Transcript CH. 2 Tools of Environmental Science I. Scientific Methods A. The

CH. 2
Tools of Environmental Science





I. Scientific Methods
A. The Experimental Method
Scientists make discoveries using the
experimental method – a series of steps that
scientists worldwide
use to identify and answer questions
First step is observing
1-Observation




1-Observation – a piece of information we
gather using our senses – sight, hearing, smell,
and touch
-after you observe, you begin to ask
questions
-scientists extend their senses by using rulers,
microscopes, even satellites
-can take many forms like descriptions,
drawings, photographs and measurements
2-Hypothesizing and Predicting


2-Hypothesizing and Predicting
To answer a specific question, a scientist may
form a hypothesis.
Hypothesis




Hypothesis – a testable explanation for an
observation
-it is more than a guess
-it should make logical sense and follow
from what you already know about the situation
To test a hypothesis, the students make a
prediction
Prediction




Prediction – a logical statement about what will
happen if the hypothesis is correct
-it is important that the hypothesis can be
disproved
-every time a hypothesis is disproved, the
number of possible explanations for an
observation is reduced
-by eliminating possible explanations, a
scientist can zero in on the best explanation with
more confidence
3-Experimenting




3-Experimenting
Experiment – a procedure designed to test a
hypothesis under controlled conditions
-should be designed to pinpoint cause-and –
effect relationships
-all experiments have 2 essential characteristics
1- a single variable is tested
2-a control is used
Variable


Variable – the factor of interest
-to test for one variable scientists study two
groups or situations at the same time and the
variable being studied is the only difference
between the two groups
Groups in an Experiment


Experimental group – the group that receives
the experimental treatment
Control group – the group that does not
receive the experimental treatment – the one
that says the same
4-Organizing and Analyzing Data



4-Organizing and Analyzing Data
Keeping careful and accurate records is
extremely important in science
A scientist cannot rely on results that are based
on sloppy observations or incomplete records
Which is easier to understand?
Data



Data- the information that a scientist gathers
during an experiment – often in numeric form
Graphs are used to display relationships or
trends in the data
-bar graph – useful for comparing the data
for several things on one graph
Organizing data into tables and
graphs helps scientist analyze and
explain the data
5-Drawing Conclusions




Scientists determine the results of the
experiment by analyzing their data and
comparing the outcome to their prediction.
Sometimes the conclusion is obvious while
other times the conclusion is not so obvious
Using mathematical tools can help scientists
determine whether such differences are
meaningful or just a coincidence
Scientists also repeat their experiments
6-Repeating Experiments



Although results from a single experiment may
seem conclusive, scientists look for a large
amount of
supporting evidence before they accept a
hypothesis
The more often an experiment can be repeated
with the same results, the more reliable the
results
7-Communicating Results



Scientists publish their results to share what they
have learned with other scientists
-publishing a scientific article
-article includes the question explored,
reasons why the question is important,
background information, precise description of
how the work was done, the data that was
collected, and the scientist’s interpretation of the
data
B. The Correlation Method

Sometimes questions cannot be studied
experimentally

-what was earth’s climate like 60 million years
ago? – we weren’t there

-does smoking cause lung cancer in humans? –
experimental testing is unethical
Correlations



Correlations – reliable associations between
two or more events
-used when testing is impossible or unethical
Correlation studies are useful but do not
necessarily prove cause-and-effect relationships
between two variables
Correlation-Rainfall and Tree Ring
Width
John Snow’s Cholera Spot Map
Scientific Habits of Mind






C. Scientific Habits of Mind
Good scientists tend to share several key habits
of mind, or ways of approaching and thinking
about things
-curiosity
-habit of skepticism
-skeptical – meaning they don’t believe
everything they are told
-leads to questioning of the status quo
Scientific Habits of Mind




openness to new ideas
-keeps an open mind as to how the world
works
-intellectual honesty
-a scientist may be convinced their
hypothesis is correct even before it has been
fully tested, but when an experiment is repeater
the results may be different than the first time
-a good scientist can admit their hypothesis
might be wrong
Scientific Habits of Mind




-imagination and creativity
-open to new ideas and can conceive of new
ideas themselves
-they can see patterns where others do not
or imagine things that others cannot
-allows them to expand the boundaries of
what we know
II. Statistics and Models




II. Statistics and Models
Statistics – the collection and classification of
data that are in the form of numbers
A. How Scientists Use Statistics
Scientists use statistics to summarize,
characterize, analyze, and compare data.
Statistics





For populations, scientists use statistic to describe
statistical populations – a group of similar things a
scientist is interested in learning about
Statistics are used to group characteristics of individuals
within a population by calculating averages, or
the mean – the number obtained by adding up the
data for a given aspect of a population and dividing
this sum by the number of individuals
The Mean


The mean provides a single numerical measure
for a given aspect of a population
-scientists can compare populations by
comparing their means
Distribution



Distribution – the relative arrangement of the
members of a statistical population
-the pattern that the bars on a bar graph
creates
-the overall shape of the bars is also part of
the distribution – the bell curve indicates a
normal distribution
Distribution



Normal distribution – a bell-curve, is when the
data are grouped symmetrically around the mean
Probability – the chance that something will
happen
-it is usually expressed as a number between 0
and 1 and written as a decimal rather than a
fraction
Sample size – the number of objects or events
sampled -it can be too small to yield an accurate
result


Sample – the group of individuals or events
selected to represent the population
Scientists try to make sure the sample they take
is large enough to give an accurate estimate for
the whole population
Statistics in Everyday Life


B. Statistics in Everyday Life
In the news there are statistics every day
-recognizing and paying attention to statistics
will make you a better consumer of information
Risk – the probability of an
unwanted outcome
if you have a 1 in 4 chance of failing a class, the
risk is ¼ or .25
 the news may show a well-publicized
environmental problem but it might not be as
statistically important as the news makes us
believe
 The most important risk is the risk of death –
most people overestimate the risk of dying from
sensational causes, and underestimate the risk
from common causes
Risk

The same with environmental problems –
overestimating sensational environmental
problems and underestimating the risk of
ordinary ones
C. Models




Models – representations of objects or systems
-4 types of models
Physical models – three-dimensional models
you can touch
-closely resemble the object or system they
represent but may be larger or smaller
Graphical & Concept models

Graphical models – maps and charts
-road maps, positions of stars, amount of forest cover
in a given area, and the depth of water in a lake

Conceptual models – verbal or graphical explanation
for how a system works or is organized
-flow chart
-can be diagrams or verbal descriptions or even
drawings of how something works or is put together
Mathematical models


Mathematical models – one or more equations
that represents a way system or process works
-very useful in cases with many variables
-many think because they use numbers they are
always right, but people are the ones who
interpret the data and write the equations
-if the data or equations are wrong, the
model will not be realistic and will provide
incorrect information
-they are only as good as the people building
them
III. Making Informed Decisions



III. Making Informed Decisions
Scientific research is the first step in solving
environmental problems
-many other factors have to be considered
such as how will the solution affect people’s
lives, how much will it cost, is it ethical?
Values


Values – principles or standards we consider
important
-examine values to answer the more difficult
questions
A. Environmental Decision-Making
Model






Decision-making model – is a conceptual
model that provides a systematic process for
making decisions
-can ease the difficulty of forming an
opinion on environmental issues
1-Gather information
2-Consider values
3-Explore the consequences
4-Make a decision
Decision Making Model