Natural Science - Year I
Unit 12: Biological Classification and Invertebrates
History Weblecture for Unit 12
| This Unit's | Homework Page | History Lecture | Science Lecture | Lab | Parents' Notes |
History Lecture for Unit 12:
Biological Observation and Invertebrate Classification
For Class
- Period: 350-280
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- Geographic Location: Greece; the Mediterranean
- People to know: Aristotle
- See science topics: Biology of Invertebrates
Outline/Summary
Scientific Methods
Last week we concentrated on the general problems of classification, and Aristotle's position as one of the first recorded scientists to try to classify organisms. This week we look briefly at Aristotle's overall scheme, and then at a sample of his observations. Most of our effort, however, will be spent on the modern classification of invertebrates.
Classification of Animals
Aristotle proposed a "ladder of nature", which organized matter from simplest to most complex forms. His ladder included all matter, both non-living (the basic elements) and living organisms.
| Man |
| Mammals |
| Whales |
| Reptiles and Fish |
| Octopuses and Squids |
| Jointed Shell Fish |
| Insects |
| Mollusks |
| Jelly Fish and Sponges |
| Higher Plants |
| Lower Plants |
| Inanimate Matter: Earth, Fire, Water, Air |
Our modern schema includes microscopic organisms Aristotle couldn't see, and many plants and animals that he could not observe in Mediterranean Greece. But two concepts are at the basis of both Aristotle's scheme and the modern one:
- classification moves from simple organisms to more complex ones
- each class is related to the one above and below it
Observing Crustaceans
Aristotle based his classifications on the close observation of over 500 species of animals. His work in marine biology is still considered among the best and most reliable set of observations available for species of the Aegean.
Read an example of Aristotle's observation and description of the Crustaceans and Cephalopods from On the Parts of Animals, Book IV Part 5 (you'll need to click on book IV then scroll down to part 5).
- What details does Aristotle include about the structure of urchins?
- What details does he include about their behavior?
Study/Discussion Questions:
- What details does Aristotle provide which support the idea that he had closely observed the behavior of cephalopods and crustaceans?
- What details does Aristotle provide which support the idea that he had done dissections on the animals?
- Why is classification necessary for biological science?
- What kinds of classification information do modern biologists use in creating taxonomies (classification groups) for living organisms?
Further Study/On Your Own
- The Franklin Institute in Philadelphia had a site about Classification Systems that demonstrated the many different possible classification schemes one could use to organize information about animals, or subgroups of animals. Not all of the links from this page still work, but the material on the one page can give you some ideas on the different characteristics one could chose to create a classification scheme.
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