THE SCIENCE OF BIOLOGY

Section 1–1 What Is Science?

What Science Is and Is Not

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

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

Evidence Based on ObservationWhat does observation involve?

• Observation involves using one or more of the senses– sight, hearing, touch, smell, and sometimes

taste—to gather information.– The information gathered from observation is

called evidence or data

Complete the table about types of observations

Types of Observations

Observations Involve

Example

Quantitative Numbers There are seven birds at the feeder.

Qualitative Characteristicsthat cannot be easily measured or counted

One of the birds has a red head.

Interpreting the Evidence Inference - is a logical interpretation based on prior knowledge and experience.

Explaining the Evidence Hypothesis -is a possible explanation for a set of observations or an answer to a scientific question.In science, a hypothesis is useful only if it can be tested.

Three ways from which hypotheses may arise are:

• From prior knowledge

• From logical inferences

• From imaginative guesses

What do scientists assume can be discovered through scientific inquiry?

• They assume that the basic rules that apply to all events in the universe can be

discovered.What are some qualities that are desirable in a scientist?

Qualities include curiosity, honesty, openness, skepticism, and a recognition that science has limits.

Section 1–2 How Scientists Work

• The idea that life can arise from nonliving matter is called Spontaneous Generation.

• Francesco Redi’s hypothesis about the appearance of maggots was that flies produce maggots.

Designing an Experiment

• What are variables in an experiment? They are factors that can change.

• Ideally, how many variables should an experiment test?

It should test only one variable at a time.

•When a variable is kept unchanged in an experiment, it is said to be a

control.

What is a controlled experiment? • A controlled experiment is an experiment in

which one variable is changed while the other variables are controlled.

TYPE OF VARIABLE DEFINITION

Independent (Manipulated)

Variable

The variable that is deliberately changed in an experiment

Dependent (Responding)

Variable

The variable that is observed and changes in response to the independent variable. What is measured.

Redi’s Experiment on Spontaneous Generation

Several Days Pass

Maggots Appeared

No Maggots Appear

In Redi’s experiment, what were the independent variable and the dependent variable? • The independent (manipulated) variable

was the presence or absence of the gauze covering

• The dependent (responding) variable was whether maggots appear.

Scientists use the data from a controlled experiment to evaluate the hypothesis and draw a conclusion.• Anton van Leeuwenhoek - discovered a world

of tiny moving objects in rainwater, pond water, and dust that he called “animalcules.”

• John Needham - claimed spontaneous generation could occur under the right conditions. He repeated Redi’s experiment using gravy which he put in a bottle, sealed and heated it. Microorganisms were found in it when he examined the contents.

Lazzaro Spallanzani - One of the first to disprove spontaneous generation. An Italian scientist who proved microorganisms could be killed by boiling. (Italian 1767)

In the late 1700's, Lazzaro Spallanzani tried to disprove this by performing a controlled

experiment with broth: • He put broth into two flasks (glass

containers) and sterlized them both by boiling the broth.

• One of the flasks was left open to the air. • The other flask was sealed up to keep out

any organisms that might be floating in the air.

• Microrganisms developed only in the uncovered flask.

From this, Spallanzani concluded:

• That the microorganisms did NOT come from the broth, but were in the air that entered the flask.

• Therefore, not even microorganisms came from nonliving things.

Louis Pasteur - a French scientist settled the spontaneous generation argument by designing a special flask that showed as long as broth was protected from microorganisms, it remained free of living things.

Louis Pasteur’s Experiment

Boil broth No Growth

Neck breaks

Microbes grow

Controlled experiments are not always possible because

• Ethics prevent most experiments with humans

• In field studies researchers try not to disturb systems they observe

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

Section 1–3 Studying Life What is biology?

• Biology is the science that seeks to understand the living world.

Characteristics of Living Things • Living things are made up of cells.• Living things reproduce and produce

new offspring. • Living things are based on a universal

genetic code. • Living things grow and develop. • Living things obtain and use materials

and energy. • Living things respond to their

environment. • Living things maintain a stable internal

environment.• Taken as a group, living things change

over time.

Living things or organisms are made up of small self-contained units called

cells.• Unicellular- single celled organisms• Multicellular- contain many cells

All organisms produce new organisms through reproduction.

2 types of reproduction:

•Sexual

•Asexual

Growth & Development - each type of organism has a distinctive life cycle a pattern of growth & change.Example: Fly eggs Larva (maggots)

Adult fly

All organisms use energy and a constant supply of materials to grow, develop & reproduce.

The amount of energy determines the organism’s metabolism.

Organisms respond to their environment.

Example: • Amount of light• Change in temperature• Combinations such as the amount of

water & temperature

Internal Balance – Living things maintain an internal stability “Homeostasis”If homeostasis is disrupted in a major way an organism cannot survive.Example: bird’s feathers maintain its body temp. during both cold & warm weather

Evolution-Organisms as a group must be able to change over time to insure survival.

• The study of biology is divided into levels of organization.

