Topics: Vertebrate, Tetrapod, Chordate Pages: 6 (2686 words) Published: March 18, 2013
An animal with cartilaginous or bony vertebrae that surrounds a nerve cord and its brain protected by a skull is called a vertebrate. A taxonomic class of animals known as the Subphylum Vertebrate is where all the vertebrates belong to (Klappenbach, n.d.). In other words, vertebrate are animals with backbones. Vertebrates are divided into five sub groups, which are the fish, amphibian, reptiles, birds and mammals. The first class of vertebrate is the fish. Classification of vertebrates (n.d.) states that fish is a kind of aquatic vertebrate with special characteristics that allow them to spend all or part of their lives in water which is their habitat. “Aquatic" means they spend their lives in water (The five classes of vertebrates, 2009). According to The five classes of vertebrates (2009), fishes are ectothermic vertebrates which mean that fishes are cold-blooded vertebrate. Fish’s body temperature is equal to the surrounding environment. The characteristics of the fish’s body make it able to easily facilitate movements through the water mainly because of its body shape. The tail is a chief "organ" of locomotion, meanwhile the fins are used to steer, swim, and maintain balance. Overlapping slimy scales cover the body of most fish, though some fish, like sharks, have rough leathery skin (Classification of vertebrates, n.d.). Gills act as the breathing organ of fishes. These special organs called gills enable fishes to perform the gas exchange between water and fish blood. They enable the fish to breathe oxygen in water. For most fishes, their gills are protected by covers called opercula. When water enters a fish's mouth, it passes over the gills where tiny blood vessels absorb oxygen from the water and release carbon dioxide into it. Water is then expelled through the gill slits (Classification of vertebrates, n.d.). For the method of reproduction, Classification of vertebrates (n.d.) states that fishes are categorised into two categories, oviparous or ovoviviparous. Most fish are oviparous, or lays egg. The female lays eggs in the water. They lay a few larger eggs with more food supply to prevent waste or eggs may be laid in nests, guarded by one or both parents (Cold blooded vertebrates, n.d.). Example of ovoviviparous is a certain shark. Their eggs remain within the mother's body until they hatch into baby fish, after which they are "born" (Classification of vertebrates, n.d.). Types of fertilisation of fish include external fertilisation and also internal fertilisation. Reproduction (n.d.) states that external fertilisation for most bony fish is the process when a female releases her eggs into the water at the same time that a male releases his sperm. Fertilisation takes place when the sperms come in contact with the eggs. Another fertilisation process for some bony fishes such as sharks and rays is called internal fertilisation. The eggs of these fish are fertilised inside the female. Males and females must mate to ensure fertilisation occur. The males have special organs for transferring sperm into the females. After fertilisation, the females hatch the eggs inside their bodies and give birth to living young (Reproduction, n.d.). The amphibian is also another class of vertebrate. Similarly to reptiles, amphibian can live on land and in water. Their adaptation to living on land is not entirely successful, as they still have to return to water to breed and keep their skin moist. Amphibians are also cold blooded animals, this means that their temperature changes according to its surrounding. This indicates that compared to warm blooded animals, amphibians’ cells are not working as hard and they do not use as much oxygen too. That is why they do not breath as regularly as humans do (Inside the human body,n.d.). The characteristic of an amphibian is the skin of amphibians is always slimy and moist; they are so due to the layer of slime that covers its skin. Unlike the other classes of vertebrate,...
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