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Haizivis ir plēsīgas jūras zivis. Tās pieder pie skrimšļzivju klases virskārtas.

Haizivīm raksturīgākā pazīme ir skrimšļa skelets. Tām nav žaunu vāku, bet ir tikai žaunu spraugas. Tām nav arī peldpūšļa, tāpēc šīm zivīm nepārtraukti ir jāpeld, lai nenosmaktu un lai negrimtu. Haizivju āda ir īpatnēja, jo tā ir klāta ar ļoti sīkām zvīņām. Visām haizivīm ir iekšējā apaugļošanās un haizivis var pieskaitīt pie dzīvdzemdētājām. Haizivīm ir ļoti labi attīstīta oža - tās sajūt asinis no ļoti liela attāluma. Haizivīm ir vāja redze. Ja jūrā nākas sastapties ar haizivi, tad jāpaliek nekustīgi guļam, jo haizivs var neredzēt cilvēku, taču ļoti jutīgi uztver elektriskos impulsus, ko izdala cilvēka locītavas, kad tas mēģina aizbēgt.

Komentāri 8

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nu,cik man zinams,vinjas deej olas un no taam izshkjiljas mazulji. Taas ir ljoti zinjkaariigas un atkariibaa,no sugas,vai nu asins kaaras,vai mazaak nezheeliigas,bet dziivot un eest grib visi. un ar vienkaarshu nekusteeshanos,iipashi no dazhaam haizivju sugaam,nepaglaabs,jo pat elposhanu,sirdspukstus taas juut. Par to,kaa pasargaat sevi no haizivju rijiibas un paarlieku lielaas zinjkaares,pameeginjaat visu uz zoba,veel zinaatnieki striidaas.
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nekā - mātītē iekšā tiek apaugļotas ļooooti daudz olas (ikri). Sīkie haizivēni tur arī izšķiļas, bet viņiem ir par maz vietas, jo viņi aug. tāpēc mātes vēderā viņi nogalina vājākos, līdz kamēr viens stiprākais ir izdzīvojis. tad viņš lien laukā un ir piedzimis. Var teikt, ka haizivs jau piedzimst kā uzvarētāja :) <aubergine>
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She is waiting for my leg
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Oviparity - Some sharks lay eggs. In most of these species, the developing embryo is protected by an egg case with the consistency of leather. Sometimes these cases are corkscrewed into crevices for protection. The mermaid's purse, found washed-up on beaches, is an empty egg case. Oviparous sharks include the horn shark, catshark, Port Jackson shark, and swellshark. Viviparity - These sharks maintain a placental link to the developing young, more analogous to mammalian gestation than that of other fishes. The young are born alive and fully functional. Hammerheads, the requiem sharks (such as the bull and tiger sharks), the basking sharks and the smooth dogfish fall into this category. Dogfish have the longest known gestation period of any shark, at 18 to 24 months. Basking sharks and frilled sharks are likely to have even longer gestation periods, but accurate data is lacking. Ovoviviparity - Most sharks utilize this method. The young are nourished by the yolk of their egg and by fluids secreted by glands in the walls of the oviduct. The eggs hatch within the oviduct, and the young continue to be nourished by the remnants of the yolk and the oviduct's fluids. As in viviparity, the young are born alive and fully functional. Some species practice oophagy, where the first embryos to hatch eat the remaining eggs in the oviduct. This practice is believed to be present in all lamniforme sharks, while the developing pups of the grey nurse shark take this a stage further and consume other developing embryos (intrauterine cannibalism). The survival strategy for the species that are ovoviviparous is that the young are able to grow to a comparatively larger size before being born. The whale shark is now considered to be in this category after long having been classified as oviparous. Whale shark eggs found are now thought to have been aborted. Most ovoviviparous sharks give birth in sheltered areas, including bays, river mouths and shallow reefs. They choose such areas because of the protection from predators (mainly other sharks) and the abundance of food.
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oo.. Raksts par mani :D
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SharK tu gan izskaties vairāk kā suns :DDD
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