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Classification of Animals

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Lesson Focus

Classification of Animals

Life Science

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You will use a dichotomous key to classify animals into different groups, or classes. After this, you will be given detailed information on eight classes of animals.

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Now You Know

After completing this tutorial, you will be able to complete the following:

  • Explain that organisms are classified according to their characteristics.
  • Give examples of organisms that are amphibians, reptiles, birds, mammals, fish, arthropods, mollusks, and annelids.
  • Explain that a dichotomous key is used to identify organisms in nature.
  • Explain that a dichotomous key consists of a series of questions with two choices for answers that ultimately lead to the name of the correct organism.
  • Judge whether organisms are amphibians, reptiles, birds, mammals, fish, arthropods, mollusks, or annelids, based on observable traits.

Everything You'll Have Covered

Animal classification helps us to understand nature. It is a process by which every organism in nature is organized and grouped according to its characteristics. By classifying organisms, we can easily understand the similarities and differences between them.

A dichotomous key is used to identify organisms using specific, observable traits. A dichotomous key consists of a series of questions. Each question has two possible answer choices. The answer choice determines the next step, or question. The purpose of using a dichotomous key is to arrive at a final answer. Dichotomous keys have been in use in some form since the days of Aristotle in Ancient Greece.

The dichotomous key used in this Activity Object first asks, "Does this animal have a vertebral column?" If the answer is yes, we ask if the animal has four limbs. We find that if it does not but has fins instead, we have identified a fish. If the animal does have limbs and moist skin, the animal is an amphibian. If the animal has a vertebral column, four limbs, does not have scaly skin, but has fur or hair, we have identified a mammal. An animal with a vertebral column, four limbs, and scaly skin is a reptile. If it has feathers instead of scaly skin, we identify it as a bird. If the answer to our first question about a vertebral column is no, we then ask, "Does this animal have a segmented body?" If it does not have a segmented body but has a soft body instead, we identify the animal as a mollusk. If the animal has a segmented body with jointed limbs, the animal is an arthropod. If it does not have jointed limbs, it is an annelid.

Tutorial Details

Approximate Time 20 Minutes
Pre-requisite Concepts There are no specific pre-requisite concepts for this lesson.
Course Life Science
Type of Tutorial Concept Development
Key Vocabulary amphibian, animal, annelid, arthropod, bird, body, class, classify, classification, dichotomous, domain, family, feather, fin, fish, fur, genus, hair, invertebrate, jointed-limb, key, kingdom, mammal, mollusk, order, organism, phylum, reptile, scaly, segmented, skeleton, skin, species, vertebra, vertebrate, x-ray