what group do birds belong to? (select all that apply).

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sea turtle (reptile). Green turtle (Chelonia mydas) (C. mydas) off the Hawaii Islands, Pacific Islands. Green sea turtle, chelonian. Homepage blog 2011, science and technology, animal — © iStockphoto/Thinkstock

How many of you think the Brady Bunch episode in which Peter was studying for a biology exam? He asked Marcia for help, and she taught him the mnemonic: "A vertebrate has a back that's direct." Well, not all vertebrates take direct backs, but all accept backbones, or vertebral columns, that help support their bodies.

Although the vertebral column is perchance the most obvious feature in vertebrates, it was not present in the first ones, which probably had only a notochord (flexible rodlike structure which plays a role in the development of the nervous system). The vertebrate has a distinct caput, with a differentiated brain and three pairs of sense organs (nasal, optic, and otic [hearing]). The body is divided into body and tail regions.

Several groups of vertebrates inhabit planet Earth. Permit'south take a bout of the v main vertebrate groups alive today: the fishes, amphibians, reptiles, birds, and mammals.

Fishes

whale shark
A whale shark (Rhincodon typus) and a snorkeler off the declension of Australia.
© Comstock Images/Jupiterimages

The first fishes are thought to have emerged some 518 million years ago during the Cambrian Flow of World's history. Today, at that place more than 30,000 species of fishes found in the fresh and salt waters of the earth. Living species range from the primitive, jawless lampreys and hagfishes through the cartilaginous sharks, skates, and rays to the abundant and diverse bony fishes.

Fishes range in developed length from less than 10 mm (0.4 inch) to more than twenty meters (60 feet) and in weight from near 1.five grams (less than 0.06 ounce) to many thousands of kilograms. Some alive in shallow thermal springs at temperatures slightly above 42 °C (100 °F), others in common cold Arctic seas a few degrees below 0 °C (32 °F) or in common cold deep waters more than 4,000 meters (13,100 feet) beneath the sea surface.

Fish reproduction methods vary, but nearly fishes lay a large number of small eggs that are fertilized and scattered outside of the body. The eggs of pelagic (open ocean) fishes usually remain suspended in the open water, while many shore and freshwater fishes lay eggs on the bottom or among plants. The mortality of the young and particularly of the eggs is very high, and oft only a few individuals grow to maturity out of hundreds, thousands, and in some cases millions of eggs laid.
Amphibians

scarlet salamander (Pseudotriton ruber)
Scarlet salamanders (Pseudotriton ruber) are found in the eastern United States.
© Liz Weber/Shutterstock.com

Amphibians evolved from fully aquatic tetrapods—(which were essentially "limbed fish") who descended from lobe-finned fish—sometime between the Early on Devonian Period (which began 419 million years agone) to the Early Pennsylvanian Subperiod (which began 323 million years ago). The name amphibian, derived from the Greek amphibious meaning "living a double life," reflects this dual life strategy—though some species are permanent land dwellers, while other species have a completely aquatic mode of existence.

At that place are 3 living groups of amphibians (caecilians, salamanders, and anurans [frogs and toads]) that, collectively, brand up more 7,300 amphibian species. I similar tendency amongst amphibians has been the evolution of directly development, in which the aquatic egg and gratis-swimming larval stages are eliminated. Development occurs fully within the egg capsule, and juveniles hatch equally miniatures of the adult body form. Most species of lungless salamanders (family Plethodontidae), the largest salamander family, some caecilians, and many species of anurans have direct evolution. In add-on, numerous caecilians and a few species of anurans and salamanders requite birth to live young.

Frogs and toads display a wide variety of life histories. Some eolith eggs on vegetation to a higher place streams or ponds; upon hatching, the tadpoles drop into the water where they continue to develop throughout their larval stage. Some species create foam nests for their eggs in aquatic (watery), terrestrial (land-based), or arboreal (tree-based) habitats; after hatching, tadpoles unremarkably develop in water. Other species deposit their eggs on land and send them to water, while marsupial frogs are so chosen because they carry their eggs in a pouch on their backs. A few species lack a pouch and the tadpoles are exposed on the back; in some species, the female deposits her tadpoles in a pond as soon as they emerge from eggs.
Reptiles

