Lesson 2: Bananas: a modern example of fungus destruction

Introduction:

This lesson is a follow up to the “What happened to the American Chestnut” lesson. Students will read a current news article about bananas and compare what is happening to the banana to what happened to the American Chestnut tree. The comparison shows that exotic species currently carry a risk to other organisms of economic importance. Recommended as a homework assignment to follow up on the previous lesson.

Learning outcomes:

Students will be able to give a brief description of what is currently happening to bananas and compare this to what has happened to the American Chestnut trees.

Curriculum alignment:

Biology Goal 5.03: Assess human population and its impact on local ecosystems, in particular, the introduction of a non-native species.

Classroom time required:

20-30 minutes for reading the article and answering question. Additional time is allotted for classroom discussion. Assignment may be given as an outside of class activity.

Materials needed:

Copies of the news article and banana article questions. (1 per student) Since the article is from an on-line source, computers may be used to have the students read the article or have them print them out and bring them to class. http://www.nytimes.com/2008/06/18/opinion/18koeppel.html?_r=1

Technology resources:

None required. Internet connection to view article by students optional.

Pre-activities:

1. Completion of “What happened to the American Chestnut?” lesson.
2. Ask students how many of them have ever eaten bananas? Some students will comment that they do not like bananas, so you may want to ask if anyone in their family eats them. Ask if they know how much bananas cost per pound? Explain that this price has increased in recent years due to a disease effecting banana trees.

Activity:

Hand out article and questions to students. Give them time to read the article and answer all questions. This can be done as a homework assignment. Follow up the article, either the same day or the following day, with a discussion of how the fate of the banana is similar to the fate of the American Chestnut. Let students discuss what they think should be done to save the banana if anything.

Assessment:

Verbally check with students about their understanding of what is happening to the banana. A few questions to ask would include:

• What disease is affecting bananas?
• How did the disease get to the bananas to begin with? (students may need help with this question, the supplemental material gives further explanation of this disease)
• What may this us as consumers who buy bananas?
• How does this compare to what happened to the American Chestnut tree?
• Do you think scientist should try to solve the problem? If so, what should they do?

Modifications:

For students that have difficulty with reading, this assignment would be best given in class so that the teacher, or others in the class could help with unfamiliar words.

Supplemental information:

An additional, but very similar article about the Panama disease: http://www.seattlepi.com/opinion/364179_bananaonline23.html?source=mypi Quick information about what the disease causes in banana trees: Panama Disease or Banana Wilt, which arises from infection by the fungus, Fusarium oxysporum f. sp. cubense originates in the soil, travels to the secondary roots, enters the corm only through fresh injuries, passes into the pseudostem; then, beginning with the oldest leaves, turns them yellow first at the base, secondly along the margins, and lastly in the center. The interior leaves turn bronze and droop. The pseudostem turns brown inside. This plague has seriously affected banana production in Central America, Colombia and the Canary Islands. It started spreading in southern Taiwan in 1967 and has become the leading local banana disease. The 'Cavendish' types have been considered highly resistant but they succumb if planted on land previously occupied by 'Gros Michel'. The disease is transmitted by soil, moving agricultural vehicles or other machinery, flowing water, or by wind. It is combatted by flooding the field for 6 months. Or, if it is not too serious, by planting a cover crop. There are reportedly two races: Race #1 affects 'Gros Michel', 'Manzano', 'Sugar' and 'Lady Finger'; Race #2 attacks 'Bluggoe'. Resistant cultivars are the Jamaican 'Lacatan', 'Monte Cristo', and 'Datil'or'Nino'. Resistant plantains are 'Maricongo', 'Enano' end 'Pelipita'.

Excerpt taken directly from http://www.hort.purdue.edu/newcrop/morton/banana.html#Diseases

Critical vocabulary:

• Banana republic: a small country, usually of the tropics, run by a dictator that is dependent on other countries for trade
• Virulent: disease marked by a rapid, severe, and destructive course
• Extinct: no longer existing species
• Diversify: to increase the variety of the products

Comments:

A later lesson will use banana for DNA extraction since it is easy to obtain and to work with.