The Ultimate Amphibian Quiz

Summary Title: Amphibians - Class of Ectothermic Tetrapods

• Amphibians are vertebrates of the class Amphibia, belonging to the group Lissamphibia; they inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems.

• They undergo metamorphosis from larva with gills to an adult air-breathing form with lungs, using their skin as a secondary respiratory surface; some small terrestrial salamanders and frogs lack lungs and rely entirely on their skin.

• Amphibians are often ecological indicators due to their complex reproductive needs and permeable skins; there has been a dramatic decline in amphibian populations for many species around the globe.

• The earliest amphibians evolved in the Devonian period from sarcopterygian fish with lungs and bony-limbed fins, features that were helpful in adapting to dry land.

• The three modern orders of amphibians are Anura (the frogs), Urodela (the salamanders), and Apoda (the caecilians); a fourth group, the Albanerpetontidae, became extinct around 2 million years ago.

• The number of known amphibian species is approximately 8,000, of which nearly 90% are frogs; the smallest amphibian in the world is a frog from New Guinea (Paedophryne amauensis) with a length of just 7.7 mm, while the largest living amphibian is the 1.8 m South China giant salamander (Andrias sligoi).

• The study of amphibians is called batrachology, while the study of both reptiles and amphibians is called herpetology.

• Amphibians as a class are defined as all tetrapods with a larval stage, while the group that includes the common ancestors of all living amphibians and all their descendants is called Lissamphibia.

• The origins and evolutionary relationships between the three main groups of amphibians are a matter of debate; they evolved from lunged fish and had to make certain adaptations for living on land, including the need to develop new means of locomotion.

• Terrestrial adults discarded their lateral line systems and adapted their sensory systems to receive stimuli via the medium of the air; they developed new methods to regulate their body heat to cope with fluctuations in ambient temperature and behaviours suitable for reproduction in a terrestrial environment.

• Modern amphibians have a simplified anatomy compared to their ancestors due to paedomorphosis, caused by two evolutionary trends: miniaturization and an unusually large genome, which result in a slower growth and development rate compared to other vertebrates.

• Amphibians require water bodies for reproduction, although some species have developed various strategies for protecting or bypassing the vulnerable aquatic larval stage; they are not found in the sea with the exception of one or two frogs that live in brackish water in mangrove swamps.

• Amphibians are restricted to moist habitats on land because of the need to keep their skin damp, and their skins are exposed to harmful ultraviolet rays that had previously been absorbed by the water.Facts about Amphibians

• Amphibians are ectothermic vertebrates that do not maintain body temperature through internal physiological processes.

• They have low metabolic rates and limited food and energy requirements.

• Amphibians have tear ducts, movable eyelids, and ears that can detect airborne or ground vibrations.

• Their skin contains many mucous glands and in some species, poison glands.

• Amphibians have three-chambered hearts, two atria and one ventricle.

• Most amphibians lay their eggs in water and have aquatic larvae that undergo metamorphosis to become terrestrial adults.

• The order Anura comprises the frogs and toads, while the order Caudata consists of the salamanders.

• The largest living amphibian is the Chinese giant salamander, while the smallest is the Paedophryne amauensis frog.

• Amphibians have fully ossified vertebrae with articular processes and their skulls are mostly broad and short, and are often incompletely ossified.

• The integumentary structure of amphibians is permeable to water and gas exchange can take place through the skin (cutaneous respiration).

• Amphibians have a skeletal system that is structurally homologous to other tetrapods, though with a number of variations.

• In frogs, the hind legs are larger than the fore legs, especially so in those species that principally move by jumping or swimming.An Overview of Amphibians

• Amphibians have unique adaptations for locomotion, including webbed feet for swimming, toe pads for climbing, and keratinised tubercles on the hind feet for digging.

• Salamanders can use their tails for defence and are capable of autotomy, shedding their tails to escape from predators. Both tails and limbs can regenerate.

• The circulatory systems of juvenile and adult amphibians are distinct. In the juvenile stage, the two-chambered heart pumps blood through the gills in a single loop, while in the adult stage, amphibians develop lungs and have a heart consisting of a single ventricle and two atria.

• The nervous system of amphibians is similar to other vertebrates, with a central brain, spinal cord, and nerves throughout the body. Tadpoles retain the lateral line system of their ancestral fishes.

• Amphibians have unique sensory systems, including well-developed ears in frogs and electroreceptors in some caecilians.

• Amphibians catch prey by flicking out an elongated tongue with a sticky tip and swallowing it whole. They possess voluminous stomachs and produce the enzyme chitinase to digest the chitinous cuticle of arthropod prey.

• Amphibians possess a pancreas, liver, and gall bladder. The kidneys filter the blood of metabolic waste, and larvae and most aquatic adult amphibians excrete nitrogen as ammonia.

• The lungs in amphibians are primitive, and ventilation is accomplished by buccal pumping. Most amphibians exchange gases with the water or air via their skin.

• Most amphibians require fresh water for reproduction, and breeding is often seasonal. Amphibians use various methods of fertilisation, including external and internal fertilisation.

• Amphibians go through metamorphosis, a process of significant morphological change after birth, regulated by thyroxine concentration in the blood and prolactin.

• The eggs of some salamanders and frogs contain unicellular green algae, which can increase the supply of oxygen to the embryo through photosynthesis.

• The variety of adaptations to specific environmental circumstances among amphibians is wide, with many discoveries still being made.Amphibian Life Cycle: Eggs, Larvae, Frogs, Salamanders, and Caecilians

• Amphibians lay their eggs in a variety of sites including water, mud, burrows, debris, plants, logs, or stones.

• Amphibian larvae, known as tadpoles, are typically herbivorous and have thick, rounded bodies with powerful muscular tails.

• At metamorphosis, rapid changes take place in the body of the frog, including the loss of gills and the development of legs and a tongue.

• Salamander larvae are carnivorous and continue to feed as predators when they are adults, so metamorphosis is less dramatic than in frogs.

• In caecilians, young are produced by viviparity, with some species developing inside the female's oviduct for long periods.

• In some species of amphibians, one or both adults play a role in the care of the young.

• Amphibians have diverse chromosomes and genomes, with karyotypes determined for at least 1,193 of the ≈8,200 known species.

• Genome sizes range from 0.95 to 11.5 pg in frogs, from 13.89 to 120.56 pg in salamanders, and from 2.94 to 11.78 pg in caecilians.

• The large genome sizes have prevented whole-genome sequencing of amphibians, although a number of genomes have been published recently.

• Iodine and T4 stimulate the evolution of nervous systems transforming tadpoles into terrestrial, carnivorous frogs with better neurological, visuospatial, olfactory, and cognitive abilities for hunting.

• Neoteny occurs when the animal's growth rate is low and is usually linked to adverse conditions such as low water temperatures that may change the response of the tissues to the hormone thyroxine.

• The genome of the African clawed frog (Xenopus tropicalis) was the first frog genome to be sequenced, and the genome of the axolotl (Ambystoma mexicanum) was the first salamander genome to be sequenced.