Biology Chapter One

The Science of Biology

WHAT SCIENCE IS & IS NOT

“The goal of science is to investigate & understand nature, to explain events in nature, & to use those explanations to make useful predictions.”

Science differs from other subjects because it relies on TESTING EXPLANATIONS (experiments).

What Sets Science Apart:

-It deals with the natural world.

-Scientists collect & organize information in a careful, orderly way looking for patterns & connections between events…COLLECT & CONNECT.

-Scientists propose explanations that can be tested through experimentation.

SCIENCE- organized way of using evidence to learn about the natural world;

SCIENCE-the body of knowledge that scientists have built up after years of using an organized approach.

The work of science begins with careful observations from which we gather data.

Information gathered from observations result in “data”…

DATA-evidence; information gathered from observation.

Observations can be classified into 2 types:

1.QUANTITATIVE-observations that involve numbers. (Counting or measuring objects)

What are some examples?

2. QUALITATIVE-observations that involve characteristics that cannot be easily measured or counted…like the color or texture of an object.

Be able to apply…know examples & applications of the 2 types of data on your test!

EXPLAINING THE EVIDENCE

HYPOTHESIS-a ‘testable prediction’ that is only useful if it can be tested.

Where do the hypotheses come from?

How are they developed?

How are they tested?

Scientists use the same kind of problem solving in their work.

*They collect data as a means of achieving their goal-a better understanding of nature.

*For Scientists- SCIENCE IS AN ONGOING PROCESS, not the discovery of an unchanging absolute truth. Scientific findings are always revised as new discoveries are made.

Hypotheses may arise from prior knowledge, logical inferences, or imaginative guesses.

INFERENCE- a logical interpretation based on prior knowledge & experience.

EX: Water samples are taken from several areas of a lake & tested. If all the samples are clean enough to drink…researchers may infer that ALL the water in the lake is safe to drink.

You will have “application” questions concerning hypotheses on your test!

A SCIENTIFIC VIEW OF THE WORLD

In a sense we all use the scientific methods to solve problems in our everyday life…

What do you do when you turn on a switch and the light does not come on?

QUALITIES OF A SCIENTIST:

*Curiosity

*Honesty

*Open-Mindedness

*Skepticism

*Recognition that science has limits

SCIENCE & HUMAN VALUES

(Read this section on page 7!)*An understanding of science & the scientific approach is essential to making intelligent decisions about science.

*The answers to scientific questions are a result of science, society, laws, & moral principles.

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1-2 HOW SCIENTISTS WORK

We must remember that what seems obvious now…was not so obvious thousands of years ago.

ARISTOTLE-Greek Philosopher who made extensive observations of the natural world & tried to explain them through reasoning.

About 400 years ago-people began to challenge those ideas & began to use experiments to answer their questions about life.

SCIENTIFIC METHOD

*Stating the problem/Asking a Question

*Forming a hypothesis

*Setting up a controlled experiment

*Recording & analyzing results

*Drawing a conclusion

*Publishing & repeating investigations

For many years people accepted the idea that living things could come from NON-LIVING things.

SPONTANEOUS GENERATION- the idea that life could arise from non-living matter.

(EX: Maggots/Flies come from rotting meat)In 1688, Francesco Redi, an Italian physician proposed a different idea. He felt that flies come from eggs too small for people to see.

He proposed that flies produce maggots.

SETTING UP A CONTROLLED EXPERIMENT

VARIABLES - the factors in an experiment that can CHANGE.

**In a controlled experiment ONLY ONE VARIABLE (manipulated variable) IS TESTED AT A TIME!!!

EX: You want to know whether an increase in water, light, or fertilizer can speed up plant growth…How would you test this experiment?

Whenever possible, a hypothesis should be tested by an experiment in which ONLY ONE VARIABLE is tested at a time.

All other variables should be kept unchanged, or controlled.

MANIPULATED VARIABLE-the variable that is DELIBERATELY changed.

RESPONDING VARIABLE- the variable that is observed and that changes IN RESPONSE to the manipulated variable.

(Overhead Illustration-Redi’s Experiment)

RECORDING & ANALYZING RESULTS

Scientists have kept written records of their observations or data in many forms: hand-written information in notebooks or journals, drawings, & in today’s world…computers store recorded information.

DRAWING A CONCLUSION

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

They use EVIDENCE to determine whether the hypothesis is supported or refuted.

