1-1 What Is Science? Copyright Pearson Prentice Hall

What Science Is and Is Not What is the goal of science? Copyright Pearson Prentice Hall

What Science Is and Is Not 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. Copyright Pearson Prentice Hall

What Science Is and Is Not Science is an organized way of using evidence to learn about the natural world. Copyright Pearson Prentice Hall

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. Copyright Pearson Prentice Hall

Thinking Like a Scientist The information gathered from observations is called data. Quantitative data Qualitative data Copyright Pearson Prentice Hall

Thinking Like a Scientist Scientists use data to make inferences. An inference is a logical interpretation based on prior knowledge or experience. Copyright Pearson Prentice Hall

Explaining and Interpreting Evidence A hypothesis is a proposed scientific explanation for a set of observations. A hypothesis may be ruled out or confirmed. Copyright Pearson Prentice Hall

Explaining and Interpreting Evidence Hypotheses are tested by performing controlled experiments or by gathering new data. Copyright Pearson Prentice Hall

Explaining and Interpreting Evidence Researchers often work in teams to analyze, review, and critique each other’s data and hypotheses. Copyright Pearson Prentice Hall

Science as a Way of Knowing Science is an ongoing process that involves: – asking questions – observing – making inferences – testing hypotheses Copyright Pearson Prentice Hall

How a Theory Develops How does a scientific theory develop? Copyright Pearson Prentice Hall

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. Copyright Pearson Prentice Hall

Major Theories in Biology  Germ Theory  Evolutionary Theory  Cell Theory  Gene Theory

Science as a Way of Knowing Scientific understanding is always changing. Good scientists are skeptics who question both existing ideas and new hypotheses. Copyright Pearson Prentice Hall

Science and Human Values An understanding of science and the scientific approach is essential to making intelligent decisions. Copyright Pearson Prentice Hall

Science and Human Values Decisions involve many factors besides scientific information, including: the society in which we live economic considerations laws moral principles Citizens decide what to do when they vote. Copyright Pearson Prentice Hall

Pseudo science looks like science but it is Not testable/falsifiable/refutable Relies on anecdotes, not experimental data Does not change in face of new evidence Uri Geller Magic water

1–1 Observations involving numbers are known as qualitative observations. hypothetical observations. quantitative observations. inferred observations. Copyright Pearson Prentice Hall

1–1 Which of the following shows the interaction of science and human values? the debate over the best way to produce electricity investigating how a manatee behaves Determining what causes a disease using a hypothesis to test an explanation Copyright Pearson Prentice Hall

1–1 A scientist takes paint chips from 10 apartments in a large building. She tests for the presence of lead in the paint and finds it in all 10 samples. She then concludes that lead paint is probably present in all 120 apartments in the building. This conclusion is an example of a scientific fact. a scientific error. proof. a reasonable inference. Copyright Pearson Prentice Hall

1–1 A possible explanation for a set of observations is known as data. a hypothesis. an inference. a result. Copyright Pearson Prentice Hall

1–1 A good scientific hypothesis must be correct. able to be tested. obvious. based on common sense. Copyright Pearson Prentice Hall

Designing an Experiment How do scientists test hypotheses? A hypothesis should be tested by an experiment in which only one variable is changed at a time. Copyright Pearson Prentice Hall

Designing an Experiment The process of testing a hypothesis includes: – Asking a question – Forming a hypothesis – Setting up a controlled experiment – Recording and analyzing results – Drawing a conclusion Copyright Pearson Prentice Hall

Designing an Experiment Setting Up a Controlled Experiment Manipulated/Independent variable Responding/Dependent variable Copyright Pearson Prentice Hall

When graphing, always title graph “Dependent variable” as a function of “Independent variable” If a scientist wants to examine how light levels affect tree growth, which is the dependent variable? Which is the independent variable? Which is X? Which is Y? Y as a function of X Copyright Pearson Prentice Hall

Designing an Experiment Asking a Question Many years ago, people wanted to know how living things came into existence. They asked: How do organisms come into being? Copyright Pearson Prentice Hall

Designing an Experiment Forming a Hypothesis One early hypothesis was spontaneous generation. For example, most people thought that maggots spontaneously appeared on meat. In 1668, Redi proposed a different hypothesis: that maggots came from eggs that flies laid on meat. Copyright Pearson Prentice Hall

Designing an Experiment Copyright Pearson Prentice Hall Redi’s Experiment Controlled Variables: jars, type of meat, Location, temperature, time Covered jars Uncovered jars

Designing an Experiment Copyright Pearson Prentice Hall Redi’s Experiment Manipulated Variable: Gauze covering that keeps flies away from meat Responding Variable: whether maggots appear Maggots appear. Several days pass. No maggots appear.

Designing an Experiment Drawing a Conclusion Scientists use the data from an experiment to evaluate a hypothesis and draw a valid conclusion. Copyright Pearson Prentice Hall

Repeating Investigations Spallanzani's Test of Redi's Findings Copyright Pearson Prentice Hall Gravy is boiled.

Repeating Investigations Spallanzani's Test of Redi's Findings Copyright Pearson Prentice Hall Flask is open. Flask is sealed.

