What’s in a Tomato? Understanding our human impact on the environment

Student Guide

Scenario:

Michelle is shopping at a No Frills grocery store and is looking to buy some fresh tomatoes for

tomato and cheese sandwiches. She notices a few choices when it comes to buying tomatoes. She can purchase 1 locally grown in Ontario tomato for $1.50 or 2 tomatoes imported from Mexico for $1.00. Michelle decides to purchases both types and returns home to make her sand-

wiches.

As she begins to slice each tomato, she observes a difference between the two. The insides of the Ontario tomato (e.g. columella, septa) appear more red in colour; feels less firm; was easier to slice; and the tomato skin wall (e.g. pericarp wall) is less thick compared to the Mexican to-

mato. Mexican tomatoes appear more pale on the inside; feels more firm; and was harder to slice. Michelle also decides to taste a slice of each tomato and discovers that the imported toma-

to had less taste compared to the local tomato. Stricken by curiosity, Michelle takes both tomato slices to her high school’s science club, and

seeks assistance from a group of interested environmental science and biology students. She asks for the students’ help in understanding the difference between the two tomatoes. She men-

tions that she is especially curious about the difference in each tomato’s skin wall.

Working in smaller groups as part of the science club, you are asked to conduct the following

investigation to help Michelle better understand the differences in tomato types.

Required Resources:

Total of 4 tomatoes halves: 2 tomatoes halves from 2 different, locally grown in Ontario tomatoes and 2 tomatoes from 2 different imported tomatoes (Mexico, US)

1 plastic knife 1 ruler

1 measurement table (see below) 1 diagram of tomato cross section (see below)

Paper Towel

Content created by Jason Tran

Activity:

Part 1: Investigating differences

Steps:

1. Watch the Story of Food as an introduction to the activity: http://usc-canada.org/storyoffood/

2. Before proceeding with any dissection, discuss with your group and generate a hypothesis

regarding the difference in the tomato skin wall. Either your group believes that there is a difference in the skin wall of the imported vs. local tomato or your group believes there is

no difference and what Michelle witnessed was a coincidence.

3. Collect the required resources to assist your group in the investigation. Make sure not to mix up the tomato halves for each of the two tomato types (local vs. imported tomatoes).

With each tomato half, cut a cross section slice of each tomato (see Figure 1 below). The cross section slice should be at least an inch in diameter. Place the tomato slice down on-

to a paper towel and label the tomato to indicate its’ type (local vs. imported) and sample number. For example, your 2 local tomato slices could be labelled “Local 1” and “Local 2”.

Finish slicing and labelling both the local and imported tomato halves. You should have a

total of 4 tomato slices – 2 from each type. Figure 1: Cross sectional view of a tomato slice (Nemose 2011)

4. With each tomato slice, measure the tomato’s pericarp wall in three different places (as shown in Figure 1). Record each measurement you take for each slice sample (using Ta-

ble 1). When finished, calculate the sample’s average skin wall diameter. Record this av-

erage value in Table 1. Be sure to add the unit measurements into your table as well. Table 1: Tomato pericarp wall measurements, with example

5. Using the data that you’ve generated in Table 1, defend whether it supports your group’s

original hypothesis described in step 1.

Tomato Sample ID Measurement 1 Measurement 2 Measurement 3 Average

Example 0.9cm 0.75cm 1.1cm 0.92cm

Local 1

Local 2

Imported 1

Imported 2

Part 2: Relating differences

Before you begin to answer these questions, each student should read chapter 1 (Red Tennis

Ball) of Thomas Pawlick’s The End of Food. You can find the reading available at: http://books.google.com/books?

id=lCfuu3Fe64QC&printsec=frontcover&dq=the+end+of+food&hl=en&ei=uHtcTbbZGcm3tgel-pGwCw&sa=X&oi=book_result&ct=book-thumbnail&resnum=2&ved=0CDgQ6wEwAQ#v=onepage&q&f=false

Or go to books.google.com and search for Thomas Pawlick The End of Food.

Answer the following questions by identifying key findings from the above reading. In some cas-

es, you will need to compare your results from Part 1 and interpret this with key findings from the above reading.

Steps:

1. Explain why tomatoes are an essential ingredient for a healthy diet.

2. How have tomatoes changed over the last 50 years?

3. What are some commonalities between the scientists and processing tomato experts’

desired traits in an ideal tomato?

4. In Pawlick’s chapter one, he claims there is a connection between the thickness of a to-mato skin wall and the tomato being imported. Can you explain why imported tomatoes

have thicker skin walls compared to local tomatoes?

5. Are your findings from Part 1 supported by Pawlick’s claim identified in question 4? If not, can you explain reasons why you didn’t observe this claim in your results from Part

1?

6. Having conducting this experiment, explanation should you be able to provide to Michelle regarding the differences between the pericarp wall in both tomatoes?

