Pond

A pond is a body of standing water, either natural or artificial, that is usually smaller than a lake. They may arise naturally in floodplains as part of a river system, or they may be somewhat isolated depressions (examples include vernal pools and prairie potholes). Usually they contain shallow water with marsh and aquatic plants and animals. A few animals also make their home in ponds, including both alligators and beavers. The type of life in a pond is generally determined by a combination of factors including water level regime (particularly depth and duration of flooding) and nutrient levels, but other factors may also be important, including presence or absence of shading by trees, presence or absence of streams, effects of grazing animals, and salinity.

Ponds are frequently human-constructed. In country side farmers and villagers dig a pond in their backyard or increase the depth of an existing pond by removing layers of mud during summer season. A wide variety of artificial bodies of water are classified as ponds. Some ponds are created specifically for habitat restoration, including water treatment. Others, like water gardens, water features and koi ponds are designed for aesthetic ornamentation as landscape or architectural features. Fish ponds are designed for commercial fish breeding, and solar ponds designed to store thermal energy.

Giant tortoise

Giant tortoises are characteristic reptiles that are found on two groups of tropical islands: the Aldabra Atoll in Seychelles and the Galapagos Islands in Ecuador (a population at the Mascarene Islands was exterminated by the 1900s) . These tortoises can weigh as much as 417 kg (919 lb) and can grow to be 1.3 m (4 ft 3 in) long. Giant tortoises originally made their way to islands from the mainland; for example, Aldabra Atoll and Mascarenes giant tortoises are related to Madagascar tortoises while Galapagos giant tortoises are related to Ecuador mainland tortoises. This phenomenon of excessive growth is known as islands gigantism or insular gigantism. It occurs when the size of the animals that are isolated on an islands increases dramatically in comparison to their mainland relatives. This is due to several factors such as relaxed predation pressure, competitive release, or as an adaptation to increased environmental fluctuations on islands. These animals belong to an ancient group of reptiles, appearing about 250 million years ago. By the Upper Cretaceous, 70 or 80 million years ago, some had already become gigantic. About 1 million years ago tortoises reached the Galápagos Islands. Most of the gigantic species began to disappear about 100,000 years ago. Only 250 years ago there were at least 20 species and subspecies in islands of the Indian Ocean and 14 or 15 subspecies in the Galápagos Islands.