Marine life individuals per square meter and accounting for about 80% of all individual animals on earth, their diversity of life cycles, and their presence at various trophic levels point at an important role in many ecosystems. Echinoderms (Greek for "spiny skin") is a phylum which contains only marine invertebrates. The adults are recognizable by their radial symmetry (usually five-point) and include starfish, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies. Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7000 living species, making it the second-largest
Eastern spiny mouse species is nocturnal, avoiding the heat of the day and foraging at night for seeds, and sometimes insects and grasses. It is a sociable animal and lives in small groups. Females become mature at about two months of age and can produce litters of up to five young after a gestation period of about 42 days. Another female in the family group may help with care of the young, which are weaned after about a fortnight. Its spiny hair may help to prevent predation, perhaps making the animal harder to swallow, and this mouse is also capable of shedding its