Simply put, invertebrates are "animals without backbones". Our definition of the word invertebrate includes all heterotrophic, spine-free organisms with a eukaryotic cell structure. This excludes any autotrophic (plant like) organisms such as phytoplankton; and bacteria because it has a prokaryotic cell structure.

Morphology Ecology Biodiversity Habitats
Morphology Ecology Biodiversity Habitats

Invertebrates compose over 99% of the animal species, and their diversity in structure and life style are extraordinary. They can be single-celled, colonial, or multi-celled and live on land, in freshwater, and in marine waters. They can be microscopic, hundreds living in a drop of water, or gigantic - the leg span of a Japanese crab is greater than 4 metres.

Invertebrates make up the majority of the links in aquatic food webs and are indispensable as both predator and prey in freshwater environments. Many invertebrates play a key role as decomposers breaking down organic substances that are often toxic in high concentrations. They also directly affect humans in day to day life as parasites (Giardia), as food stores (clams and snails), and as pests (zebra mussels). For a detailed look into the world of the invertebrates, read on. . .

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