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Gaining Ground The Origin And Evolution Of Tetrapods Pdf

gaining ground the origin and evolution of tetrapods pdf

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Marcelo R. Copeia 1 December ; 4 : — Jennifer A.

Jennifer Clack (1947–2020)

What are evograms? That's because the group includes all the organisms living and extinct that descended from the last common ancestor of amphibians, reptiles, and mammals. So, for example, the ichthyosaur, an extinct swimming reptile, is a tetrapod even though it did not use its limbs to walk on land. So is the snake, even though it has no limbs. And birds and humans are tetrapods even though they only walk on two legs.

All these animals are tetrapods because they descend from the tetrapod ancestor described above, even if they have secondarily lost their "four feet. Tetrapods evolved from a finned organism that lived in the water. However, this ancestor was not like most of the fish we are familiar with today. Most animals we call fishes today are ray-finned fishes, the group nearest the root of this evogram.

Ray-finned fishes comprise some 25, living species, far more than all the other vertebrates combined. Some, such as coelacanths, retain lepidotrichia at the ends of these fleshy limbs, but in most fleshy-finned animals these have been lost. The common ancestor of all those different organisms ray-fins, coelacanths, lungfishes, tetrapods, etc.

This ancient vertebrate lineage had fins with lepidotrichia , scales, gills, and lived in the water. Yet they also had air bladders air-filled sacs connected to the back of their throats that could be used for breathing air i.

The air bladders of many ray-fins no longer connect to their throats, and so they are not able to breathe air. In these ray-fins, the air bladder is used mainly for buoyancy control and is known as a swim bladder. By contrast, tetrapods have taken an alternative route: they have lost the buoyancy control function of their air bladders, and instead this organ been elaborated to form the lungs that we all use to get around on land.

When we get past coelacanths and lungfishes on the evogram, we find a series of fossil forms that lived between about and million years ago during the Devonian Period. During this interval, this lineage of fleshy-finned organisms moved from the water to the land.

Many parts of the skeleton changed as new innovations that permitted life on land evolved. For example, the ancestors at the base of this evogram lived fully in the water and had skulls that were tall and narrow, with eyes facing sideways and forwards. This allowed them to look around in their watery environments for predators and prey.

However, as ancestors of the first tetrapods began to live in shallower waters, their skulls evolved to be flatter, with eyes on the tops of their heads. This probably allowed them to look up to spot food. Then, as tetrapods finally moved fully onto land and away from the water, many lineages once again evolved skulls that were tall and narrow, with eyes facing sideways and forwards, allowing them to look around their terrestrial environments for predators and prey.

As lineages moved into shallower water and onto land, the vertebral column gradually evolved as well. You may have noticed that fishes have no necks. Their heads are simply connected to their shoulders, and their individual vertebrae look quite similar to one another, all the way down the body.

Mobile necks allow land animals to look down to see the things on the ground that they might want to eat. In shallow water dwellers and land dwellers, the first neck vertebra evolved different shapes, which allowed the animals to move their heads up and down.

Eventually, the second neck vertebra evolved as well, allowing them to move their heads left and right. Later tetrapods evolved necks with seven or more vertebrae, some long and some short, permitting even more mobility. The vertebrae you are probably most familiar with like our own! On top of the centra are vertebral spines and arches to which muscle segments attach, and lateral to the centra are the ribs; these anchor muscles that flex as the animals move.

Fishes swim with simple lateral motions, so their arches are relatively straight and needle-like, and so are their ribs. When you eat fish and pick out the bones, these are mostly what you're finding. Because fishes live in the water, gravity is not a big problem for them.

But on land, a quadruped with a backbone between forelimbs and hindlimbs faces the same problems as a bridge designer: sag. As the fleshy-finned organisms began to venture onto land, they evolved a series of interlocking articulations on each vertebra, which helped them overcome sag and hold the backbone straight with minimal muscular effort.