Scientists publish the details of important experiments so that:

-Their work can be repeated

-Experimental procedures can be reviewed

-Others can try to reproduce the results

Publishing is an essential part of science to further the development of science.

BIOLOGY & HISTORY

(see time line page 12-13)

Anton van Leeuwenhoek-A scientist working in the same time frame as Francesco Redi who was preparing lenses that let him magnify objects.

He looked at pond water & found moving objects…he inferred that they were alive & called them ‘ANIMALCULES’ = “tiny animals”;

The animalcule discovery greatly impacted spontaneous generation…for the next 200 years-arguments continued over whether or not animalcules were alive and how they came to exist.

In the mid 1700’s JOHN NEEDHAM, an English scientist, used an experiment involving animalcules to attack the work of Redi.

Needham thought that under the “right” conditions that spontaneous generation could occur.

NEEDHAM’S EXPERIEMENT

(see page 11 Figure 1-10)

-Sealed & heated a bottle of gravy

-Claimed that heat should kill anything that is living in the gravy.

-Several days later the gravy content was examined & found to be “swarming” with animalcules.

-He concluded that the animals had to have

Come from the juice of the gravy.

SPALLANZANI’S TEST OF REDI’S FINDINGS

-Performed the same procedure as Needham with one exception…

He left one flask open & SEALED the other.

-Days later…open flasks were full of ‘animalcules’…and the sealed jar remained free of any ‘animalcules’.

Spallanzani concluded that nonliving gravy DID NOT produce living things.

The micro-organisms in the unsealed jar came from the air into the jar.

**This experiment supported Redi’s work & hypothesis that living things come only from other living things.

Louis Pasteur’s Test of Spontaneous Generation…

In the 1800’s there was still argument for the spontaneous generation hypothesis…

Scientists argued that the micro-organisms could not live in the sealed flask because they did not have air.

Louis Pasteur’s Experiment

In 1864, French scientist Louis Pasteur conducted an experiment to settle the spontaneous generation dispute…

Pasteur designed a flask with a curved neck… this allowed air but kept dust & other particles out…

Pasteur put broth in the flask & it was kept free of micro-organisms until…about a year later when the neck on the flask broke!

The broth quickly became filled with micro-organisms.

*Pasteur finally settled the argument over whether or not life could arise from non-living matter.

Pasteur’s Contributions In Other Areas:

-He helped save the wine industry, which was troubled by unexplained souring of wine.

-He helped save the silkworm industry which was endangered by a silkworm disease.

-He began to uncover the very nature of infectious diseases…and linking them to micro-organisms.

Pasteur is considered one of Biology’s most remarkable problem solvers.

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Controlled experiments are sometimes not possible. Ethics prevent most experiments with humans.

In field studies, researchers try not to disturb the systems they observe.

HOW A THEORY DEVELOPS

*When enough experimental data support a hypothesis, the hypothesis becomes a THEORY.

THEORY-a well-tested explanation that unifies a broad range of observations.

Sometimes more than one theory is needed to explain a particular circumstance.

As new evidence is uncovered, a theory may be revised or replaced by a more useful explanation.

*Science is characterized by both continuity & change.

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1-3 STUDYING LIFE

Biology is not just the study of plants & animals but ALL living things.

BIOLOGY- bio=life…

ology= study of…

Biology is the study of science that seeks to understand the living world.

Characteristics of Living Things…

They:-Are made up of units called CELLS-Reproduce-Are based on a genetic code-Grow & Develop-Obtain & use materials & energy-Respond to the environment-Maintain a stable internal environment-Change over time (as a group)

CELL- A collection of living matter enclosed by a barrier that separates the cell from its surroundings.

*Cells are the smallest units of an organism that can be considered alive.

*UNICELLULAR- single celled;

*MULTICELLULAR- many celled;

In some multi-cellular organisms, each type of cell is SPECIALIZED to perform a different function.

*CELL SPECIALIZATION-allows cells to perform different functions.

The human body is made up of at least 85 different cell types.

REPRODUCTION

2 Types of Reproduction:

1.SEXUAL REPRODUCTION-two cells from two different parents unite to produce the first cell of the new organism.

2.ASEXUAL REPRODUCTION-the new organism has a single parent…sometimes a single cell divides into 2 cells…see figure 1-16 page 17;

BASED ON GENETIC CODE….offspring always resemble

their parents!

