The History of a Meal
OBJECTIVE(S):
Upon completion of this activity, students should be able to:
1.
Analyze a food to determine the plants it contains.
2.
Name the place of origin of 15 food crops.
3.
Define plant breeding, domesticated plants, crop evolution, natural and artificial selection,
genetic variation.
4.
With a partner, outline a procedure that early plant breeders might have used to domesticate
a wild plant species.
5.
Write a paragraph explaining why it is important to on serve wild plants, from a plant
breeder's point of view.
MATERIALS AND/OR EQUIPMENT:
●
Nonmeat food products brought from home by students
●
World map showing continents, countries, bodies of water
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Crop origin cards (included)
●
World crop map with some countries and regions labeled (included)
TIME REQUIRED FOR ACTIVITY:
Three class periods
BACKGROUND MATERIAL:
(Adapted from "Crop Origins and Plant Improvement", by Sonja Williams, College of Agriculture,
University of Illinois.)
Imagine that the entire history of humans of Earth has been compressed into a single day. It is now
midnight, the end of that day. At what time do you suppose people began farming? They began just 14
minutes ago at about 11:46 p.m.!
Archaeologists think that people have been farming for less than 10,000 years. This is a very short time
compared to the million years that people are thought to have been on Earth.
Before people cultivated plants, they got their food by a way of life called, "hunting and gathering." In the
20th century, we depend on agriculture for most of our food. Very few people anywhere in the world
survive by hunting and gathering today, but until 7000 or 8000 B.C. all people lived this way.
Agriculture is defined as "the science or art of cultivating the soil, producing crops, and raising livestock,
and ... preparation of these products for ... use." While agriculturists depend on domesticated (tame)
plants or animals, hunters and gatherers depend on stands of wild plants or herds of wild animals. People
who live by hunting and gathering must move from place to place as their food resources become
depleted.
Many events had to occur over a very long period of time for people to change from hunter-gatherers to
farmers and city dwellers. Early hunter-gatherers found natural populations (stands) of wild grain and
harvested these stands by hand. You can understand how difficult this may have been if you imagine
gathering tiny seeds of a wild plant such as foxtail for your food. Fortunately, hunter-gatherers had many
kinds of plants and animals from which to choose.
Modern archaeologists and agronomists have discovered evidence that very productive varieties of wild
wheat and other grains existed in prehistoric times. These grain plants grew in scattered natural stands in
various areas of the Near East, especially in Turkey, Iran, and Iraq.
Those plants may have had other traits (phenotypes) that made them appealing to the early huntergatherers. They may have had larger kernels, different colors, or may have grown taller than today's
common wild varieties. Some may have had seed heads that didn't "shatter," but held on to their mature
seeds. Groups of hunter-gatherers settled in villages near large stands of productive wild grains.
Because many seed heads did shatter easily, many of the seeds produced in wild stands would be planted
naturally each year as they were collected by hunter-gatherers. (In much the same way today, corn seeds
germinate in fields and along roadsides from grain dropped by combines during harvest.) People in
villages began to count on the yearly production of "naturally planted" grains in the areas surrounding
their villages.
The next step in the development of farming in the Near East was actual domestication of wild plants.
Domestication included deliberately collecting, saving, and planting seeds, not just setting up camp near a
natural stand of wild plants.
When people realized they could collect seeds and plant them the following season, they may have
noticed that some seeds developed into more vigorous and healthier plants. At the end of the growing
season, they saved seeds from these plants to sow the next year. In this way, early people became
involved in plant selection and improvement.
Plants can be improved by selection. Plants possessing desirable phenotypes (traits) are selected or saved.
Desired traits might include higher yield, disease resistance, better taste, production of fruit or seeds at a
certain time of year, and many other characteristics. Seeds from selected plants usually develop into a
high (or predicable) percentage of offspring with traits similar to the parents.
Although prehistoric people had no idea how traits were passed from one generation to the next, they
made use of their observations to select plants with characteristics they wanted to preserve. It has only
been in our century that plant breeders have begun to understand that a blueprint or plan for organisms'
traits exists in every living cell in the form of a chemical called DNA. DNA is usually contained in
structures called genes, which are segments of larger structures called chromosomes. The DNA carried in
the chromosomes is passed from one generation of organisms to their offspring in observable and
understandable ways. The study of biological properties that are transmitted through DNA from one
generation to the next is called genetics.