Part 3: Interpreting differences

To answer the questions in this section, you will need to consider key findings from chapter one

and think broadly (e.g. in relation to the environment, which includes humans).

Steps: 1. Assuming that your data from Part 1 supported the claim that imported tomatoes have

thicker pericarp walls, can you explain how humans have played a key role in the domi-nance of these selected tomato types in supermarkets.

2. Chapter one mentions that southern US states and Mexico are primarily tomato produc-

ers year round, while southern Ontario only has a presence during summer months. US and Mexico’s dominance is related to its climate and large scale greenhouse production systems. How might these large scale greenhouses influence water use (and other envi-

ronmental problems, if any) in some of these southern regions?

3. Because of Ontario’s colder climate, we cannot grow our own tomatoes during winter

months. Instead, we import our tomatoes from the US and Mexico. Can you explain

some environmental problems that result from the constant transportation of tomatoes into food supermarkets in Canada?

4. What is a carbon footprint and how does the everyday transportation of tomatoes from

international areas affect our carbon footprint in terms of annual carbon emission pro-duced? Assume that the daily distance from California or Mexico to Ontario is 5000km

and that the car fuel efficiency is 1km/L. Assume that local grown tomatoes travel a daily distance of 50km with the same car fuel efficiency rate previously described. Graph the differences in terms of annual carbon produced and discuss.

Final Write up/ What is Expected from you (the student):

Students are expected to produce a formal write up that includes the following. Each student is

expected to hand in their own lab report.

Introduction, Goals/Objectives/Hypothesis, Methods, Results, Discussion, Conclusion Students will have to use info from the scenario to be used as part of the introduction.

Identify what the group’s goal/objective/hypothesis is. Explain the methods that they used

in the experiment. Report on the results found and then in the discussion, answer the above questions in addition to producing a conclusion statement.

References: Nemose. 2011. Solanum lycopersicum, tomato. Retrieved Jan 11, 2011 from: http://

www.geochembio.com/biology/organisms/tomato/#fruit

Pawlick, T. 2006. The End of Food. Greystone Books. Vancouver, BC, Canada. 265pp.

USC Canada. 2011. The Story of Food. Retrieved Jan 11, 2011 from: http://usc-canada.org/

storyoffood/

What’s in a Tomato?

Teacher Guide

This lesson plan demonstrates the use of research, experimental design, writing and critical

thinking skills by exploring linkages between tomato diversity and human impacts on the (food) environment.

Subject/Course: Environmental Sciences SVN3E

Grade Level: Grade 11

Topic: The impact of human activities on the environment

Specific Curriculum Expectations Met:

A1.1 Formulate relevant scientific questions about observed relationships, ideas, problems or issues, make informed predictions and or formulate educated hypothesis to focus inquir-ies

A1.6 Compile accurate data from laboratory and other sources and organize and record the data, using appropriate formats, including tables, flow charts, graphs and or diagrams

A1.8 Synthesize, analyze, interpret and evaluate qualitative and or quantitative data to de-termine whether the evidence supports or refutes the initial prediction or hypothesis and whether it is consistent with scientific theory; identify sources of bias and or error and sug-

gest improvements to the inquiry to reduce the likelihood of error A1.10 draw conclusions based on inquiry results and research findings and justify their

conclusions with reference to scientific knowledge. B1. Analyse selected current environmental problems in terms of the role human activities

have played in creating or perpetuating them, and propose possible solutions to one such problem;

B2.1 use appropriate terminology relating to the environmental impact of human activity,

including, but not limited to: carbon footprint, carbon neutral, biodegradable, biodiversity, carrying capacity, sustainability, and invasive and native species.

B3.4 explain the concept of a “carbon footprint” and how it is used to measure the impact on the environment of a range of human activities

Required Resources: Total of 4 tomatoes halves: 2 tomatoes halves from 2 different, locally grown in Ontario

tomatoes and 2 tomatoes from 2 different imported tomatoes (Mexico, US) 1 plastic knife 1 ruler

1 measurement table (see below) 1 diagram of tomato cross section (see below)

Paper Towel

Scenario:

Michelle is shopping at a No Frills grocery store and is looking to buy some fresh tomatoes for

tomato and cheese sandwiches. She notices a few choices when it comes to buying tomatoes. She can purchase 1 locally grown in Ontario tomato for $1.50 or 2 tomatoes imported from Mexico for $1.00. Michelle decides to purchases both types and returns home to make her sand-

wiches.

