英语翻译鱼类是最古老的脊椎动物.它们几乎栖居于地球上所有的水生环境━━从淡水的湖泊、河流到咸水的大海和大洋.世界上现存的鱼类约2万4千种.在海水里生活者占三分之二,其余的生活

Question

英语翻译
鱼类是最古老的脊椎动物.它们几乎栖居于地球上所有的水生环境━━从淡水的湖泊、河流到咸水的大海和大洋.世界上现存的鱼类约2万4千种.在海水里生活者占三分之二,其余的生活在淡水中.中国计有2千5百种,其中可供药用的有百种以上.鱼类终生生活在海水或淡水中,大都具有适于游泳的体形和鳍.用鳃呼吸,以上下颌捕食.出现了能跳动的心脏分为一心房和一心室.血液循环为单循环.脊椎和头部的出现,使鱼纲发展进化成最能适应水中生活的一类脊椎动物.鱼纲是现存脊椎动物亚门中最大的一纲,从动物进化的角度看,本纲是有颌类的开始,故为有颌类中最原始、最古老的一纲.这是脊椎动物亚门中最大的分类类群,远在泥盆纪就已派生出很多的边缘支系,发展和演变至今成为各种复杂体形的鱼类.现存鱼类分为软骨鱼系和硬骨鱼系.

Answer 1

Fish is the most ancient vertebrate.They inhabit almost all the aquatic environment on Earth -- from freshwater lakes,rivers and oceans of salty sea.The world now about 20,004 thousands of fish.Two thirds of those living in the sea and the remainder live in fresh water.China has two thousand five hundred dollars,of which more than 100 have medicinal properties.Fish living in seawater or freshwater life,armed with the appropriate shape and fin swimming.Breathing with gills,and lower predation.A beating heart can be bent into a room and atrium.Blood circulation for the cycle.The emergence of the spine and head,Pisces evolutionary development can be adapted to life in the water into the category of most vertebrates.PISCES existing vertebrates is the largest in the Asia-Gate program,from the point of view of animal evolution,the program is a kind of jaw,Therefore,for the most primitive jaw category,the oldest one program.This is the largest classification of vertebrate groups doors Asia and as far as the Devonian have been derived by many to the brink of lineage.development and evolution has become a complex shape of fish.Department of Fish and fish into existing cartilage between the bony fish.