1.4 what is science? science is the systematic inquiry – through observation and experiment –...

1.4 What Is Science?

Science is the systematic inquiry – through observation and experiment – into the origins, structure, and behavior of living and nonliving environments


Science is based on the principle that all events have natural causes The belief that some events happen through supernatural forces

(e.g., the actions of Greek gods)

The belief that all events can be traced to natural causes that we can comprehend (natural causality)

Corollary: Evidence gathered from nature has not been deliberately distorted to fool us


The scientific method is an important tool of scientific inquiry The scientific method consists of six interrelated elements

ObservationQuestionHypothesisPredictionExperimentConclusion


The scientific method is an important tool of scientific inquiry (continued) Scientific inquiry is a rigorous method for making observations

The scientific method for inquiry follows six steps


The six steps of scientific inquiry

1. Observation of a specific phenomenon

2. The observation, in turn, leads to a question

3. The question leads to formulation of a hypothesis, based on previous observations, which is offered as an answer to the question


The six steps of scientific inquiry (continued)

4. The hypothesis leads to a prediction, which isthe expected outcome of testing if the hypothesis is correct

5. The prediction is tested by carefully designed additional observations or carefully controlled manipulations called experiments

6. The experiments produce results that either support or refute the hypothesis, allowing the development of a conclusion


Biologists test hypotheses using controlled experiments Two types of situations are established

A baseline or control situation in which all possible variables are held at a constant

An experimental situation in which one factor, variable, is manipulated to test the hypothesis to determine that this variable is the cause of an observation

Science is useless unless communicated

The scientific method is illustrated by experiments by Francesco Redi and Malte Andersson

Figure E1-1 The experiment of Francesco Redi illustrates the scientific method

Observation:

Question:

Hypothesis:

Prediction:

Experiment:

Conclusion:

Experimental variable:

Controlled variables:

Experimental situationControl situation

Results

Leave the jaruncovered

Leave exposedfor several days

Flies swarm aroundand maggots appear

Cover the jarwith gauze

Leave coveredfor several days

Flies are kept fromthe meat;

no maggots appear

gauze prevents theentry of flies

time, temperature,place

Obtain identical pieces of meat and two identical jars

Place meat in each jar

IF the hypothesis is correct, THEN keeping the flies away from the meatwill prevent the appearance of maggots.

The experiment supports the hypothesis that flies are the source ofmaggots and that spontaneous generation of maggots does not occur.

Flies swarm around meat left in the open; maggots appear on the meat.

Where do maggots on the meat come from?

Flies produce the maggots.

Figure E1-2 The experiment of Malte AnderssonObservation:

Question:

Hypothesis:

Prediction:

Experiment:

Conclusion:

Experimentalvariable:

Controlledvariables:

Experimental groupsControl groups

Results

Do notchange the tail

Release the males,wait a week,

count the nests

Average ofabout one nest

per male

Male widowbirds have extremely long tails.

Why do males, but not females, have such long tails?

Males have long tails because females prefer to mate with long-tailed males.

IF females prefer long-tailed males, THEN males with artificially lengthened tails will attract more mates.

Divide male birdsinto four groups

Manipulate thetails of the males

length of tail

location, season,time, weather

Cut the tail andre-glue in place


count the nests

Average ofabout one nest

per male

Cut the tail to half ofthe original length


count the nests

Average of lessthan half a nest

per male

Add feathers todouble the tail length


count the nests

Average ofAbout two nests

per male

The hypothesis that female widowbirds prefer to mate with long-tailed males (and are less likely to matewith short-tailed males) is supported.


Scientific theories have been thoroughly tested A scientific theory is a general and reliable explanation of

important natural phenomena that has been developed through extensive and reproducible observations and experiments

A scientific theory is best described as a natural law, a basic principle derived from the study of nature, which has never been disproven by scientific inquiry


Scientific theories have been thoroughly tested (continued) The cell theory (that all living organisms are composed of cells) and

the theory of evolution are fundamental to the study of biology

Natural causality is the principle that all events can be traced to natural causes

Natural laws apply to every time and place

Scientific inquiry is based on the assumption that people perceive natural events in similar ways


Scientific theories have been thoroughly tested (continued) New scientific evidence may prompt radical revision of existing

theory

For example, the discovery of prions


Scientific theories have been thoroughly tested (continued) Before 1980, all known infectious diseases contained DNA or

RNA In 1982, Stanley Prusiner showed that the infectious sheep

disease scrapie is caused by a protein (a “protein infectious particle,” or prion)

Prions have since been shown to cause “mad cow disease” and diseases in humans

The willingness of scientists to revise accepted belief in light of new data was critical to understanding and expanding the study of prions


Scientific theories involve both inductive and deductive reasoning Inductive reasoning is used in the development of scientific

theories

A generalization is created from many observations that support it and none that contradict it

For example, the theory that Earth exerts gravitational forces on objects began from repeated observations of objects falling downward toward Earth and from no observations of objects falling upward away from Earth


Scientific theories involve both inductive and deductive reasoning (continued) Deductive reasoning is the process of generating hypotheses

based on a well-supported generalization (such as a theory)

For example, based on the cell theory, any newly discovered organism would be expected to be composed of cells


Scientific theories are formulated in ways that can potentially be disproved Basic principles of science are referred to as theories because

theories can be disproved or falsified

Falsifying theories is distinctly different between scientific theories and faith-based beliefs

“Each creature on Earth was separately created” cannot be subjected to scientific inquiry because it is a belief rooted in faith


Science is a human endeavor Human personality traits are part of “real science”

Scientists, like other people, may be driven by pride, ambition, or fear

Scientists sometimes make mistakes

Accidents, lucky guesses, intellectual powers, and controversies with others contribute strongly to scientific advances


Science is a human endeavor (continued) In the 1920s, bacteriologist Alexander Fleming grew bacteria in

cultures

One of the bacterial cultures became contaminated with a mold

Fleming was about to destroy the culture when he noticed the mold (Penicillium) inhibited bacterial growth in the culture


Science is a human endeavor (continued) Fleming hypothesized that the mold produced an antibacterial

substance

Further tests using broth from pure Penicillium cultures lead to the discovery of the first antibiotic, penicillin

1.4 what is science? science is the systematic inquiry – through observation and experiment –...

Documents

scientific method observation

observation science

steps of scientific

source of maggots

open maggots

appearance of maggots

rigorous method

systematic inquiry