At a later stage in the history of plant domestication, plant growers learned they could sometimes use two
different plants as parents and get offspring with a combination of the two parents' traits. Repro-duction
which involves male and female reproductive cells (eggs and sperm) is called sexual reproduction. The
process of selective mating of plants is called plant breeding. If plants with a different DNA code are
mated, the process is called hybridization. The offspring (the F1 generation) are called hybrid plants.
Hybridization worked best between similar plants because the plants often had very similar types and
numbers of chromosomes. Popula-tions of similar plants which can be hybridized belong to the same
species. Occasionally, plants that are not similar to each other can mate and produce live offspring.
However, many times offsprings of crosses between species with different types and numbers of
chromosomes are sterile and cannot produce offspring by mating or sexual reproduction.
Through a painstaking process of selection, planting, hybridization, and further selection of plants with
desired traits, early farmers developed most of the cultivars or varieties we know today. Wheat and many
other crops were domesticated in the Near East. Plant domestications occurred in their parts of the world,
too. China, Southeast Asia, Mexico, and South America are all regions where important crops were first
domesticated. In all these place, farmers were discovering wild plants, selecting, and breeding them to
increase the populations of plants with desired characteristics.
This process can be described as crop evolution. Evolution is the change in the frequency of
characteristics of a population over time. The process of crop evolution is dependent on variation in traits
of plants, selection of individuals with certain traits, and reproduction of the selected individuals.
Crop evolution, as described above, occurs as a result of artificial selection, in which people select the
plants that will reproduce. However, in the natural environment sometimes members of a plant population
are able to survive and reproduce while other members don't survive and therefore do not reproduce. This
process (which does not require that people do the selecting) is called natural selection.
Natural selection has also played a role in crop evolution. An example of the role of natural selection in
crop evolution is the development of species or varieties of plants suited to certain climates. Because of
differences in climate in different parts of the world, crops from specific regions may have greater
tolerance for cold, drought, heat, or flooding than crops from other regions. The climate, not people, has
acted to select the individuals most capable of reproducing in that environment.
Because early plant breeders had little understanding of genetics, development of new or improved
varieties of plants took a long time. Crop evolution and improvement occurred mostly through a process
of trial and error. But modern plant breeders use an understanding of genetics to speed up the process of
plant improvement.
Plant improvement requires more than just a knowledge of genetics. It requires genetic variation, so that
breeders can choose different traits to breed into crops. The variation comes from different individuals of
the same species of plants, or it may come from traits contained in different species.
Today, only about 150 species of plants are cultivated as crop plants. Another 1,000 species are not
cultivated, but are important to people for wood, fiber, medicine, and food. Worldwide, there are over
350,000 species of plants. Some of these 350,000 species can provide much variation for future crop
development. The wild plants of today may become the crops of tomorrow.
PROCEDURE:
(Adapted from "Crop Origins and Plant Improvement", by Sonja Williams, College of Agriculture,
University of Illinois.)
Imagine that there are no grocery stores. Imagine that you can't have a garden because there are
no seeds to buy. Where would you get your food?
You would probably learn to harvest wild plants, just as hunter-gatherer cultures still do in remote
parts of the world. This is a difficult way to get your goods and becomes even more difficult
when there are many people in a small area of and. Cultivated plants can be grown in much
greater densities and can feed greater populations.
It is important to remember that all food corps began as wild plants. Through the long process of
domestication described in the Background section of this unit, you learned some of the steps in
domesticating or selecting wild plants. Archaeologists and agronomists specializing in crop
evolution have worked like patient detectives to uncover evidence of the origins of crop plants.
This activity investigates the history of some of the food plants that people in our society take for
granted. You will see how long ago people first domesticated food plants and will get an idea of
how far food plants have spread from their original homes.
Class Preparation
Display nonmeat food products brought by students from home for this activity. Suitable foods
are fruits, vegetables or processed products. Make sure students bring the container or box for
processed foods such as breakfast cereals, cookies, or macaroni so that plant products contained
in the foods can be identified.
Copy and cut out a set of crop origin cards for each five students if each students does not have a
workbook.
Copy one map sheet per student if each student does not have a workbook.
(Read the Background section and the Introduction to Activity before class.)
1.
Look at all the foods that were brought to class by other students. List 15 different plants
that are contained in these food items. You may have to do some detective work in the
library to discover the plants that make up certain foods.
1.
9.
2.
10.
3.
11.
4.
12.
5.
13.
6.
14.
7.
15.
8.
2.
Use the crop origin cards to find the original home of each of the 15 food plants on your
crop map. Write the name of a crop plant near its place of origin. Since exact places of
origin are not known for most plants, you need only find the general area where the crop
is thought to have originated. (You may have to look at a more detailed world map to find
a specific country. You can enter the information on your crop map.)
