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The Biology website is at http://www.midpac.edu/~biology/Intro%20Biology/

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The Science of

Biology

3 Goals of Science

Provide natural explanations for events in the natural world

Use these explanations to: Understand patterns in nature Make useful predictions about

natural events

What is Science?

An organized way of gathering and analyzing evidence about the natural world

A way of observing, thinking, and “knowing” about the world

A process - not a “thing” A body of knowledge scientists have

gathered over many years

Scientific Methodology

• The common steps that biologists and other scientists use to gather information and

answer questions are collectively known as scientific method.

The Steps

Making observations and asking questions Making inferences and forming hypotheses Conducting controlled experiments Collecting and analyzing data Drawing conclusions (Stating Sources of Error)

Observation

Scientific methodology usually begins with scientists identifying a problem to solve by observing the world around them.

Observation: Marsh grass grows to different heights in different locations

Question: Why does marsh grass grow different heights in different locations?

Making Inferences

Inference is a logical interpretation based on what you know or have observed – a guess at how things work

Inferences lead to a hypothesis - a TESTABLE logical explanation for the observations.

Hypotheses are SUPPORTED or REJECTED (not proved or disproved)

Formulating a Hypothesis

Always use an If… then… statement

Inference: something is limiting the growth of the marsh grass - like available nitrogen

Hypothesis: IF available nitrogen is related to the growth of marsh grass THEN locations with more nitrogen will grow taller marsh grass

Conducting an Experiment

Hypotheses are tested by conducting experiments

An experiment is an investigation that collects information under controlled conditions

The results of the experiment will either support or refute the hypothesis

Identifying Variables

In a controlled experiment only ONE condition is changed at a time. All other variables must be kept the same!

The condition in an experiment that is deliberately changed is the independent or manipulated variable. (Nitrogen level)

The variable that you observe changing in response to the independent variable is called the dependent or responding variable. (Grass height)

Controlled variables = variables that stay the same between control group and experimental group

Controlled Experiment

Many experiments involve at least two groups: the control group and the experimental group

The experimental group is the test group, in which all conditions are kept the same except for the single condition being tested (the experimental variable - added nitrogen)

The control group is the group in which all other conditions are kept the same, but there is no experimental variable (no added nitrogen)

Recording Data

Information collected during experiments is called data

There are 2 types of data Quantitative Qualitative

Quantitative – numerical data like length, mass, temperature and time.

Qualitative – verbal data or written observations like color or smell.

Data should be organized into tables

Qualitative or Quantitative?

Data Table

Table to show Marsh Grass growth in response to added Nitrogen

Time (weeks) Control GroupGrass Height (cm)

Expt GroupGrass Height (cm)

0 2 2

1 3 4

2 4 6

3 5 8

Analyzing Results

Analysis of results can include graphing data or applying statistical formula.

It makes any patterns in the data easy to see

Sources of Error

It is important to avoid errors in experimental procedure, data collection and analysis.

All measuring tools have limited accuracy

Sample size should be large enough to be representative of the general population

Repeating Investigations

After results of an investigation have been published, other scientists can try to verify the results by repeating the procedure

When a hypothesis is supported by data from additional investigations, it is considered valid and is generally accepted by the scientific community

Drawing a Conclusion

After careful review of the results a conclusion must be reached Is the hypothesis supported by the

data? Is the hypothesis refuted by the data? Is more data needed? Should changes be made to the

experiment?

Revisions to Hypothesis

During investigations hypotheses often need to be revised and experiments redone several timesPython video

Field Studies

Sometimes lab experiments are not possible

For animal behavior in the wild - Field observations are made – disturbing nature as little as possible

For cancer causing chemicals in humans – need to study people who have already been exposed vs. those who haven’t

Scientific Attitudes that help generate New Ideas

Curiosity Skepticism Open-mindedness Creativity

Scientists share ideas and review each others’ work, which often triggers new

questions and ideas

Why is Peer Review important

Scientific papers are reviewed by anonymous, independent experts

Ensures published work meets the standards of the scientific community

Publishing work in scientific journals allows scientists to share ideas and test and evaluate each other’s work.

Wikipedia is NOT peer reviewed!!

Developing a Theory

Once scientists have gathered a large body of evidence that supports a hypothesis it becomes a theory - a well tested explanation that unifies a broad range of observations and hypotheses and that enables scientist to make accurate predictions about new situations.

