Baliqlar katta sinfining umumiy tavsifi va sistematikasi. Tog‘ayli baliqlar sinfi vakillarining tuzilishi, ko‘payishi va rivojlanishi

4. Tog`ayli baliqlarning iqtisodiy ahamiyati. Tog`ayli baliqlarning turlari kam (600 tur) va zich to`dalar hosil qilmaydi. Dunyoda tutiladigan baliqlarning 1,5-2% ini tog`ayli baliqlar tashkil etadi. Avstraliya va Yaponiyada tog`ayli baliqlarning go`shti oziqa sifatida ishlatiladi, Yevropa mamlakatlari va AQShda qayta ishlanib, asosan oziqa uni tayyorlanadi.
Akula jigaridan baliq yog`i olinadi. Uning tarkibida ko`p miqdorda A vitamini mavjud va oziqa sifatida hamda tibbiyotda ishlatiladi. Akula yog`idan optik asboblarni yog`lash uchun va pardozlash maqsadida foydalaniladi. Akula va skatlarning terisidan turli-tuman teri buyumlari, jumladan, poyabzal tayyorlanadi.
Adaptatasiya antarktika baliqlari uchun eng qulay suv harorati o’rtacha -1.87 C va umumiy qorong’ulik bir yilda to’rt oy. Sovuq ko’pincha energiya cheklangan suvlarda mavjudligiga qarab ikki xil moslanishi ma’lum. birinchidan ularning qon tana FL suyuqliklarning muzlash nuqtasiga qaraganda sovuqroq suvda yashash uchun samarali birikmalarni o’z ichiga oladi¹.
Our emphasis throughout this text on evolved traits and the selection pressures responsible for them does not mean that we view every characteristic of a fish as an adaptation. It is important to realize that a living animal is the result of past evolutionary events, and that animals will be adapted to current environmental forces only if those forces are similar to what has happened to the individual’s ancestors in the past. Such phylogenetic constraints arise from the long-term history of a species. Tunas are masters of the open sea as a result of a streamlined morphology, large locomotory muscle mass connected via efficient tendons to fused tail bones, and highly effi cient respiratory and circulatory systems. But they rely on water flowing passively into their mouths and over their gills tbreathe and have reduced the branchiostegal bones in the throat region that help pump water over their gills.

1^The Diversity of fishes page 405