If the cards don't contain a description of one or more of the food plants, you can use the library
to research the origin of a crop plant. The Learning More resources found in the reference
section gives some suggested books to help you research crop origins.
3.
Work with a partner to outline the steps early farmers could have used to develop crop
plants and improve their characteristics. You can look for these steps in the background
reading. It might help to think about a plant that is part of the food product you brought to
class. The first step will be the wild version of the plant; use as many steps as you need.
STEP 1:Find a group of wild plants.
__________________________________________________________________
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STEP 2:
____________________________________________________________
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STEP 3:
________________________________________________________________________
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STEP 4:
________________________________________________________________________
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4.
Write a paragraph to describe why it is important to preserve wild plants, from a plant
breeder's point of view.
Crop Origin Cards
Crop: Wheat
Scientific Name:
Triticum aestivum
Crop: Sugarcane
Scientific Name:
Saccharam officinarum, a grass
Place of origin/history of cultivation: Wheat
was first cultivated in the Near East (Turkey,
Iran, Iraq), North Africa, and Afghanistan.
Fossil grains 9,000 to 10,000 years old have
been discovered.
Place of origin/history of cultivation: Sugarcane
is thought to be from New Guinea or Java in
Southeast Asia. It is known to have been grown
for thousands of years.
Crop: Corn
Scientific Name:
Zea mays
Crop: Green pepper
Scientific Name:
Capsicum annuum
Place of origin/history of cultivation: Field corn
looks very different from existing wild corn
plants, so its history is not clear. Scientists think
it originated in Mexico and South America. A
wild relative of corn, teosinte, has been found in
Mexico. Teosinte has the same number of
chromosomes as modern corn, and both annual
and perennial forms exist. It was cultivated as
long ago as 5000 B.C.
Place of origin/history of cultivation: This plant
was first grown by Indians of North and South
America. It grows to eight feet tall and survives
for many years in tropical areas. In North
America the plant is grown as an annual.
Crop: Rice
Scientific Name:
Oryza sativa
Crop: Cashew
Scientific Name:
Anacardium occidentale
Place of origin/history of cultivation: This crop is
Place of origin/history of cultivation: Rice is
native to the dry areas of eastern Brazil. Wild
thought to be a native of China or Southeast
Asia. Rice was used in China as early as 3000 cashew trees still grow in South America.
B.C.
Crop: Winter Squash and pumpkin
Scientific Name:
Cucurbita maxima
Crop: Cucumber
Scientific Name:
Cucumis sativus
Place of origin/history of cultivation: Seeds
have been found in ancient archaeological
sites in North and South America. some seeds
from Mexico are nearly 7,000 years old.
Place of origin/history of cultivation: Cucumbers
are unknown in the wild, but are thought to be
from India. They spread east and west before the
birth of Christ. By A.D. 800, cucumbers were
cultivated in France.
Crop: Tomato
Scientific Name:
Lycopersicon esculentum
Crop: Apple
Scientific Name:
Malus domestica
Place of origin/history of cultivation: Tomatoes
are thought to be native to northwestern South
America. Mexico has many wild and cultivated
forms of tomato. Early European explorers of the
Americas took tomatoes back to Europe in the
1500s.
Place of origin/history of cultivation: Scientists
think that apples came from Western Asia
(Turkey, Iraq, Lebanon) because many wild
varieties are still found in Western Asia.
Crop: Lettuce
Scientific Name:
Lactuca sativa
Crop: Peach
Scientific Name:
Prunus persica
Place of origin/history of cultivation: Probably
lettuce was first cultivated in the Near East. There
is evidence that is was grown by the Egyptians as
early as 5000 B.C. It was popular with the
Romans. It had spread to China by A.D. 500.
Place of origin/history of cultivation: The peach
is thought to have been domesticated first in
China. It had spread to the Middle East (Iraq,
Iran, Turkey) before the birth of Christ.
Crop: Orange
Scientific Name:
Citrus sinensis
Crop: Potato
Scientific Name:
Solanum tuberosum
Place of origin/history of cultivation: Scientists
think the orange came from Southeast Asia. Most
citrus fruits were introduced to Europe by the
Arabs during the Middle Ages.
Place of origin/history of cultivation: Indians
living on the high slopes of the Andes of
western South America grew potatoes for
thousands of years before they introduced them
to Spanish invaders around A.D. 1600. In the
Andes mountains today, you can find 90 species
of wild potatoes in colors ranging from white, to
black, to pink, to yellow.
