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Chapter 1 Introduction: Themes in the Study of Life Lecture Presented By Shilla Chakrabarty, Ph.D. Objectives • Explain fundamental concepts of biological sciences and how these concepts are connected within various areas of the biological sciences at the survey level (SLO#1) • Understand that evolution is the core theme of biology, and accounts for the unity and diversity of life • Learn how to design and conduct a scientific experiment by stating a hypothesis, recording and analyzing data, and writing conclusions (SLO#2) • Appreciate that science benefits from a cooperative approach and diverse viewpoints © 2011 Pearson Education, Inc. Overview: Inquiring About Life • Evolution is the process of change that has transformed life on Earth • Evolution accounts for the unity and diversity of life • As a result of evolution an organism can adapt to its environment Example: The mother-of-pearl plant or ghost plant can survive in the crevices of rock walls because it is adapted to conserving water © 2011 Pearson Education, Inc. What is Biology? • Biology is the scientific study of life (Bios – life; logy – study) • Biologists ask questions such as – How does a single cell develop into an organism? – How does the human mind work? – How do living things interact in communities? • Life defies a simple, one-sentence definition • Life is recognized by what living things do © 2011 Pearson Education, Inc. Properties And Processes Associated With Life Order Response to the environment Evolutionary adaptation Reproduction Regulation Energy processing Growth and development Themes In Biology • Themes help to organize biological information • There are at least 8 unifying themes that pervade all of biology: 1. 2. 3. 4. 5. 6. 7. 8. New properties emerge at each level in the biological hierarchy Organisms interact with other organisms and the physical environment Life requires energy transfer and transformation Structure and function are correlated at all levels of biological organization The cell is an organism’s basic unit of structure and function Continuity of life is based on heritable information in the form of DNA Feedback mechanisms regulate biological systems Evolution is the core theme that accounts for the unity and diversity of life © 2011 Pearson Education, Inc. Theme 1: New properties emerge at each level in the biological hierarchy The biosphere Tissues Ecosystems Organs and organ systems Communities Organelles Organisms Populations Cells Atoms Molecules Emergent Properties Emergent properties: • Properties that emerge at each step and are not present at the preceding level • Arise from the arrangement and interaction of parts as complexity increases Example: Photosynthesis does not occur in a disorganized testtube mixture of chlorophyll and chloroplast molecules. Photosynthesis requires a specific organization of these molecules in the chloroplast. • Characterize non-biological entities as well Example: A functioning bicycle can only emerge when all the necessary parts are connected properly © 2011 Pearson Education, Inc. Biology Balances Reductionism With Study Of Emergent Properties Reductionism: Reduction of complex systems to simpler components that are more manageable to study Example: By studying the molecular structure of DNA, Watson and Crick (1953) inferred how this molecule could serve as the chemical basis of inheritance The central role of DNA in cells and organisms could however, only be derived from studies of emergent properties involving the interactions of DNA with other molecules © 2011 Pearson Education, Inc. Systems Biology • System: Combination of components that function together – Can be studied at any level of organization • Systems biology: Constructs models for the dynamic behavior of whole biological systems – Successful models enable biologists to predict how a change in one or more variables will affect other components and the whole system Example: – How does a drug for blood pressure affect other organs? – How does increasing CO2 alter the biosphere? © 2011 Pearson Education, Inc. Theme 2: Organisms Interact with Other Organisms and the Physical Environment Sunlight Leaves absorb light energy from the sun. CO2 Leaves take in carbon dioxide from the air and release oxygen. O2 Cycling of chemical nutrients Leaves fall to the ground and are decomposed by organisms that return minerals to the soil. Water and minerals in the soil are taken up by the tree through its roots. Animals eat leaves and fruit from the tree. Drastic Consequences Of Human Interactions With The Environment • About half the human-generated CO2 stays in the atmosphere and contributes to global warming • Global warming, a major aspect of global climate change, has dire effects on life-forms and habitats all over the Earth • There is an urgent need to find ways of reducing humangenerated CO2 in order to save the environment and protect lifeforms and habitats of the Earth © 2011 Pearson Education, Inc. Theme 3: Life Requires Energy Transfer and Transformation • • • • A fundamental characteristic of living organisms is their use of energy