Transcript Lecture - UCI - School of Biological Sciences

Rain Upon The Radishes
RS: Christine Goedhart
CT: Analu Garcia
Santa Ana High School
Adapted from
Rain upon the Radishes
Purpose:
- Investigate the effects of pH on seed germination
- Relate results to the environmental problem of acid rain
Student Learning Outcomes:
1) Design an experiment via the scientific method.
2) Using an example scenario, describe why the
scientific method—and strict methodologies based
upon the scientific method—are standards in
research.
3) Define hypothesis, observation, replicate, constants,
independent and dependent variables, control, and
theory as they relate to scientific experiments.
4) Effectively communicate the results of a scientific
experiment, orally and in written form.
California Content Standards – 10th
grade Biology
Cell Biology
1b. Students know that enzymes are proteins that catalyze biochemical reactions without altering the
equilibrium and the activities of enzymes depend on the temperature, ionic conditions, and the pH of
the surroundings.
h. Students know most macromolecules (polysaccarides, nucleic acids, proteins, lipids) in cells and
organisms are synthesized from a small collection of simple precursors.
Ecology
6b. Students know how to analyze change in an ecosystem resulting from changes in climate, human
activity, introduction of non-native species, or changes in population size.
Investigation and Experimentation
1a. Select and use appropriate tools and technology (such as computer-linked probes, spreadsheets, and
graphing calculators) to perform tests, collect data, analyze relationships, and display data.
b. Identify and communicate sources of unavoidable experimental error.
c. Identify possible reasons for inconsistent results, such as sources of error or uncontrolled conditions.
d. Formulate explanations by using logic and evidence.
f. Distinguish between hypothesis and theory as scientific terms.
j. Recognize the issues of statistical variability and the need for controlled tests.
k. Recognize the cumulative nature of scientific evidence.
m. Investigate a science-based societal issue by researching the literature, analyzing data, and
communicating the findings. Examples of issues include irradiation of food, cloning of animals by
somatic cell nuclear transfer, choice of energy sources, and land and water use decisions in California.
Human Fossil Fuel Use
• Nighttime lights 1994-1995
http://www.nasa.gov/vision/earth/lookingatearth/NIGHTLIGHTS.html
Burning Fossil Fuels
• Releases gases into
the atmosphere
– CO2 (global warming,
ocean acidification)
– SO2 (acid rain)
– NOx (acid rain, nitrogen
deposition)
CO2
Acid Rain Formation
• Pollution mixes with water in the atmosphere
• Atmospheric water becomes more acidic
(lower pH)
pH describes the acidity or basicity of a
solution (amount of H+ ions)
Soda
Lemon
juice
Baking
soda
Coffee
Ammonia
Pure
water
Bleach
Drain
cleaner
Battery acid
Stomach
acid
Tomato
juice
Rain water
Unpolluted rain water
has a pH ~ 5.5
Rain water
with lower pH
is known as
acid rain
Effects of Acid Rain
•
•
•
•
Structure damage
Loss of aquatic life
Forest dieback
Inability of seeds
to germinate
Seed Germination
• Seed dormant until
right conditions for
growth
• Energy for growth
stored as starch
• Starch must be
broken down into
glucose
– Requires enzymes
http://www.biologyjunction.com/images/dicotseedling.jpg
Starch broken down into
glucose by enzymes
Enzymes
• Protein complex that increases the rate of reactions
• Lowers activation energy of reaction
• Activity affected by:
- Temperature
- Amount of substrate
- pH
http://lhs2.lps.org/staff/sputnam/Biology/U4Metabolism/enzyme.gif
Rain upon the Radishes Lab
Question: Can changes in pH affect seed germination?
Hypothesis: “If we make the pH more acidic, then radish
seed germination will ______.”
Independent Variable:
Dependent Variable:
Control:
Constant Variables:
Methods
1) To initiate germination of seeds, soak the seeds in water for 30 minutes
then drain and place on paper towels.
2) Label petri dishes with name, period, solution, and pH.
3) Fold a paper towel in half. Trace a circle using petri dish and cut out.
Place 2 paper towel circles in each petri dish.
4) Using the pipette wet the paper towel with 1-2 ml of solution.
5) Place 10 radish seed inside each petri dish.
6) Place petri dishes in a darker location that is not too hot or too cold.
7) Record the germination process and results over a 3-5 day period.
Data Collection
Solution
Hypothesis
Day Three
Day Five
Data Analysis
• Graph data using bar graph (individual and
class)
# of seeds germinated
12
10
8
6
4
2
0
2
3
4
Solution pH
6
7
Conclusion Questions
•
Was your hypothesis supported or rejected? Explain.
•
Identify your control in this experiment. Why was it important to
have in your experimental design?
•
What happens during the process of germination? Include
glucose and starch in your answer.
•
How is the pH of rain altered? (acid precipitation)
•
Why do you hypothesize that pH would affect germination?
•
What would be the implications of your lab data (economic, social,
etc.)?
•
Knowing the effects of pH on germination, what other factors do
you hypothesize might have an effect on germination?