Echinoderms are not arthropods like the others. Starfish and sand dollars are echinoderms.
Fungi are heterotrophic. They get their nutrition by absorbing organic compounds from the environment. Fungi, along with bacteria that are found in soil, are the primary decomposers of organic matter in terrestrial ecosystems.
Plants cannot get too much light, but they can get too much of the heat energy that comes with the light.