to carry out life’s activities Work, including moving, growing, and reproducing, requires a source of energy Living organisms transform energy from one form to another Example: Light energy is converted to chemical energy, then kinetic energy Energy flows through an ecosystem, usually entering as light and exiting as heat Sunlight Heat When energy is used to do work, some energy is converted to thermal energy, which is lost as heat. Producers absorb light energy and transform it into chemical energy. An animal’s muscle cells convert chemical energy from food to kinetic energy, the energy of motion. Chemical energy Chemical energy in food is transferred from plants to consumers. (a) Energy flow from sunlight to producers to consumers (b) Using energy to do work A plant’s cells use chemical energy to do work such as growing new leaves. Theme 4: Structure and Function are Correlated at all Levels of Biological Organization (a) Wings (b) Bones Infoldings of membrane Mitochondrion 100 µm (c) Neurons 0.5 µm (d) Mitochondria Theme 5: The Cell Is an Organism’s Basic Unit 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 DNA as their genetic information • Cells may be: – Eukaryotic: has membrane-enclosed organelles, the largest of which is usually the nucleus – Prokaryotic: simpler and usually smaller than eukaryotic cell; does not contain a nucleus or other membrane-enclosed organelles © 2011 Pearson Education, Inc. Theme 5: The Cell Is an Organism’s Basic Unit of Structure and Function Eukaryotic Cell Membrane DNA (no nucleus) Membrane Prokaryotic Cell Cytoplasm Nucleus (membraneenclosed) Membraneenclosed organelles DNA (throughout nucleus) 1 m Theme 6: 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) • Each DNA molecule is made up of two long chains of nucleotides arranged in a double helix • DNA is the substance of genes • Genes are the units of inheritance that transmit information from parents to offspring • The ability of cells to divide is the basis of all reproduction, growth, and repair of multicellular organisms © 2011 Pearson Education, Inc. DNA: The Genetic Material Nucleus DNA Nucleotide Cell (a) DNA double helix (b) Single strand of DNA 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 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 Functions of DNA • Genes encode the information necessary to build other molecules, such as proteins in the cell • DNA of genes provide blueprints for making proteins necessary for the cell • DNA is first transcribed into RNA and then translated into a protein • Gene expression is the process of converting information from gene to cellular product © 2011 Pearson Education, Inc. Genomics: Large-Scale Analysis of DNA Sequences • Genome: An organism’s entire set of genetic instructions – The human genome and those of many other organisms have been sequenced using DNA-sequencing machines • Genomics is the study of sets of genes within and between species – The genomics approach depends 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 © 2011 Pearson Education, Inc. Biology As An Information Science Theme 7: Feedback Mechanisms Regulate Biological Systems • Feedback mechanisms allow biological processes to selfregulate – Negative feedback: As more of a product accumulates, the process that creates it slows down and less of the product is produced – Positive feedback: As more of a product accumulates, the process that creates it speeds up and more of the product is produced © 2011 Pearson Education, Inc. Theme 7: Feedback Mechanisms Regulate Biological Systems A Negative feedback Enzyme 1 B Excess D blocks a step. D D Enzyme 2 D C Enzyme 3 D (a) Negative feedback W Enzyme 4 Positive feedback Excess Z stimulates a step. Z X Enzyme 5 Y Z Z Enzyme 6 Z (b) Positive feedback Theme 8: Evolution, the Overarching Theme of Biology • Evolution makes sense of everything we know about biology • Organisms are modified descendants of common ancestors • Evolution explains patterns of unity and diversity in living organisms • Similar traits among organisms are explained by descent from common ancestors • Differences among organisms are explained by the accumulation of heritable changes © 2011 Pearson Education, Inc. Evolution: The Core Theme of Biology • The history of life is a saga of a restless Earth billions of years old, inhabited by a changing cast of living forms – This cast is revealed through fossils and other evidence. • Evolution unifies biology at different scales of size, and accounts for the unity and diversity of life – Each species is one twig on a branching tree of life extending back through ancestral species. “Nothing in biology makes sense except in the light of evolution” Theodosius Dobzhansky © 2011 Pearson Education, Inc. Classifying the Diversity of Life • Approximately 1.8 million species already identified and named to date; thousands more identified each year • Total number of species that actually exist is estimated to range from 10 million to over 100 million • Taxonomy: The branch of biology that names and classifies species into groups of increasing breadth • Domains, followed by kingdoms, are the broadest units of