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Book Chapter |
The search for the fundamental building blocks in nature has gone on for more than two thousand years. Aristotle felt that all the materials around us were composed of varying quantities of four basic elements—earth,…
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Sources, sinks, and gaussian spheres
Book Chapter |
Conservation of mass requires that the flow of mass into the volume be equal to the flow of mass out of the volume. Another way of stating this is that the net flow of mass—or flux—through the surface must be zero. This…
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Book Chapter |
Archimedes’s law was a great achievement. Everybody knew that an object dropped in water made the water level rise (that is, it displaced some water). But Archimedes was the first to recognize that the amount of water…
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Book Chapter |
Up to now, all of the roller coasters of the world use a continuous track. But that does not restrict our imagination. In this chapter, we imagine that the top portion of the track is removed in a vertical loop,…
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Book Chapter |
Imagine paddling in a rowboat from one shore to the opposite shore with no current. The trip takes you 15 minutes. If you return to the river and venture across again, paddling to the opposite shore with the same…
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It Skips a Generation: Traits, Genes, and Crosses (Student Edition)
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Long before they understood why the strategy worked, farmers knew how to crossbreed plants to obtain more desirable traits. Even today, a farmer who knows nothing about genetics can tell you that when a blue type of…
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It Skips a Generation: Traits, Genes, and Crosses (Teacher Edition)
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Many of the early discoveries in genetics occured in plants. Plants have a few special characteristics that make them ideal for studying genetics. From one known cross, many genetically similar "siblings" are produced.…
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Bitterness and Non-Bitterness in Cucumbers: A Story of Mutation (Teacher Edition)
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In this chapter, students explore the history of the bitter gene in cucumbers, which was found in a genebank and traded internationally between cucumber breeders. The students then explore transcription, translation,…
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Survival Strategies (Teacher Edition)
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This chapter focuses on ecological principles of plant defenses and insect adaptations to these defenses. Insects either are generalists, often deterred by plant chemical defense compounds, or they are specialists that…
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Domestication: Evolving Toward Home (Teacher Edition)
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This chapter explores the concept of domestication and the changes that occur in plants as they transition from wild to cultivated. Domestication is a form of evolution driven by artificial selection rather than natural…
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The Risks of Improvement: Genetic Uniformity and an Epidemic (Teacher Edition)
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This chapter explores the role of genetic diversity in crops. Using hybrid corn as an example, it discusses selection—the genetic narrowing that accompanies gains in traits like yield and disease resistance—and the…
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Genetic Engineering (Teacher Edition)
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This chapter focuses on genetically engineered foods. Bt corn has bacterial genes that encode a protein toxic to many insects. Therefore the corn plant makes its own pesticide. This chapter explores the DNA basis for…
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Sweet Genes in Corn (Teacher Edition)
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This chapter begins with consideration of sugars made by the plant during photosynthesis and the movement of those sugars within the plant by diffusion along concentration gradients and by other processes. By exploring…
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Centers of Diversity (Teacher Edition)
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This chapter discusses genetic diversity of food plants in the context of the geographic regions from which they originate. The center of origin is the site where the plant was domesticated. The center of diversity is…
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Quantitative Traits (Teacher Edition)
Book Chapter |
This chapter begins with single-gene Mendelian traits and compares them to quantitative traits where many genes are involved in determining phenotype. Quantitative trait loci (QTL) studies use molecular markers to…
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