V E R T E B R A T E S
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animals
with backbones…
Vertebrates are
animals that are members of the subphylum Vertebrata / (chordates
with backbones
and spinal columns). Vertebrates include the
overwhelming majority of the phylum chordata, with currently about 64,000 species
described. Vertebrates include the jawless
fishes, bony fishes, cartilaginous fishes,
amphibians,
reptiles,
mammals,
and birds.
Extant
vertebrates range in size from the frog species Paedophryne amauensis, at as little as
7.7 mm (0.3 inch), to the Baleonoptera
musculus, blue whale, at up to 33 m (110 ft).
Vertebrates make up about 4% of all described animal species and are the group
of animals very familiar to us!
Classification
of Vertebrates
Vertebrates can be classified in 8 main classes: · Class Agnatha (jawless fishes) · Class Chondrichthyes (cartilaginous fishes) · Class Osteichthyes (bony fishes) · Class Amphibia (amphibians) · Class Reptilia (reptiles) · Class Aves (birds) · Class Mammalia (mammals) |
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Birds (class Aves) are feathered,
winged,
bipedal,
endothermic (warm-blooded),
egg-laying,
vertebrate
animals. With around 10,000 living species, they are the most speciose
class of tetrapod
vertebrates. Extant
birds range in size from the 5 cm (2 in) Bee
Hummingbird to the 2.75 m (9 ft) Ostrich.
Modern birds are characterized by feathers, a beak with no teeth, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a lightweight but strong skeleton. All living species of birds have wings—the now extinct flightless moa of New Zealand being the only exception. Wings are evolved forelimbs, and most bird species can fly. Flightless birds include ratites, penguins, and a number of diverse endemic island species. Birds also have unique digestive and respiratory systems that are highly adapted for flight. |
Reptiles are members of the class Reptilia comprising the amniotes
that are neither birds
nor mammals. Living reptiles can be
distinguished from other tetrapods in that they are cold-blooded
and bear scutes
or scales.
Reptiles are tetrapod vertebrates, either having four limbs or, like snakes, being descended from four-limbed ancestors. Most reptiles are oviparous (egg-laying), although certain species of squamates retain the eggs until hatching and a few are viviparous (give birth to live young). As amniotes, reptile eggs are surrounded by membranes for protection and transport that adapt them to reproduction on dry land. Many of the viviparous species feed their fetuses through various forms of placenta analogous to those of mammals, with some providing initial care for their hatchlings. Extant reptiles range in size from a tiny gecko, Sphaerodactylus ariasae, which can grow up to 17 mm (0.7 in) to the saltwater crocodile, Crocodylus porosus, which may reach 6 m (19.7 ft) in length and weigh over 1,000 kg (2,200 lb). |
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Amphibians are members of the class Amphibia, whose
living forms include frogs, toads, salamanders, newts and caecilians. They are
cold-blooded, tetrapod vertebrates. Most have four limbs
and live in fresh water or on land but the caecilians, though included in the
group, live in burrows in damp soil and are limbless. The
young undergo metamorphosis from a larval form with
gills to an adult air-breathing form with lungs. Amphibians also use their skin
for respiration and some small terrestrial salamanders rely entirely on this
and have no lungs.
The three modern orders of amphibians are Anura (the frogs and toads), Caudata/Urodela (the salamanders), and Gymnophiona/Apoda (the caecilians). The total number of known amphibian species is approximately 7,000, of which nearly 90% are frogs. |
Fish is any member of a paraphyletic
group of organisms that consist of all gill-bearing aquatic
craniate
animals that lack limbs with digits. Included in this definition are
the living hagfish,
lampreys,
and cartilaginous
and bony fish,
as well as various extinct related groups. Most fish are ectothermic
("cold-blooded"), allowing their body temperatures to vary as ambient
temperatures change, though some of the large active swimmers like white shark
and tuna
can hold a higher core temperature. Fish are abundant in most bodies of water.
They can be found in nearly all aquatic environments, from high mountain
streams to the abyssal
and even hadal
depths of the deepest oceans .
At 32,000 species, fish exhibit greater species diversity than any other group
of vertebrates.
Fish are an important resource worldwide, especially as food. Commercial and subsistence fishers hunt fish in wild fisheries or farm them in ponds or in cages in the ocean. They are also caught by recreational fishers, kept as pets, raised by fishkeepers, and exhibited in public aquaria. |
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