Yiziphi izinhlobo zama-germ cells ezifihliwe?
Ngakho-ke ku-biology, kuye ngokuthi inani eliqukethwe ku-yolk ovoplazme (izakhi zokudla), kuyisiko ukuhlukanisa izinhlobo ezine ze-ova:
- i-alecital - i-oocyte, lapho i-isikhuphazi engekho ngokuphelele;
- oligoletsitalnnye - ekubunjweni kukhona inani elincane le-yolk. Lolu hlobo luyisici sezinambuzane eziningi, kanye nezilwane ezincelisayo. Uhlobo olufanayo lweqanda kumuntu;
- i-mesolecital - iqukethe inani elilinganiselwe le-yolk (ama-amphibians);
- ama-pollecital - amasondo omzimba, ocebile kakhulu ku-yolk. Lolu hlobo lweqanda luyisici sezilwane ezinwabuzelayo, izinhlanzi, izinyoni.
Futhi, kuye ngokuthi i-yolk isakazwa kanjani ngqo kwi-ovoplasma, kuyisiko ukuhlukanisa:
- i-isoletsitalny - ukusabalalisa okufanayo kwesikhupha ku-ovoplazme;
- i-anisoletsitalny - i-yolk isatshalaliswa ngokungalingani eqandeni. Kule nkinga, le subtype nayo ingahlukaniswa nge-telolecital (i-yolk igxila kwelinye lamapulangwe) kanye ne-centrolecital (i-yolk igxiliwe phakathi, ikhona eduze kwe-nucleus futhi ihambele umgudu omncane we-ovoplasm).
Uyini umehluko ekuhlelweni kwamaqanda?
Uhlu olungenhla lwezinhlobo zeqanda lubonisa umehluko esakhiweni sabo futhi lubonisa ngokugcwele izinguquko zesakhiwo kumaseli wesondo ohlelweni lwe-phylogenesis.
Amaqabunga azo zonke izilwane ezincelisayo, kuhlanganise nabantu, okuphezulu kokuthuthukiswa komlando, ngokusho kwesakhiwo sabo sangaphakathi kuwu-oligolecital.
Lesi sakhiwo, okokuqala, kungenxa yokuthi isidingo sokuqoqa izinto ezakhiwe nge-ovoplasma asikho, ngoba ukuthuthukiswa kombungu kuvela esibelethweni. Izakhi zomzimba ezitholakalayo umfutho uthola kanye nokugeleza kwegazi.
Ezilwaneni, izigaba zokuqala ze-phylogenesis, kuze kube yizinyoni, i-yolk eqanda iqukethe kancane, ngoba ukuthuthukiswa komzimba kwenzeka emvelweni wamanzi.
Ukwanda kwendwangu ye-yolk ezikhukhulayo nezinyoni kuchazwa, okokuqala, ngoba imibungu yalezi zilwane isendaweni evaliwe futhi ihaqwe amaqanda amaqanda angenakuphepheka.