomycin - 5 of 12 lived –100mg/gm streptomycin - 3 of 12 lived –Saline - all mice died Conclusion - Bacteriophage treatment can be as good or better than antibiotics 46

Minimizing Variables All mice were same age and sex, reared under same conditions Each mouse in each test group received exact same treatment All mice in control group received same amount of saline Variable tested was antibiotic treatment versus bacteriophage treatment 47

Limits of Science Scientific approach cannot provide answers to subjective questions Cannot provide moral, aesthetic, or philosophical standards 48

Science and the Supernatural Science has run up against religious belief systems –Copernicus suggested that sun, not the Earth, was center of universe –Darwin suggested that life was shaped by evolution, not a single creation event 49

Asking Questions Scientists still ask questions that challenge widely held beliefs The external world, not internal conviction, is the testing ground for scientific beliefs 50