Chapter 1(1.1-1.2)

Before we delve into the world of BIOLOGY, we need to examine

the question: What is a “FACT?”• Something that can

be proved or verified by observation or measurement

What are some other types of facts besides the kind you just

listed?Examples: historical facts,scientific facts, facts read in the newspaper

Is it possible for a fact to change?

• It depends on the type of fact.• Historical facts: No. They

already happened.• Scientific facts: Yes. These

facts are based on current knowledge & since we will never know everything, scientific facts can change when new data is discovered.

Science is flexible!● It is a process and a way of looking

at the world around us. Science explains the world today, based on research and evidence we have collected so far.

1.1 & 1.2: What is the Nature of Science / Biology?What Methods are Used in

Science? Vocabulary:

Science Controlled experiment

Observation Independent variable

Data Dependent variable

Inference Theory

Hypothesis

The Goal of Science…

• To investigate and understand nature• To explain events in nature• To use those explanations to make

useful predictions

The scientific method makes science different

from non-science.

Science is an organized way of using EVIDENCE to learn

about the natural world

FossilsDNA

Scientific Method1. Observation: use senses

2. Gather Data from Observations

3. Form a Hypothesis using Prior Knowledge Data

4. Test Hypothesis by Observation & Experiment

5. Record & Analyze Data (charts & graphs)

Quantitative: numbers (ex: plant height= 32cm)

Qualitative: characteristics (ex: red hair)

6. Form a Conclusion based on Evidence

Evidence & Observations

How do you make observations?

Observation vs. Inference

Be careful with your observations!• Observation: use of one or more of the

senses to gather information• Ex: water tested at 1 site at a lake shows that the

bacteria count is low

• Inference: A conclusion or interpretation drawn from observation and prior knowledge

• Ex: the entire lake has a low bacteria count

Hypothesis

• Definition: a scientific explanation for a set of observations

• Useful only if it can be tested!

• Arises from prior knowledge, logical inferences, or informed guesses

• A hypothesis always has value!

So you’ve made an observation…

• The information gathered from observations is called: DATA!

• Data can be divided into two types:

1) Qualitative: descriptions (things NOT counted/measured)

2) Quantitative: measured or counted values with a numerical value assigned to them

Which of the following is an inference?

a) The plant is yellowish and wilting

b) The plant should be moved to where there is more sun

c) The plant needs water

d) B and C only

e) None of the above

Which statement would a knowledgeable scientist agree with?

a) A hypothesis must be correct for it to be valuable

b) Science is a collection of truths

c) Scientific facts are not able to be changed

d) The scientific method makes science different from non-science

Why Do Scientists Write Lab Reports?

• So their work can be reviewed & replicated by either themselves or other researchers

– WHY? to assure us that the results aren’t due to

chance & that they are accurate

Remember, the Scientific Method is…

an organized way of using evidence to learn about the

natural world

Steps of the Scientific Method1) observations which lead to a problem

2) form a hypothesis (testable scientifaic explanation for observations)

3) test hypothesis by setting up a CONTROLLED EXPERIMENT

Controlled Experiment- isolate & test effects of a single factor or variable; everything else is CONTROLLED(remains identical between the 2 experimental set-ups)

Controlled Experiments…only 1 thing (called a variable)

changes

*variable that is deliberately changed =

INDEPENDENT variable

*variable that is observed and changes in response =

DEPENDENT variable

Control Group vs. Experimental Group

• typically, an experiment is divided into control and experimental groups

• CONTROL GROUP: exposed to the same conditions as the EXPERIMENTAL GROUP except for ONE independent variable

**a scientist will usually set up several sets of control & experimental groups!

Prior to the Scientific Method:• Philosophers such as Aristotle tried to

explain their observations of the world though reasoning

• They thought that special “vital” forces brought some living things into being from non-living things Recipe for Bees:

1. Kill a bull during the first thawof winter.2. Build a shed.3. Place the dead bull on branches & herbs inside the shed.4. Wait for summer. The decaying body of the bull will produce bees.

• This idea is called…

SPONTANEOUS GENERATION(Life from non-life)

• It was accepted for centuries– Ex: Maggots are formed from

meat; mice from grain; beetles from cow dung

Redi’s Experiment on Spontaneous Generation

Redi’s Experiment on Spontaneous Generation

Independent Variable What did Redi change?

Dependent Variable What changed as a result & became his data?

What were the variables?

Controlled variables (what did Redi keep the same?)

• jars, types of meat, location, temperature

Independent variable (what did Redi change?)

• gauze coverings

Dependent variable (what changed as a result?)

• if maggots appeared or not

Pasteur’s Test of Spontaneous Generation

Was air needed for the spontaneous generation of life?

“ A remarkable problem solver”

Pasteur’s Test of Spontaneous Generation:

• Pasteur’s experiment:–Expose both flasks (containing

boiled broth) to air–BUT: Protect one sample of

broth from microorganisms by curving the neck

Pasteur’s Test of Spontaneous Generation

RESULTS:● Microorganisms grew in broth

exposed directly to air (straight neck);

● Microorganisms did NOT grow in flask with curved neck;

Pasteur’s Test of Spontaneous Generation

● When Pasteur broke the neck of the curved flask, the broth quickly became filled with microorganisms

What did Pasteur’s experiment finally show?

• ALL living things come from other living things!!

When does a hypothesis become a theory?

● when a hypothesis is tested and confirmed often enough that it is unlikely to be disproved by future tests

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

● No theory is considered absolute truth; a theory may be revised or replaced as new evidence is uncovered… SCIENCE IS A PROCESS!!

For your information…• THEORIES and LAWS are DIFFERENT

kinds of knowledge• LAW = generalizations / description of a

pattern in nature (i.e. we OBSERVE the phenomenon of gravity; or that things change over time)

• THEORY = a well-tested explanation of those generalizations

Theories do NOT become laws (or vice versa)

What is a controlled experiment?

a) An experiment in which the scientist controls every aspect and records all data accurately

b) An experiment in which there is an experimental group and a controlled group

c) An experiment in which all groups tested have many differences between them (they are all considered experimental groups)