1-1 What Is Science? Copyright Pearson Prentice Hall.

1-1 What Is Science?

Copyright Pearson Prentice Hall

What Science Is and Is Not

What Science Is and Is NotWhat is the goal of science?



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.



Science is an organized way of using evidence to learn about the natural world.


Thinking Like a Scientist

Thinking Like a ScientistScientific 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 is called data.

• Quantitative data• Qualitative data



Scientists use data to make inferences.An inference is a logical interpretation based on prior knowledge or experience.


Explaining and Interpreting Evidence

Explaining and Interpreting EvidenceA hypothesis is a proposed scientific explanation for a set of observations.

A hypothesis may be ruled out or confirmed.



Hypotheses are tested by performing controlled experiments or by gathering new data.



Researchers often work in teams to analyze, review, and critique each other’s data and hypotheses.


Science as a Way of Knowing

Science as a Way of KnowingScience is an ongoing process that involves:

– asking questions– observing– making inferences– testing hypotheses


How a Theory Develops

How does a scientific theory develop?


How a Theory Develops

How a Theory DevelopsAs 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.



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.


Science and Human Values

Science and Human ValuesAn understanding of science and the scientific approach is

essential to making intelligent decisions.


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.



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

http://www.youtube.com/watch?v=E7OH10_V244&feature=related

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Observations involving numbers are known as • qualitative observations.• hypothetical observations.• quantitative observations.• inferred observations.


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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


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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.


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A possible explanation for a set of observations is known as

• data.• a hypothesis.• an inference.• a result.


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A good scientific hypothesis must be• correct.• able to be tested.• obvious.• based on common sense.


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.



Designing an ExperimentThe process of testing a hypothesis includes:

– Asking a question– Forming a hypothesis– Setting up a controlled experiment– Recording and analyzing results– Drawing a conclusion



Setting Up a Controlled Experiment

Manipulated/Independent variable

Responding/Dependent variable


• 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



Asking a QuestionMany years ago, people wanted to know how living things came into existence. They asked:

How do organisms come into being?



Forming a HypothesisOne 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.




Redi’s Experiment

Controlled Variables:jars, type of meat,Location, temperature,time

Covered jarsUncovered jars



Redi’s Experiment

Manipulated Variable:Gauze covering that keeps flies away from meat

Responding Variable:whether maggots appear Maggots appear.

Severaldays pass.

No maggots appear.


Drawing a ConclusionScientists use the data from an experiment to evaluate a hypothesis and draw a valid conclusion.


Repeating Investigations

Spallanzani's Test of Redi's Findings


Gravy is boiled. Gravy is boiled.




Flask is open. Flask is sealed.




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 boiledBroth is freeof microorganismsfor a year.

Curved neck isremoved.

Broth is teeming with microorganisms.


The Impact of Pasteur’s WorkPasteur 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.


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In an experiment, the variable that is deliberately changed is called the

• control.• manipulated variable.• responding variable.• constant control


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The mistaken belief that living organisms can arise from nonliving matter is called

• biogenesis.• Pasteur's theory.• spontaneous generation.• Spallanzani’s hypothesis.


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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


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A well-tested explanation that unifies a broad range of observations is a

• hypothesis.• variable.• control.• theory.


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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.


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


What is Life?

• Which of these are alive?– Virus?– Protein?– Fire?– Computer virus?– Mule?



Leroy

Me

19–2 Viruses


What Is a Virus?

What Is a Virus?Viruses are particles of nucleic acid, protein, and in some cases, lipids.

Viruses can reproduce only by infecting living cells.


What Is a Virus?


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.


Viral Infection

Viral InfectionOnce 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.


Viral Infection


Bacteriophage injects DNA into bacterium

Bacteriophage DNA forms a circle

Lytic Infection Lysogenic Infection

Viral Infection

Lytic InfectionIn a lytic infection, a virus enters a cell, makes copies of itself, and causes the cell to burst.


Viral Infection


Viral Infection


Viral Infection


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.


Viral Infection


Viral Infection


Viral Infection


Viral Infection



RetrovirusesRetroviruses

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.


Viruses that contain RNA as their genetic information are known as

• prions.• oncoviruses.• retroviruses.• bacteriophage.


The first type of virus to be studied was the • bacteriophage.• tobacco mosaic virus.• influenza virus.• AIDS virus.


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.


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.


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.


1-1 What Is Science? Copyright Pearson Prentice Hall.

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