Chapter Introduction: Themes in the Study of Life Biology _ \ Eighth Edition Neil Campbell and Jane = > aT ees ee Ee Overview: Inquiring About the World of Life * Evolution is the process of change that has transformed life on Earth * Biology is the scientific study of life * Biologists ask questions such as: — How a single cell develops into an organism ~— How the human mind works — How living things interact in communities* Life defies a simple, one-sentence definition * Life is recognized by what living things do Concept 1.1: Themes connect the concepts of biology ¢ Biology consists of more than memorizing factual details + Themes help to organize biological informationEvolution, the Overarching Theme of Biology * Evolution makes sense of everything we know about living organisms * Organisms living on Earth are modified descendents of common ancestors Theme: New properties emerge at each level in the biological hierarchy + Life can be studied at different levels from molecules to the entire living planet * The study of life can be divided into different levels of biological organizationThe Power and Limitations of Reductionism * Reductionism is the reduction of complex systems to simpler components that are more manageable to study — For example, the molecular structure of DNA + An understanding of biology balances reductionism with the study of emergent properties — For example, new understanding comes from studying the interactions of DNA with other molecules Systems Biology « Asystem is a combination of components that function together + Systems biology constructs models for the dynamic behavior of whole biological systems * The systems approach poses questions such as: — How does a drug for blood pressure affect other organs? — How does increasing CO, alter the biosphere?Theme: Organisms interact with their environments, exchanging matter and energy * Every organism interacts with its environment, including nonliving factors and other organisms + Both organisms and their environments are affected by the interactions between them — For example, a tree takes up water and minerals from the soil and carbon dioxide from the air; the tree releases oxygen to the air and roots help form soil 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‘Sunlight x Producers is (plantsandother | 45 photosynthetic Cycling organisms) of chemical {| nutrients | Energy Conversion - Work requires a source of energy + Energy can be stored in different forms, for example, light, chemical, kinetic, or thermal * The energy exchange between an organism and its environment often involves energy transformations * Energy flows through an ecosystem, usually entering as light and exiting as heatTheme: Structure and function are correlated at all levels of biological organization * Structure and function of living organisms are closely related — For example, a leaf is thin and flat, maximizing the capture of light by chloroplasts <« 4 (a) Wings (b) Bones Infoldings of membrane (c) Neurons (d) MitochondriaTheme: Cells are an organism’s basic units of structure and function * The cell is the lowest level of organization that can perform all activities required for life + All cells: — Are enclosed by a membrane — Use DNAas their genetic information * The ability of cells to divide is the basis of all reproduction, growth, and repair of multicellular organisms + Aeukaryotic cell has membrane-enclosed organelles, the largest of which is usually the nucleus - By comparison, a prokaryotic cell is simpler and usually smaller, and does not contain a nucleus or other membrane-enclosed organelles ¢ Bacteria and Archaea are prokaryotic; plants, animals, fungi, and all other forms of life are eukaryoticcyte prokaryotic cell Eukaryotic cell DNA (no nucleus). so Organelles: Nucleus (contains DNA): Theme: The continuity of life is based on heritable information in the form of DNA + Chromosomes contain most of a cell’s genetic material in the form of DNA (deoxyribonucleic acid) + DNAis the substance of genes * Genes are the units of inheritance that transmit information from parents to offspringDNA Structure and Function « Each chromosome has one long DNA molecule with hundreds or thousands of genes + DNAis inherited by offspring from their parents * DNAcontrols the development and maintenance of organisms rigs Sperm cell / Fertilized egg Embryo's cells with ze with DNA from copies of inherited DNA Egg cell both parents Offspring with traits inherited from both parents,+ 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 (a) DNA double helix (b) Single strand of DNA* Genes control protein production indirectly ¢ DNAis transcribed into RNA then translated into a protein + Anorganism’s genome is its entire set of genetic instructions Systems Biology at the Levels of Cells and Molecules * The human genome and those of many other organisms have been sequenced using DNA- sequencing machines * Knowledge of a cell’s genes and proteins can be integrated using a systems approachyen rig tie Outer membrane and cell surface \+ Advances in systems biology at the cellular and molecular level depend on — “High-throughput” technology, which yields enormous amounts of data — Bioinformatics, which is the use of computational tools to process a large volume of data — Interdisciplinary research teams Theme: Feedback