classification © 2011 Pearson Education, Inc. Species Genus Family Order Class Phylum Ursus americanus (American black bear) Ursus Ursidae Carnivora Mammalia Chordata Animalia Classifying Life Eukarya Kingdom Domain The Three Domains of Life • Organisms are divided into three domains • Domain Bacteria and domain Archaea compose the prokaryotes – Most prokaryotes are single-celled and microscopic • Domain Eukarya includes all eukaryotic organisms that are classified into three multicellular kingdoms – Plantae, which produce their own food by photosynthesis – Fungi, which absorb nutrients – Animalia, which ingest their food NOTE: Other eukaryotic organisms were formerly grouped into the Protist kingdom, though these are now often grouped into many separate groups © 2011 Pearson Education, Inc. The Three Domains Of Life 2 m (b) Domain Archaea 2 m (a) Domain Bacteria (c) Domain Eukarya Kingdom Animalia 100 m Kingdom Plantae Protists Kingdom Fungi Unity in the Diversity of Life A striking unity underlies the diversity of life Example: • DNA is the universal genetic language common to all organisms • Unity is evident in many features of cell structure 15 m 5 m Cilia of Paramecium Cilia of windpipe cells 0.1 m Cross section of a cilium, as viewed with an electron microscope Charles Darwin and the Theory of Natural Selection • • • • Charles Darwin published On the Origin of Species by Means of Natural Selection in 1859 © 2011 Pearson Education, Inc. Darwin observed that – Individuals in a population vary in their traits, many of which are heritable – More offspring are produced than survive, and 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 Evolution occurs as the unequal reproductive success of individuals. Thus, the environment “selects” for the propagation of beneficial traits Darwin called this process Natural Selection Unity And Diversity In The Orchid Family Charles Darwin And The Theory of Natural Selection 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 Population of organisms Hereditary variations Overproduction and competition Environmental factors Differences in reproductive success of individuals Evolution of adaptations in the population Darwin’s Theory of Natural Selection Population of organisms Hereditary variations Overproduction of offspring and competition Environmental factors Differences in reproductive success of individuals Evolution of adaptations in the population 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 and Adaptation • 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” Example: The forelimb of the bat, human, and horse and the whale flipper all share a common skeletal architecture • Fossils provide additional evidence of anatomical unity from descent with modification © 2011 Pearson Education, Inc. Evolution of Adaptations In The Population Darwin proposed that natural selection can, by its cumulative effects over vast spans of time, produce new species from ancestral species. Example: A population may be fragmented into several isolated populations in different environments. • What began as one species could gradually diversify into many species. • Each isolated population would adapt over many generations to different environmental problems NOTE: Evolutionary relationships are often illustrated with treelike diagrams that show ancestors and their descendants © 2011 Pearson Education, Inc. Insect-eaters Warbler finches Gray warbler finch Certhidea fusca Bud-eater Seed-eater COMMON ANCESTOR Green warbler finch Certhidea olivacea Sharp-beaked ground finch Geospiza difficilis Vegetarian finch Platyspiza crassirostris Mangrove finch Cactospiza heliobates Insect-eaters Tree finches Woodpecker finch Cactospiza pallida Medium tree finch Camarhynchus pauper Large tree finch Camarhynchus psittacula Small tree finch Camarhynchus parvulus Cactus-flowereaters Seed-eaters Ground finches Descent With Modification: Adaptive Radiation Of Finches On The Galapagos Islands Large cactus ground finch Geospiza conirostris Cactus ground finch Geospiza scandens Small ground finch Geospiza fuliginosa Medium ground finch Geospiza fortis Large ground finch Geospiza magnirostris The Process of Studying Science: • The word science is derived from Latin and means “to know” • Inquiry is the search for information and explanation • Scientists study science by making observations, forming logical hypotheses and testing them © 2011 Pearson Education, Inc. The Scientific Process • Making observations – Biologists describe natural structures and processes – This approach is based on observation and data analysis Collecting data Data or recorded observations or items of information fall into two categories: – Qualitative data, or descriptions rather than measurements Example: Jane Goodall’s observations of chimpanzee behavior – Quantitative data, or recorded measurements, which are sometimes organized into tables and graphs © 2011 Pearson Education, Inc. Jane Goodall collecting qualitative data on chimpanzee behavior The Scientific Process • Forming and Testing Hypotheses – Observations and inductive reasoning can lead us to ask questions and propose hypothetical explanations