Vertebra shape and connections in the early tetrapod Acanthostega. One element of the human vertebral column. The connection between the pelvis and hindlimbs in early tetrapods is a prime example of exaptation.

We call this fused connection the sacrum. It is extremely useful for terrestrial organisms because it allows them to use their hindlimbs efficiently for locomotion on land.

Since the aquatic ancestors of fishes and tetrapods had no such connection, one might guess that this feature first evolved serving the function of enabling terrestrial locomotion.

However, the earliest form of this connection as seen in Acanthostega evolved while these tetrapod precursors were still living in the water.

Based on current evidence, Acanthostega appears to have been fully aquatic, so this connection likely evolved to function in something other than terrestrial locomotion. As the limbs and their connections to the rest of the skeleton evolved, limb bones took on distinct roles and many bones were lost.

The humerus and the femur were already connected to two outer bones the radius and ulna in the forelimb, the tibia and fibula in the hindlimb.

This is something that evolved about 30 million years before vertebrates came onto land. However, muscular connections between these bones began to change on the road to land and allowed the limbs to be used for terrestrial locomotion. The ankle was originally composed of many small bones arranged in two rows, but gradually many of these small bones were lost. The first animals to get close to walking on land had eight digits on each limb.

Over time, some of these digits were lost, leading to animals with seven digits, then six, and then five, which is the common condition now seen in living tetrapods.

As these animals evolved to live on land, other changes in the rest of their bodies evolved. Many would eventually lose their gills, which only work well for getting oxygen when wet, and their tail fins got smaller. Similarly they lost the lateral line system, a network of vibration-sensitive canals along the skull and jaw, which doesn't work out of water. The environments of the animals shown in this evogram also changed through time.

In fact, if you were to venture back to Arizona at the beginning of the "Age of Dinosaurs" in the Triassic Period, some million years ago, you would find ray-fins, coelacanths, and lungfishes living in the marshes, streams, and temporary ponds of that day, along with freshwater sharks. So the habitats that these animals occupy today are not necessarily the ones in which they have always lived, or in which they originally evolved. It is still unclear exactly where the transition from water to land took place ecologically.

Paleontologists have discovered fossils involved in this transition preserved from freshwater, brackish, and marine habitats. Some, like the whales, made the transition back into the water.

Introduction What are evograms? The evolution of whales. The origin of tetrapods. Jaws to ears in the ancestors of mammals. The origin of birds. The emergence of humans.

Search Glossary Home. Support this project. Evogram examples The evolution of whales The origin of tetrapods Jaws to ears in the ancestors of mammals The origin of birds The emergence of humans.

Gaining Ground, Second Edition

What are evograms? That's because the group includes all the organisms living and extinct that descended from the last common ancestor of amphibians, reptiles, and mammals. So, for example, the ichthyosaur, an extinct swimming reptile, is a tetrapod even though it did not use its limbs to walk on land. So is the snake, even though it has no limbs. And birds and humans are tetrapods even though they only walk on two legs.

Evolution of the Vertebrate Auditory System pp Cite as. The Ostariophysi are the hearing specialists of the ray-finned world. They are placed cladistically within the euteleosts and include the gonorynchiforms and a much larger group called the Otophysi see Fig. Although lacking the Weberian apparatus, other euteleosts nonetheless have hearing capabilities, if not always as acute as those of the otophysans. Weberian ossicles, however, represent a hearing apparatus whose evolution can be traced in the fossil record.

gaining ground the origin and evolution of tetrapods pdf

Gaining Ground, Second Edition: The Origin and Evolution of Tetrapods

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Что случилось. По голосу Стратмора, мягкому и спокойному, никто никогда не догадался бы, что мир, в котором он жил, рушится у него на глазах. Он отступил от двери и отошел чуть в сторону, пропуская Чатрукьяна в святая святых Третьего узла. Тот в нерешительности застыл в дверях, как хорошо обученная служебная собака, знающая, что ей запрещено переступать порог. По изумлению на лице Чатрукьяна было видно, что он никогда прежде не бывал в этой комнате. Какова бы ни была причина его волнения, когда он колотил в стеклянную стену Третьего узла, она моментально улетучилась. Он разглядывал роскошную внутреннюю отделку, выстроившиеся в ряд компьютеры, диваны, книжные полки, залитые мягким светом.

