vit
acti ies
33&34 Plants as Producers (Sessions I and II)II
BROWARD COUNTY ELEMENTARY SCIENCE BENCHMARK PLAN
Grade 4—Quarter 4
Activities 33 &34
SC.G.1.2.3
The student knows that green plants use carbon dioxide, water, and sunlight energy to turn
minerals and nutrients into food for growth, maintenance, and reproduction.
SC.H.1.2.1
The student knows that it is important to keep accurate records and descriptions to provide
information and clues on causes of discrepancies in repeated experiments.
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The student knows that a successful method to explore the natural world is to observe and
record, and then analyze and communicate the results.
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The student knows that to work collaboratively, all team members should be free to reach,
explain, and justify their own individual conclusions.
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The student knows that to compare and contrast observations and results is an essential
skill in science.
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The student knows that data are collected and interpreted in order to explain an event or
concept.
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ACTIVITY ASSESSMENT OPPORTUNITIES
The following suggestions are intended to help identify major concepts covered in the activity
that may need extra reinforcement. The goal is to provide opportunities to assess student
progress without creating the need for a separate, formal assessment session (or activity) for
each of the 40 hands-on activities at this grade level.
1. Session I—Activity 33: Ask, What are some things that might happen to the plants in a
location having a drought? (Plants will wilt and may die, fewer plants will grow, and so
on.) Ask, What are some things that might happen to cattle in an area where they may still
have access to water but where plants have died after a long drought? (Plants are
producers eaten by cattle, so the cattle would have less food and thus also weaken and
die.) What are some things that might happen to the people who live in this same drought
area? (Without plants as producers and without cattle, the people will have little food
available, and may have to leave the area.) So, why are plants important to humans?
(Besides the fact that we eat them directly, they are also food for animals that we use as a
food source.)
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2. Session II—Activity 34: Remind students that scientists must make very careful
observations. Ask, Thinking back on how the plants without sunlight looked in this
activity, what are some other words or phrases you could have also used to describe how
the plants looked? (Answers will vary, but students should be encouraged to use similes
and metaphors as well as some new vocabulary words.)
3. Use the Activity Sheet(s) to assess student understanding of the major concepts in the
activity.
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activities 33 & 34 Plants as Producers
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In addition to the above assessment suggestions, the questions in bold and tasks that
students perform throughout the activity provide opportunities to identify areas that may
require additional review before proceeding further with the activity.
vit
acti ies
33&34
Plants as Producers
OBJECTIVES
For the class
16
1
1 pkt
1 bag
1 roll
3
Students learn about the needs of plants by
observing how grass grows with and
without sunlight and with and without
water.
The students
discuss
the needs of plants
conduct
an experiment to determine the
effect of sunlight and of water on plant
growth
identify
plants as producers
flowerpots
plastic sheet, large
seeds, ryegrass
soil, potting
tape, masking
trays, plastic
water, tap*
* provided by the teacher
PREPARATION
Session I—Activity 33
SCHEDULE
1
One week before the activity begins, fill
sixteen flower pots with potting soil to a
depth of 3 cm (1.25 in.) and scatter fifteen
ryegrass seeds in each pot. Gently cover
the seeds with about 0.5 cm (0.25 in.)
more soil.
• Place eight of the pots on one plastic
tray and eight on another. Water each
pot.
• Place the trays in a moderately warm
spot and cover them with the plastic
sheet. The seeds should begin to
sprout in 3 days.
• Keep the soil moist but not soaking
wet, and remove the plastic sheet when
the grass has grown tall enough to
touch the sheet.
2
Make a copy of Activity Sheet 33 for each
student.
3
Locate a spot to place one tray of the
flowerpots where they will get no sunlight.
(A closet that is rarely opened is a good
choice.)
