Transcript Chapter 1
The Science of Biology Chapter 1 1-1 What is the goal of Science? • Investigate and understand nature • Explain events in nature • Use those explanations to make useful predictions What is Science? • An organized way of using evidence to learn about the natural world • Body of knowledge that scientists have built up after years of using this process The Scientific Method 1) 2) 3) 4) 5) Stating Problem/Observations Hypothesis Experimentation Data collection and analysis Conclusion a. b. c. d. e. Answer to problem Validity (restate data) Prove/Disprove hypothesis Errors Improvements Observations *using the senses to gather/collect data Quantitative -observations based on numbers or quantities Qualitative -observations based on description Ex.Counting/measuring 7 birds, 14 miles, 200 people Ex. Color/texture blue neck, large teeth, soft cushion Objective vs. Subjective Observations • Objective-without a predetermined point of view, unbiased • Subjective-with a predetermined point of view, biased (dangerous-Jews inferior to Germans) Hypothesis • A possible answer to a scientific question or an explanation for a series of observations. Ex. Use hypothesis to discover how infected disease was contracted: -spread by human contact? -spread through insect bites? -spread through contaminated air/water/food? **All of these are then tested to find the correct explanation. Experimentation • • Controlled steps used to test the hypothesis Controlled Experiment-only 1 variable is changed and all others are kept unchanged, or controlled. Variables • Independent/Manipulated: the one that is deliberately changed/tested (only 1); on X axis. • Dependent/Responding: the one that is measured and changes in RESPONSE to the independent variable; on Y axis. • Controls: those that remain constant/unchanged Data Collection and Analysis • Clear, precise, and objective – Displayed in table/graph • Understanding and making sense of observations – What does your data tell you about the experiment? Conclusion • Analyzing data brings you to a final decision/conclusion • Evidence found supports or refutes hypothesiswill test correct or wrong 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 no independent variable present • Experimental group – Independent variable present and being tested 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 1-2 Spontaneous Generation Belief that living things arose from non-living things Examples: Maggots come from meat Mice from wheat Beetles from cow dung Their Explanation… **Gods, witchcraft, mythology, devil Francesco Redi and Spontaneous Generation Section 1-2 OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat. HYPOTHESIS: Flies produce maggots. PROCEDURE Uncovered jars Controlled Variables: jars, type of meat, location, temperature, time Covered jars Several days pass Independent Variables: gauze covering that keeps flies away from meat Dependent Variable: whether maggots Maggots appear No maggots appear appear CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur. What is Redi’s Conclusion? • Spontaneous generation does not occur. The Return of Spontaneous Generation Anton van Leeuwenhoek – uses a microscope to find tiny organisms swimming in pond water. “animalcules” John Needham (mid 1700’s) performs an experiment that refutes Redi Lazzaro Spallanzani – improves Needham’s experiment Figure 1-10 Spallanzani’s Experiment Section 1-2 What are the controlled variables? What are the independent variables? Gravy is boiled. Flask is open. Gravy is teeming with microorganisms. Gravy is boiled. Flask is sealed. Gravy is free of microorganisms. What are the dependent variables? Controlled variables: Gravy, flask, heat Independent variables: sealed flask Dependent variables: presence/absence of microorganisms The debate continues In the 1800’s some believe the air contained a “life force” perpetuating the belief of spontaneous generation. Louis Pasteur –1864, his experiment finally disproved spontaneous generation Figure 1-11 Pasteur’s Experiment Section 1-2 Broth is boiled. Broth is free of microorganisms for a year. Curved neck is removed. Broth is teeming with microorganisms. Figure 1-11 Pasteur’s Experiment Broth is boiled. Broth is free of microorganisms for a year. Curved neck is removed. Broth is teeming with microorganisms. Figure 1-11 Pasteur’s Experiment Broth is boiled. Broth is free of microorganisms for a year. Curved neck is removed. Broth is teeming with microorganisms. Pasteur’s Conclusions • All living things must come from other living things. • Opening the jar (Redi) exposes the contents to come in contact with organisms in the air, just as breaking neck of flask • (pg.13)What improvement did Pasteur make to Redi’s experiment? What is a Theory? A well tested explanation that unites many observations (evidence builds up to make hypothesis very well supported) Can be proven wrong when new data arises to refute it. May be revised or replaced by a more useful explanation. 1-3 Studying Life • What do all living things have in common? List 5 things that all living things do: Is a hurricane alive? Are flowers alive? Is a fire alive? Is a dragon fly alive? Is a river alive? Is a crowd alive? • • • • • • • • Characteristics of Living Things: Made of units called cells Reproduce Based on universal genetic code Grow and develop Obtain/use materials and energy Respond to environment Maintain stable internal environment Change over time Living Things are Made of Cells A Cell • Collection of living matter enclosed by barrier separating the cell from its surroundings. • Smallest units of an organism that can be considered alive. • Small size, but highly organized and complex. Asexual Reproduction New organism has a single parent (ex. Budding hydra) Sexual Reproduction 2 cells from different parents unite to produce new organism (ex. Sperm and egg) Universal Genetic Code **Everything living is based on this the molecule of inheritance Growth and Development Required for Life… Metabolism -chemical reactions an organism uses to build up and break down materials -how cells acquire and use energy to grow and survive (ex. Digestion, making proteins) Homeostasis -keeping the internal conditions of an organism stable (ex. Body temperature, breathing, heart rate) Nothing Lives Without Energy Energy = Capacity to do work Homeostasis • Maintenance of internal environment within range suitable for cell activities • Ex. pancreas maintains level of sugar in blood by secreting hormones 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 Evolution - as a group all living things change over time Evolution • Genetically based change in a line of descent over time • Population changes, not individuals Figure 1-21 Levels of Organization Biosphere The part of Earth that contains all ecosystems Ecosystem Community and its nonliving surroundings Biosphere Hawk, snake, bison, prairie dog, grass, stream, rocks, air Community Populations that live together in a defined area Hawk, snake, bison, prairie dog, grass Population Group of organisms of one type that live in the same area Bison herd Figure 1-21 Levels of Organization continued Organism Individual living thing Groups of Cells Tissues, organs, and organ systems Bison Nervous tissue Cells Brain Nervous system Smallest functional unit of life Nerve cell Molecules Groups of atoms; smallest unit of most chemical compounds Water DNA What are the different levels of organization in Biology? Smallest to Largest Atom • Smallest unit of an a element that retains the properties of that element Molecules - groups of atoms Organelle • Membrane-bound internal compartment for specialized reactions • Not found in most prokaryotic cells Cells - smallest functional unit of life Tissues Organs Organ Systems Organism - an individual living thing Population - group of organisms of one type (species) living in the same area Community - Populations that live together in a defined area Ecosystem - community and its nonliving surroundings Biosphere - Part of the Earth that contains all ecosystems 1-4 Tools and Procedures Metric System-SI-International System of Units • To collect data and perform experiments • Decimal system of units scaled on multiples of 10 • Measures: length, mass, volume, and temperature How can a graph help biologists to organize this data? Microscopes-produce magnified images of structures too small for naked eye • Light Microscopeproduce magnified images by focusing visible light rays. • Up to 1000 times. • Live and dead organisms • Fig. 1-25 (compound light microscope) • Electron Microscopesproduce magnified images by focusing beams of electrons. • Form images 1000 times more detailed than light microscope. • • • Fig. 1-26 Only dead organisms. Have no color. Why?