the science of biology— an introduction

The Science of Biology—An Introduction

Chapter 1

What is science?Science is built up of facts, as a house is built of stones; but an accumulation of facts is no more a science than a heap of stones is a

house.  ~Henri Poincaré,Science and Hypothesis,

1905

The whole of science is nothing more than a refinement of everyday thinking. 

~Albert EinsteinMen love to wonder, and that is the seed of science. 

~Ralph Waldo Emerson Science is organized knowledge.Herbert Spencer (1820-1903)

Science is the systematic classification of experience.George Henry Lewes (1817-78) English writer and critic.

[Science is] a great game. It is inspiring and refreshing. The playing field is the

universe itself.Isidor Isaac Rabi (1898-1988) U. S.

physicist. Nobel prize 1944.

[Science is] not belief, but the will to find out.Anonymous

In essence, science is a perpetual search for an intelligent and integrated comprehension of the

world we live in.Cornelius Bernardus Van Neil (1897- ) U. S.

microbiologist.

What science is and is not The goal of science is to investigate

and understand the natural world, to explain events in the natural world, and to use those explanations to make useful predictions.

Deals only with natural world

Collect and organize info in careful, orderly way

Looks for patterns and connections between events

Proposed explanations can be tested by examining evidence

Organized way of using evidence to learn about the natural world

Also, the body of knowledge we have built up over time using this process

Thinking like a scientist

Make careful, orderly observations/ ask questions

Form testable hypotheses Design appropriate

experiments/testsEquipped with his five senses, man explores

the universe around him and calls the adventure Science.  ~Edwin Powell

Hubble, The Nature of Science, 1954

Perform tests carefully Gather data methodically Record and analyze data

An experiment is a question which science poses to Nature, and a measurement is the recording of Nature's answer. 

~Max Planck, Scientific Autobiography and Other Papers, 1949

Draw a conclusion Publish (repeatable if

desired) Reform/refine

hypotheses, go through process again

Science is always wrong.  It never solves a problem without creating

ten more.  ~George Bernard Shaw

DataQuantitative data-

“quantity”; can count or measure results in numbers

Qualitative data- “quality”; descriptive, observational

Inference- logical interpretation based on prior knowledge/data

Hypothesis

Proposed scientific explanation for a set of observations

Must be testable Should be generated based on prior

knowledge and inference Often framed as an “if… then”

statement

Conclusion

To be valid; must be base on logical interpretation of reliable, repeatable data

Must consider possible sources of experimental error

Science as a way of knowing Science is not a set of

unchanging truths or knowledge; it is an ongoing process

Scientific understanding is always changing due to new tools, techniques and discoveries

If an older theory is discarded, it does not mean science has failed, only that it continues to succeed in advancing understanding

Good scientists are skeptics that question both existing ideas and new hypotheses, and continually evaluate the strengths and weaknesses of each.

They must be open minded to change, based on data.

The scientist is not a person who gives the right answers, he's one who asks the right questions. 

~Claude Lévi-Strauss, Le Cru et le cuit, 1964

Science is limited- it does not include value judgments, opinions or un-testable beliefs; it can only be concerned with what can be tested.

Science can only ascertain what is, but not what should be, and outside of its domain value judgments of all kinds

remain necessary.

Albert Einstein (1879-1955) U. S. physicist, born in

Germany.

Science as a way of knowing is based on the idea that the whole physical universe is a system: a collection of parts and processes and smaller systems that interact and are interconnected.

Scientific information can inform understanding and decision making on every level, from the personal, to the societal, governmental and international levels.

When we try to pick out anything by itself, we find it is tied to everything else in the universe.

John Muir (1838-1914) U. S. naturalist, explorer.

How Scientists Work

People have always sought to explain the world around them, but many early explanations of natural phenomena were not scientific.

Asking a question– step 1 How do living things come into

being?

Forming a hypothesis– step 2 Early hypothesis = spontaneous

generation

Aristotle- (384-322BC) in History of Animals, he talks about the idea of spontaneous generation— the idea that living things can come from non-living things.

People held this belief long before Aristotle, up until the mid-1800s!

Spontaneous generation of honey bees from dead ox

The Theory of Miasma “Bad Air”

Diseases such as cholera, chlamydia and the Black Death

People didn’t understand the concept of germ theory in ancient times and this was actually part of class segregation as well.

Click icon to add pictureDoctors would use nice smelling flowers and herbs to block the “bad air” and put them in the “beaks.”

But they would have their hands exposed or other parts of their body where bacteria and viruses could collect and be transferred to a patient.

• *Assassin's Creed**• Ever notice how the

doctors are dressed?

A New Hypothesis 1668– Italian physician

Francesco Redi developed the hypothesis that living things came from other living things– tested his idea on maggots.

