The Diversity of Corn

The Diversity of Corn

Target Grade Level / Age Range:

3rd

Time:

40 minutes

Purpose:

To help students learn scientific skills like observation and understand what traits are and that traits can vary within a single species through the lens of types of corn and their ancient ancestor.

Materials:

Suggested Companion Resources (books and websites)

Vocabulary (with definitions)

  • Heredity: the passing on of physical or mental characteristics from one generation to another genetically
  • Diversity: to have a variety or range of different things
  • Traits: a distinguishing quality or characteristic
  • Characteristics: a distinguishing trait or quality
  • Teosinte: a grass native to Mexico that is the early ancestor to modern corn
  • Popcorn: a type of corn that pops when heated
  • Sweet corn: a type of corn with a higher sugar content that humans like to eat
  • Field corn: a type of corn, also called #2 yellow dent corn, that is harvested when dry and used for animal feed, ethanol production, and other things
  • Decorative corn: also called flint or Indian corn, this type of corn is primarily used for decoration

Background – Agricultural Connections (what would a teacher need to know to be able to teach this content)

Corn or maize was not always available in the form it is now. Originally, the crop was called teosinte and was from Mexico. Teosinte was more similar to other grasses. It had thinner leaves, more branches per plant, and each ear had only a few, tough kernels that were hard to work with. Over time, people selected seeds from the teosinte plant to plant the next year. They specifically chose plants with variations that made them more suitable for cultivation. Today, corn plants are tall, have a single stalk, have more broad leaves, and produce large ears with many kernels.

Today, there are hundreds of variations of corn. However, these variations fit more or less into a handful of categories based on their purposes. The ones discussed in this lesson are field corn, sweet corn, popcorn, and decorative corn.

Field corn is the kind of corn grown most often in Iowa. It is used for animal feeds, ethanol production, fiber production, food production, and other industrial uses. It is said that in an average grocery store, there will be about 4,000 products with ingredients that came from corn. These ingredients can be anything from high fructose corn syrup (a sugar), to vitamin D, to corn starch and corn oil. Field corn is not always called field corn. It is also called “#2 yellow dent corn” or “dent corn.” This is because when the kernel dries, the starch in the seed shrinks, creating a dent at the top of the kernel. This dent is not prevalent with other kinds of corn.

The texture of field corn may seem like plastic or like fake corn to students. This is because field corn is dried before it is stored to avoid mold and other issues.

Sweet corn is different because of the amount of sugar in the kernels. However, we also harvest this corn at a different time, so it is soft, sugary, and “milky,” unlike other types of corn. Sweet corn is the kind of corn we humans like to enjoy in the summers on the cob!

Since we harvest sweet corn at a different developmental stage than other types of corn, it can be more sticky feeling than others. It is also soft, as opposed to the hard, dried kernels on other types of corn.

Popcorn is visibly much different than other types of corn. It has a smaller ear with small, round kernels. The dents present in field corn will not be present in popcorn, even though popcorn is also dried. The starch in the seed of popcorn is different from field corn, in that there’s a small amount of water inside of the starch. When the kernel is heated, that moisture is heated, causing pressure inside the strong hull. The hull will eventually pop.

Decorative corn, also called flint corn, ornamental corn, or Indian corn, also has a hard kernel. This type of corn is most visibly different because of its multicolored kernels. In terms of seed content, this type of corn is somewhere in between field corn and popcorn. You’ll notice that decorative corn also does not have dents in each kernel like the field corn does. However, it is less likely to pop as consistently as popcorn does. Today, this type of corn is used mostly for decoration during Thanksgiving and other fall festivities.

The purpose of this lesson is to (a) help students learn scientific skills like observation, and (b) understand what traits are and that they can vary within a single species. In order to meet these objectives, using vocabulary words and asking leading questions during the lesson may be necessary. The students will be observing each type of corn and taking notes or drawing their depiction of what they look like in the graphic organizer.

Towards the end of the lesson, teosinte is introduced as an ancestor of modern corn. While the intricacies of how corn evolved won’t be explored in depth, a basic understanding that humans chose seeds based on the variety of traits displayed should be covered. If this is confusing, it’s possible to use other species as an example. For instance, dogs are all one specie, too, but there are many kinds of dogs with many different features. This is because people raised dogs and chose them based on the traits that they liked. Corn is the same way.

It is also mentioned in the lesson that corn isn’t the only food crop that was artificially selected over long periods of time to be what it is today. Other examples are watermelons, bananas, peaches, eggplants, and carrots. Here’s an article with pictures of the wild vs. cultivated versions of these plants: http://www.sciencealert.com/here-s-what-fruits-and-vegetables-looked-like-before-we-domesticated-them.

Interest Approach or Motivator

Ask students how many types of corn there are. Take guesses from them. Inform students that there are four different major types of corn, and each type has multiple variations!