 Немец. Какой немец. - Тот, что был в парке. Я рассказал о нем полицейскому. Я отказался взять кольцо, а эта фашистская свинья его схватила. Беккер убрал блокнот и ручку. Игра в шарады закончилась.

Она решила включить громкую связь. - Слушаю, Джабба. Металлический голос Джаббы заполнил комнату: - Мидж, я в главном банке данных. У нас тут творятся довольно странные вещи. Я хотел спросить… - Черт тебя дери, Джабба! - воскликнула Мидж.  - Именно это я и пыталась тебе втолковать. - Возможно, ничего страшного, - уклончиво сказал он, - но… - Да хватит .

 Что ты говоришь? - Хейл невинно вздохнул.  - И в качестве милого побочного развлечения читать переписку простых граждан.

 Сто десять? - оживился Джабба.  - Сколько будет сто десять минус тридцать пять и две десятых. - Семьдесят четыре и восемь десятых, - сказала Сьюзан.

Джабба принялся устанавливать на место новый чип. Через минуту его усилия увенчались успехом, а телефон все звонил и звонил. Христа ради, Мидж. Ну хватит. Телефон заливался еще секунд пятнадцать и наконец замолк.

Rise of the Earliest Tetrapods: An Early Devonian Origin from Marine Environment

Глаза ее были затуманены. - Танкадо успел отдать его за мгновение до смерти. Все были в растерянности. - Ключ… - Ее передернуло.  - Коммандер Стратмор отправил кого-то в Испанию с заданием найти ключ.

Беккер пожал плечами: - Наверное, в тот день я прогулял лекцию. - Испанская церковь гордится тем, что ей принадлежат его останки. Испанская церковь. Беккер отлично знал, что в Испании только одна церковь - римско-католическая.

 - За счет заведения. Превозмогая шум в голове, Беккер представил себе грязные улицы Трианы, удушающую жару, безнадежные поиски в долгой нескончаемой ночи. Какого черта.

Я всегда добиваюсь своей цели, - подумал Стратмор. Не обращая внимания на пролом в стене, он подошел к электронной двери. Створки с шипением разъехались в стороны. Он вошел. Сьюзан стояла перед ним, промокшая, взъерошенная, в его пиджаке, накинутом на плечи.

 - Посылает сообщение о том, что Танкадо ликвидирован. Сьюзан повернулась к Беккеру и усмехнулась: - Похоже, у этого Халохота дурная привычка сообщать об убийстве, когда жертва еще дышит.

 - Что еще это может. Иначе Танкадо не отдал бы ключ. Какой идиот станет делать на кольце надпись из произвольных букв.

 Может быть, и нет, - сказала Сьюзан.  - Во множестве шифров применяются группы из четырех знаков. Возможно, это и есть ключ.

The Evolution of Single- and Multiple-Ossicle Ears in Fishes and Tetrapods

Я здесь проездом, из Бургоса. Прошу прощения за беспокойство, доброй вам но… - Espere.


  1. Chelsea L.

    26.04.2021 at 14:00

    David Norman; C lack , J.

  2. Tallucite1972

    27.04.2021 at 19:46

    Conceived and designed the experiments: DG.

  3. Riley O.

    29.04.2021 at 04:49

    Gaining Ground, Second Edition: The Origin and Evolution of Tetrapods Read Online · Download PDF The reason for this is that after about million years of earlier evolution, the vertebrates—animals with backbones—had produced.

  4. Juancruz H.

    01.05.2021 at 02:16

    It includes extant and extinct amphibians , reptiles including dinosaurs and therefore birds , and synapsids including mammals.

  5. Michelle F.

    02.05.2021 at 02:18

    There was a problem with your download, please contact the server administrator.

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