As she begins to slice each tomato, she observes a difference between the two. The insides of the Ontario tomato (e.g. columella, septa) appear more red in colour; feels less firm; was easier to slice; and the tomato skin wall (e.g. pericarp wall) is less thick compared to the Mexican to-

mato. Mexican tomatoes appear more pale on the inside; feels more firm; and was harder to slice. Michelle also decides to taste a slice of each tomato and discovers that the imported toma-

to had less taste compared to the local tomato. Stricken by curiosity, Michelle takes both tomato slices to her high school’s science club, and

seeks assistance from a group of interested environmental science and biology students. She asks for the students’ help in understanding the difference between the two tomatoes. She men-

tions that she is especially curious about the difference in each tomato’s skin wall.

Working in smaller groups as part of the science club, you are asked to conduct the following

investigation to help Michelle better understand the differences in tomato types.

Activity and Answer Key: Part 1: Investigating differences

Steps:

1. Watch the Story of Food as an introduction to the activity: http://usc-canada.org/storyoffood/

2. Before proceeding with any dissection, discuss with your group and generate a hypothesis

regarding the difference in the tomato skin wall. Either your group believes that there is a difference in the skin wall of the imported vs. local tomato or your group believes there is

no difference and what Michelle witnessed was a coincidence.

Ho: The pericarp wall in imported tomatoes (Mexico, US) will be thicker in diameter

compared to those in local Ontario grown tomatoes.

Ha: There is no difference in the diameter thickness of the pericarp wall of imported

or locally Ontario grown tomatoes

3. With each tomato slice, measure the tomato’s pericarp wall in three different places (as shown in Figure 1). Record each measurement you take for each slice sample (using Ta-

ble 1). When finished, calculate the sample’s average skin wall diameter. Record this av-

erage value in Table 1. Be sure to add the unit measurements into your table as well. Figure 1: Tomato diagram

Table 1: Tomato pericarp wall measurements, with example

4. Using the data that you’ve generated in Table 1, defend whether it supports or refutes

your group’s original hypothesis described in step 1.

Tomato Sample ID Measurement 1 Measurement 2 Measurement 3 Average

Example 0.9cm 0.75cm 1.1cm 0.92cm

Local 1

Local 2

Imported 1

Imported 2

Part 2: Relating differences

Answer the following questions by identifying key findings from the above reading. In some cas-

es, you will need to compare your results from Part 1 and interpret this with key findings from the above reading.

Steps:

1. Explain why tomatoes are an essential ingredient for a healthy diet.

2. How have tomatoes changed over the last 50 years?

3. What are some commonalities between the scientists and processing tomato experts’

desired traits in an ideal tomato?

Either the data (average calculations) supports that imported tomatoes have greater

pericarp walls or that there is no relationship between tomato origin and pericarp

wall. Some students (although rare) may find that local tomatoes have thicker peri-

carp walls. In this case, consider the student’s rationale as to why the opposite hap-

pened.

Tomatoes are: rich in Vitamin A (for good eyesight, sexual reproductive health and

body growth), Vitamin C (disease prevention, stress control, heal cuts and wounds),

potassium, phosphorus, iron, calcium, and lyocpene (shown to suppress cancer).

Today’s fresh tomato contains 30.7% less vitamin A;16.9% less vitamin C; 61.5%

less calcium (required to maintain strong bones and teeth); 11.1% less phosphorus;

9% less potassium; 7.97% less niacin; 10% less iron and 1% less thiamine than its

1963 counterpart.

Fat (lipid) content in tomato has increased by 65 percent since 1963, and sodium

has increased upward of 200 percent.

4. In Pawlick’s chapter one, he claims there is a connection between the thickness of a to-mato skin wall and the tomato being imported. Can you explain why imported tomatoes have thicker skin walls compared to local tomatoes?

5. Are your findings from Part 1 supported by Pawlick’s claim identified in question 4? If not, can you explain reasons why you didn’t observe this claim in your results from Part

1?

Firmness, in terms of thickness and hardness of the outer pericarp wall (which

provides the ability to withstand pressure and between 25 000 and 50 000

pounds of weight when bouncing along in a truck during shipment, thus in-

creasing yield (in pounds per acre))

Firmness, provides the ability to withstand rough handling during mechanical

harvesting

Resistance to disease

Heat tolerance

Firmness

Identified in both scientist and processing experts, firmness, in terms of thick-

ness and hardness of the outer pericarp wall is desired in tomatoes, especially

imported, since they need to withstand 25 000 to 50 000 pounds of weight

when bouncing along a truck during shipment, or withstanding rough handling

during mechanical harvesting

Thicker tomatoes are desired because they more likely will survive transporta-

tion and harvesting, whereas local tomatoes do not have to travel as far and so

no need for thickness

Findings from part 1 should support Pawlick’s claim that imported tomatoes

have a thicker pericarp wall.

If findings do not support this, assess student’s explanation. Several factors in-

clude: mixing of the tomato samples (on student’s part), local grown tomatoes

are of the same genetic type, local grown tomatoes are not actually local grown

but imported and masked as being locally grown (e.g. this is very typical of

produce purchased from farmer markets early in the season), difference in tim-

6. Having conducting this experiment, explanation should you be able to provide to Michelle regarding the differences between the pericarp wall in both tomatoes?