Repeating Investigations Spallanzani's Test of Redi's Findings Copyright Pearson Prentice Hall Gravy is teeming with microorganisms. Gravy is free of microorganisms.

Repeating Investigations 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. Copyright Pearson Prentice Hall

Repeating Investigations Copyright Pearson Prentice Hall Pasteur’s Experiment Broth is boiled Broth is free of microorganisms for a year. Curved neck is removed. Broth is teeming with microorganisms.

Repeating Investigations The Impact of Pasteur’s Work Pasteur saved the French wine industry, which was troubled by unexplained souring of wine. He began to uncover the nature of infectious diseases, showing that they were the result of microorganisms. Copyright Pearson Prentice Hall

1–2 In an experiment, the variable that is deliberately changed is called the control. manipulated variable. responding variable. constant control Copyright Pearson Prentice Hall

1–2 The mistaken belief that living organisms can arise from nonliving matter is called biogenesis. Pasteur's theory. spontaneous generation. Spallanzani’s hypothesis. Copyright Pearson Prentice Hall

1–2 Which of the following was the manipulated variable in Redi’s experiment? the kind of meat used the temperature the jars were kept at the gauze covering on some jars the kind of fly that visited the jars Copyright Pearson Prentice Hall

1–2 A well-tested explanation that unifies a broad range of observations is a hypothesis. variable. control. theory. Copyright Pearson Prentice Hall

1–2 A scientific explanation does not become a theory until a majority of scientists agree with it. it has been supported by evidence from numerous investigations and observations. it is first proposed as an explanation. it is published in a textbook. Copyright Pearson Prentice Hall

What is Life? What are some characteristics of life? – Made up of cells – Reproduce – Based on universal genetic code – Grow and develop – Respond to environment – Obtain and use materials and energy – Maintain a stable internal environment – Taken as a group, living things evolve Copyright Pearson Prentice Hall

What is Life? Which of these are alive? – Virus? – Protein? – Fire? – Computer virus? – Mule? Copyright Pearson Prentice Hall

Leroy Me

19–2 Viruses Copyright Pearson Prentice Hall

What Is a Virus? Viruses are particles of nucleic acid, protein, and in some cases, lipids. Viruses can reproduce only by infecting living cells. Copyright Pearson Prentice Hall

What Is a Virus? Copyright Pearson Prentice Hall Head Tail sheath DNA T4 Bacteriophage Tobacco Mosaic Virus Influenza Virus RNA Membrane envelope Tail fiber RNA Capsid proteins Capsid Surface proteins

What Is a Virus? A typical virus is composed of a core of DNA or RNA surrounded by a protein coat. A capsid is the virus’s protein coat. Copyright Pearson Prentice Hall

Viral Infection Once the virus is inside the host cell, two different processes may occur. – Some viruses replicate immediately, killing the host cell. – Others replicate, but do not kill the host cell immediately. Copyright Pearson Prentice Hall

Viral Infection Copyright Pearson Prentice Hall Bacteriophage injects DNA into bacterium Bacteriophage DNA forms a circle Lytic Infection Lysogenic Infection

Viral Infection Lytic Infection In a lytic infection, a virus enters a cell, makes copies of itself, and causes the cell to burst. Copyright Pearson Prentice Hall

Viral Infection Copyright Pearson Prentice Hall

Viral Infection Copyright Pearson Prentice Hall

Viral Infection Copyright Pearson Prentice Hall

Viral Infection Lysogenic Infection Other viruses cause lysogenic infections in which a host cell makes copies of the virus indefinitely. In a lysogenic infection, a virus integrates its DNA into the DNA of the host cell, and the viral genetic information replicates along with the host cell's DNA. Copyright Pearson Prentice Hall

Viral Infection Copyright Pearson Prentice Hall

Viral Infection Copyright Pearson Prentice Hall

Viral Infection Copyright Pearson Prentice Hall

Viral Infection Copyright Pearson Prentice Hall

Retroviruses Retroviruses contain RNA as their genetic information. When retroviruses infect cells, they make a DNA copy of their RNA. This DNA is inserted into the DNA of the host cell. Copyright Pearson Prentice Hall

Viruses that contain RNA as their genetic information are known as prions. oncoviruses. retroviruses. bacteriophage. Copyright Pearson Prentice Hall

The first type of virus to be studied was the bacteriophage. tobacco mosaic virus. influenza virus. AIDS virus. Copyright Pearson Prentice Hall

Which of the following statements about viruses is true? Viruses appear similar to bacteria when studied with a light microscope. Viruses display the essential characteristics of living things. Viruses can reproduce independently if they contain DNA. Viruses cannot reproduce unless they infect a living cell. Copyright Pearson Prentice Hall

A virus integrates its DNA into the DNA of the host cell but remains inactive for a while in a lytic infection. a lysogenic infection. neither a lytic nor a lysogenic infection. retroviral infection. Copyright Pearson Prentice Hall

Retroviruses are considered unique because they have RNA in their capsid and not DNA. they have DNA in their capsid and not RNA. after infection of a host cell, their RNA makes DNA. after infection of a host cell, their DNA makes RNA. Copyright Pearson Prentice Hall