Teacher Guide and Answers, continued
Lab 5 • Classic
How do we measure biodiversity?
Data and Observations
Sample graph
Annual Average Grams of Biomass
Objectives
120
160
Process Skills
grams biomass per 0.3 m2
100
120
80
100
60
80
60
40
40
20
20
0
0
graph, model, infer, predict, draw conclusions
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
Year
Time Allotment
Community 1
45 minutes
Community 3
Community 2
Community 4
Materials
pen
graph paper
ruler
cm
• Analyze data from four test sites.
• Infer trends in biodiversity.
• Predict what environmental factors impact
biodiversity.
140
colored pencils
calculator
Alternative Materials
• You might want students to graph the data using a
computer and graphing program.
Preparation
Teaching the Lab
• Make sure students choose appropriate scales for
their graph.
• Explain that each of the farms has been abandoned
and then left undisturbed. Secondary succession is
slowly returning each site to its natural habitat.
• Assist students in their understanding of how the
original data was collected. The average of grams
of biomass per site was determined by collecting,
drying, and measuring the mass of all the plant
material that could be clipped from a 0.3-m2 area.
The study was done over the course of 11 years at
the Cedar Creek Natural History Area just north
of the Minneapolis-St. Paul metropolitan area.
The natural disaster of a drought during 1987–1988
provided an unusual opportunity to measure
biomass effects and recovery in the area.
168 TEACHER GUIDE AND ANSWERS
Analyze and Conclude
1. Organisms will likely include field grasses
(forbes or weeds), small shrubs, rodents, insects,
birds, and larger animals such as coyotes.
2. Community 1 is most diverse. The data indicate
that Community 1 consistently had greater
biomass, and even after the drought, it was able
to show the most biomass.
3. The precipitation data indicate a period of drought
from approximately 1987–1989. The biodiversity in
all communities decreased during this time.
4. Community 2 had the greatest change in
biomass. This is probably because there is less
diversity in the community. The community
with the least change is Community 1. Because
of its greater diversity, its overall biomass
remained at more consistent levels.
5. Community 1 recovered most quickly.
Community 2 recovered most slowly.
6. Inability to analyze the data presented could be a
source of error.
7. It appears that the greater the diversity and the
more biomass in a community, the more stable it is.
Inquiry Extensions
1. Students could cite events such as fire, flooding,
or disease invasion as factors. Their predictions
should show the greatest impact on and slowest
recovery in Community 2. Communities with the
Laboratory Manual
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
• Make sure you have enough graph paper for each
student
• Review graphing techniques with students if necessary.
Annual
Precipitation
Teacher Guide and Answers, continued
most diverse biomass would rebound faster because
the soil has more nutrients to support new growth.
2. Students could design an experiment in which
an affected area is examined over a period of
time. Real-estate development would adversely
affect biodiversity. In addition to loss of biomass,
students could mention habitat destruction,
changes in water runoff patterns, or wind
erosion. Because three of the communities were
once farms, students might try to analyze the
impact of fertilizers and pesticides. Human
impact in the form of conservation efforts could
result in more rapid naturalization through
selected species re-introduction, protection for
water, or removal of litter and pollutants.
Lab 6 • Design Your Own
How much vitamin C are you getting?
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Objectives
• Make predictions about the amounts of vitamin C
in a variety of drinks.
• Design an experiment to compare the amounts of
vitamin C in these beverages.
• Measure how different substances react in the
presence of iodine.
• Draw conclusions about the nutritional value of
the beverages.
Process Skills
measure, make predictions, design an experiment,
draw conclusions, use titration as a testing method
Materials
50-mL beakers (6)
plastic droppers
starch solution
tincture of iodine
vitamin-C solution
orange juice
juices and sports drinks with added vitamin C (4)
(Note: Because the students will be looking for a
blue-purple color change, do not provide drinks that
are dark in color.)
envelope containing copies of nutritional
information labels keyed to each drink, to be
distributed after the students complete the
procedure
Laboratory Manual
Alternative Materials
• Any type of juice or sports drink that makes a
claim about vitamin-C content can be used.
Possible Hypothesis
Orange juice has the most vitamin C; therefore, a
sample of orange juice will require the most drops of
iodine to observe a reaction with the starch.
Possible Procedure
1. Choose five beverages to test. Predict which one
has the highest level of vitamin C and which has
the lowest. Rank each sample according to the
prediction.
2. Create a data table to record this information.
3. Set out and label six 50-mL beakers. In the first
beaker, place 25 mL of vitamin-C solution. Add
25 mL of each beverage to its own beaker.
4. Add two drops of starch solution to each beaker.
5. Beginning with the vitamin-C solution, add one
drop of iodine to the beaker, and gently swirl.
Observe any change. Continue to add the iodine,
one drop at a time, until the liquid turns a dark
blue color. Record the number of iodine drops
needed to form this color.
6. Repeat step 5 for the beverages in the remaining
five beakers.
Preparation
• Prepare the starch solution by directing a stream
of spray starch into 75–100 mL of water in a beaker while stirring rapidly. A mixture at the correct
strength will have a pale blue tinge.
• Tincture of iodine, which is used as a skin antiseptic, works well. Use a brand that comes with
a dropper.
• Prepare a 1-percent ascorbic-acid solution.
[See Preparation of Solutions, pp. T13–T15.]
• Small containers of beverages will provide enough
samples for a class.
• Choose a variety of juices and sports or energy
drinks that students might be familiar with or
drink on a daily basis. This will make the experiment more interesting for them.
TEACHER GUIDE AND ANSWERS 169