People believed that maggots were spontaneously generated from rotting meat.

Redi hypothesized that instead, perhaps flies laid eggs on spoiled meat that were too small to see, and the maggots came from these eggs.

He set up an experiment to test this hypothesis.

Setting up a Controlled ExperimentVariables- the factors in an

experiment that can change. A hypothesis should be tested by an

experiment in which only one variable is changed at a time.

All other variables should be kept the same, or controlled.

Called a controlled experiment.

Manipulated variable = independent variable- the variable that is deliberately changed.

Responding variable = dependent variable- the variable that is observed (measure results from this variable)- changes in response to the manipulated variable.

DRY MIX

D = dependent R = responding Y = Y axis

M = manipulated I = independent X = X axis

Back to Redi… Based on his hypothesis, he

predicted that if flies were kept away from meat, maggots would not appear.

Recording and Analyzing Results

Experimental data must be recorded, in words, pictures, tables, etc. either by hand or on a computer.

The data must be analyzed for meaning, and is often compiled in graphs for visual analysis and to see trends in data.

Drawing a Conclusion

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

Publishing and Repeating Investigations Key assumption in science:

experimental results can be reproduced because nature behaves in a consistent manner.

A controlled experiment performed the same way every time should always yield the same results.

Communicating how an experiment was done allows scientists to verify each others’ work.

Most scientists publish their findings in scientific journals to be reviewed by others.

Students write lab reports.

Redi wrote his findings in a book. At the time, many people did not

believe Redi’s conclusion– more tests were performed to verify his findings.

Needham’s Test of Redi’s Findings Around the time of Redi’s

experiments, early microscopes turned up the first descriptions of microscopic life– so called “animalcules.”

1700’s– John Needham sets out to disprove Redi’s findings (and prove spontaneous generation).

Needham’s Experiment Sealed a bottle of gravy. Heated it to kill “animalcules”. Waited a few days. Saw living things swarming inside

the bottle. Concluded the gravy produced the

living things.It is a capital mistake to theorise before one has data. Insensibly one begins to

twist facts to suit theories instead of theories to suit facts.Sherlock Holmes, the fictional creation of Arthur Conan Doyle (1859-1930)

British physician and novelist.

Spallanzani’s Test of Redi’s Findings Lazzaro Spallanzani read both Redi’s

and Needham’s experiments. He hypothesized that Needham’s

results were due to not heating the flask enough to kill everything.

Performed his own experiment.

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 Spallanzani concluded that the

nonliving gravy did not produce living things.

People were still not convinced!! They said air contained the “life

force” needed for spontaneous generation to occur, and S’s experiment was unfair because the flask was sealed airtight.

Finally, in 1864, French scientist Louis Pasteur settled the argument.

Louis Pasteur conclusively disproved the hypothesis of spontaneous generation.

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

Chance favors the prepared mind.Louis Pasteur (1822-95) French chemist and

bacteriologist.

Pasteur’s Experiment

Broth is boiledBroth is freeof microorganismsfor a year.

Curved neck isremoved.

Broth is teeming with microorganisms.

Curved neck allows air in, but keeps microorganisms out.

Impact of Pasteur’s Work Showed all living things come only from

other living things. Changed the way scientists view things. Saved French wine industry (unexplained

wine souring). Saved silk industry (silkworm disease). Showed that many infectious diseases are

caused by entry of microorganisms into body.

Process of Pasteurization to keep foods unspoiled longer.

Develops first vaccine against anthrax.

When Experiments Are Not PossibleSome examples: Time constraints Studying the past Scale too large Wild animals Inaccessible locations Ethical concerns/ harm to subjects

What to do?

Get as close as possible to an experiment; control for as many variables as possible; use large sample sizes; exclude outliers.

Types of investigations: Experimental (not always possible) Descriptive Comparative

Descriptive InvestigationsDescriptive investigations involve

collecting qualitative and/or quantitative data to draw conclusions about a natural or man-made system (e.g., rock formation, animal behavior, etc).

Includes a question, but no hypothesis.

Observations are recorded, but no comparisons are made and no variables are manipulated.

Comparative Investigations Comparative investigations involve

collecting data on different organisms/objects/ features/events, or collecting data under different conditions (e.g., time of year, air temperature, location) to make a comparison.

Hypothesis identifies one independent variable and one dependent variable.

Fair test can be designed to measure variables so that the relationship between them is determined.

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.

Studying LifeWhat characteristics do ALL living things have in common?

Characteristics of 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

(homeostasis) change over time

Homeostasis

Organisms must keep internal conditions fairly constant to survive.

Homeostasis = the tendency to maintain a state of equilibrium by monitoring internal conditions and responding to deviations by adjusting physiological processes.

Often involves internal feedback mechanisms.

Maintaining constant body temperature is one example.