A theory is NOT an absolute truth A theory can be revised or replaced if

new evidence supports a different explanation

Spontaneous Generation

Life comes from nonliving material

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

HYPOTHESIS: Flies produce maggots.PROCEDURE

Controlled Variables (keptthe same between exp):jars, type of meat,location, temperature,timeManipulated Variables:gauze covering thatkeeps flies away from meat

Uncovered jars Covered jars

Several days pass

Maggots appear No maggots appearResponding Variable: whether maggots appear

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

Section 1-2

Figure 1-8 Redi’s Experiment on Spontaneous Generation

Leuwenhoek developed the first simple microscope in the 17th century and was the first to see microorganisms.

Gravy is boiled. Flask isopen.

Gravy is teeming with microorganisms.

Gravy is boiled. Flask issealed.

Gravy is free of microorganisms.

Section 1-2

Figure 1-10 Spallanzani’s Experiment

Needham believed that Spallanzani did not disprove spontaneous generation What problem did he point out?

Needham showed microorganisms growing from boiled gravy

Spallanzani showed sealing the flask prevented growth

Broth is boiled. Broth is free ofmicroorganismsfor a year.

Curved neckis removed.

Broth is teeming with microorganisms.

Section 1-2

Figure 1-11 Pasteur’s Experiment

Broth is boiled. Broth is free ofmicroorganismsfor a year.

Curved neckis removed.

Broth is teeming with microorganisms.

Section 1-2

Figure 1-11 Pasteur’s Experiment

In Pastuer’s experiment what was the dependent (responding) variable?

What was the independent (manipulated) variable?

What variables were controlled?

Variables

Link to Lab

Studying Life

Chapter 1-3

Biology

Bios means life and -logy means study of

So Biology is the study of living things.

Characteristics of Living Things

Biologists have made a list of characteristics that living things share

Organisms must have ALL the characteristics to be considered living.

8 Characteristics

Based on a genetic code

Grow and develop Respond to their

environment Reproduce Maintain internal

balance Use materials and

energy Made up of cells Evolve

1.Based on the Universal Genetic Code

DNA carry the directions for inheritance

Asexual same as parent

Sexual mix of both parents

2. Grow and Develop Grow = get bigger Develop =

change and mature

Cells become specialized – have specific jobs

3. Respond to their Environment

React to a change in the environment

Stimulus = signal Blink in bright sun Flinch if you are

hurt Plants

roots/shoots respond to gravity

4. Reproduce

One of the most obvious of all the characteristics of life is reproduction, the production of offspring.

• Sexual reproduction• Asexual reproduction• EX: budding, vegetative

reproduction, mitosis

5. Maintain Internal Balance

Homeostasis Keep conditions

constant Body Temperature

control Shiver warmer Sweat cooler 98.6oF or 37oC

6. Use Materials and Energy

Organisms need materials and energy to grow and develop

Metabolism = building up or breaking down materials

Plants need solar energy

We need food

7. Made up of Cells Cells are the basic unit

of life. Whether an organism

is made up of one cell (unicellular) or billions of cells (multicellular), all of its parts function together in an orderly, living system.

8. Evolve As a group organisms change over

time

Additional Themes of Biology

Structure and Function

Each major group of organisms have their own particular traits that allowed them to evolve in particular ways

Unity and Diversity of Life

Although life is diverse, at a basic level they have many things in common. DNA code, carbon based, etc. Share many traits

Interdependence of Nature

All organisms depend on each other in the biosphere

Science as a way of Knowing

Science helps to explain and predict the natural world so that we can take action. We must understand its strengths and limitations.

Big Ideas in Biology Cellular Basis of Life Information and Heredity Matter and Energy Growth, Development Reproduction Homeostasis Evolution Structure and Function Unity and the Diversity of Life Interdependence of Nature Science as a way of Knowing

A Common Measurement System

In science we always use the Metric System or SI (Systeme International)

Easy to use multiples of 10

The whole world uses the same units

SI Base UnitsMeasurement Unit SymbolLength meter mMass kilogram kg

Time second sElectric current ampere ATemperature kelvin KAmount of substance mole molIntensity of light candela cd

Common Biology Units of Measure

Meters and centimeters (length) Celsius (temperature) Grams and kilograms (mass) Milliliters and liters and

cm3(volume) Seconds and minutes (time)