The purpose of this resource is to develop an understanding of plants' response to light. Students will do simple investigations to observe plant responses to light. Educational levels: Primary elementary, Intermediate elementary, Middle school

The GLOBE Program, University Corporation for Atmospheric Research (UCAR)

English

Digital Library for Earth System Education

GLOBE® 2005  P4: Photosynthesis Learning Activity - 1 Earth System Science
A
ppendix
W
elcom
e
Introduction
Protocols
Learning A
ctivities
!
?
P4: A Beginning Look at  
Photosynthesis: Plants Need Light
Purpose
To develop an understanding of plants’ 
response to light
Overview
Students will do simple investigations to 
observe plant responses to light. 
Student Outcomes
Students demonstrate their understanding 
that the same plant species may show 
observable differences under different light 
conditions (i.e. kinds of light or duration 
of exposure). Students demonstrate their 
ability to set up and conduct a simple 
investigation, and to use process skills. 
Science Concepts
Life Sciences
Organisms’ functions relate to their 
environment.
Plants and animals have life cycles.
All organisms must be able to obtain 
and use resources while living in a 
constantly changing environment.
Scientific Inquiry Abilities
Observing
Inferring
Predicting
Collecting data
Analyzing data
Setting up and carrying out a simple  
 investigation
Design and develop scientific 
investigations.
Use appropriate tools and techniques.
Develop explanations and predictions 
using evidence.
Use appropriate mathematics to analyze 
data.
Time
Two full class periods and a number of short 
sessions over the next two to three weeks to 
check branches and record observations
Level
Primary and Middle
Materials and Tools
Small brown paper bags
Brown paper bags
Colored cellophane
Various plants with leaves (inside and/or 
outside)
Various light sources (incandescent, cool 
and warm fluorescent, full spectrum, 
sun, etc.)
Rulers
GLOBE Science Log with two columns, 
one for narrative description and one 
for pictorial/graphic
Preparation
Collect a variety of plants. Plants need to 
be large enough for students to cover three 
branches of one plant or you will need three 
replicate plants of each type/species.
Prerequisites
None
GLOBE® 2005  P4: Photosynthesis Learning Activity - 2 Earth System Science
Background
Photosynthesis is the process by which plants, 
algae and some bacteria use light energy to 
produce food (sugars) out of carbon dioxide 
and water. Chlorophyll, a pigment which gives 
plants their green color, traps light energy 
for these organisms to use in making food. 
Photosynthetic organisms are producers that 
provide food to nearly all consumers on Earth. 
For most living organisms, photosynthesis is 
the first step in the food chain which connects 
living things. Every land animal depends to 
some degree on green plants. Photosynthesizing 
plants take carbon dioxide from the air, water 
from the soil, and use energy from the sun. 
Some of the light energy as it interacts with 
chlorophyll, is used to split water molecules 
into hydrogen and oxygen. Light energy is 
then used to join hydrogen and carbon dioxide 
together to form a new molecule: sugar. The 
sugar formed is glucose, the food a plant uses 
for growth and maintenance. The process of 
photosynthesis is illustrated in the equation at 
the bottom of the page.
Sugars that plants make out of carbon dioxide 
and water are their only source of food that 
can be used immediately for energy, to make 
cell materials, or stored for later use. Water and 
minerals such as nitrogen and phosphorus 
dissolved in it (which may come from soil) are 
not sources of energy for plants or animals; 
therefore these are not considered plant food 
even though they are required for growth and 
survival. 
What to Do and How to Do It
Getting Ready
1. Ask and discuss the following questions:
• What do you think would happen if I  
put my favorite classroom plant in the  
closet for the rest of the year? Why do  
you think that might be? 
• What do you think plants need to live? 
• Have you heard the word 
photosynthesis? 
• What do you know about it? (Do not go  
into detail at this point, however.) 
• Do you think plants can grow with any  
kind of light? 
• Ask students what they think would  
happen if trees outside were covered  
and had no light. Ask what could cause  
this (lack of light and trees being   
covered) to happen.
• Why do you think plant survival is   
important? (Be sure students   
understand that because of the food  
chain, all animals rely on plants for  
survival.)
2. Tell students they are going to set up a 
test to  see what happens when part 
of a plant or a whole plant does not get 
light.
Exploration
Note: Beginning students will most likely need 
to do this as a group. Intermediate students 
can work independently in small groups using 
the following Work Sheet.
1. If appropriate for your students, discuss 
what variables (things that can change 
the result of the investigation) need to be 
6 CO
2      
+      6 H
2
O      +  light energy                            C
6 
H
12
O
6
   +   6 O
2
 