mechanisms regulate biological systems * Feedback mechanisms allow biological processes to self-regulate * Negative feedback means that as more of a product accumulates, the process that creates it slows and less of the product is produced + Positive feedback means that as more of a product accumulates, the process that creates it speeds up and more of the product is producedfig ie Negative feodback@ cw Ll Seco (@) Negative feedback Postive feedback® Excess Z simulates a = Enaymes (0) Poste feedback Negative feedback Mug, =Enzyme1= THA (=) Enzyme2 Excess D blocks a step ») Enzyme3 (a) Negative feedbackEnzyme4 Positive feedback® SMa, =Enzyme5 = TATE Excess Z stimulates a step Enzyme6 Concept 1.2: The Core Theme: Evolution accounts for the unity and diversity of life « “Nothing in biology makes sense except in the light of evolution’—Theodosius Dobzhansky + Evolution unifies biology at different scales of size throughout the history of life on EarthOrganizing the Diversity of Life + Approximately 1.8 million species have been identified and named to date, and thousands more are identified each year ¢ Estimates of the total number of species that actually exist range from 10 million to over 100 million Grouping Species: The Basic Idea * Taxonomy is the branch of biology that names and classifies species into groups of increasing breadth + Domains, followed by kingdoms, are the broadest units of classificationigo The Three Domains of Life + The three-domain system is currently used, and replaces the old five-kingdom system + Domain Bacteria and domain Archaea comprise the prokaryotes * Domain Eukarya includes all eukaryotic organisms“ae (2) DOMAINBACTERIA (b) DOMAIN ARCHAEA {c) DOMAINEUKARYA Kingdom Fungi Kingdom Animalia Unity in the Diversity of Life - Astriking unity underlies the diversity of life; for example: — DNAis the universal genetic language common to all organisms — Unity is evident in many features of cell structureFee cin & HA Cla of 6, J windpipe 2th cells 0.1 um tim, Cross section of a cilium, as viewed with an electron microscope Charles Darwin and the Theory of Natural Selection + Fossils and other evidence document the evolution of life on Earth over billions of yearsCharles Darwin published On the Origin of Species by Means of Natural Selection in 1859 Darwin made two main points: Species showed evidence of “descent with modification” from common ancestors Natural selection is the mechanism behind “descent with modification” Darwin’s theory explained the duality of unity and diversity Darwin observed that: Individuals in a population have traits that vary Many of these traits are heritable (passed from parents to offspring) — More offspring are produced than survive — Competition is inevitable — Species generally suit their environmentDarwin inferred that: — Individuals that are best suited to their environment are more likely to survive and reproduce — Over time, more individuals in a population will have the advantageous traits In other words, the natural environment “selects” for beneficial traits Natural selection is often evident in adaptations of organisms to their way of life and environment Bat wings are an example of adaptationThe Tree of Life * “Unity in diversity” arises from “descent with modification” — For example, the forelimb of the bat, human, horse and the whale flipper all share a common skeletal architecture * Fossils provide additional evidence of anatomical unity from descent with modification * Darwin proposed that natural selection could cause an ancestral species to give rise to two or more descendent species — For example, the finch species of the Galapagos Islands ¢ Evolutionary relationships are often illustrated with tree-like diagrams that show ancestors and their descendentscig ree ‘won worier finch cae Qe SP sD Woodpecker ch ‘Ceceospz pale cesroR —ses pores tute cacas ‘tend tach ‘Seospaa conrastis ‘cactus ground tach ‘Seospa scandens matron ch Soe a cs > ee —_ cma Lage ground nen eS eos Imagaresns Concept 1.3: Scientists use two main forms of inquiry in their study of nature + The word Science is derived from Latin and means “to know” * Inquiry is the search for information and explanation * There are two main types of scientific inquiry: discovery science and hypothesis-based scienceDiscovery Science + Discovery science describes natural structures and processes * This approach is based on observation and the analysis of data Types of Data + Data are recorded observations or items of information * Data fall into two categories — Qualitative, or descriptions rather than measurements — Quantitative, or recorded measurements, which are sometimes organized into tables and graphsInduction in Discovery Science + Inductive reasoning draws conclusions through the logical process of induction + Repeat specific observations can lead to important generalizations — For example, “the sun always rises in the east” Hypothesis-Based Science * Observations can lead us to ask questions and propose hypothetical explanations called hypothesesThe Role of Hypotheses in Inquiry + Ahypothesis is a tentative answer to a well- framed question - Ascientific hypothesis leads to predictions that can be tested by observation or experimentation + For example, Observation: Your flashlight doesn’t work — Question: Why doesn’t your flashlight