From Seed to Seed:
Plant Science for K-8 Educators

Darwin's Theories

Previously, we mentioned Swedish botanist Carl Linnaeus' role in crafting the binomial system of nomenclature, giving every plant a two-word scientific name. In 1753 he published the results of his attempt to classify all known plants in his monumental work Species Plantarum. Linnaeus based his classification on various plant characteristics, usually focusing on the plant's reproductive structures. He grouped plants according to the knowledge available at the time-freely admitting that his system was not comprehensive and would certainly be modified as more knowledge was acquired. The general thinking during this time period was that every individual plant and animal species had been created independently, and that individual species were immutable-incapable of changing their form. As a result, any perceived relationships between plants were based on appearance, not on historical or biological connection.

About 50 years after the publication of Linnaeus' work, French biologist Jean Baptiste de Lamarck put forward the first theory of evolution. He suggested that certain features of animals evolved based on the use-or disuse-of these parts. For example, a giraffe has a long neck because it uses it so much. His theory received relatively little attention and support.

Fifty years later-about 100 years after the publication of Linnaeus' work-Charles Darwin challenged the still-popular theories of special creation with the publication of his revolutionary work On the Origin of Species. In this manuscript, published in 1859, Darwin postulated that individual species were the result of the process he termed natural selection-a process by which the healthiest, strongest, and most well-adapted organisms flourished and went on to reproduce.

Darwin further theorized that the diversity of species could be attributed to the adaptations of organisms to environmental factors. These adaptations are based on mutations, which are random genetic changes that are passed on to offspring. Some mutations cause harm to the organism; other mutations result in changes that are beneficial to the survival of the organism in that particular environment. Organisms with these novel features outcompete other species members, or survive where others perish. Over time, the surviving organisms reproduce and perpetuate these new characteristics.

Keep in mind that evolution isn't over-it continues, but usually at a very slow pace. Perhaps the best example of evolution and adaptation in our everyday lives occurs in the fields of medicine and pest management. Occasionally, news of penicillin-resistant strains of bacteria or pesticide-resistant insects makes the headlines. Small organisms with short life cycles are usually the quickest to adapt to environmental change, because with each generation comes the opportunity for genetic mutations that may lead to increased ability to withstand stresses-including antibiotics and pesticides.

Would you like to know more?
Additional Online Resources

• BBC Education-Evolution Web site.
  http://www.bbc.co.uk/education/darwin/index.shtml

• The Franklin Institute Online: Classifying Plants and Animals-Educational material for K-12 grade students on the classification of plants and animals.
  http://sln.fi.edu:80/tfi/units/life/classify/classify.html
  

Relevant Books
K-4
Heller, Ruth. 1984. Plants That Never Ever Bloom. Sandcastle Books. ISBN: 0-4484-1092-3.

5-8
Campbell, Carol Anne. 1993. Wildflower Field Guide and Press for Kids. Workman Publishing. ISBN: 1-5630-5242-3.

Greenaway, Theresa. 1990. Grasses and Grains. Steck-Vaughn Company. ASIN: 0-8114-2729-3.

Hickman, Pamela. 1999. Starting with Nature: Trees. Kids Can Press. ISBN: 1-5507-4485-2.

Kelly, M. A. 1992. A Child's Book of Wildflowers. Four Winds Press. ASIN: 0-0275-0142-6.

Madgwick, Wendy. 1990. Flowering Plants. Steck-Vaughn Company. ASIN: 0-8114-2730-7.

Madgwick, Wendy. 1990. Fungi and Lichen. Steck-Vaughn Company. ASIN: 0-8114-2728-5.