Procedures

  1. As a class, read the book My Family’s Corn Farm by Katie Olthoff aloud.
  2. Discuss the book as a class. What do students remember from the book? What was the main idea? What surprised them about Presley’s farm or about corn production? What didn’t they know before?
  3. Lead the discussion into types of corn. Presley’s family raises field corn. Ask the students how many types of corn do they think there are. Take a few guesses from the class.
  4. Tell students that there are four different major types of corn in Iowa. They are field corn, sweet corn, popcorn, and decorative corn. Each type of corn has many different varieties that are slightly different!
  5. Give each student the graphic organizer worksheet. Tell the students that they will use this to organize their thoughts about each kind of corn. They can draw small pictures, write key words, and full sentences to show or explain what they notice about each type of corn.
    1. Throughout the lesson and in the explanation of the worksheet, use words like observe, traits, and characteristics.
  6. Bring out an example of an ear of field corn (or show pictures if actual ears are not possible). Ask students what they notice about the corn.
    1. Talk about things like color, size, and texture.
    2. Talk about uses of field corn, like animal feed, fiber, ethanol, and some food products (like high fructose corn syrup in pop, corn starch, or ingredients in vitamins).
    3. Tell students to take notes in this section of their graphic organizer.
  7. Next, bring out an example of an ear of sweet corn. Ask the same types of questions as you did with field corn.
    1. Ask students what the color, size and texture are like. In what way is sweet corn different from field corn? How are they similar?
    2. Point out the texture specifically. Sweet corn isn’t as dry as field corn because we like to eat it fresh, unlike field corn, which is dried and processed (ground, cracked, flaked, etc.) before livestock eat it. Sweet corn has more sugar in the kernels than field corn!
    3. Tell students to take notes in this section of their graphic organizer.
  8. Next, bring out an example of an ear of popcorn. Again, talk with students about its appearance, and how it compares and contrasts with the previous ears.
    1. Students may notice size and color right away, but point students toward the shape of the kernel. Popcorn kernels are small and round. They have a very hard external shell and a soft starchy center. When they get heated, that starch explodes into the popcorn we like to eat!
    2. Tell students to take notes in this section of their graphic organizer.
  9. Lastly, bring out an example of decorative corn. Talk about its appearance and how it compares and contrasts with the other kinds.
    1. Tell students to take notes in this section of their graphic organizer.
  10. Now that students have seen each kind of corn, ask them what kind of corn they think is most commonly grown in Iowa. Take guesses from the class.
    1. Tell them that 99% of corn in Iowa is field corn! The remaining 1% is split between the other three kinds of corn.
  11. Ask students to recall some of the uses for field corn. They should say things like animal feed, ethanol, fiber, and foods.
  12. Talk to students about what makes field corn good for these things. Point out traits they may have already noticed, like large ears, many kernels, and uniformity. Would it be easier for people to make food out of corn if it had small, hard ears with only a few small kernels on each ear? No, it wouldn’t! But that’s originally what corn was!
    1. Plant characteristics such as a single stalk and wide leaves could also be mentioned.
  13. Show the class a photo of teosinte. Explain that this is what corn originally looked like. It was a smaller grass, with small seeds that were hard to harvest. Over time, people chose seeds from plants that were easier to work with. Through these people’s choices and selections of seed, we now have corn with different uses and characteristics!
    1. Explain to students that this happened with many crops over the years. Many fruits, including watermelons, bananas, and peaches used to be very small and not as sweet as they are today. Over time, people chose the seeds from the best plants to use for the next planting.
  14. Summarize the learning by asking specific questions.
    1. What are traits?
    2. What traits do you see in the different types of corn?
    3. How did corn evolve from teosinte?
    4. How did the changes from teosinte make corn easier to use today?

On the back of the graphic organizer handouts, have students write three to four sentences summarizing the similarities or differences between the different types of corn. Collect the graphic organizers at the end of class.

Essential Files (maps, charts, pictures, or documents)

Did you know? (Ag facts)

  • Iowa is the top corn producing state.
  • 99% of the corn grown in Iowa is field corn.
  • In 2015, Iowa corn growers grew an average of 192 bushels per acre. Nationally, the average is 168 bushels per acre.

Extension Activities (how students can carry this beyond the classroom)

  • Students can research more types of corn and the locations where they are cultivated. Students can present this research to the class, or write a short essay explaining what they find.
  • Students can research one of the other crops that has evolved over time and write a short explanatory paper about the crop.
  • Students can make posters explaining one of the vocabulary words using pictures and words to make a visual representation of the word.

Sources/Credits

Author(s)

Chrissy Rhodes

Organization Affiliation

Iowa Agriculture Literacy Foundation

Agriculture Literacy Outcomes

  • T4.3-5.c: Identify examples of how the knowledge of inherited traits is applied to farmed plants and animals in order to meet specific objectives

Iowa Core Standards

  • Science:
    • 3-LS3-1: Analyze and interpret data to provide evidence that plants and animals have traits inherited from parents and that variation of these traits exists in a group of similar organisms
    • 3-LS4-2: Use evidence to construct an explanation for how the variations in characteristics among individuals of the same species may provide advantages in surviving, finding mates, and reproducing.
  • Social studies:
    • SS.3.13. Identify how people use natural resources, human resources, and physical capital to produce goods and services.
  • English Language Arts:
    • RI.3.2:  Determine the main idea of a text; recount the key details and explain how they support the main idea.
    • RI.3.4:  Determine the meaning of general academic and domain-specific words and phrases in a text relevant to a grade 3 topic or subject area.

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