What makes vertebrates different from other animals

In chordates, the central nervous system is based on a hollow nerve tube that runs dorsal to the notochord along the length of the animal. In vertebrates, the anterior end of the nerve tube expands and differentiates into three brain vesicles. Vertebrates are the largest group of chordates, with more than 62, living species. Vertebrates are grouped based on anatomical and physiological traits.

Tetrapods can be further divided into two groups: amphibians and amniotes. Amniotes are animals whose eggs are adapted for terrestrial living; this group includes mammals, reptiles, and birds. Amniotic embryos, developing in either an externally-shelled egg or an egg carried by the female, are provided with a water-retaining environment and are protected by amniotic membranes.

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The amniotic egg is the key characteristic of amniotes. In amniotes that lay eggs, the shell of the egg provides protection for the developing embryo while being permeable enough to allow for the exchange of carbon dioxide and oxygen.

The albumin, or egg white, provides the embryo with water and protein, whereas the fattier egg yolk is the energy supply for the embryo, as is the case with the eggs of many other animals, such as amphibians. However, the eggs of amniotes contain three additional extra-embryonic membranes: the chorion, amnion, and allantois.

Extra-embryonic membranes are membranes present in amniotic eggs that are not a part of the body of the developing embryo. While the inner amniotic membrane surrounds the embryo itself, the chorion surrounds the embryo and yolk sac. The amnion protects the embryo from mechanical shock and supports hydration. The allantois stores nitrogenous wastes produced by the embryo and also facilitates respiration.

In mammals, membranes that are homologous to the extra-embryonic membranes in eggs are present in the placenta. Reptiles are tetrapods, although some lineages have only vestigial structures since descending from four-limbed ancestors. Reptiles, even aquatic ones, lay eggs enclosed in shells on land. One of the key adaptations that permitted reptiles to live on land was the development of their scaly skin, containing the protein keratin and waxy lipids, which reduced water loss from the skin.

This occlusive skin means that reptiles cannot use their skin for respiration, like amphibians, and thus all breathe with lungs. Reptiles are ectotherms, animals whose main source of body heat comes from the environment. In addition to being ectothermic, reptiles are categorized as poikilotherms, or animals whose body temperatures vary rather than remain stable. Reptiles have behavioral adaptations to help regulate body temperature, such as basking in sunny places to warm up and finding shady spots or going underground to cool down.

The advantage of ectothermy is low metabolic energy needed to survive e. In the past, the most common division of amniotes has been into the classes Mammalia, Reptilia, and Aves Birds. Birds are descended, however, from dinosaurs, which are reptiles, so this classical scheme results in groups that are not true clades. We will consider birds as a group distinct from reptiles for the purpose of this discussion with the understanding that this does not completely reflect phylogenetic history and relationships.

The most obvious characteristic that sets birds apart from other modern vertebrates is the presence of feathers, which are modified scales. Birds are endothermic, and because they fly, they require large amounts of energy, necessitating a high metabolic rate. Like mammals, which are also endothermic, birds have an insulating covering that keeps heat in the body: feathers. Specialized feathers called down feathers are especially insulating, trapping air in spaces between each feather to decrease the rate of heat loss.

Feathers not only act as insulation but also allow for flight, enabling the lift and thrust necessary to become airborne. The feathers on a wing are flexible, so the collective feathers move and separate as air moves through them, reducing the drag on the wing.

Like the question of how flight evolved, the question of how endothermy evolved in birds still is unanswered. Feathers provide insulation, but this is only beneficial if body heat is being produced internally. Similarly, internal heat production is only viable if insulation is present to retain that heat. It has been suggested that one or the other— feathers or endothermy— evolved in response to some other selective pressure.

The evolutionary history of birds is still somewhat unclear. Due to the fragility of bird bones, they do not fossilize as well as other vertebrates. Birds belong to a group called the archosaurs, which also includes crocodiles and dinosaurs. This helps me alot with my school work Invertebrate vs.

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Animals with an internal skeleton made of bone are called vertebrates. Multicellular; no back bone; no cell walls; reproduce sexually; heterotrophic.