Chapter 6 Summary

• All animals share key biological traits: Animals are eukaryotic, multicellular, heterotrophic organisms with specialized tissues. Most are motile at some life stage and reproduce sexually, progressing through defined developmental stages that result in a set body plan.
• Animals are classified based on body structure and genetics: Major classification features include body symmetry (asymmetrical, radial, or bilateral), tissue development, and embryonic traits. These characteristics help determine an animal’s placement within one of approximately 35 recognized phyla.
• Invertebrates dominate animal diversity: About 95% of all animal species lack a backbone and fall into diverse phyla such as Porifera (sponges), Cnidaria (jellies, corals), Platyhelminthes (flatworms), Nematoda (roundworms), Mollusca, Annelida (segmented worms), Arthropoda (insects, crustaceans, arachnids), and Echinodermata (sea stars, sea urchins).
• Arthropods are the most numerous and adaptable animals: With jointed limbs, segmented bodies, and exoskeletons, arthropods include insects, crustaceans, arachnids, and myriapods. Insects are particularly diverse and undergo metamorphosis, contributing significantly to ecosystems and bioindication.
• Chordates are defined by four key features: These include a notochord, dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail. While vertebrates (like mammals and fish) are the most familiar, invertebrate chordates like tunicates and lancelets help illustrate the evolutionary history of this phylum.
• Body plans, feeding strategies, and habitats vary widely: From filter-feeding sponges and stinging cnidarians to regenerative echinoderms and intelligent cephalopods, animals exhibit remarkable structural and functional diversity adapted to aquatic and terrestrial environments.

OpenAI. (2025). ChatGPT. [Large language model]. https://chat.openai.com/chat
Prompt: Summarize the following content into six key takeaways.

OpenAI. (2025). ChatGPT. [Large language model]. https://chat.openai.com/chat
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