Most animals and plants are part of more than one food chain. If one part of a food chain alters, the whole food chain is affected. For example, if a disease suddenly wiped out caterpillars, it would affect mice, owls and many other animals.
This phylum consists of the jellyfish, hydra, sea anemones, corals, sea pens, sea wasps, and box jellyfish. There are about 9,000 species. Almost all are marine. This is another ancient group, with fossils perhaps reaching back to 700 mya.
The phylum Echinodermata, which contains about 6000 species, gets its name from the Greek, literally meaning âspiny skin.â This phylum exists exclusively in the sea and includes sea stars, urchins, brittle stars, and sea cucumbers. They are simple animals, lacking a brain and complex sensing organs.haracteristic of all echinoderms is the presence of an internal skeleton covered with spines and skin. The skeleton varies with the type of echinoderms. In sea stars and brittle stars, the skeleton consists of multitudes of small calcareous plates called âossiclesâ that move with one another, forming flexible joints.