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Plants: Structure, Classification,
The Role of Cultivated Plants in the Living World
After reading the chapter you should be able to:
Understand the role of cultivated plants as food sources.
Understand the benefits of cultivated plants in addition to supplying food.
Understand the challenges to plant scientists as they try to increase or improve food and other plant benefits to the peoples of the world.
If we could look back some 150 million years to the middle of the geologic period known as the Mesozoic era, the world would not appear entirely strange to us. Among plants, we might recognize some members of the angiosperms,1 to which belong our present-day grasses, flowers, vegetables, shrubs, and most of our modern trees. In the animal kingdom, by contrast, we would confront those ancient reptiles known as dinosaurs. The careful observer also might note the existence of some small primitive mammals-to which we human beings can trace our own beginnings. Thus, both forms of life dominant today originated during the height of the dinosaur reign. It is still a matter of conjecture why the dinosaurs became extinct, but we do know that mammals flourished during the subsequent Cenozoic era, beginning about 65 million years ago. The human race can be traced back some 3 million years. However, the modern human species, Homo sapiens (archaic), came much later, toward the end of the Pleistocene epoch, some 250,000 years ago, with H. sapiens (modern) about 28,000 years ago.
Plants evolved much earlier than humans. The gymnosperms, which include the cone-bearing timber and ornamental trees of today, had their beginnings 300 million years ago. The angiosperms, which humans and other animals depend on for much of their food and other uses, appeared about 90 million years ago. Fossil records show that plants such as hickories, oaks, beans, grapes, and other species were well established by the time even the most ancient forms of humankind appeared. These species would have provided shelter and food then as they do today. However, the plants would have been gathered from the wild, not grown specifically for use. The growing or cultivation of plants for use came about 10,000 years after the appearance of modern humans. With the development of cultivation came the need to understand how plants grow. Thus, plant science was germinated and began to grow. The first plant scientists were those who observed how plants grew, developed ideas about the process and how to improve it, tested those ideas, and then came to conclusion.
Today the growing and cultivation of plants for use requires the same understanding of basic plant science. Anyone who makes decisions regarding cultivated crops, their development, and their use-whether it is in the lab or in the field-is a plant scientist and must use sound, scientific-based information when making decisions.
The first cultivated food crops apparently were cereals such as wheat and barley. Several grains of barley have been recovered from archeological sites in Egypt, indicating that ground grain was an important economic resource as early as 18,000 years ago. An agricultural type of existence spread to the European continent some 6,000 years ago, replacing a nomadic hunting existence. There is evidence that corn was first cultivated in what is now Mexico about 5,000 years ago, followed about 1,500 years later by potatoes in South America and rice in the Far East. Some of our present-day fruit crops-grapes, figs, olives, dates, pomegranates, and mulberries-were being cultivated in the eastern Mediterranean when history was first being recorded.
It is startling to realize that if animals ceased to exist on earth, plants