male flying lizardPremaphotos/Nature Picture Library

Reptiles are air-breathing vertebrates. They have internal fertilization, amniotic development (in which the embryo develops within a fix of protective actress-embryonic membranes—the amnion, chorion, and allantois), and epidermal scales covering part or all of their body. The major groups of living reptiles—the turtles, tuataras, lizards and snakes, and crocodiles account for over 8,700 species.
Reptiles evolved from amphibians during the first role of the Pennsylvanian subperiod (323 million to 299 million years ago) and retained many amphibian structural characteristics. While about reptiles feed on other organisms, a few are herbivorous (eastward.g., tortoises). As cold-blooded animals, reptiles tend to exist limited to temperate and tropical areas, but, where they occur, they are relatively mutual; however, they are not as big or conspicuous as birds and mammals. Most reptiles are terrestrial, but a few are aquatic. They motion about by creeping or swimming in a fashion similar to amphibians. Some reptiles, withal, can lift the body from the ground and run chop-chop either in a quadrupedal or bipedal fashion. Reptiles lay relatively large, shelled eggs. In a few instances, the eggs and immature are cared for by the female; in others, the young are born alive.
Birds

European white pelican
European white pelicans (Pelecanus onocrotalus) in flying.
© Digital Vision/Getty Images

Birds brand upwardly any of the 9,600 living species unique in having feathers, the major characteristic that distinguishes them from all other animals. They are warm-blooded vertebrates more related to reptiles than to mammals. They accept a four-chambered centre (as do mammals), forelimbs modified into wings (a trait shared with bats), a difficult-shelled egg, and keen vision. Their sense of smell is not highly adult, and their auditory range is limited.

Although almost are capable of flight, others are sedentary, and some are flightless. In a manner like to their relatively close relatives the reptiles, birds lay shelled eggs. The young are usually cared for in a nest until they are capable of flight and self-feeding, merely some birds hatch in a well-developed state that allows them to begin feeding immediately or even take flight. (Nesting activities like to those of some birds are seen in the crocodilians.)

The origin of birds, feathers, and avian flight have long been hotly debated; the evolution of birds from reptilian ancestors is universally accustomed, however. The diversity of theropod dinosaurs (a various group of carnivorous "cadger-hipped" dinosaurs), some with feathers, has greatly expanded our perspective of the development and early diversification of birds. While it is known that the critical menstruum in avian evolution and flight took place during the Early on Cretaceous (145.5 million to 99.vi meg years ago), there is testify that feathers on theropods emerged much earlier, perchance during the Triassic and Jurassic Periods (some 252 million to 145 1000000 years ago).
Mammals

Okapi (Okapia johnstoni).
© IMPALASTOCK/iStock/Getty Images Plus

There are approximately five,000 species of mammals living today. Mammals differ from other vertebrate animals in that their immature are nourished with milk from special mammary glands of the female parent. Mammals are distinguished by several other unique features. Hair is a typical mammalian feature, although in many whales it has disappeared except in the fetal stage. The mammalian lower jaw is hinged directly to the skull, instead of through a dissever bone (the quadrate) as in all other vertebrates. A chain of 3 tiny bones transmits sound waves across the middle ear. A muscular diaphragm separates the heart and the lungs from the abdominal cavity. Mature blood-red blood cells (erythrocytes) in all mammals lack a nucleus; all other vertebrates have nucleated reddish blood cells. The oldest known animals classified equally mammals evolved near the boundary of the Triassic and Jurassic Periods, some 200 meg years ago.

This group of vertebrates ranges in size from tiny shrews or small bats weighing merely a few grams to the largest known animals, the whales. Well-nigh mammals are terrestrial, feeding on both animal and vegetable matter, but a few are partially aquatic or entirely then, as in the example of the whales or porpoises. Mammals move almost in a great variety of means: burrowing, bipedal or tetrapedal (4-legged) running, flying, or swimming. Reproduction usually involves the young developing inside the uterus, where nutritive materials are made bachelor through an allantoic placenta or, in a few cases, a yolk sac. In placental mammals, immature have a longer developmental period within the uterus. In marsupials, the relatively undeveloped young are carried in a pouch, where they adhere themselves to their mother'south nipple until they get fully adult. Monotreme mammals (that is, the platypus and echidna) differ from other mammals in that they lay eggs which hatch.