BIOL 1002 Chapter : Ch 23 Invertebrate Animals Part 3
Document Summary
In numbers and diversity, arthropods rule (about 1 million species: arthropods - phylum arthropoda, roundworms - phylum nematoda. The other major group of protostomes is the ecdysozoans and there are two major groups: Arthropods are represented by 3 large diverse classes: Class crustacea - crustaceans crawfish, shrimp, crabs, lobsters. Segments are fused and specialized in insects (fig 23-19: head sensory and feeding structures, thorax structures for locomotion are attached here, abdomen digestive structures. Exoskeleton is a hard external skeleton made of chitin that must be periodically shed or molted. Insects may also go through metamorphosis during development: metamorphosis is any change in shape or proportion, this can be either incomplete metamorphosis or complete metamorphosis, growth and molting (get defintions) Roundworms phylum nematoda: these are everywhere! Some are important for breaking down organic matter, others are parasitic: this is the only group we"ll look at with a pseudocoelom. Large number of species 50,000 identified (may be as many as 500,000)
