Putting It Together: Invertebrates

As we’ve seen, invertebrates include a broad scope of animals, from the simplest of animals—the sponges—to the complex arthropods and annelids. As you review the phyla we’ve discussed in this lesson, remember the characteristics that set apart each phyla. Remember: animals are grouped together based on their structure and appearance.

Simple Animals

This video introduces us to the “simplest” of the animals. We differentiate animals by the number of tissue layers they have, and by the complexity of those layers.

Complex Animals

This video continues our exploration of invertebrates. We discuss the more complex annelids and arthropods.


It is tempting to view different topics as completely separate, but in fact the ideas we cover in this course are often connected to one another. If you don’t retain the vocabulary from module to module, those connections can be missed. As you continue on, remember to come back and review the terms you’ve learned in order to increase your depth of knowledge.


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