Session I—Activity 33 About 50 minutes,
with continuing observation sessions every
day for 6–8 days
Session II—Activity 34 About 30 minutes,
after completing the final observation session
VOCABULARY
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chlorophyll
producer
MATERIALS
For each student
1
Activity Sheet 33
1 pair safety goggles*
For each team of four
1
1
cup, plastic, small
ruler, metric
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379
Green plants have the unique capacity to
convert some of the energy from sunlight into
the chemical energy in food. In the presence
of sunlight, plants combine water (H2O) from
the soil and carbon dioxide (CO2) from the air
to produce glucose (C6H12O6). This process,
known as photosynthesis, can take place only
in the presence of light. Chlorophyll, the
green pigment that is found in all green
plants, traps the energy in sunlight. During
photosynthesis, this energy is converted to
chemical energy. Some of this chemical
energy is used by the plant to perform its own
metabolic functions. But much of it is stored
within the plant and used by other organisms
that eat the plant.
Because of this ability to produce their own
food, green plants are known as producers.
All other living things on Earth are directly or
indirectly dependent upon the food that
producers make.
BACKGROUND INFORMATION
Activity Sheet 33
Plants as Producers
Session I—Activity 33
1. What do you think will happen when you grow plants without sunlight? What
will happen when you grow plants without water?
Possible answer: They won’t grow much.
2. Observe and measure your plants. Record the independent variable you are
testing on the line. Then, record your data in the chart.
Independent variable tested: sunlight
or water
Circle the term at the top of each column that describes your experiment.
Day and date
Pot 1: Water or Sunlight
Pot 2: No Water or No Sunlight
height (cm)
observations
height (cm)
observations
Answers will vary
Session II—Activity 34
3. How does having no sunlight affect the grass plants? How does having no
water affect the grass plants?
No sunlight: The plants lose their green color and
grow thin.
No water: The plants get droopy.
4. What three things do green plants need to make food? Why do they need
these three things in order to grow and live?
Green plants need sunlight, water, and carbon dioxide
to make food. They need the energy in food to grow,
reproduce, make food, and repair worn-out body parts.
In this activity, students set up an experiment
to determine the results of depriving grass
plants of sunlight and water. Without sunlight
to power photosynthesis, a plant cannot
make food. If the plants are kept in the dark
long enough, the entire plant will die due to
lack of food.
Plants grown without water also cannot
perform photosynthesis because water is a
needed reactant in the process. In addition,
water plays an important role in maintaining
the internal pressure of plant cells. Without
this pressure, plant parts become limp.
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activities 33 & 34 Plants as Producers
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Energy moves through the food chains and
webs of Earth and is eventually dissipated
into forms that are no longer useful for
sustaining life. As a result, chemical energy
must continually be replenished by the
photosynthesizing work of producers.
Guiding the Activity
1
Session I—Activity 33
Distribute a copy of Activity Sheet 33 to each
student. Hold up one of the grass plants that
you have prepared for the activity. Ask, What
does this plant need in order to live? Write
all student suggestions on the board.
2
Students will probably answer that green
plants need water, soil, sunlight, and
nutrients. Some of them may know that
plants also need air. A few may say that
plants need food or fertilizer in order to live.
Remind students that an experiment is a test
carried out under careful conditions in order
to learn whether an idea is true or not.
Ask, Do plants need sunlight to live?
Students will probably say that they do.
Ask, How could we set up an experiment to
test this?
Students are likely to suggest that they
should try to grow plants without sunlight.
Hold a class discussion on how you might set
up this experiment. Remind students that a
variable is anything that can change in an
experiment. All variables except for one, the
one they are testing, should be controlled in
their experiment. Ask, What variable are we
testing in this experiment?
Now ask, What variables should we control
in this experiment?
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Additional Information
Students should say that they are testing the
variable of sunlight. Remind students that the
variable being tested in an experiment is
called the independent variable.
Variables such as amount of water,
temperature, and soil type should be
controlled, or kept the same.
Tell students that they will set up two sets of
plants—one set grown in sunlight, and an
identical set grown without sunlight—and
see what happens to each set.
3
Ask, Do plants need water to live?
Students will probably say that they do.
