Lab 1
Biology: Exploring Life
Antibiotics
Too Much of a
Good Thing?
Antibiotics
Your doctor prescribes an antibiotic and
specifically cautions you to take every
pill.
Why?
Antibiotics
Checkpoint
What is an antibiotic?
a. It is a toxin used by bacteria to kill molds.
b. It is a drug that can kill infectious bacteria.
c. It is a chemical produced by the body to defend itself
against viruses.
d. It’s an area with
conditions that
don’t support life.
e. None of the
above are correct.
Antibiotics
Checkpoint
Human white blood cells ________.
a. carry oxygen and carbon dioxide to the lungs
b.
store antibiotics for release at sites of
infection
c. serve as one of the body’s natural lines of
defense against microbial invaders
d. gather and eliminate antibiotics from the site of
an infection
e. All of these are correct.
Antibiotics
Checkpoint
About half of the antibiotics produced today
__________.
a. end up in animal feed
b.are used by field hospitals in war zones
c. are shipped to third-world countries
d.become useless due to developing
resistance by bacterial populations
e. are stored for later use
Antibiotics
Checkpoint
How do bacteria populations become drug resistant?
a. Antibiotics remove drug-susceptible individuals
but leave those that are drug-resistant.
b. Natural selection drives bacterial populations to
change.
c. Some individuals are genetically resistant to
antibiotics.
d. All of these are correct.
Antibiotics
Checkpoint
Which of these is not an effective strategy to prevent
antibiotic resistance?
a. Don’t stockpile antibiotics.
b. Don’t demand antibiotics from your physician.
c. Use antibiotics only as long as symptoms
remain.
d. Use antibiotics as prescribed.
e. Don’t share antibiotics with others.
Antibiotics
Biology and Society
The development of antibiotic
resistance by bacteria illustrates
how natural selection affects our
lives. Can you name another way
our society experiences the
effects of natural selection?
Antibiotics
Biology and Society
Discussion Question
The development of antibiotic resistance by bacteria illustrates how natural
selection affects our lives. Can you name another way our society experiences
the effects of natural selection?
Follow-Up Questions
• Is it likely that insect or plant pests (weeds) might develop resistance to
pesticides and herbicides?
• Some plants, like BT corn and BT cotton, are being engineered to include a
pesticide gene. What do you predict to be the long-term success of such a
strategy? What strategies should a farmer employ to prevent pests from
becoming resistant?
Antibiotic resistance in bacteria is not the only case in which humans are causing
pressures that contribute to the natural selection of a population. Other examples
include insect resistance to BT corn, BT cotton, and other natural and genetically
altered crops (http://www.nature.com/nsu/021202/021202-2.html). A great deal of
research is being conducted to develop strategies to prevent pest populations from
developing pesticide resistance (http://www.biotech-info.net/ECB.pdf).
Antibiotics
Biology and Society
Many antibiotics—like penicillin—are no longer
effective, but it is costly to develop replacements.
Do we have an obligation to societies that cannot
afford to develop these new and expensive
antibiotics?
Antibiotics
Biology and Society
About 50% of the antibiotics produced today
are used in the livestock industry. What
impact does this have on the treatment of
human diseases?
Antibiotics
Internet Research
Antibacterial Soap Doesn’t Prevent Viral Infection
(http://kidshealth.org/research/antibacterial_products.html) This article outlines our
use and misunderstanding of antibacterial soaps. Are there concerns that bacteria
will develop resistance to antibacterial soaps?
Drug Companies Snub Antibiotics
(http://www.nature.com/nsu/030915/030915-6.html) The article speculates that drug
companies are spending less money and less effort to develop new antibiotics. What
evidence does the author cite? What are the consequences to global health if this is
the case?
Is Your Meat Safe?
(http://www.pbs.org/wgbh/pages/frontline/shows/meat/safe/) This site outlines the
debate over the use of antibiotics in the livestock industry. Familiarize yourself with
the issues, then share your thoughts
(http://www.pbs.org/wgbh/pages/frontline/shows/meat/talk/). Was the coverage fair
and unbiased?
Antibiotics
Summary
• We didn’t have antibiotics before the 1940s.
• Alexander Fleming helped to develop the first
antibiotic from a mold.
• Antibiotics work to kill infecting bacteria.
• Natural variations exist within bacterial
populations that make some bacteria resistant
to antibiotics.
• Abuse of antibiotics promotes the
development of antibiotic-resistant bacteria.
Antibiotics
Preventing
the
development
of
antibiotic-resistant bacteria is in the
hands of every individual. What actions
will you take?
Five Steps of the scientific method
1. Observation come from others or results of earlier
tests
2. Questions are asked about unclear aspects of the
observations: How? Why? When?
3. Hypotheses are tentative explanation of a
phenomenon phrased in such a way as to be
testable.
4. Predictions are logical, testable outcomes of the
hypotheses developed by the use of deductive
reasoning. Predictions take the form of if (statement
of hypotheses) is true, then (predictions).
5. Tests of prediction are performed to determine if the
predictions are supported (fail to falsify) or falsified.
