Terrestrial animal Terrestrial animal The term terrestrial is typically applied for species that live primarily on the ground, in contrast to arboreal species, which live primarily in trees. There are other less common terms that apply to specific groups of terrestrial animals: Terrestrial invasion is one of the most important events in the history of life. Terrestrial lineages evolved in several animal phyla, among which vertebrates, arthropods, and mollusks are representatives of more successful groups of terrestrial animals. Terrestrial animals do not form a unified clade; rather, they share only the fact that they live on land. The transition from an aquatic
Photosensitivity in animals Photosensitivity in animals Photosensitivity is an abnormal skin reaction to direct sunlight exposure. It is unrelated to a sunburn. These reactions are due to photosensitization, the accumulation of photosensitive compounds beneath the skin. In some cases, the photodynamic substances come from ingested plants or drugs, after being metabolized or not. In other cases, the photodynamic substances may be produced in the body itself due to inborn errors in pigment metabolism, especially those involving the heme synthesis. Photosensitivity reactions are usually seen in herbivorous or omnivorous animals, though such reactions are not uncommon among carnivores. Photosensitivity reactions are characterized by severe