Boshskeletsizlar kenja tipi Boshskeletsizlar kenja tipi vakillarining umumiy tavsifi Lantsetnikning tuzilishi va hayot kechirishi Исполнитель

Boshskeletsizlar kenja tipi. Boshskeletsizlar kenja tipi vakillarining umumiy tavsifi. Lantsetnikning tuzilishi va hayot kechirishi.

1. Boshskeletsizlar kenja tipining umumiy tavsifi.
2. Xordaboshlilar sinfi vakili lansetnikning tashqi va ichki tuzilishi.
3. Lansetnikning embrional rivojlanishi.

Xordalilar tipi. Ma’lumki barchaxordali hayvonlarning tabiati umumiy plan asosida tuzilgan. Ular 3 ta asosiy o’ziga xos belgi asosida shakllangan.
1.Xorda- bu tipning barcha vakillarida o’ziga xos ichki asosiy skelet, ichiga botib ki

rgan о‘zaklar, kuchli vakuollashgan kletkalar xordasi yelka tomonida joylashgan. 

2. Mark. nerv sistemasi- naysimon shaklda bо‘lib orqa tomonida joylashgan.

3.Halqum-yoriqlari bо‘lib tashqi muhit bilan shu yoriqlari bilan bog‘langan.

Four features characterize the cxordates and have played an important role in the evolution of the phylum: 1.A single, hollow nerve cord runs just beneath the dorsal surface of the animal. In vertebrates, the dorsal nerve cord differentiates into the brain and spinal cord. 2.A flexible rod, the notochord,forms on the dorsal side of the primitive gut in the early embryo and is present at some developmental stage in all cxordates. The notochord is located just below the nerve cord. The notochord may persist throughout the life cycle of some cxordates or be displaced during embryological development as in most vertebrates by the vertebral column that forms around the nerve cord.

3. Pharyngeal slitsconnect the pharynx,a musculartube that links the mouth cavity and the esophagus,with the outside. In terrestrial vertebrates, the slits donot actually connect to the outside and are bettertermed pharyngeal pouches. Pharyngeal pouches arepresent in the embryos of all vertebrates. They become slits, open to the outside in animals with gills,but disappear in those lacking gills. The presence ofthese structures in all vertebrate embryos provides evidence to their aquatic ancestry.[1]
4. Boshskeletsizlar kenja tipining umumiy tavsifi. Bosh skeletsizlar kichik dengiz hayvonlari bo`lib, juda sodda tuzilgan. Bosh skeletsizlar xordalilar tipining hamma belgilarini o`zida ifoda etgan: xordasi bor, nerv nayining ichi bo`sh, halqumida jabra teshiklari bor va bu nafas olish organi bo`lib xizmat qiladi, hazm qilish kanalida jigar o`simtasi bor. Qon aylanish sistemasi tutash (yopiq), ammo yuragi yo`q. Juft harakat organlari bo`lmaydi.

Bu kenja tip o`z ichiga bitta xordaboshlilar sinfini oladi va sinf o`ziga 30-35 to`rni birlashtiradi.

2. Xordaboshlilar sinfi vakili lansetnikning tashqi va ichki tuzilishi. Xordaboshlilar  xordalilar tipining hamma belgilarini umrbod o`zida ifoda etgan, dengizlarda yashaydigan hayvonlar bo`lib, turlari uncha ko`p emas. Xordaboshlilar tuzilishini ularning tipik vakili hisoblangan lansetnik (Branchiostoma lanceolatum) misolida ko`rib chiqamiz.

[1]Animal diversity Chapter XII.pages 946- 947