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Scientific Method. How Scientists Work. How Scientists Work: Solving the Problems. Much of biology deals with solving problems These problems can be environmental, ecological, health related, etc.

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scientific method

Scientific Method

How Scientists Work

how scientists work solving the problems
How Scientists Work:Solving the Problems
  • Much of biology deals with solving problems
  • These problems can be environmental, ecological, health related, etc.
  • No matter what types of problemsare being studied, scientists use the same problem-solving steps called…
  • The Scientific Method
scientific method definition
Scientific Method Definition
  • The scientific method is-
    • A logical and systematic approach or process to problem solving. 
    • An organized way of using evidence to learn about the natural world.
scientific method listing the steps
Scientific MethodListing the Steps
  • Make an Observation
  • Define the Problem
  • Research the Problem
  • State the Hypothesis
  • Experiment to test Hypothesis
  • Collect and Record Data
  • Analyze Data
  • Draw Conclusions
  • Determine Limitations
  • Report Results


What does the scientist want

to learn more about?




Gathering of information



An “Educated” guess of an

answer to the question




Written and carefully

followed step-by-step

experiment designed to test

the hypothesis

Scientific Method

An Overview



Information collected during

the experiment




Written description of what

was noticed during the




Was the hypothesis correct

or incorrect?

scientific method1
Scientific Method

Ask Question

  • Let’s break each of these steps down into their individual components:

Do Background



Try Again



Test with an


Analyze Results

Draw Conclusion

Hypothesis is True

Hypothesis is False

or Partially True

Report Results

  • Let’s look at the text book example of the Scientific Method using Redi’s Experiment on Spontaneous Generation
  • He was trying to disprove the idea of SpontaneousGeneration (or actually that flies came frommaggots, which camefrom flies)

Francesco Redi (1668)

stating the problem
Stating the Problem
  • Example: How do new living things come into being?
  • Spontaneous generation once commonly accepted
  • Redi wanted to show what caused the appearance of maggots (and then flies) on meat
belief based on prior observations
Belief based on prior observations
  • If leaf lands on water it becomes a fish
  • If bale of hay left in barn it produces mice
  • Muddy soil gives rise to frogs
  • Meat hung out in the market is the source of flies
belief based on prior observations1
Belief based on prior observations

Redi observed that maggots appeared on meat a few days after flies were on meat

No microscope = no way to see eggs

But Redi believed that maggots came from eggs that were laid by flies

forming a hypothesis
Forming a Hypothesis

Redi’s Hypothesis:

Flies produce maggots.

  • How could he test this?
    • Through a controlled experiment
redi s controlled experiment

Jars with meat

Uncovered jars

Covered jars

Redi’s Controlled Experiment
  • Redi used two groups of jars
    • Jars that contained meat and no cover
    • Jars that contained meat and gauze cover
control and experimental groups

Uncovered jars

Two groups of jars

Covered jars

Control and Experimental Groups

Control group:

  • used as a standard of comparison
  • the group containing the factor (variable) that has been changed

Experimental group:

(manipulated or independent variable)

variables in an experiment
Variables in an Experiment
  • Variables - Factors that can be changed
  • Controlled Variables - all the variables that remain constant
  • Independent Variable - (also called the Manipulated Variable) - factor in an experiment that a scientist purposely changes
  • Dependent Variable- (also called the Responding Variable) - the outcome or results, factor in an experiment that may change because of the manipulated variable….what a scientist wants to measure or observe
variables in redi s experiment
Variables in Redi’s Experiment
  • Controlled Variables: jars, type of meat, location, temperature, time
  • Manipulated Variables: gauze covering that keeps flies away from meat
let s think about this

Two groups of Jars with meat

Uncovered jars

Covered jars

Let’s think about this.…

Uncovered jars

  • Which is the control group?
  • Which is the experimental group?

Covered jars


Redi’s Experiment on Spontaneous Generation

OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat.

HYPOTHESIS: Flies produce maggots.


Covered jars


Controlled Variables:

jars, type of meat,

location, temperature,



days pass

Manipulated Variables:

gauze covering that

keeps flies away from


Responding Variable:

whether maggots


Maggots appear

No maggots appear

CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur.

6 collect and record data
6. Collect and Record Data

observations and measurementsmade in an experiment


Types of Recorded Data

  • Quantitative - observations that involve measurements/numbers; i.e. 3 days, 12 maggots, 4 g, 13 sec, 8 liters
  • Qualitative - observations thatdo not involve numbers, are of a descriptive naturei.e. white maggots covered the meat, leaves were all wilting
recording the data
Recording the data

Setting up a data table

Graphing data

7 analyze the data
7. Analyze the Data
  • Examine data tables, charts, and graphs
  • Examine experimental notes
  • Look for trends, patterns, and averages
  • What does the data show
  • Put your data into words
8 draw conclusions
8. Draw Conclusions
  • Restate the hypothesis:

Example: Flies produce maggots.

