EEOB 4240 — Set 4: Starch Foods

[Week 6] A potato is a tuber. What part of the plant is a tuber?
A. A swollen root
B. An underground modified stem
C. A modified leaf base
D. A fruit

B. An underground modified stem. That's why "seed potatoes" (pieces of tuber) must include a bud (an "eye") to grow a new plant.

[Week 6] Cereal grains (grass family) don't grow well in the tropics. Where do most tropical starch staples store their starch instead?
A. In seeds, like grains
B. In leaves
C. In underground organs such as roots, tubers, and corms
D. In tall above-ground stems

C. In underground organs such as roots, tubers, and corms. Cassava, sweet potato, yam, taro, and oca all store starch underground; bananas and breadfruit are the exceptions, storing it in fruit.

[Week 6] The glycemic index (GI) measures how quickly a carbohydrate food raises blood sugar. Which of these foods has the lowest GI?
A. White bread
B. White rice
C. Lentils (a legume)
D. Corn flakes

C. Lentils. Legumes, nuts, seeds, and whole grains break down slowly (low GI); refined starches like white bread, white rice, and corn flakes break down fast (high GI). Potatoes are medium GI.

[Week 6] True or False: When people eat more starch than their bodies need, the extra glucose from digestion is converted to fat and stored.

True. Starch is digested into glucose, and excess glucose is converted to lipids and stored as fat. Starch makes up about 1/3 of the average American diet.

[Week 6] The potato was domesticated about 8,000 BCE in the Andes of South America. Compared with wild potatoes, domesticated potatoes were selected for:
A. Smaller, more bitter tubers that resist pests
B. Larger, less bitter tubers
C. More seeds and fewer tubers
D. Tubers that store for many years

B. Larger, less bitter tubers. Wild potatoes are small and contain bitter, toxic compounds, so early farmers selected bigger, milder tubers.

[Week 6] On a phylogenetic tree (a family tree of species built from DNA), all cultivated potato varieties cluster on one branch that comes out of a single group of wild potatoes. What does this show?
A. Potatoes were domesticated many separate times
B. Cultivated potatoes had a single origin (domesticated once)
C. Cultivated potatoes are not related to wild potatoes
D. Potatoes were first domesticated in Europe

B. A single origin. If all crop varieties share one branch from one wild group, they trace back to one domestication; multiple origins would scatter crop varieties across different wild branches.

[Week 6] In the Andes, people make chuño by leaving potatoes out to freeze, stomping them as they thaw, and repeating the cycle. What does this processing accomplish?
A. Makes the potatoes sweeter for brewing
B. Freeze-dries them for long storage and removes bitter compounds
C. Kills the buds so the potatoes can't sprout
D. Raises their protein content

B. Freeze-dries them and removes bitter compounds. Chuño is a traditional preserved potato that stores well and is safer to eat.

[Week 6] True or False: When potatoes reached Spain in the 1500s, Europeans quickly accepted them because they resembled familiar food crops.

False. Europeans were slow to accept potatoes because they were unlike known food crops and resembled poisonous plants in the same nightshade family (Solanaceae), like belladonna and mandrake.

[Week 6] True or False: Potatoes yield more food energy per acre than grain, and their spread through Europe in the 1700s helped fuel rapid population growth.

True. Potatoes produce more calories per acre than grain and were a reliable crop during wartime, so once accepted they supported rapid population growth.

[Week 6] Why did the potato become the dominant food of poor Irish farmers by the 1800s?
A. It only grew well on the best farmland
B. One acre of potatoes on poor (marginal) land could feed a family, while the good land grew grain sold to England
C. It could be stored for many years without spoiling
D. It was Ireland's most valuable export crop

B. Potatoes grew on marginal land and one acre fed a family. Discriminatory laws had pushed many Catholic farmers into subsistence farming, while good land grew grain for export. (The Irish variety didn't store longer than about a year, so C is wrong.)

[Week 6] Why did potato blight destroy nearly all of Ireland's potato crop in 1845–1846?
A. Potatoes cannot survive Ireland's cold climate
B. Potatoes were grown from tuber pieces (clones) of very few varieties, so nearly every plant was genetically alike and equally vulnerable
C. A harsh winter froze the crop in the ground
D. Blight only attacks plants grown from seed

B. Vegetative propagation in a monoculture left almost no genetic diversity, so one disease hit every plant. Over 1 million people died and about 1.5 million emigrated to North America.

