Frogs are valued as food by humans and also have many cultural roles in literature, symbolism and religion. Frog populations have declined significantly since the 1950s. More than one third of species are considered to be threatened with extinction and over one hundred and twenty are believed to have become extinct since the 1980s. [1] The number of malformations among frogs is on the rise and an emerging fungal disease, chytridiomycosis , has spread around the world. Conservation biologists are working to understand the causes of these problems and to resolve them.

The name frog derives from Old English frogga , abbreviated to frox , forsc , and frosc , probably deriving from Proto-Indo-European preu = "to jump". [2] About 88% of amphibian species are classified in the order Anura. [3] These include around 4,810 species in 33 families , of which the Leptodactylidae (1,100 spp.), Hylidae (800 spp.) and Ranidae (750 spp.) are the richest in species . [3]

Some species of anurans hybridize readily. For instance, the edible frog ( Pelophylax esculentus ) is a hybrid between the pool frog ( P. lessonae ) and the marsh frog ( P. ridibundus ). [12] The fire-bellied toads Bombina bombina and B. variegata are similar in forming hybrids. These are less fertile than their parents, giving rise to a hybrid zone where the hybrids are prevalent. [13]

Temporal Foam: A Novel of Accidental Time Travel eBook.

Temporal Foam: A Novel of Accidental Time Travel eBook.

Posted by 2018 article