Concept Check
Not all science discoveries strictly follow the “scientific
method”. Which of the following would best be described as
discovery science?
•
Sequencing the human genome.
•
Describing a new bird species from the Philippines.
•
A project to find preserved specimens of the probably
extinct Rocky Mountain locust frozen in glaciers .
•
All of the above.
Answer
Not all science discoveries strictly follow the “scientific
method”. Which of the following would best be described as
discovery science?
•
All of the above.
A Case Study of Hypothesis-Based Science
• In experiments designed to test hypotheses
–
The use of control groups and experimental
groups helps to control variables
Figure 1.8B
Figure 1.8C
Percent of total attacks
on artificial snakes
100
80
84%
83%
Artificial brown snakes
60
40
20
0
17%
Coral snakes
absent
Figure 1.8E
Figure 1.8D
Artificial king snakes
16%
Coral snakes
present
Interpreting Data
These two snakes look remarkably similar to each other. The coral
snake (right) is very poisonous to vertebrates. Hypotheses:
H1: The coral snake’s bright color pattern serves to warn off
potential predators.
H2: The the king snake suffers less predation because it mimics or
looks like the coral snake.
H3: The protection that king snakes receive by mimicking coral
snake will depend on the presence of coral snakes.
Interpreting Data
A team of scientists designed an
investigation that used artificial
snakes
to
test
the
previous
hypotheses. Which of the previous
hypotheses are supported by the
results displayed at the right?
•
H1: The coral snake’s bright
color pattern serves to warn
off potential predators.
•
H2: The the king snake suffers
less predation because it
mimics or looks like the coral
snake.
•
H3: The protection that king
snakes receive by mimicking
coral snake will depend on the
presence of coral snakes.
•
Both A and B
Answer
A team of scientists designed
an investigation that used
artificial snakes to test the
previous hypotheses. Which of
the previous hypotheses are
supported
by
the
results
displayed at the right?
•
Both A and B
Interpreting Data
Biologists placed artificial snake
mimics in two different localities
to test the hypothesis that looking
like a poisonous snake only
works where the poisonous snake
is found:
1. Outside of the coral snake
range—only king snakes present.
2. Inside the coral snake range—
both coral and king snakes are
present.
Interpreting Data
The data graphed at the right
__________ the hypothesis that the
effectiveness of mimic coloration
depends upon the presence of the
poisonous model is:
•
supports
•
does not support
•
is irrelevant to
Answer
The data graphed at the right
__________ the hypothesis that the
effectiveness of mimic coloration
depends upon the presence of the
poisonous model is:
•
supports
Interpreting Data
Based on this data which of the
following is a logical hypothesis or
prediction?
•
King snakes outside of the range
of coral snakes will more closely
resemble coral snakes than
populations of king snake living
within the range of coral .
•
King snakes outside of the range
of coral snakes will not resemble
coral snakes as closely as
populations of king snakes that
live within the range coral
snakes.
•
Neither prediction is valid.
Answer
Based on this data which of the
following is a logical hypothesis or
prediction?
•King snakes outside of the range
of coral snakes will not resemble
coral snakes as closely as
populations of king snakes that live
within the range coral snakes.
Controls
•This case study provides an example of a
controlled experiment, one that is designed to
compare an experimental group (the artificial king
snakes, in this case study) with a control group
(the artificial brown snakes).
•Ideally, the experimental and control groups
differ only in the one factor the experiment is
designed to test–in our example, the effect of the
snakes’ coloration on the behavior of predators.
Controls
•Without the control group, the researchers would
not have been able to rule out the number of
predators in the different test areas as the cause
of the different number of attacks on the artificial
king snakes.
•The clever experimental design left coloration as
the only factor that could account for the low
predation rate on the artificial king snakes placed
within the range of coral snakes.
Hypothesis
Theory needing investigation: a tentative
explanation for a phenomenon, used as a basis
for further investigation
The hypothesis of the big bang is one way to
explain the beginning of the universe.
Hypothesis - defined
 A conjecture advanced for heuristic purposes,
cast in a form that is amenable to confirmation
or refutation by conducting of definable
experiments and the critical assembly of
empiric data; not to be confused with
assumption,
postulation,
or
unfocused
speculation.
 Heuristic: LOGIC procedure for getting
solution: a helpful procedure for arriving at a
solution but not necessarily a proof
Deduction
•Conclusion drawn: a conclusion drawn from
available information.
•Drawing a conclusion: the process of drawing
a conclusion from available information.
•LOGIC logical conclusion: a conclusion
reached by applying the rules of logic to a
premise.
•LOGIC reasoning: the forming of conclusions
by applying the rules of logic to a premise
A Case Study from Everyday Life
• Deductive reasoning is used in testing hypotheses as
follows
–
If a hypothesis is correct, and we test it, then we
can expect a particular outcome
Two important qualities of the hypotheses-based science
1. A hypothesis must be testable.
2. A hypothesis must be falsifiable.
A hypothesis becomes credible when
repeated attempts to disprove it fail.