Ask, How could we set up an experiment to
test this?
Students are likely to suggest that they
should try to grow plants without water.
Hold a class discussion on how you might set
up this experiment. Ask, What is the
independent variable we are testing in this
experiment?
Students should say that the independent
variable is water.
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381
Guiding the Activity
Now ask, What variables should we control
in this experiment?
Additional Information
Variables such as amount of sunlight,
temperature, and soil type should be
controlled, or kept the same.
Tell students that they will set up two more
sets of plants—one set grown with regular
watering, and an identical set grown without
watering—and see what happens to each set.
Ask students to predict what will happen to
the plants grown without sunlight or without
water. Tell them to complete question 1 on
their activity sheets.
4
Tell students that half the groups will test
sunlight as the independent variable. The
other groups will test water as the
independent variable.
Distribute two pots with grass seedlings, a
metric ruler, and two pieces of masking tape
to each team. Have teams use the tape to
label the pots with the name of their team
and one of the following four descriptions:
Water, No water, Sunlight, or No sunlight.
Each group will have either a pair of pots
labeled “Water” and “No water,” or a pair
labeled “Sunlight” and “No sunlight.”
Have students measure the height of their
plants and record the data in the chart on
their activity sheets.
Have students measure from the soil level to
the top of the highest plant.
Place all the Water and Sunlight plants on a
tray, and leave the tray in the sunlight. These
plants will be watered. Place all the No
sunlight plants on a second tray, and put this
tray in the dark location you have chosen
(see Figure 33–1). Place all the No water
plants on a third tray, and put this tray in
sunlight next to the tray of Water and
Sunlight plants.
Figure 33-1. Place the No sunlight plants in a dark
location.
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activities 33 & 34 Plants as Producers
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Divide students into groups of four. Assign a
variable to each group.
Guiding the Activity
5
Every 2 days for the next 6–8 days, have
students observe and care for the plants. Tell
them to use the small plastic cups to water
each plant EXCEPT the No water plants with
exactly 5 mL of water every 2 days. Have
students measure the height of their plants
and record the data on the activity sheets.
Additional Information
You may wish to move the tray with the No
water plants to a safe location during
watering time to ensure that they are not
watered by mistake.
Be careful to expose the No sunlight plants to
as little light as possible when watering and
observing them.
At the end of the final observation session,
collect Activity Sheet 33 for use in Session II.
6
Session II—Activity 34
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Redistribute each student’s copy of Activity
Sheet 33. Have the students observe their
plants and record data one more time. Have
students examine the plants from groups that
tested the other variable so that all students
observe all four sets of plants. Instruct
students to answer question 3 on their
activity sheets.
Figure 34-1. A plant grown in sunlight versus a plant
grown in darkness.
When they have finished, ask, Which of the
plants are the healthiest?
The plants that had both light and water look
the healthiest.
Ask, What happened to the plants grown
without sunlight?
These plants have lost their green color and
look thin.
Write the word chlorophyll on the board.
Explain that chlorophyll is the substance in
green plants that makes it possible for them
to produce food from sunlight, air, and water.
Tell students that chlorophyll is green and is
the reason why plants are green.
Ask, Why do you think the grass grown
without sunlight lost its green color?
Students may be able to infer that, without
sunlight, the plants must have lost their
chlorophyll.
Tell students that when green plants are
deprived of sunlight, they stop producing
chlorophyll, and eventually run out of it.
Ask, Do grass plants need sunlight for
healthy growth?
Based on data from their experiments,
students should conclude that grass plants
need sunlight to grow well.
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Guiding the Activity
7
8
Additional Information
Ask, What happened to the plants grown
without water?
These plants were very droopy and limp.
Ask, Do grass plants need water for healthy
growth?
Based on data from their experiments,
students should conclude that grass plants
need water to grow well.
Tell students that plants, like all organisms,
need energy to live. Have students
brainstorm the reasons why plants need
energy. Write their responses on the board.
Plants need energy to grow, make food,
repair worn-out body parts, and reproduce.
