Ocean Animals With Vertebrae
Marine vertebrates are vertebrates that live in marine vironmts. These are the marine fish and the marine tetrapods (primarily seabirds, marine reptiles, and marine mammals). Vertebrates are a subphylum of chordates that have a vertebral column (backbone). The vertebral column provides the ctral support structure for an internal skeleton. The internal skeleton gives shape, support, and protection to the body and can provide a means of anchoring fins or limbs to the body. The vertebral column also serves to house and protect the spinal cord that lies within the column.
Fish fall into two main groups: fish with bony internal skeletons and fish with cartilaginous internal skeletons. Fish anatomy and physiology gerally includes a two-chambered heart, eyes adapted to seeing underwater, and a skin protected by scales and mucous. They typically breathe by extracting oxyg from water through gills. Fish use fins to propel and stabilise themselves in the water. Over 33, 000 species of fish have be described as of 2017,
Hagfish form a class of about 20 species of eel-shaped, slime-producing marine fish. They are the only known living animals that have a skull but no vertebral column. Lampreys form a superclass containing 38 known extant species of jawless fish.
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The adult lamprey is characterized by a toothed, funnel-like sucking mouth. Although they are well known for boring into the flesh of other fish to suck their blood,
Together hagfish and lampreys are the sister group to vertebrates. Living hagfish remain similar to hagfish from around 300 million years ago.
The lampreys are a very ancit lineage of vertebrates, though their exact relationship to hagfishes and jawed vertebrates is still a matter of dispute.
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And so also are vertebrates in a monophyletic sse. Others consider them a sister group of vertebrates in the common taxon of craniata.
Pteraspidomorphi is an extinct class of early jawless fish ancestral to jawed vertebrates. The few characteristics they share with the latter are now considered as primitive for all vertebrates.
Cartilaginous fish, such as sharks and rays, have jaws and skeletons made of cartilage rather than bone. Megalodon is an extinct species of shark that lived about 28 to 1.5 Ma. It looked much like a stocky version of the great white shark, but was much larger with fossil lgths reaching 20.3 metres (67 ft).
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Bony fish have jaws and skeletons made of bone rather than cartilage. About 90% of the world's fish species are bony fish. Bony fish also have hard, bony plates called operculum which help them respire and protect their gills, and they oft possess a swim bladder which they use for better control of their buoyancy.
Bony fish can be further divided into those with lobe fins and those with ray fins. Lobe fins have the form of fleshy lobes supported by bony stalks which extd from the body.
Lobe fins evolved into the legs of the first tetrapod land vertebrates, so by extsion an early ancestor of humans was a lobe-finned fish. Apart from the coelacanths and the lungfishes, lobe-finned fishes are now extinct. The rest of the modern fish have ray fins. These are made of webs of skin supported by bony or horny spines (rays) which can be erected to control the fin stiffness.
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A tetrapod (Greek for four feet) is a vertebrate with limbs (feet). Tetrapods evolved from ancit lobe-finned fishes about 400 million years ago during the Devonian Period wh their earliest ancestors emerged from the sea and adapted to living on land.
This change from a body plan for breathing and navigating in gravity-neutral water to a body plan with mechanisms abling the animal to breath in air without dehydrating and move on land is one of the most profound evolutionary changes known.
Marine tetrapods are tetrapods that returned from land back to the sea again. The first returns to the ocean may have occurred as early as the Carboniferous Period
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Amphibians (Greek for both kinds of life) live part of their life in water and part on land. They mostly require fresh water to reproduce. A few inhabit brackish water, but there are no true marine amphibians.
There have be reports, however, of amphibians invading marine waters, such as a Black Sea invasion by the natural hybrid Pelophylax escultus reported in 2010.
Reptiles (Late Latin for creeping or crawling) do not have an aquatic larval stage, and in this way are unlike amphibians. Most reptiles are oviparous, although several species of squamates are viviparous, as were some extinct aquatic clades
Part Cards: Marine Vertebrates Printable Pdf
— the fetus develops within the mother, contained in a placta rather than an eggshell. As amniotes, reptile eggs are surrounded by membranes for protection and transport, which adapt them to reproduction on dry land. Many of the viviparous species feed their fetuses through various forms of placta analogous to those of mammals, with some providing initial care for their hatchlings.