Part 3: Interpreting differences

To answer the questions in this section, you will need to consider key findings from chapter one and think broadly (e.g. in relation to the environment, which includes humans).

Steps:

1. Assuming that your data from Part 1 supported the claim that imported tomatoes have thicker pericarp walls, can you explain how humans have played a key role in the domi-

nance of these selected tomato types in supermarkets.

Locally grown tomatoes stay on the vine for much longer, allowing them to rip-

en naturally, which gives flavour. These tomatoes do not have thick pericarp

walls as it is not in their genetic makeup.

Imported tomatoes are selected for their thick pericarp wall characteristic,

which takes away from flavour since this is not what they’re bred for. Imported

tomatoes are picked earlier (while still green and not yet ripe) and sprayed

with ethylene gas, a naturally produced gas, to speed up ripening during trans-

portation.

Consumers demand/expect tomatoes to be fresh year round.

Supermarkets address/meet this need by importing from US/Mexico during

winter months

This has skewed the desire for certain tomatoes (that have more desirable

traits) over other types of tomatoes and explains why only 5 of approximately

5000 tomato varieties are commonly found in supermarkets.

2. Chapter one mentions that southern US states and Mexico are primarily tomato produc-ers year round, while southern Ontario only has a presence during summer months. US and Mexico’s dominance is related to its climate and large scale greenhouse production

systems. How might these large scale greenhouses influence water use (and other envi-ronmental problems, if any) in some of these southern regions?

3. Because of Ontario’s colder climate, we cannot grow our own tomatoes during winter

months. Instead, we import our tomatoes from the US and Mexico. Can you explain some environmental problems that result from the constant transportation of tomatoes into food supermarkets in Canada?

In some southern regions such as California, fresh water is a scare resource that

may not be efficiently used for large scale agricultural production.

Use of scarce freshwater resources in warm or desert like regions reduces water

availability for humans and other ecosystems (e.g. aquatic ecosystems), creating

water starved conditions. This is exacerbated during drought-like conditions.

As a result, water may be piped in from other regions or over pumped from

groundwater resources. A piped waterline is associated with huge environmental

costs (e.g. land lost to development) and over extraction of groundwater aquifers

may collapse the aquifer/land.

Water may also be trucked in but at the costs of transportation, oil/gas needed as

well as carbon/greenhouse gas emissions.

Use of scarce crude oil and long distance transportation creates carbon and green-

house gas emissions which contributes to climate change.

Large scale food production in southern regions may degrade soil quality from

pesticide/chemical use to protect crops. Use of these chemicals may run off into

water sources and pollute the water.

Over breeding due to selection of more desirable tomatoes ideal for shipping, re-

duces the diversity (biodiversity) of our food availability, which can influence the

amount of nutrients that we receive, influencing human health

Food packaging (non recyclable plastic food containers) that sore the tomatoes

create unnecessary waste.

4. What is a carbon footprint and how does the everyday transportation of tomatoes from international areas affect our carbon footprint, in terms of annual carbon emission pro-duced? Assume that the daily distance from California or Mexico to Ontario is 5000km

and that the car fuel efficiency is 1km/L. Assume that local grown tomatoes travel a daily distance of 50km with the same car fuel efficiency rate previously described.

Graph the differences in terms of annual carbon produced and discuss.

Carbon footprint is a measure of how much carbon or greenhouse gas emissions

we produced as a result of our daily activities/lifestyle choices.

By choosing to purchase imported over local, we create a larger carbon footprint

as a family/community/city/province etc.

The more transportation, especially from international destinations, the larger the

footprint, as shown in the graph.

Additional Teacher Notes: SVN 3E students may find Pawlick’s reading a bit difficult. If this is the case, the teacher can synthesis Pawlick’s reading into a PowerPoint presentation or a 1-2 page summary.

References:

Nemose. 2011. Solanum lycopersicum, tomato. Retrieved Jan 11, 2011 from: http://www.geochembio.com/biology/organisms/tomato/#fruit

Pawlick, T. 2006. The End of Food. Greystone Books. Vancouver, BC, Canada. 265pp.

USC Canada. 2011. The Story of Food. Retrieved Jan 11, 2011 from: http://usc-canada.org/

Acknowledgements:

Writer

Jason Tran

Editor; Designer: Karen Nelson Hamilton, OAC Liaison Officer

Further Resources: Ontario Agricultural College - Outreach

www.uoguelph.ca/oac/outreach

For more information, contact Karen Nelson Hamilton, OAC Liaison Officer

519-824-4120 ext. 56812 | knelson@uoguelph.ca | www.uoguelph.ca/oac/outreach