BIOSPHERE

ECOSYSTEM

COMMUNITY

POPULATION

ORGANISM

GROUP OF CELLS

CELLS

MOLECULES

Chapter 1 Section 1-4 Tools & Procedures• What measurement system do most

scientists use?

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

• The metric system is based on multiples of 10

Common Metric UnitsLength (meter) Mass (gram)

1 m = 100 cm 1kg = 1000 g1 m = 1000 mm 1 g = 1000 mg1000 m = 1 km 1000 kg = 1 t

(metric ton)

Volume (liter) Temperature ( B C)

1 L = 1000 mL 0 E C freezing point of 1 L = 1000 cm3 water

100 E C boiling point of water

Terms:– Observation: What is seen or measured.– Inference: A conclusion based on

observation or evidence.– Hypothesis: A prediction based on

available evidence. A good hypothesis states both cause and effect.

– A correct hypothesis can be tested and falsified (proven incorrect) using an experiment.

– The easiest way to write a correct hypothesis is as an “if-then” statement. (ex: If I give patients this pill, then they will not get sick.)

– Theory: An explanation of natural events that is supported by strong evidence. • Misconception: “Theories are things

that are opinions, or are not proven.” This is an incorrect use of the word “theory” in a scientific context. A scientific theory is not a simple guess or conjecture, and is strongly supported by evidence.

• Theories tie together many scientific facts, hypotheses and laws.

• Controlled Experiment: Compares the results of an experiment between two (or

more) groups.

– Experimental group: Group being tested or receiving treatment.

– Control group: “Normal” group. Should be identical to experimental group in every way except one: it does not receive the new treatment.

– Placebo: A sugar pill or other “fake” treatment given to the control group.

– Independent Variable: Variable that is being tested (ex: new drug, new fertilizer).

• The “If” part of an “If-then” hypothesis.

• The independent variable is always plotted on the X axis.

– Dependent Variable: Variable that is measured at the end of an experiment; the results.

• The “then” part of an “If-then” hypothesis.

• The dependent variable is always plotted on the Y axis.

Characteristics of a good experiment:

– Can be repeated the same way and get the same results.

– Have large sample size/many test subjects.

– Are performed for longer periods of time.

– Test only one independent variable. All other characteristics of the tested groups should be the same.

– Are peer reviewed – examined by several scientists to determine its accuracy.

– Must test the hypothesis and show whether it is wrong or right.

– Is objective – the experiment and conclusion are fair and unbiased. Fact and opinion are not mixed.

– The experiment follows established ethical and legal standards

D. Graphs and Data Tables

– Data tables are used to organize data which will be plotted in a graph.

• First column in the table is for the independent variable.

• Second column is another for the dependent variable.

• Each column should be titled, and include units of measurement.

• Data in the table must be arranged in ascending or descending order.

Making a Line Graph• Line graphs can be used to show how

something changes over time. They have an x-axis (horizontal) and a y-axis (vertical).

1. Always refer to your ‘Guide to Good Graphs’

2. Always give your graph a title

3. The x-axis (horizontal line) of a graph is always your independent variable and the y-axis (vertical line) is the dependent variable. Usually, the x-axis has numbers for the time period, and the y-axis has numbers for what is being measured.

4. Always label the x and y axes and give the units.   For example- Time in seconds

5. Make sure your data is graphed as large as possible in the space you've been given.

X-axis (independent variable)

Title of the Graph

0 1 2 3 4 5

Both the x and y axis of the graph must be labeled or titled. These labels are typically the same ones used in the data table. Once again units of measurement must be written with the title.

The independent variable is always plotted on the x-axis.

The dependent variable is always plotted on the y-axis.

The x and y axis must be numbered.

• These numbers must increase by a uniform increment (that is you must count by 1’s, 2’s, 5’s, 10’s, etc).

• Your numerical scales should take up most of the axes. Squeezing it all into the bottom corner makes the graph impossible to read and no credit will be given.

• The numbers must line up with the grid lines of the graph, not with spaces between them.

• You do not need to start numbering your axis with 0.

All points plotted on your graph must be surrounded by a circle (or sometimes a square or triangle, depending on the directions)

Microscopes• comes from greek words

– micro means small– skop means see

• Most commonly used microscope is the Compound Light Microscope

-allows light to pass through specimen & uses two lenses to form an image

-can be used for both dead or living tiny organisms

-chemical stains or dyes may be used to help see structures better

Electron microscope-used to study very small objects-can visualize objects 1000x smaller than what

is seen with a light microscope-Can not be used with living organisms

2 types:1.) Transmission electron microscope

(TEMs)-shines a beam of electrons through a

thin specimen2.) Scanning electron microscope (SEMs)

-runs a pencil like beam of electrons back & forth across the specimen’s surface-good for 3D surface images

Laboratory TechniquesHow biologists study cells• Cell Cultures

•a single cell is put into a nutrient solution•the cell reproduces to produce a group of cells

•the cells are than used to test– cell responses– cell interactions– specific cells

• Cell Fractionation -separates one part of a cell from the rest of the cell using a centrifuge so it may be studied