work? — Hypothesis 1: The batteries are dead — Hypothesis 2: The bulb is burnt out + Both these hypotheses are testableDeduction: The “If...Then” Logic of Hypothesis Based Science + Deductive reasoning uses general premises to make specific predictions + For example, if organisms are made of cells (premise 1), and humans are organisms (premise 2), then humans are composed of cells (deductive prediction)A Closer Look at Hypotheses in Scientific Inquiry * Ahypothesis must be testable and falsifiable + Hypothesis-based science often makes use of two or more alternative hypotheses * Failure to falsify a hypothesis does not prove that hypothesis For example, you replace your flashlight bulb, and it now works; this supports the hypothesis that your bulb was burnt out, but does not prove it (perhaps the first bulb was inserted incorrectly) The Myth of the Scientific Method * The scientific method is an idealized process of inquiry + Hypothesis-based science is based on the “textbook” scientific method but rarely follows all the ordered steps * Discovery science has made important contributions with very little dependence on the so-called scientific methodA Case Study in Scientific Inquiry: Investigating Mimicry in Snake Populations * Many poisonous species are brightly colored, which warns potential predators + Mimics are harmless species that closely resemble poisonous species * Henry Bates hypothesized that this mimicry evolved in harmless species as an evolutionary adaptation that reduces their chances of being eaten + This hypothesis was tested with the poisonous eastern coral snake and its mimic the nonpoisonous scarlet kingsnake - Both species live in the Carolinas, but the kingsnake is also found in regions without poisonous coral snakes * If predators inherit an avoidance of the coral snake’s coloration, then the colorful kingsnake will be attacked less often in the regions where coral snakes are presentScarlet kingsnake (nonpoisonous) Key (Range of scarlet kingsnake only {Overlapping ranges of scarlet kingsnake and eastern coral snake Eastern coral snake (poisonous) Scarlet kingsnake (nonpoisonous) Field Experiments with Artificial Snakes * To test this mimicry hypothesis, researchers made hundreds of artificial snakes: — Anexperimental group resembling kingsnakes — Acontrol group resembling plain brown snakes - Equal numbers of both types were placed at field sites, including areas without poisonous coral snakes(a) Artificial kingsnake e that has been attacked - After four weeks, the scientists retrieved the artificial snakes and counted bite or claw marks * The data fit the predictions of the mimicry hypothesis: the ringed snakes were attacked less frequently in the geographic region where coral snakes were found100 Artificial kingsnakes 2 @ Brown £ g8 e artificial os snakes m4 z= 60 Ste cs e& 40 oc a ° oa Coralsnakes Coral snakes absent present Designing Controlled Experiments + Acontrolled experiment compares an experimental group (the artificial kingsnakes) with a control group (the artificial brown snakes) + Ideally, only the variable of interest (the color pattern of the artificial snakes) differs between the control and experimental groups + Acontrolled experiment means that control groups are used to cancel the effects of unwanted variables + Acontrolled experiment does not mean that all unwanted variables are kept constantLimitations of Science * In science, observations and experimental results must be repeatable * Science cannot support or falsify supernatural explanations, which are outside the bounds of science Theories in Science * In the context of science, a theory is: Broader in scope than a hypothesis General, and can lead to new testable hypotheses Supported by a large body of evidence in comparison to a hypothesisModel Building in Science * Models are representations of natural phenomena and can take the form of: — Diagrams — Three-dimensional objects Computer programs — Mathematical equations From From body lungs Right Left atrium atrium Right Left ventricle ventricle 4 To lungs To bodyThe Culture of Science + Most scientists work in teams, which often include graduate and undergraduate students * Good communication is important in order to share results through seminars, publications, and websitesScience, Technology, and Society * The goal of science is to understand natural phenomena * The goal of technology is to apply scientific knowledge for some specific purpose * Science and technology are interdependent + Biology is marked by “discoveries,” while technology is marked by “inventions” * The combination of science and technology has dramatic effects on society — For example, the discovery of DNA by James Watson and Francis Crick allowed for advances in DNA technology such as testing for hereditary diseases + Ethical issues can arise from new technology, but have as much to do with politics, economics, and cultural values as with science and technologyYou should now be able to: 1. Briefly describe the unifying themes that characterize the biological sciences 2. Distinguish among the three domains of life, and the eukaryotic kingdoms 3. Distinguish between the following pairs of terms: discovery science and hypothesis- based science, quantitative and qualitative data, inductive and deductive reasoning, science and technology