[Week 6] Most "yams" sold in US grocery stores (including "candied yams") are actually:
A. True yams, a monocot domesticated in tropical Africa
B. Sweet potatoes, a dicot (morning glory family) domesticated in tropical America
C. Taro corms
D. White potatoes with orange flesh

B. Sweet potatoes. True yams (yam family) are monocots that are starchier and firmer and are mostly found in specialty shops; sweet potatoes are tuberous roots with more calories than white potatoes.

[Week 6] Yams have low yield per acre, a long growing season, and need intensive labor. Why are they still a staple in West Africa, which grows about 95% of the world's yams?
A. They are the only crop that grows there
B. They have a long cultural tradition there; yams were domesticated in tropical Africa over 5,000 years ago
C. They have far more protein than other starch crops
D. They never need processing to remove toxins

B. Long cultural tradition. Yams are only about 2% protein (C is wrong), and bitter yams do need toxins removed (D is wrong).

[Week 6] True or False: A compound extracted from yams was used to make steroid hormones such as cortisone and progesterone and led to the development of the birth control pill.

True. Yams' medicinal importance comes from this hormone starting material, which was found to block ovulation.

[Week 6] Bitter cassava roots must be soaked, peeled, grated, squeezed, and roasted before eating, while sweet cassava can simply be boiled. Why?
A. Bitter cassava contains much more starch
B. Bitter cassava has higher levels of compounds that release cyanide, and the processing removes them
C. Bitter cassava is too hard to chew when raw
D. The processing adds protein to bitter cassava

B. Higher toxin levels. Sweet and bitter varieties differ in how much of the cyanide-releasing compound they contain, so bitter types need thorough processing.

[Week 6] In some communities that rely on cassava as their main food, people develop leg paralysis, vision loss, and nerve damage. What causes this?
A. Eating too much starch and too little sugar
B. Shortcuts in processing that leave cyanide in the cassava, combined with a low-protein diet that leaves the body unable to neutralize it
C. Eating cassava leaves instead of roots
D. Eating sweet cassava raw

B. Leftover cyanide plus protein deficiency. The body uses sulfur from dietary protein to neutralize small amounts of cyanide; without enough protein, "cassava paralysis" can result.

[Week 6] True or False: Cassava roots are a good source of protein, which is why cassava is replacing yams and bananas as a staple in many tropical regions.

False. Cassava roots have less than 1% protein (the leaves have about 30%). Cassava is replacing more nutritious staples like yams and bananas because it tolerates drought, poor soils, and locusts, not because it is more nutritious.

[Week 6] Wild bananas have small fruits packed with seeds. How do modern cultivated bananas differ?
A. They are larger and seedless; the fruit develops without fertilization, so plants are grown from cuttings
B. They have more and larger seeds
C. They grow on true trees instead of herbaceous plants
D. They are grown only from seed

A. Larger and seedless. Modern bananas have three chromosome sets (triploid), so they're sterile and must be propagated vegetatively. Banana plants are herbaceous, not trees, so C is wrong.

[Week 6] The 'Gros Michel' banana was wiped out by Panama disease (a soil fungus) by the 1950s. Its replacement, 'Cavendish' (now over 80% of international trade), is also highly susceptible and has no cure. What do this and the Irish potato famine have in common?
A. Both diseases spread through seeds
B. Both crops were vegetatively propagated monocultures with little genetic diversity
C. Both crops were grown only on marginal land
D. Both diseases were spread by insects

B. Vegetatively propagated monocultures. When every plant is a genetic copy, one disease can wipe out the whole crop.

[Week 6] Taro was the primary starchy staple of Polynesia. Which statement about taro is correct?
A. Its fruit is the main part eaten, and it is eaten raw
B. Its corms are the main part eaten; they contain irritating crystals that boiling destroys, and they are fermented into poi
C. It was domesticated in the Andes
D. Its leaves are toxic and never eaten

B. Corms are eaten and processed by boiling or fermenting into poi. Taro was domesticated in Southeast Asia, carried as cuttings to each Polynesian island, and its leaves are eaten too (the luau is named for them).

[Week 6] True or False: The Jerusalem artichoke (sunchoke), a sunflower-family (Asteraceae) plant native to North America, stores mostly inulin instead of starch, making it a good choice for diabetics.

True. Its tubers are about 76% inulin (a fructose polymer) with very little starch, so they don't spike blood sugar the way starchy staples do.

[Week 6] Which crop is correctly matched with the region where it was domesticated?
A. Potato: tropical Africa
B. Yam: the Andes
C. Banana: Papua New Guinea (Southeast Asia)
D. Cassava: Southeast Asia

C. Banana: Papua New Guinea. The correct matches are potato (Andes), yam (tropical Africa), cassava (South America), and banana (Southeast Asia/Papua New Guine