Crop: Carrot
Scientific Name:
Daucus carota
Crop: Vanilla
Scientific Name:
Vanilla planifolia, an orchid
Place or origin/history of cultivation: Afghanistan
is the home of the first carrots. Some wild carrots
are still found in the Near East. They have roots up
to 3 feet long! The ancient Greeks ate carrots as
medicine.
Place of origin/history of cultivation: The plant
that gives us vanilla grows in Mexico, Central
America, and South America. Vanilla flavoring
is made from the unripe seed pod, which is
fermented. Most plants are propagated from
cuttings, not from seed.
Crop: Banana
Scientific Name:
Musa paradisiaca sapientum
Crop: Green bean
Scientific Name:
Phaseolus vulgaris and other species
Place or origin/history of cultivation: The banana
is probably native to tropical Asia (Vietnam,
Cambodia, Malaysia area). Alexander the Great
found it in India on his explorations.
Place of origin/history of cultivation:
Archeologists have found beans in a Mexican
burial site from 5600 B.C. There are still many
wild beans found in Mexico. Many of these
wild beans have pods that pop open (shatter),
which makes it difficult to gather seeds.
Crop: Oat
Scientific Name:
Avena sativa
Crop: Peanut
Scientific Name:
Arachis hypogaca
Place of origin/history of cultivation: Oats were
first cultivated in the Near East around 2500 B.C.
The Greeks and Romans used oats as feed for
domestic animals.
Place of origin/history of cultivation: Peanut
shapes were carved on Peruvian pots from as
long ago as 4000 B.C. The plant is thought to
have originated in Brazil or elsewhere in South
America.
Crop: Onion
Scientific Name:
Allium cepa
Crop: Coffee
Scientific Name:
Coffea arabica
Place of origin/history of cultivation: Onions
originated in the Near East, perhaps around
Afghanistan. They were used by the ancient
Egyptians. The Spanish brought onions to the
new world.
Place of origin/history of cultivation: This plant
is native to northeastern Africa. It was
domesticated during the Middle Ages. Arabian
traders near the Red Sea were the first to buy and
sell coffee.
Crop: Cacao (chocolate or cocoa)
Scientific Name:
Theobroma cacao
Crop: Cabbage, broccoli, cauliflower Scientific
Name:
Brassica oleracea
Place of origin/history of cultivation: Cocoa was
used by the Aztecs in southern Mexico. Cocoa
beans had more value than gold and were used as
money by the Aztecs and the Mayans.
Place of origin/history of cultivation: Wild
cabbages did not form heads. They are thought to
have come from the Eastern Mediterranean area.
They have been cultivated for more than 2,000
years. By Roman times, cabbages that formed
heads were being grown.
Crop: Sunflower
Scientific Name:
Helianthus annuus
Crop:
Scientific Name:
Place of origin/history of cultivation: This plant
was a treasured plant of the Indians of Mexico
and North America for centuries before the
Europeans arrived. The plant produces a large
amount of seeds and oil, which were used by the
Indians. The seeds were easy to gather and were
an important source of dietary protein.
Place of origin/history of cultivation:
Crop: Soybean
Scientific Name:
Glycine max
Crop:
Scientific Name:
Place of origin/history of cultivation: Soybeans
originated in Eastern Asia. There are 5,000 year
old records of cultivated soybeans. There are still
wild species in China. Soybeans were first
imported into the U.S. in 1804, but weren't grown
widely until the 20th century.
Place of origin/history of cultivation:
Crop: Tea
Scientific Name:
Thea sinensis
Crop:
Scientific Name:
Place of origin/history of cultivation: This crop
was originally used as medicine in southwestern
China and northeastern India. It was introduced to
Europe in the 1600s.
Place of origin/history of cultivation:
World Crop Map
Label the area of origin for each of the 15 crops on your list.
REFERENCE(S):
Learning More: Library Resources
Books
Bassett, M.J. (1986). Breeding Vegetable Crops. Westport, CT: AVI Publishing Co.
Harlan, J.R. (1975). Crops and Man. Madison, WI: American Society of Agronomy.
Jaques, H.E. (1975). Plants We Eat and Wear. New York: Dover Press.
Klein, R.M. (1979). The Green World: An Introduction to Plants and People. New York: Harper and Row.
Leonard, J.N. (1973). The First Farmers. New York: Time-Life Books
Poehlman, J.M. (1987). Breeding Field Crops. Westport, CT: AVI Publishing Co.
Schery, R.W. (1972). Plants for Man. Englewood Cliffs, NJ: Prentice-Hall.