called hypotheses What is Inductive reasoning? – Inductive reasoning draws conclusions through the logical process of induction – Repeating specific observations can lead to important generalizations Example: “The sun always rises in the east” © 2011 Pearson Education, Inc. Hypothesis-Based Science • The observations of discovery science lead to further questions and proposal of hypothetical explanations called hypotheses • A hypothesis is a tentative answer to a well-framed question • A scientific hypothesis leads to predictions that can be tested by observation or experimentation © 2011 Pearson Education, Inc. Observations A Campground Example Of Hypothesis-based Inquiry Question Hypothesis #1: Dead batteries Hypothesis #2: Burnt-out bulb Prediction: Replacing batteries will fix problem Prediction: Replacing bulb will fix problem Test of prediction Test of prediction Test falsifies hypothesis Test does not falsify hypothesis Alternative Hypotheses in Hypothesisbased Inquiry • Hypothesis-based science often makes use of two or more alternative hypotheses • Failure to falsify a hypothesis does not prove that hypothesis 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) © 2011 Pearson Education, Inc. Inductive Versus Deductive Reasoning • Inductive reasoning draws conclusions through the logical process of induction – Repeating specific observations can lead to important generalizations Example: “The sun always rises in the east” • Deductive reasoning uses the “if….then” logic of hypothesis-based science to make specific predictions Example: If organisms are made of cells (premise 1), and humans are organisms (premise 2), then humans are composed of cells (deductive prediction) © 2011 Pearson Education, Inc. Questions That Can and Cannot Be Addressed by Science • A scientific hypothesis must be testable and falsifiable Example: A hypothesis that ghosts fooled with the flashlight cannot be tested • Supernatural and religious explanations are outside the bounds of science © 2011 Pearson Education, Inc. The Flexibility 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 © 2011 Pearson Education, Inc. A Case Study in Scientific Inquiry: Investigating Mimicry in Snake Populations Scarlet kingsnake (nonvenomous) Key Range of scarlet kingsnake only Overlapping ranges of scarlet kingsnake and eastern coral snake North Carolina South Carolina Eastern coral snake (venomous) Experiment to test Henry Bates’ Hypothesis Scarlet kingsnake (nonvenomous) Field Experiments with Artificial Snakes • To further test Henry Bates’ 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 poisonous coral snakes (a) Artificial kingsnake (b) Brown artificial snake that has been attacked © 2011 Pearson Education, Inc. RESULTS NOTED AFTER 4 WEEKS 100 84% Percent of total attacks on artificial snakes 83% Brown artificial snakes 80 60 40 20 Artificial kingsnakes 17% 16% 0 Coral snakes absent Coral snakes present Conclusion From The Data Obtained • 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 © 2011 Pearson Education, Inc. Experimental Controls and Repeatability • A controlled experiment compares an experimental group (the artificial king snakes) with a control group (the artificial brown snakes) • Ideally, only the variable of interest (the effect of coloration on the behavior of predators) 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 • In science, observations and experimental results must be repeatable © 2011 Pearson Education, Inc. 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 Example: The Theory of Natural Selection © 2011 Pearson Education, Inc. Science benefits from a cooperative approach and diverse viewpoints • 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 • Scientists check each others’ claims by performing similar experiments, and often build upon the work of others to advance the field • It is not unusual for different scientists to work on the same research question • Scientists cooperate by sharing data about model organisms (e.g., the fruit fly Drosophila melanogaster) © 2011 Pearson Education, Inc. Science As A Social Process 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 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 © 2011 Pearson Education, Inc. DNA Technology And Crime Scene Investigation The Value of Diverse Viewpoints in Science • Many important inventions have occurred where different cultures and ideas mix Example: The printing press relied on innovations from China (paper and ink) and Europe (mass production in mills) • Science benefits from diverse views from different racial and ethnic groups, and from both women and men © 2011 Pearson Education, Inc. Key Concepts 1. 2. 3. 4. 5. 6. A number of unifying themes characterize the biological sciences Evolution is the core theme in Biology, and accounts for the unity and diversity of life All organisms can be classified into three domains of life The theory of natural selection explains the unity and diversity in life In studying nature, scientists make observations, form and test hypotheses Science benefits from a co-operative approach and diverse viewpoints © 2011 Pearson Education, Inc.