Some reptiles are more closely related to birds than other reptiles, and many scitists prefer to make Reptilia a monophyletic group which includes the birds.
Extant non-avian reptiles which inhabit or frequt the sea include sea turtles, sea snakes, terrapins, the marine iguana, and the saltwater crocodile. Currtly, of the approximately 12, 000 extant reptile species and sub-species, only about 100 of are classed as marine reptiles.
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Except for some sea snakes, most extant marine reptiles are oviparous and need to return to land to lay their eggs. Apart from sea turtles, the species usually spd most of their lives on or near land rather than in the ocean. Sea snakes gerally prefer shallow waters nearby land, around islands, especially waters that are somewhat sheltered, as well as near estuaries.
Some extinct marine reptiles, such as ichthyosaurs, evolved to be viviparous and had no requiremt to return to land. Ichthyosaurs resembled dolphins. They first appeared about 245 million years ago and disappeared about 90 million years ago. The terrestrial ancestor of the ichthyosaur had no features already on its back or tail that might have helped along the evolutionary process. Yet the ichthyosaur developed a dorsal and tail fin which improved its ability to swim.
The earliest marine reptiles arose in the Permian. During the Mesozoic many groups of reptiles became adapted to life in the seas, including ichthyosaurs, plesiosaurs, mosasaurs, nothosaurs, placodonts, sea turtles, thalattosaurs and thalattosuchians. Marine reptiles were less numerous after mass extinction at the d of the Cretaceous.
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Marine birds are adapted to life within the marine vironmt. They are oft called seabirds. While marine birds vary greatly in lifestyle, behaviour and physiology, they oft exhibit striking convergt evolution, as the same vironmtal problems and feeding niches have resulted in similar adaptations. Examples include albatross, pguins, gannets, and auks.
In geral, marine birds live longer, breed later and have fewer young than terrestrial birds do, but they invest a great deal of time in their young. Most species nest in colonies, which can vary in size from a few doz birds to millions. Many species are famous for undertaking long annual migrations, crossing the equator or circumnavigating the Earth in some cases. They feed both at the ocean's surface and below it, and ev feed on each other. Marine birds can be highly pelagic, coastal, or in some cases spd a part of the year away from the sea tirely. Some marine birds plummet from heights, plunging through the water leaving vapour-like trails, similar to that of fighter planes.
Gannets plunge into the water at up to 100 kilometres per hour (60 mph). They have air sacs under their skin in their face and chest which act like bubble-wrap, cushioning the impact with the water.
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Mammals (from Latin for breast) are characterised by the presce of mammary glands which in females produce milk for feeding (nursing) their young. There are about 130 living and rectly extinct marine mammal species such as seals, dolphins, whales, manatees, sea otters and polar bears.
They do not represt a distinct taxon or systematic grouping, but are instead unified by their reliance on the marine vironmt for feeding. Both cetaceans and sirians are fully aquatic and therefore are obligate water dwellers. Seals and sea-lions are semiaquatic; they spd the majority of their time in the water, but need to return to land for important activities such as mating, breeding and molting. In contrast, both otters and the polar bear are much less adapted to aquatic living. Their diet varies considerably as well: some may eat zooplankton; others may eat fish, squid, shellfish, and sea-grass; and a few may eat other mammals.
In a process of convergt evolution, marine mammals such as dolphins and whales redeveloped their body plan to parallel the streamlined fusiform body plan of pelagic fish. Front legs became flippers and back legs disappeared, a dorsal fin reappeared and the tail morphed into a powerful horizontal fluke. This body plan is an adaptation to being an active predator in a high drag vironmt. A parallel convergce occurred with the now extinct ichthyosaur.image:Traces of neural arch and intercentra shape convergence characterized by environment. Top row: Reconstructions borrowed with permission from Nobu Tamura. From left to right: Cacops aspidephorus Paracyclotosaurus davidi, Archegosaurus decheni. Middle row: a) Cacops aspidephorus (ancestrally terrestrial); b) Paracyclotosaurus
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