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The Characteristics of Life http://www.youtube.com/watch?v= juxLuo-sH6M 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 What is Biology? The study of living things (organisms) The study of interactions of living things “bio”-life “ology”-study of 1. Living Things are made up of Cells. Unicellu lar a.) CELL: Collection of living material enclosed within a barrier b.) cells are basic unit of life c.) Unicellular: made up of one cell d.) Multicellular: made up of many cells Multicellular Asexual 2. Living Things Reproduce: a.) produce offspring which resemble parents b.) asexual reproduction: has only one parent Sexual c.) sexual reproduction: requires two parents, usually with egg and sperm. 3. Living things are based on a universal genetic code. a. Offspring always resemble their parents b. Genetic code of DNA determines inherited traits 4. Living things Grow and Develop a.) GROWTH: increase in size & shape b.) DEVELOPMENT: mature over time c.) living things have a lifespan Growth Development As development occurs process called aging takes place. Death, too, is a process of change that separates living and nonliving things. Cell Death is called Apoptosis 5. Living Things Use & Need Energy a.) energy comes from food, used to maintain body b.) AUTOTROPH: produce own food c.) HETEROTROPH: must consume food d.) DECOMPOSER: breaks down dead material for food 6. Living things respond to their surroundings a.) they react to a stimulus b.) an action causes a reaction c. ) reaction is called a response d.) this involves one individual 7. Living things maintain a stable internal environment a.) HOMEOSTASIS: internal balance b.) examples: sweating, panting, shivering, etc. 8. Living things Evolve a.) adapt to long-range changes in environment b.) change to better survive in environment c.) these changes take place over a long period of time & involve the entire species 8. Taken as a group, living things change over time (evolution– individuals don’t usually change basic traits over lifetime, but as group can evolve, or change over time) B. Branches and Levels of Study 1. The broad field of Biology contains many branches a. Some divisions based on type of organism studied (ie. Zoologists, botanist, microbiologists, herpetologists, b. Others study life etc.) from a particular perspective (ie. Ethologist– study animal behavior, paleontologists, etc,) 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 Higher Levels of Organization Cell Tissue Organ Organ System Organism Population Community Ecosystem Biosphere Molecules of Life • All things are made up of the same units of matter: – atoms, molecules • Living things are made of up of a certain subset of molecules: – nucleic acids, proteins, carbohydrates, lipids DNA (Deoxyribonucleic acid) • The signature molecule of life • Molecule of inheritance • Directs assembly of amino acids 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 DNA Guides Development Development – Transformation from fertilized egg to adult – Series of stages – Instructions for each stage in DNA Nothing Lives Without Energy Energy = Capacity to do work Metabolism = Reactions by which cells acquire and use energy to grow, survive, and reproduce 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 Homeostasis • Maintenance of internal environment within range suitable for cell activities • Pancreas maintains level of sugar in blood by secreting hormones Higher Levels of Organization Cell Multicelled Organism Population Community Ecosystem Biosphere Interdependencies Among Organisms Producers Make their own food Consumers Depend on energy stored in tissues of producers Decomposers Break down remains and wastes 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 P roducers capture, convert, and use or store some energy from the sun. PRODUCERS NUTRIENT CYCLING CONSUMERS,DECOMPOSERS ONE-WAY FLOW OF ENERGY Energy gets transferred from one organism to another; in time, all flows back to the environment. Fig. 1.6, p. 7 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 Diversity of Life • Millions of living species • Additional millions of species now extinct • Classification scheme attempts to organize this diversity 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 Taxa Kingdom Phylum Class Order Genus Species The Six Kingdoms Archaebacteria or Archaea Eubacteria Protista Fungi Plantae Animalia Prokaryotic Kingdoms • Archaebacteria and Eubacteria • Single cells • No nucleus or organelles • Includes producers, consumers, and decomposers Eukaryotic Kingdoms • Protista, Fungi, Plantae, Animalia • DNA is inside a nucleus • Most are larger and more complex than the prokaryotes Protistans • Not an easily defined group • Producers and consumers • Single-celled and multi-cellular species Fungi • Most are multicelled • Consumers and decomposers • Extracellular digestion and absorption Plants • All are multicelled • Most are photosynthetic producers • Make up the food base for communities, especially on land Animals • Multicelled consumers – Herbivores – Carnivores – Parasites – Scavengers • Move about during at least some stage of their life Mutation: Source of Variation • Mutation = change in structure of DNA • Basis for the variation in heritable traits • Most are harmful Adaptive Trait A trait that gives the individual an advantage in survival or reproduction, under a given set of circumstances Evolution • Genetically based change in a line of descent over time • Population changes, not individuals Artificial Selection • Breeders favor some form of traits over others • Individuals exhibiting favored traits are bred • Favored traits increase in the population 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 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 antibioticresistant bacteria increases Scientific Method • Observe phenomenon • Develop hypotheses • Make predictions • Devise test of predictions • Carry out test and analyze results Inductive Logic • Using observations and facts to arrive at generalizations or hypotheses • Observation: Eagles, swallows, and robins have feathers • Hypothesis: All birds have feathers Deductive Logic • Drawing a specific conclusion based on a generalization – Generalization - Birds have feathers – Example - Eagles are birds – Conclusion - Eagles have feathers 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 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 Draw samples from some aspect of nature CONTROL GROUP The variable being tested is absent EXPERIMENTAL GROUP The variable being tested is present Compile results Compile results Compare and analyze the test results Report on experimental design, test results, and conclusions drawn from results Fig. 1.10, p. 12 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 Biological Therapy Experiments Can we use viruses that attack bacteria (bacteriophages) to fight infections? Experiment 1 • Hypothesis - Bacteriophages can protect mice against infectious bacteria • Prediction - Mice injected with bacteriophages will not die as a result of bacterial injection Experiment 1 - Test • Experimental group Inject with bacteria and bacteriophage • Control group Inject with bacteria and saline Experiment 1 Results & Conclusion • Experimental group All mice lived • Control group All mice died • Conclusion - Bacteriophage injections protect mice against bacterial infections 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 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 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 Limits of Science • Scientific approach cannot provide answers to subjective questions • Cannot provide moral, aesthetic, or philosophical standards 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 Asking Questions • Scientists still ask questions that challenge widely held beliefs • The external world, not internal conviction, is the testing ground for scientific beliefs