  • Accept or reject the hypothesis.
  • Support your conclusion with specific, numerical data.
  • What was Redi’s conclusion?
    • Flies lay eggs too small to be seen.
    • Maggots found on rotting meat are produced

from the eggs laid by flies.

    • Maggots are not appearing due to spontaneous generation!
9 determine limitations
9. Determine Limitations
  • Scientists look for possible flaws in their research
  • They look for faulty (inaccurate) data
  • They look for experimental error or bias\'s
  • They decide on the validity of their results
  • They make suggestions for improvement or raise new questions
10 publish results
10. Publish Results
  • Communication is an essential part of science
  • Scientists report their results in journals, on the internet, or at conferences
  • This allows their experiments to be evaluated and repeated
  • Scientists can build on previous work of other scientists

Redi’s experiment

on insects generation


What is the difference

  • between
  • Hypothesis
  • Theory
  • Law
the scope of biology
  • Biology is the scientific study of life
  • Interactions between different kinds of organisms affect the lives of all
life s levels of organization define the scope of biology
Life’s levels of organization define the scope of biology
  • A structural hierarchy of life, from molecules to ecosystems, defines the scope of biology
  • An ecosystem consists of:
    • Biotic factors
      • all organisms living in a particular area
    • Abiotic factors
      • all nonliving physical components of the environment that affect the organisms (soil, water)

Ecosystems include:

    • all the organisms in an area, which make up a community
    • interbreeding organisms of the same species, a population
  • At the top of life’s hierarchy is the ecosystem

organ systems

  • organs
  • tissues
  • cells
  • molecules
  • Organisms are made up of:
scientists use two main approaches to learn about nature


Scientists use two main approaches to learn about nature
  • In discovery science, scientists describe some aspect of the world and use inductive reasoning to draw general conclusions
    • Example: birds migrate

South each year during

colder months

because it is warmer.


They propose a hypothesis

  • They make deductions leading to predictions
  • They then test the hypothesis by seeing if the predictions come true
  • In hypothesis-driven science, scientists use the “scientific method”
with the scientific method we pose and test hypotheses
With the scientific method, we pose and test hypotheses
  • The main steps of the scientific method
experimental design
Experiments designed to test hypotheses must be controlled experimentsExperimental Design
  • Control groups must be tested along with experimental groups for the meaning of the results to be clear
    • Independent variable
    • Dependent variable
the diversity of life can be arranged into three domains


The diversity of life can be arranged into three domains
  • Grouping organisms by fundamental features helps make the vast diversity of life manageable for study
  • Scientists classify organisms into a hierarchy of broader and broader groups

Domain Bacteria - Domain Eukarya

  • Most classification schemes group organisms into three domains:
  • Domain Archaea
unity in diversity all forms of life have common features
Unity in diversity: All forms of life have common features
  • All organisms share a set of common features, signs of unity in life’s vast diversity
    • All are made of cells
    • All have DNA as their genetic blueprint
  • These orchids show the variety possible within one species

Each species has its own nucleotide sequence

  • DNA is made of chemical units called nucleotides
Characteristics of Living Things:
  • The genetic information in DNA underlies all of the features that distinguish life from non-life
  • Order and regulation (homeostasis)
  • Growth and development
  • Use of energy from the environment
  • Response to environmental stimuli
  • Ability to reproduce
  • Evolutionary change
evolution explains the unity and diversity of life
Evolution explains the unity and diversity of life
  • Charles Darwin is a central figure in biology
  • He synthesized the theory of evolution by natural selection
    • A theory in science is a comprehensive idea with broad explanatory power
  • Evolution is the core theme of biology
The theory of natural selection explains the main mechanism whereby all species of organisms change, or evolve
Evolution happens when populations of organisms with inherited variations are exposed to environmental factors that favor the success of some individuals over others
  • Natural selection is the editing mechanism
  • Evolution is based on adaptations
connection biology is connected to our lives in many ways


Connection: Biology is connected to our lives in many ways
  • Biology is connected to a great number of important issues
    • Environmental problems and solutions
    • Genetic engineering
    • Medicine

Evaluating everyday reports in the press about a large range of subjects requires critical thinking and some familiarity with many areas of biology

  • Many technological advances stem from the scientific study of life
your turn
Your turn….
  • WAIT for Ms. Allard tell you to turn on your clicker and log in.
  • NO talking. You can use your notes but do not use each other!
  • You will NOT be able to change your answer so be sure you have read and understand the question(s) before you hit SEND!
  • Do NOT log off until Ms. Allard tells you to do so!

iRespond Question

Multiple Choice


The ability to move and use oxygen are 2 characteristics of all living things.

A.) true

B.) false





iRespond Question

Multiple Choice


Biology can be related to our every day lives.

A.) true

B.) false





iRespond Question

Multiple Choice


The core theme of biology is

A.) a hierarchy

B.) the scientific method


D.) evolution



iRespond Question

Multiple Choice


The prefix "a" means

A.) with

B.) without

C.) single or solitary

D.) one



iRespond Question

Multiple Choice


The prefix "bio" means

A.) self

B.) story

C.) life

D.) study of