Intro to Intro to BiologyBiology

The goal of science is to:The goal of science is to:

•investigate and investigate and understand the natural understand the natural world.world.

•explain events in the explain events in the natural world.natural world.

•use those explanations to use those explanations to make useful predictions.make useful predictions.

Thinking Like a ScientistThinking Like a Scientist

Scientific thinking begins with Scientific thinking begins with observation. observation.

ObservationObservation is the process of is the process of gathering information about gathering information about events or processes in a careful, events or processes in a careful, orderly way. orderly way.

The The informationinformation gathered from gathered from observations =observations = data. data.

•Quantitative data Quantitative data -- -- expressed as numbers, expressed as numbers, (counting or measuring)(counting or measuring)

•Qualitative data Qualitative data -- -- descriptive -- characteristics descriptive -- characteristics that can’t easily be measured.that can’t easily be measured.

Scientists use Scientists use datadata to make to make inferences.inferences.

An An inferenceinference is a logical is a logical interpretation based on prior interpretation based on prior knowledge or experience.knowledge or experience.

HypothesisHypothesis

•a proposed scientific explanation a proposed scientific explanation for a set of observations. for a set of observations.

•may be ruled out or confirmed.may be ruled out or confirmed.

•must be testablemust be testable

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

How do scientists test How do scientists test hypotheses?hypotheses?

Hypotheses should be tested by a Hypotheses should be tested by a controlled experimentcontrolled experiment

• only one variable is only one variable is changed at a timechanged at a time

• all other variables should be all other variables should be kept unchanged, or controlledkept unchanged, or controlled..

Designing an ExperimentDesigning an Experiment

•Asking a questionAsking a question

•Forming a hypothesisForming a hypothesis

•Setting up a controlled Setting up a controlled experimentexperiment

•Recording and analyzing resultsRecording and analyzing results

•Drawing a conclusionDrawing a conclusion

Asking a QuestionAsking a Question

•Many years ago, people wanted Many years ago, people wanted to know how living things came to know how living things came into existence. They asked:into existence. They asked:

•How do organisms come into How do organisms come into being? being?

Forming a HypothesisForming a Hypothesis

•Early hypothesis: Early hypothesis: spontaneous spontaneous generationgeneration

•life could come from nonliving life could come from nonliving mattermatter

Ex., most people thought that Ex., most people thought that maggots spontaneously maggots spontaneously appeared on meat.appeared on meat.

•In 1668, Redi proposed a hypothesis: In 1668, Redi proposed a hypothesis: that maggots came from eggs that that maggots came from eggs that flies laid on meat.flies laid on meat.

Setting Up a Controlled ExperimentSetting Up a Controlled Experiment

The variable that is deliberately The variable that is deliberately changed is called the changed is called the manipulated manipulated variablevariable..

The variable that is The variable that is observedobserved and that and that changeschanges in response to the in response to the manipulated variable is called the manipulated variable is called the responding variableresponding variable..

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.

Redi’s Experiment

Recording and Analyzing Recording and Analyzing ResultsResults

•Scientists keep written records of Scientists keep written records of their observations, or data.their observations, or data.

•Sometimes drawings are used to Sometimes drawings are used to record certain kinds of record certain kinds of observations.observations.

Drawing a ConclusionDrawing a Conclusion

•Scientists use the data from an Scientists use the data from an experiment to evaluate a experiment to evaluate a hypothesis and draw a valid hypothesis and draw a valid conclusion.conclusion.

•Redi’s results supported the Redi’s results supported the hypothesis that maggots were hypothesis that maggots were produced by flies, not produced by flies, not spontaneous generation.spontaneous generation.

Repeating InvestigationsRepeating Investigations

•Scientists repeat experiments to Scientists repeat experiments to be sure that the results match be sure that the results match those already obtained.those already obtained.

Spallanzani's Test of Redi's Findings Spallanzani's Test of Redi's Findings 

Gravy is boiled. Gravy is boiled.

Spallanzani's Test of Redi's Findings Spallanzani's Test of Redi's Findings 

Flask is open. Flask is sealed.

Spallanzani's Test of Redi's Findings Spallanzani's Test of Redi's Findings 

Gravy is teemingwith microorganisms.

Gravy is free ofmicroorganisms.