Introduction to Lab 1
• scientific inquiry is a particular way of answering
questions
• questions that can be answered by science
must meet specific guidelines and scientific
investigations must be carried out using certain
rules
• an investigator cannot show that his or her
experiment was done according to the guidelines,
then the results of that experiment will not be
recognized as valid by other scientists
Introduction to Lab 1
• The purpose of such guidelines can be
understood by comparing them to sports records.
For example, a new record set in a track and field
event only counts if the meet was approved by
the governing body that sets the guidelines. The
site and equipment used are scrutinized to be
sure that they are within the regulations and the
athlete is tested for use of illicit substances. Only
when these required conditions are met is the
record certified as valid.
Introduction to Lab 1
• In this laboratory you will learn about the basic
elements of scientific inquiry and how to apply
this process to solving problems.
Exercise 1.3: The Elements of an Experiment
Objectives:
1. Define and give examples of dependent,
independent, and standardized variables.
2. Identify the variables in an experiment.
3. Explain what control treatments are and why
they are used.
4. Explain what replication is and why it is
important.
Exercise 1.3: The Elements of an Experiment
• Variables are things that may be expected to
change during the course of the experiment.
•The investigator deliberately changes the
independent variable
•He measures the dependent variable to learn
the effect of changing the independent variable.
•To eliminate the effect of anything else that
might influence the dependent variable, the
investigator tries to keep standardized variables
constant.
Dependent Variables
The dependent variable is what the investigator
measures (or counts or records). It is what the
investigator thinks will vary during the experiment. For
example, she may want to study peanut growth. One
possible dependent variable is the height of the peanut
plants. Name some other aspects of peanut growth that
can be measured.
Number of peanuts, weight of the plants, leaf area, time
to maturation.
All of these aspects of peanut growth can be measured
and can be used as dependent variables in an
experiment. There are different dependent variables
possible for any experiment. The investigator can
choose the one she thinks is most important, or she can
choose to measure more than one dependent variable.
Independent Variables
The independent variable is what the
investigator deliberately varies during the
experiment. It is chosen because the investigator
thinks it will affect the dependent variable. Name
some factors that might affect the number of
peanuts produced by peanut plants.
Amount of fertilizer, type of fertilizer, temperature,
amount of water, day length, genetic type of the
peanuts.
Standardized Variables
• A third type of variable is the standardized
variable. Standardized variables are factors that
are kept equal in all treatments, so that any
changes in the dependent variable can be
attributed to the changes the investigator made in
the independent variable.
Standardized Variables
• Since the investigator's purpose is to study the
effect of one particular independent variable, she
must try to eliminate the possibility that other
variables are influencing the outcome.
• This is accomplished by keeping the other
variables at constant levels, in other words, by
standardizing these variables.
Standardized Variables
•For example, if the scientist has chosen the
amount of fertilizer as the independent variable,
she wants to be sure that there are no
differences in the type of fertilizer used. She
would use the same formulation and same brand
of fertilizer throughout the experiment. What
other variables would have to be standardized in
this experiment?
Amount of water, temperature, day length,
genetic type of peanuts.
Predictions
• A hypothesis is a formal, testable statement
• The investigator devises an experiment or
collects data that could prove the hypothesis
false
• He should also think through the possible
outcomes of the experiment and make
predictions about the effect of the independent
variable on the dependent variable in each
situation.
• It is useful to think of a prediction as an if/then
statement: If the hypothesis is supported, then
the results will be ...
Levels of Treatment
• Once the investigator has decided what the
independent variable for an experiment should
be, he must also determine how to change or
vary the independent variable.
• The values set for the independent variable are
called the levels of treatment.
Control Treatments
• It is also necessary to include control
treatments in an experiment.
•A control treatment is a treatment in which the
independent variable is either eliminated or is set
at a standard value.
•The results of the control treatment are
compared to the results of the experimental
treatments
Control Treatments
1. An investigator studies the amount of alcohol
produced by yeast when
it is incubated with different types of sugars. Control
treatment:
A treatment with no sugar.
2. The effect of light intensity on photosynthesis is
measured by collect
ing oxygen produced by a plant. Control treatment:
Put a plant in the dark.
3. The effect of NutraSweet sweetener on tumor
development in laboratory rats is investigated.
Control treatment:
One group of rats receives no NutraSweet
sweetener.
4. Subjects are given squares of paper to taste that
have been soaked in a bitter-tasting chemical. The
investigator records whether each person can taste
the chemical. Control treatment:
Use some papers that do not contain the chemical.
5. A solution is made up to simulate stomach acid at pH
2. Maalox antacid is added to the solution in small
amounts, and the pH is measured after each
addition. Control treatment:
Add water instead of Maalox antacid.
Replication
•Replicating the experiment means that the
scientist repeats the experiment numerous times
using exactly the same conditions to see if the
results are consistent.
•A concept related to replication is sample size.
•It is risky to draw conclusions based upon too
few samples.
Methods
investigator must find a method to measure the
dependent variable; otherwise, there is no
experiment. investigator must find a method to
measure the dependent variable; otherwise,
there is no experiment.