carbon    water chlorophyll glucose    oxygen 
dioxide
➤  
GLOBE® 2005  P4: Photosynthesis Learning Activity - 3 Earth System Science
A
ppendix
W
elcom
e
Introduction
Protocols
Learning A
ctivities
controlled (or kept constant) to make this 
investigation a fair test of the need for 
light without having other factors come 
into play. Help students to understand 
that, as much as possible, everything 
needs to be kept the same except for the 
one thing that they will be changing, the 
kind or the duration of light. 
2. Have each group decide what aspect 
of light they want to test (kind of light 
source, duration of exposure to light, 
distance from light source, etc.). Have 
each group give a prediction of what 
they think might happen depending on 
the variable they chose to test.
3. Have groups set up their investigation. 
Be sure to allow for replication by having 
students use more than one plant of the 
same species or more than one plant part 
per variable being tested. If necessary, 
discuss with each group how they are 
controlling all variables except the 
selected one. For example, if they chose 
to test the type or kind of light source, is 
the distance of the light source and the 
duration of exposure time the same for 
all the plants?
4. Have each group of students select 
three plants of the same species or three 
branches on one plant for the variable 
they are testing, and another set of three 
plants/branches for the control or, if 
possible, set up a control for the entire 
class. Students may use whole plants or 
plant parts, depending on the size and 
availability. 
5. Decide as a group how often plants 
will be checked (observed) and data 
gathered. For intermediate students, 
discuss with each group what they think 
are ways of observing quantitatively or 
collecting quantitative data (Will they do 
any measurements, i.e. length or width 
of leaves, height of plant, count number 
of healthy looking or sick looking leaves 
etc.?)
6. Have students check plants carefully 
on a regular basis and write and draw 
their observations (what is happening), 
inferences (“why do you suppose it 
happened” idea), and predictions (“what 
is going to happen next” idea), in their 
science logs. Take a minute regularly 
to have students share and discuss 
these observations, inferences, and 
predictions. Be sure they understand 
that an observation is detected by one 
or more of their five senses, whereas an 
inference is a guess at what might have 
caused the effect they are observing. This 
is worth reviewing regularly, so students 
have a clear picture that observation and 
inference are two very different skills 
that are important in science. Prediction 
is a guess at what might happen given 
a scenario or set of circumstances. It 
may help to make three columns on a 
chart labeled Observation, Inference, 
and Prediction and put each observation 
in the correct columns. If students give 
you an inference when they should 
have observed, ask for the evidence that 
led them to their inference. For older 
students, you may want to require that 
they do quantitative observations or 
collect quantitative data. See step 5.
Discussion Questions/Generalize
Ask each group to report the results of 
the investigation on their plant(s). Discuss 
conclusions as a group. Ask students why they 
think they got the results that they did. If they 
say that plants need light to live or be healthy, 
ask them why they think that is. For what do 
they think the plant needs light? For younger 
students, don’t worry about a thorough 
explanation of photosynthesis at this time 
if students don’t already have a grasp of the 
concept. It is sufficient that they understand 
that plants need food, and that plants use 
sunlight to help make food (in the form of 
sugar) in a process called photosynthesis. 
For older students, it might be appropriate 
to discuss photosynthesis at this time (See 
background) and include information they 
have read on similar investigations done by 
other workers.
GLOBE® 2005  P4: Photosynthesis Learning Activity - 4 Earth System Science
Assessment 
Science Log Entry
Have students write and draw in their GLOBE 
Science Logs their ideas about: 
• Why observation and inference is 
important in science and how they used 
these skills in their test or investigation
• Why it is important to cover their three 
test branches of plants with the same 
bags, water plants the same, and fertilize 
them the same
• How plants respond to various light 
conditions and why
Use the following rubric to score the writing. 
Primary students who have difficulty writing 
can be interviewed for understanding.
Skills Checklist
Use the checklist during the lesson to document 
students’ skill abilities.
Performance Task
Have students observe a plant or plant part 
from your local environment. Tell them to use 
the most possible number of senses except 
taste. Students should be able to use four of 
their five senses (sight, touch, hearing, smell). 
Record their observations (qualitative and/or 
quantitative). 
Have students infer some reasonable 
explanations why several leaves on the same 
plant are different.
Use the following rubric to score the writing. 
Primary students who have difficulty writing 
can be interviewed for understanding.
GLOBE® 2005  P4: Photosynthesis Learning Activity - 5 Earth System Science
 Criteria
 Identifies and controls  
 variables 
 
 Sets up investigation 
 (including replication) 
 
 Observes carefully using four  
 senses, qualitative observations 
 
 
 Measures accurately,  
 quantitative observations 
 
 Records data 
 (observations of plants) 
 
 Infers reasonable causes  
 for results          
A Beginning Look at Photosynthesis
Skills of Science Assessment Checklist
       Student Names
GLOBE® 2005  P4: Photosynthesis Learning Activity - 6 Earth System Science
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A Beginning Look at Photosynthesis: Plants Need Light

http://www.globe.gov/documents/356823/356868/earth_la_seaphen_p4.pdf

A Beginning Look at Photosynthesis: Plants Need Light

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