1: Lecture Introduction Invitation to Biology Chapter 1 Life's Levels of Organization The world of life shows levels of organization, from the simple to the complex, which extend through: Cells (Cell is the basic unit of life; cells>tissues>organs>Organisms) Populations >communities -> ecosystems ->the 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 callednucleic acids, proteins, carbohydrates, lipids DNA (deoxyribonucleic acid) The signature molecule of life it is unique to each individual or organism Molecule of inheritance responsible for passing on traits generation to generation Directs assembly of amino acids- to form precise enzymes with specific functions Heritability of DNA Inheritance: -Acquisition of traits by way of transmission of DNA from parent to offspring for countless generations Reproduction: -Mechanisms by which an organism produces offspring governed by instructions in DNA DNA Guides Development Development Transformation from fertilized egg to adult ( in mammals it occurs during gestation) Series of stages (Insects: Fertilized egg>larva>pupa> adult moth) Instructions for each stage are coded in DNA Energy Is the Basis of Metabolism Energy = Capacity to do work Metabolism = Reactions by which cells acquire and use energy to grow, survive, and reproduce Interdependencies among Organisms Producers: Make their own food (plants) Consumers: Depend on energy stored in tissues of producers (animals, humans) Decomposers: Break down remains and wastes (microbes) 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 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 Unity of Life: All organismsAre composed of the same substances Engage in metabolism Sense and respond to the environment Have the capacity to reproduce based on instructions in DNA If so much Unity, Why so many species? Diversity of Life: Organisms differ enormously in their structure, function and behavior Millions of living species Additional millions of species now extinct (99.9% extinct in 3.9 billion years) Classification scheme attempts to organize this diversity Scientific Names A two-part naming system was devised by Carolus Linnaeus First name is genus (plural, genera); Second name is species within genus Ex: Homo sapiens is the scientific name for human; genus is Homo species is sapiens -- Scarus gibbus is the scientific name for humphead parrotfish Three-Domain Classification Bacteria Archaea Eukarya (includes protists, plants, fungi, and animals) Life's Diversity Prokaryotes: Archaea and Bacteria These single-celled are and do not contain nucleus or other organelles Include producers, consumers, decomposers Eukaryotes: Eukarya (plants, fungi, animals, protists) DNA is inside a nucleus within the cell Most are larger and more complex than the prokaryotes Plants All are multi-celled, with roots, stems and leaves and most are photosynthetic producers Make up the food base for communities, especially on land Fungi Most are multicelled (some single celled), many parasites and pathogens. Consumers and mostly decomposers without fungal and bacterial decomposers, communities would be filled with wastes Their enzymes digest food outside (extracellularly) and absorb the digested material Animals Multicelled consumers Herbivores, Carnivores, Parasites and Scavengers Move about during at least some stage of their life Protists: Diverse single celled to multi-celled giant seaweeds Mutation: is the Source of Variation in traits Mutation = change in structure of DNA Basis for the variation in heritable traits Most are harmful- lead to cancer
Adaptive Trait A trait that gives the individual an advantage in survival or reproduction, under a given set of circumstances Evolution To biologists, evolution means genetically based heritable change in a line of descent over time. Charles Darwin discovered that- first populations increase (competition), second individuals differ in their traits and third the individuals with better traits to survive and reproduce will become common population it is by natural selection 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 Artificial Selection Breeders favor some form of traits over others (livestock; crops) Individuals exhibiting favored traits are bred Favored traits increase in the population Observations, Hypotheses, and Tests Observe phenomenon Develop hypotheses Make predictions Devise test of predictions Carry out test and analyze 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 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 Objective- to test if olestra, a synthetic fat, causes gastrointestinal cramps Prediction: If Olestra causes GI cramps, then people who eat chips made with olestra should end up with GI cramps Control group - for comparison-was given normal potato chips; 17.6% had GI cramps Experimental group variable being studied was given potato chips made with Olestra; 15.8% suffered from GI cramps; both groups had about the same %. Conclusion drawn: Eating Olestra potato chips does not cause intestinal distress Sampling error Non-representative sample skews results Minimize by using large samples