Pasteur's Test of Pasteur's Test of Spontaneous GenerationSpontaneous Generation

•Louis Pasteur conclusively Louis Pasteur conclusively disproved the hypothesis of disproved the hypothesis of spontaneous generation.spontaneous generation.

•Pasteur showed that all living Pasteur showed that all living things come from other living things come from other living things. things.

Pasteur’s Experiment

Broth is boiledBroth is freeof microorganismsfor a year.

Curved neck isremoved.

Broth is teeming with microorganisms.

When Experiments Are Not PossibleWhen Experiments Are Not Possible

•It is not always possible to do an It is not always possible to do an experiment to test a hypothesis. For experiment to test a hypothesis. For example:example:

•Wild animals must be observed without Wild animals must be observed without disturbing them.disturbing them.

•Ethical considerations prevent some Ethical considerations prevent some experiments.experiments.

•By carefully planning alternative By carefully planning alternative investigations, scientists can discover investigations, scientists can discover reliable patterns that add to scientific reliable patterns that add to scientific understanding.understanding.

How a Theory DevelopsHow a Theory Develops

As evidence from numerous As evidence from numerous investigations builds up, a hypothesis investigations builds up, a hypothesis may become so well supported that may become so well supported that scientists consider it a theory.scientists consider it a theory.

In science, the word In science, the word theorytheory applies to applies to a well-tested explanation that unifies a a well-tested explanation that unifies a broad range of observations.broad range of observations.

BIOLOGY: BIOLOGY: the study of living thingsthe study of living things

Characteristics of Living ThingsCharacteristics of Living Things

•No single characteristic is No single characteristic is enough to describe a living thing.enough to describe a living thing.

•Some nonliving things share one Some nonliving things share one or more traits with living things.or more traits with living things.

Living things share the following Living things share the following characteristics:characteristics:

•made up of units called cellsmade up of units called cells

•reproducereproduce

•based on a universal genetic codebased on a universal genetic code

•grow and developgrow and develop

•obtain and use materials and energyobtain and use materials and energy

•respond to their environmentrespond to their environment

•maintain a stable internal environmentmaintain a stable internal environment

•change over timechange over time

Living things are made up of cellsLiving things are made up of cells..

A cell is the smallest unit of an A cell is the smallest unit of an organism that can be considered alive.organism that can be considered alive.

Living things reproduce.Living things reproduce.

Sexual reproduction: cells from two Sexual reproduction: cells from two different parents unite to form the first different parents unite to form the first cell of the new organism.cell of the new organism.

Asexual reproduction: a single parent Asexual reproduction: a single parent produces offspring that are identical to produces offspring that are identical to itself.itself.

Living things grow and develop.Living things grow and develop.

During an organism’s development, During an organism’s development, cells differentiate, which means that cells differentiate, which means that the cells look different from one the cells look different from one another and perform different another and perform different functions.functions.

Living things are based on a Living things are based on a universal genetic code.universal genetic code.

Organisms store the information they Organisms store the information they need to live, grow, and reproduce in a need to live, grow, and reproduce in a genetic code in a molecule called genetic code in a molecule called DNADNA

Living things obtain materials and Living things obtain materials and use energy.use energy.

The combination of chemical reactions The combination of chemical reactions through which an organism builds up or through which an organism builds up or breaks down materials is called breaks down materials is called metabolism.metabolism.

Living things respond to their Living things respond to their environment.environment.

A stimulus is a signal to which an A stimulus is a signal to which an organism responds.organism responds.

Living things maintain a stable Living things maintain a stable internal environment.internal environment.

Although conditions outside an Although conditions outside an organism may change, conditions inside organism may change, conditions inside an organism tend to remain constant.an organism tend to remain constant.

This process is called homeostasis.This process is called homeostasis.

Livings things change over timeLivings things change over time

Over many generations, groups (not Over many generations, groups (not individuals) of organisms typically individuals) of organisms typically evolve.evolve.

1 meter (m) = 100 centimeters (cm)1 meter = 1000 millimeters (mm)1000 meters = 1 kilometer (km)

1 kilogram (kg) = 1000 grams (g)1 gram = 1000 milligrams (mg)1000 kilograms = 1 metric ton (t)

00C = freezing point of water1000C = boiling point of water

1 liter (L) = 1000 milliliters (mL)1 liter = 1000 cubic centimeters (cm3)

A Common Measurement A Common Measurement SystemSystem