With ASEXUAL reproduction…offspring & their parents have the SAME traits;

With SEXUAL reproduction…offspring differ from their parents in some ways.

The “directions for inheritance” are carried by a molecule called:

DEOXYRIBONUCLEIC ACID (DNA)

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GROWTH & DEVELOPMENT

Each organism has a distinct life cycle.

During “development”, the cells in an organism not only increase in #, but also become different or “DIFFERENTIATE”.

NEED FOR MATERIALS & ENERGY

*Organisms need materials & energy just to stay alive.

*METABOLISM- the combination of chemical reactions through which an organism builds up or breaks down materials as it carries out its life processes.

Plants, some bacteria, & most algae get their energy directly from SUNLIGHT…this process is referred to as PHOTOSYNTHESIS.

Through photosynthesis these organisms convert light into a form of energy that is stored certain molecules.

Most other organisms rely on the energy stored during photosynthesis.

DECOMPOSER-organisms that get their energy from the remains of organisms that have died.

RESPONSE TO ENVIRONMENT

Organisms live in constantly changing environments…variables such as light & temperature change from day to day and from season to season.

MAINTAINING INTERNAL BALANCE

HOMEOSTASIS-the process by which organisms keep their internal conditions relatively stable.

If homeostasis is disrupted in a major way, an organism cannot survive.

BRANCHES OF BIOLOGY

•Zoologists- scientists who study animals

•Botanists-scientists who study plants

•Ethologists- scientists who study animal behavior

•Paleontologists-scientists who study life as it was in the past

LEVELS OF ORGANIZATION

The many levels at which life can be studied include:-Molecules-Organelles-Cells-Tissues, Organs, Organ Systems, Organism-Populations of a single organism-Communities of populations living in the same area-Biosphere…see figure 1-21 page 21

1-4 Tools & Procedures

Most scientists use the metric system when collecting data & performing experiments.

METRIC SYSTEM- a decimal system of measurement whose units are based on certain physical standards & are scaled on multiples of 10.

A revised version of the metric system is called the International System of Units or SI.

The abbreviation for SI comes from the French:

Le System International d’Unites

Since the SI system is based on the number 10…it is easy to use.

COPY COMMON METRIC UNITS TABLE ON PAGE 24…

FIGURE 1-23

***KNOW FOR TEST!

ANALYZING BIOLOGICAL DATA

Today through the use of computers & graphs scientists can detect patterns & better interpret data.

A graph of collected data can make a pattern much easier to recognize & understand. (See figure 1-24 page 25)

MICROSCOPES

Defined: devices that produce magnified images of the structures that are too small for the unaided eye.

LIGHT MICROSCOPES produce magnified images by focusing visible light rays.

ELECTRON MICROSCOPES produce images by focusing beams of electrons.

A COMPOUND LIGHT MICROSCOPE allows light to pass through the specimen & uses 2 lenses to form an image.

Chemical stains, fluorescent dyes, video cameras, 3-D imaging, & computer processing are techniques that have helped light microscopes to become more useful.

ELECTRON MICROSCOPES focus beams of electrons on specimens…they can form images of objects 1000 times smaller than those visible under light microscopes.

Since light (from the visible spectrum) is not used…an untouched electron microscope image has no color.

Two Types of Electron Microscopes:

1.TRANSMISSION ELECTRON MICROSCOPES (TEM)-they shine a beam of electrons through a small specimen.

2.SCANNING ELECTRON MICROSCOPE (SEM)-they run a pencil like beam back and forth across the surface of a specimen.

SEM’s produce realistic & often dramatic 3-Dimensional images of the surfaces of objects.

They are VERY powerful…however-the samples that are being viewed must be completely dried out & placed in a vacuum inside the microscope. So only dead & preserved cells can be observed.

LABORATORY TECHNIQUES

CELL CULTURE-placing a single cell into a culture dish so that the cell can produce a group of cells for studying.

Cell cultures can be used to study interactions between cells & to select specific cells for further study.

CELL FRACTIONATION- a technique that separates the different cell parts.

HOW?

1.Cells are broken into pieces by a special blender.

2.Broken cell bits are added to a liquid & placed into a tube.

3.The tube is inserted into a centrifuge which causes the cell parts to separate…the most dense parts settle to the bottom.

CENTRIFUGE- an instrument that can spin a tube up to 20,000 times per minute.

***Read “Working Safely In Biology” page 28

TEST CHAPTER 1