The Course Unit aims at introducing invertebrates as a taxonomically wide range of resources, with emphasis on beneficial aspects (food, environmental indicators, components of food chains and nutrient cycling in ecosytems, etc) and harmful ones (pests, parasites and disease vectors). A general classification of invertebrates based on structure will be made with empahasis on or tracking those taxa that contain beneficial or harmful individuals. Aquaculture of invertebrates to increase food production from aquatic environments, particularly the shellfisheries industry, will be emphasized.