Describe how dog breeds, for example, are the result of thousands of years of artificial selection, with a wolf as the original animal about 14,000 years ago.
Other examples include the variety of foods of the cabbage family (brussels sprouts, kohlrabi, Chinese cabbage) that have all been developed from a single species of Brassica.
Lead a discussion with your students involving their beliefs (religious) on the origin of life on earth. Ask several students how they think they, as humans, got to be here. Then describe Creationism and Naturalist Evolution as two distant ends of the spectrum and point out that there is also the potential for some middle ground. Add your personal beliefs as you wish. (There is little harm in discussing your own personal beliefs so long as you do not impose them upon your students.) By introducing evolution in this manner, many students who fear discussing evolution will relax and feel more open to the subject.
Many software programs on the market are aimed at helping people construct family trees. Students can be asked to construct their family trees ahead of class, and can share and discuss them in small groups during the class period. As was mentioned in the text in chapter 10, people also tend to use binomial nomenclature in naming themselves. Bill Carr, for example, is called Bill, but his family name is Carr. The name Carr is derived from the Irish "O'Cara," which indicates something about ancestry for at least one side of the family. Building a family tree is not directly a biological exercise, and therefore not one to dwell on for this course, but it helps students identify with classification schemes and may help them see how and why they are important.
It is difficult to know exactly how many different species occupy the earth at this point in time, especially since only about 1.5 million species have been named, but at least some biologists think there may be as many as 10 million species of life on earth. Probably two-thirds of these are located in the tropics.
Aside from the inherent right of every living creature to live out its life in its natural, undisturbed habitat, many plants also have the potential to produce medicinal compounds that may one day cure a cancer, heal a disease, or help us live longer. Regardless, extinction is going on now at rates unprecedented in nature, presumably due to the activities of humans.
Extinction is part of living on this planet. Probably 500 million species have existed here over time, and at least 95% of those have either become extinct or have evolved into other forms. With the advent of agriculture about 10,000 years ago, species extinctions have increased dramatically as human populations have increased throughout the world. From 8000 B.C. to A.D. 1600, probably one species went extinct every thousand years. From 1600 to 1900, one species went extinct every four years. From 1900 to 1975, one went extinct each year. At about 1975, that number increased to 100 or so each year. Then in 1985, it was 1000 per year. The estimate for the year 1990 was the extinction of 10,000 species. By the time we arrive at the year 2000, between 20,000 and 50,000 species are estimated to be doomed to extinction each and every year. (Source: G. Tyler Miller, 1990. Living in the Environment, 6th ed. Wadsworth Publishing Co., Belmont, CA.)
Most students will find this information unfathomable, but they need to be aware of it. One of the most amazing facets of biology is the diversity of life on earth. How sad to think that our activities have led to the demise of so many types of creatures.