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Intro to Biology. The goal of science is to: investigate and understand the natural world. explain events in the natural world. use those explanations to make useful predictions. Thinking Like a Scientist Scientific thinking begins with observation.
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The goal of science is to: • investigate and understand the natural world. • explain events in the natural world. • use those explanations to make useful predictions.
Thinking Like a Scientist • Scientific thinking begins with observation. • Observation is the process of gathering information about events or processes in a careful, orderly way.
The information gathered from observations = data. • Quantitative data -- expressed as numbers, (counting or measuring) • Qualitative data -- descriptive -- characteristics that can’t easily be measured.
Scientists use data to make inferences. • An inference is a logical interpretation based on prior knowledge or experience.
Hypothesis • a proposed scientific explanation for a set of observations. • may be ruled out or confirmed. • must be testable • Hypotheses are tested by performing controlled experiments or by gathering new data.
How do scientists test hypotheses? • Hypotheses should be tested by a controlled experiment • only one variable is changed at a time • all other variables should be kept unchanged, or controlled.
Designing an Experiment • Asking a question • Forming a hypothesis • Setting up a controlled experiment • Recording and analyzing results • Drawing a conclusion
Asking a Question • Many years ago, people wanted to know how living things came into existence. They asked: • How do organisms come into being?
Forming a Hypothesis • Early hypothesis: spontaneous generation • life could come from nonliving matter • Ex., most people thought that maggots spontaneously appeared on meat. • In 1668, Redi proposed a hypothesis: that maggots came from eggs that flies laid on meat.
Setting Up a Controlled Experiment • The variable that is deliberately changed is called the manipulated variable. • The variable that is observed and that changes in response to the manipulated variable is called the responding variable.
Redi’s Experiment Uncovered jars Covered jars Controlled Variables: jars, type of meat, location, temperature, time
Redi’s Experiment Manipulated Variable: Gauze covering that keeps flies away from meat Severaldays pass. Responding Variable: whether maggots appear No maggots appear. Maggots appear.
Recording and Analyzing Results • Scientists keep written records of their observations, or data. • Sometimes drawings are used to record certain kinds of observations.
Drawing a Conclusion • Scientists use the data from an experiment to evaluate a hypothesis and draw a valid conclusion. • Redi’s results supported the hypothesis that maggots were produced by flies, not spontaneous generation.
Repeating Investigations • Scientists repeat experiments to be sure that the results match those already obtained.
Spallanzani's Test of Redi's Findings Gravy is boiled. Gravy is boiled.
Spallanzani's Test of Redi's Findings Flask is sealed. Flask is open.
Spallanzani's Test of Redi's Findings Gravy is teemingwith microorganisms. Gravy is free ofmicroorganisms.
Pasteur's Test of Spontaneous Generation • Louis Pasteur conclusively disproved the hypothesis of spontaneous generation. • Pasteur showed that all living things come from other living things.
Pasteur’s Experiment Broth is freeof microorganismsfor a year. Curved neck isremoved. Broth is teeming with microorganisms. Broth isboiled
When Experiments Are Not Possible • It is not always possible to do an experiment to test a hypothesis. For example: • Wild animals must be observed without disturbing them. • Ethical considerations prevent some experiments. • By carefully planning alternative investigations, scientists can discover reliable patterns that add to scientific understanding.
How a Theory Develops • As evidence from numerous investigations builds up, a hypothesis may become so well supported that scientists consider it a theory. • In science, the word theory applies to a well-tested explanation that unifies a broad range of observations.
BIOLOGY: the study of living things • Characteristics of Living Things • No single characteristic is enough to describe a living thing. • Some nonliving things share one or more traits with living things.
Living things share the following characteristics: • made up of units called cells • reproduce • based on a universal genetic code • grow and develop • obtain and use materials and energy • respond to their environment • maintain a stable internal environment • change over time
Living things are made up of cells. • A cell is the smallest unit of an organism that can be considered alive. • Living things reproduce. • Sexual reproduction: cells from two different parents unite to form the first cell of the new organism. • Asexual reproduction: a single parent produces offspring that are identical to itself.
Living things grow and develop. • During an organism’s development, cells differentiate, which means that the cells look different from one another and perform different functions. • Living things are based on a universal genetic code. • Organisms store the information they need to live, grow, and reproduce in a genetic code in a molecule called DNA
Living things obtain materials and use energy. • The combination of chemical reactions through which an organism builds up or breaks down materials is called metabolism. • Living things respond to their environment. • A stimulus is a signal to which an organism responds.
Living things maintain a stable internal environment. • Although conditions outside an organism may change, conditions inside an organism tend to remain constant. • This process is called homeostasis. • Livings things change over time • Over many generations, groups (not individuals) of organisms typically evolve.
A Common Measurement System 1 kilogram (kg) = 1000 grams (g) 1 gram = 1000 milligrams (mg) 1000 kilograms = 1 metric ton (t) 1 meter (m) = 100 centimeters (cm) 1 meter = 1000 millimeters (mm) 1000 meters = 1 kilometer (km) 1 liter (L) = 1000 milliliters (mL) 1 liter = 1000 cubic centimeters (cm3) 00C = freezing point of water 1000C = boiling point of water
