AP BIOLOGY

Detailed explanation-1: -Echinoderms are “spiny-skinned” invertebrate animals that live only in marine environments.

Detailed explanation-2: -Classification: Starfish are also referred to as sea stars because of their star-shaped appearance. They are a part of the phylum Echinodermata and are related to sand dollars, sea urchins, and sea cucumbers. Echinoderms are found in nearly all marine habitats and constitute a major proportion of the biomass.

Detailed explanation-3: -Sea stars are related to sand dollars, sea urchins, and sea cucumbers, all of which are echinoderms, meaning that they have five-point radial symmetry.

Detailed explanation-4: -Note: The phylum Echinodermata, as mentioned above is purely marine. So, if the habitat of an organism is known then the phylum of that organism becomes easy to determine. For example-The starfishes are purely marine and also all the organisms in Echinodermata are exclusively marine.

Detailed explanation-5: -Echinoderms belong to the phylum Echinodermata having 5 classes namely Crinoidea (Sea lilies and Feather stars), Ophiuroidea (Brittle stars and basket stars), Asteroidea (Sea stars), Echinoidea (Sea urchins) and Holothuoidea (Sea cucumbers) (Fig. 8.11).