what are the chief characteristics of a cactus
Cactus A cactus (plural: cacti, cactuses, or cactus)[3] is a member of the plant family Cactaceae,[Note 1] a family comprising about 127 genera with some 1750 known species of the order Caryophyllales.[4] The word "cactus" derives, through Latin, from the Ancient Greek κάκτος, kaktos, a name originally used by Theophrastus for a spiny plant whose identity is not certain.[5] Cacti occur in a wide range of shapes and sizes. Most cacti live in habitats subject to at least some drought. Many live in extremely dry environments, even being found in the Atacama Desert, one of the driest places on earth. Cacti show many adaptations to conserve water. Almost all cacti are succulents, meaning they have thickened, fleshy parts adapted to store water. Unlike many other succulents, the stem is the only part of most cacti where this vital process takes place. Most species of cacti have lost true leaves, retaining only spines, which are highly modified leaves. As well as defending against herbivores, spines help prevent water loss by reducing air flow close to the cactus and providing some shade. In the absence of leaves, enlarged stems carry out photosynthesis. Cacti are native to the Americas, ranging from Patagonia in the south to parts of western Canada in the north—except for Rhipsalis baccifera, which also grows in Africa and Sri Lanka.
Ring-necked snake Diadophis punctatus, commonly known as the ring-necked snake or ringneck snake, is a harmless species of colubrid snake found throughout much of the United States, central Mexico, and southeastern Canada. Ring-necked snakes are secretive, nocturnal snakes, so are rarely seen during the day time. They are slightly venomous, but their nonaggressive nature and small, rear-facing fangs pose little threat to humans who wish to handle them. They are best known for their unique defense posture of curling up their tails, exposing their bright red-orange posterior, ventral surface when threatened. Ring-necked snakes are believed to be fairly abundant throughout most of their range, though no scientific evaluation supports this hypothesis. Scientific research is lacking for the ring-necked snake, and more in-depth investigations are greatly needed.[4] It is the only species within the genus Diadophis, and currently 14 subspecies are identified, but many herpetologists question the morphologically based classifications.[5]