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Chapter 1 Introduction: Themes in the Study of Life PowerPoint® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Overview: Inquiring About the World of Life • Evolution is the process of change over time 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Evolutionary adaptation 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Some properties of life Order Response to the environment Evolutionary adaptation Regulation Energy processing Reproduction Growth and development 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Levels of biological organization The Biosphere Cells 10 µm Organs and organ systems Cell Ecosystems Organelles Communities 1 µm Tissues Atoms 50 µm Molecules Populations Organisms Emergent Properties • Emergent properties result from the arrangement and interaction of parts within a system. • Emergent properties characterize nonbiological entities as well. – For example, a functioning bicycle emerges only when all of the necessary parts connect in the correct way. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Systems Biology • A system 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 CO2 alter the biosphere? Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Ecosystem Dynamics • Dynamics of an ecosystem include two major processes: – Cycling of nutrients, in which materials acquired by plants eventually return to the soil. – Flow of energy from sunlight to producers to consumers. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Nutrient cycling and energy flow in an ecosystem Sunlight Ecosystem Cycling of chemical nutrients Producers (plants and other photosynthetic organisms) Heat Chemical energy Consumers (such as animals) Heat 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Form fits function in a gull’s wing (a) Wings (b) Bones Infoldings of membrane Mitochondrion 100 µm (c) Neurons 0.5 µm (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. Cells are the basic units of life - Cell Theory. • All cells: – Are enclosed by a membrane – Use DNA as their genetic information • The ability of cells to divide is the basis of all reproduction, growth, and repair of multicellular organisms Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • A eukaryotic 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Eukaryotic cell Membrane Prokaryotic cell DNA (no nucleus) Membrane Cytoplasm Organelles Nucleus (contains DNA) 1 µm 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). • DNA is the substance of genes. • Genes are the units of inheritance that transmit information from parents to offspring. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings DNA Structure and Function • Each chromosome has one long DNA molecule with hundreds or thousands of genes. • DNA is inherited by offspring from their parents. • DNA controls the development and maintenance of organisms. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Inherited DNA directs development of an organism Sperm cell Nuclei containing DNA Egg cell Fertilized egg with DNA from both parents Embryo’s cells with copies of inherited DNA 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 or monomers called nucleotides. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Nucleus DNA: The genetic material DNA Nucleotide Cell (a) DNA double helix (b) Single strand of DNA • Genes control protein production indirectly. • DNA is transcribed into RNA then translated into a protein. • Central Dogma: DNA --> RNA --> protein • An organism’s genome is its entire set of genetic instructions. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Systems Biology at the Levels of Cells and Molecules • The human genome and those of many other organisms have been sequenced using DNAsequencing machines. • Knowledge of a cell’s genes and proteins can be integrated using a systems approach. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Advances in systems biology at the cellular and molecular level depend on – “High-throughput” technology, which yields enormous amounts of data. – Bioinformatics = the use of computational tools to process a large volume of data. – Interdisciplinary research teams. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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. Negative feedback reverses a trend. • Positive feedback means that as more of a product accumulates, the process that creates it speeds up and more of the product is made. Positive feedback accelerates a trend. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Regulation by Feedback Mechanisms Negative feedback  A Enzyme 1 B D Excess D blocks D Enzyme 2 D C a step Enzyme 3 D (a) Negative feedback W Enzyme 4 Positive feedback + Z Excess Z stimulates a step X Enzyme 5 Y Z Z Enzyme 6 Z (b) Positive feedback 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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 … AND growing … Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Classifying life Species Genus Family Order Class Phylum Kingdom Domain Ursus americanus (American black bear) Ursus Ursidae Carnivora Mammalia Chordata Animalia Eukarya 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. (No nucleus) • Domain Eukarya includes all eukaryotes. (Nucleus) Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings (a) DOMAIN BACTERIA The three domains of life (b) DOMAIN ARCHAEA (c) DOMAIN EUKARYA Protists Kingdom Plantae Kingdom Fungi Kingdom Animalia • The domain Eukarya (cells have a nucleus) includes three multicellular kingdoms: – Plantae – Fungi – Animalia • Other eukaryotic organisms were formerly grouped into a kingdom called Protista, though these are now often grouped into many separate kingdoms Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Protists Kingdom Plantae Kingdom Fungi (c) DOMAIN EUKARYA Kingdom Animalia Unity in the Diversity of Life • A striking unity underlies the diversity of life; for example: – DNA is the universal genetic language common to all organisms. – Unity is evident in many features of cell structure. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings An example of unity underlying the diversity of life: the architecture of cilia in eukaryotes 15 µm 5 µm Cilia of Paramecium Cilia of windpipe cells 0.1 µm 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Digging into the past • 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Natural Selection 1 Population with varied inherited traits. 2 Elimination of individuals with certain traits. 3 Reproduction of survivors. 4 Increasing frequency of traits that enhance survival and reproductive success. • Natural selection is often evident in adaptations of organisms to their way of life and environment. • Bat wings are an example of adaptation. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Evolutionary 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. These are called homologous structures. • Fossils provide additional evidence of anatomical unity from descent with modification. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • Darwin proposed that natural selection could cause an ancestral species to give rise to two or more descendent species: adaptive radiation. – For example, the finch species of the Galápagos Islands. • Evolutionary relationships are often illustrated with tree-like diagrams that show ancestors and their descendents: phylogenetic trees. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Discovery Science • Discovery science describes natural structures and processes. • This approach is based on observation and the analysis of data. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Jane Goodall collecting qualitative data on chimpanzee behavior 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.” Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Hypothesis-Based Science • Observations can lead us to ask questions and propose hypothetical explanations called hypotheses. • A hypothesis is a tentative answer to a wellframed question. • A scientific hypothesis leads to predictions that can be tested by observation or experimentation. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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 and falsifiable. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings A campground example of hypothesisbased inquiry Observations Question Hypothesis #1: Dead batteries Hypothesis #2: Burnt-out bulb Prediction: Replacing batteries will fix problem Prediction: Replacing bulb will fix problem Test prediction Test falsifies hypothesis Test prediction Test does not falsify hypothesis Deduction: The “If…Then” Logic of Hypothesis Based Science • Deductive reasoning uses general premises to make specific predictions General --> specific • For example, if organisms are made of cells (premise 1), and humans are organisms (premise 2), then humans are composed of cells (deductive prediction). Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings A Closer Look at Hypotheses in Scientific Inquiry • A hypothesis 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). Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The geographic ranges of a poisonous snake and its mimic Scarlet kingsnake (nonpoisonous) Key Range of scarlet kingsnake only Overlapping ranges of scarlet kingsnake and eastern coral snake North Carolina South Carolina Eastern coral snake (poisonous) Scarlet kingsnake (nonpoisonous) Field Experiments with Artificial Snakes • To test this mimicry hypothesis, researchers made hundreds of artificial snakes: – An experimental group resembling kingsnakes – A control group resembling plain brown snakes • Equal numbers of both types were placed at field sites, including areas without poisonous coral snakes. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Artificial Snakes used in Field Experiments to test the Mimicry hypothesis (a) Artificial kingsnake (b) Brown artificial snake 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. • The hypothesis was TESTED and was NOT falsified. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Does the presence of poisonous coral snakes affect predation rates on their mimics, kingsnakes? RESULTS Percent of total attacks on artificial snakes 100 84% 83% 80 60 40 20 17% 16% 0 Coral snakes absent Coral snakes present Artificial kingsnakes Brown artificial snakes Designing Controlled Experiments • A controlled 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. • A controlled experiment means that control groups are used to cancel the effects of unwanted variables. • A controlled experiment does not mean that all unwanted variables are kept constant. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Model Building in Science • Models are used to study life. Models are representations of natural phenomena and can take the form of: – Diagrams – Three-dimensional objects – Computer programs – Mathematical equations. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Model of Blood Flow through the Heart From body From lungs Right atrium Left atrium Right ventricle Left ventricle 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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.” Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings • 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. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Energy Flow and Nutrient Cycling Producers Consumers Eukaryotic vs. Prokayotic Cells Feedback Loop Natural Selection Population of organisms Hereditary variations Overproduction and competition Environmental factors Differences in reproductive success of individuals Evolution of adaptations in the population 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 hypothesisbased science, quantitative and qualitative data, inductive and deductive reasoning, science and technology. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings