Segmented worms like earthworms and leeches with a closed circulatory system.
Phylum Annelida. Metameric segmentation allows specialised segments. Setae aid movement; hydrostatic skeleton and closed circulation with hearts (aortic arches). Earthworms aerate soil.
Segmentation allows efficient movement. Polychaetes include marine worms; oligochaetes include earthworms. Closed circulation and nephridia excrete waste.
Key idea: metamerism is repeated body segments.
Segmented worms like earthworms and leeches with a closed circulatory system.
Annelids is one of the 53 topics in Zoology & Animal Diversity. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Arthropods, Echinoderms, Vertebrates and Invertebrates.
Leeches secrete hirudin, an anticoagulant used medically.
Annelids is a Beginner topic, so no earlier topic is required. Other Beginner topics in Zoology & Animal Diversity that pair well with it include Animal Kingdom, Vertebrates and Invertebrates, Sponges.
The closest topics to Annelids are Arthropods, Echinoderms, Vertebrates and Invertebrates, Body Cavities. Comparing them side by side is a good way to see how the ideas connect.
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Annelids. To practise the whole of Zoology & Animal Diversity, use the Zoology & Animal Diversity quiz.
Annelids: Segmented worms like earthworms and leeches with a closed circulatory system. Arthropods: Animals with jointed legs, exoskeleton and segmented bodies, the largest animal phylum. Read both side by side and note what each one explains.
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Arthropods and explain the difference aloud. Finally, take the Zoology & Animal Diversity quiz and come back to this page for any question you miss.
Animals with jointed legs, exoskeleton and segmented bodies, the largest animal phylum.
🦁 Zoology & Animal DiversityMarine animals with radial symmetry as adults and a water vascular system, like starfish.
🦁 Zoology & Animal DiversityVertebrates have a backbone; invertebrates, which are over 95 percent of animals, do not.
🦁 Zoology & Animal DiversityAcoelomate, pseudocoelomate and coelomate animals differ in how the fluid-filled cavity around organs is formed.
🦁 Zoology & Animal Diversity