Write the word producer on the board.
Explain that green plants are called producers
because they are able to produce their own
food from sunlight, water, and a gas in air
called carbon dioxide.
Explain that plants need the energy from the
food they produce to live. This is why green
plants need sunlight and water.
Ask, What do you think would have
happened to the grass plants if we had
kept them completely in the dark for 2
months?
They would have died because they would
not have been able to produce any food for
themselves.
Ask, What do you think would have
happened to the grass plants if we had not
watered them for 2 months?
Again, they would have died because they
would not have been able to produce any
food for themselves.
Have students answer question 4 on their
activity sheets
Have students design and carry out an
additional experiment to determine whether
plants also need air to live.
Assessment Opportunity
This Reinforcement also may be used
as an ongoing assessment of students’
understanding of science concepts and
skills.
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activities 33 & 34 Plants as Producers
SCIENCE JOURNALS
Have students place their completed
activity sheets in their science journals.
CLEANUP
The grass plants can be transplanted into a
spare terrarium. Wash the flowerpots and
the trays, and return them to the kit.
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REINFORCEMENT
Connections
Science Challenge
Strictly speaking, plants need light, but not
sunlight specifically, to produce chlorophyll
and carry out photosynthesis. Suggest that
teams design and conduct their own
experiments to determine whether artificial
light from different types of light bulbs will
produce plants as healthy as plants grown in
sunlight. Students might like to try an
ordinary incandescent bulb, a red bulb, a
yellow “bug light” bulb, an ordinary
fluorescent bulb, and a “gro-lite” bulb
intended specifically for house plants.
Remind students to control all other
variables, including the type of plants used,
the amount of water they are given, and the
amount of time they are exposed to light
each day. When students have completed
their experiments, let the teams share their
experimental designs, results, and
conclusions in a class discussion. Have
students research each type of bulb used in
the experiment and report on the makeup of
each.
• Investigate plants’ need for air: Use
petroleum jelly to coat the upper and lower
surfaces of all the leaves on one plant.
Place the coated plant and an identical but
uncoated plant in the same location, and
water them equally as needed to keep the
soil moist. Observe their general
appearance for 2 or 3 weeks. (Students
will notice that the petroleum-coated plant
died. Explain that this is because air could
not enter the plant through the leaves.)
• Investigate plants’ need for light: Have
students cut a 3-cm × 3-cm (1.25-in. × 1.25in.) piece of black construction paper into
a distinctive shape, then use a paper clip
to cover part of a leaf of a house plant with
the black paper. After 4 days, remove the
paper. A similarly shaped part of the
house-plant leaf should be pale and
lacking in chlorophyll, demonstrating again
that without light, chlorophyll is lost.
Science and Math
If students investigated plants’ need for
water as described in the first Science
Extension connection, have them make a
bar graph of their results, with the vertical
axis labeled Height, the horizontal axis
labeled Amount of Water, and each cup’s
number and the amount of water it
received labeled on or below its bar.
Tell students that only 2% of the sunlight
that reaches Earth is available to plants for
photosynthesis. About 50% of the sunlight
is reflected back into space by clouds and
dust in Earth’s atmosphere, about 20% is
absorbed by the atmosphere, and about
28% heats the land and water. Help
students make a pie graph showing these
proportions.
Science Extension
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Encourage teams to investigate plants’ need
for water, air, and light. Some students may
like to design and conduct their own
experiments. For students who need more
direction, you may want to suggest the
following investigations:
• Investigate plants’ need for water: Plant
four or five bean seedlings or other small
plants in each of five numbered cups filled
with potting soil, and place all cups in a
location where they will receive sunlight
for at least several hours each day. Water
each cup differently on a continuum from
no water to too much water, with cup 3
receiving enough water to keep the soil
moist but not wet. Record the height of the
plants and their general appearance every
2 or 3 days for at least 2 weeks. (Also see
the first Science and Math connection.)
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activities 33 & 34 Plants as Producers