Ngenxa yemvelo yethu, kulula ngathi ukucabanga ukuthi izilwane zizalana kanjani, njengoba inqubo yazo yokuzala ivame ukufana neyethu. Nokho, kuthatha isikhathi eside ukuthola lokho kufana nomhlaba wezitshalo. Bakwenza kanjani lokho? Kuyini ukuvundiswa kwezitshalo?
Inhloso yalesi sihloko ukuchaza ukuthi kuyini ukuvundiswa kwezitshalo. Kulokhu sizokhuluma ngamaqembu amabili amakhulu akhona: Ama-angiosperms nama-gymnosperms. Ngakho ungangabazi ukuqhubeka nokufunda uma unesithakazelo kule ndaba futhi ufuna ukwazi okwengeziwe mayelana nokuvundiswa kwezitshalo.
Ukuvundiswa kwezitshalo
Ngaphambi kokuba sichaze ngokuvundiswa kwezitshalo, sizoqala siphawule ngokuthi uyini umqondo wokuvundisa. Kuyinqubo eyenziwa ngayo Ama-gametes amabili, iduna nensikazi, ayahlangana ngesikhathi sokuzala. Ngale ndlela, kwakhiwa i-zygote equkethe i-genome, umkhiqizo wabazali.
Emhlabeni wezitshalo, Impova iyenzeka kuqala. Amaqabunga wesilisa enzalo akhiqiza izinhlamvu zempova ezithwalwa izinambuzane noma umoya ziye esikhunjeni. Yilapho ezimila khona. Uma sikhuluma ngezitshalo, ngokuvamile asibhekiseli kuma-gametes, kodwa ezinhlamvu. Imbewu ngayinye yempova ngokuvamile iqukethe amangqamuzana amabili okuzala wesilisa, noma ama-gamete. Nokho, kunezindlela ezihlukene ezisetshenziswa izitshalo, njengoba kungezona zonke izinhlobo ezifanayo, eqinisweni ziyehluka kancane uma kuziwa ekuzaleni.
Njengoba wazi kahle, izitshalo zingahlukaniswa ngezindlela eziningi. Kunenqwaba yamaqembu, amakilasi kanye nezinhlobo zemifino futhi uhlobo ngalunye lungolwambalwa. Nokho, kunamaqembu amabili amakhulu ahlukene ngendlela azalana ngayo. Ukuze, Kunemifino enezimbali naleyo engenazimbali. Ezakuqala zaziwa ngokuthi ama-angiosperms futhi ziyizitshalo ezitholakala kakhulu kule planethi. Ngaphezu kwalokho, kulezi zinhlobo ezimbili zemifino yizona zakamuva. Ngakolunye uhlangothi, izitshalo ezingenazo izimbali ziyingxenye yeqembu ukuzivocavoca. Laba kwakungabokuqala ukuvela eMhlabeni, ngisho nangaphambi kwama-dinosaurs.
Phakathi kwama-angiosperms kukhona izitshalo ezihlukahlukene ezifana nezihlahla, izihlahla, azaleas, dimorphothecae, njll. Ngokuphathelene nama-gymnosperms, lawa akhiwe ikakhulukazi ama-conifers. Ezinye izibonelo zaleli qembu kungaba imisedari, ama-yews, amaphayini. Ama-Cycad nawo angawezitshalo ze-gymnosperm. Kodwa ungakhathazeki, sizokhuluma kabanzi mayelana nezinhlobo zombili zezitshalo, izakhiwo zazo nokuthi ukuvundiswa kwenzeka kanjani.
Ama-Gymnosperms
Ake siqale ngama-gymnosperms. Nakuba kuyiqiniso ukuthi lezi zitshalo zaziwa ngokungabi nazo izimbali, zikhona, kodwa hhayi ezijwayelekile esizicabangayo. Izimbali zawo azinawo ama-sepals noma ama-petals, kodwa ezinsikazi zakha uhlobo lwe-cone enokhuni neluhlaza okotshani olugcina luba izithelo ezingamanga, njengezigaxa zikaphayini.
Izitshalo zaleli qembu zinezimbali zesilisa nezinsikazi. Lesi sakamuva sinesilinganiso, ama-ovules amabili kanye ne-bract akha ikhoni yesifazane ngokuqoqana eduze kwe-eksisi yezimbali. Iqanda ngalinye liqukethe isaka le-embryo eline-archegonia emibili ngaphakathi kwalo. okuthi, kube nama-gametes amabili abesifazane noma ama-oospheres ngayinye. Ake sicacise le mibono:
- I-Archegonia: Yisitho sowesifazane sokuzala. amakhowe, ulwelwe y ama-bryophytes, njenge-mosses nezinye izitshalo ze-vascular ezifana nama-ferns. Iphelezelwa yisitho sowesilisa esibizwa ngokuthi i-antheridium.
- Ama-Oospheres: I-gamete yesifazane yezitshalo. Zivela kulokho okubizwa ngokuthi i-megaspore ngenqubo ebizwa ngokuthi i-megagametogenesis. Ezingeni eliyisisekelo singasho ukuthi lokhu kuqukethe ukuhlukaniswa kwe-mitotic. Ngesikhathi sokuvundiswa kabili, ama-oospheres ahlangana ne-nuclei ekhiqizayo evela kunhlamvu yempova futhi ngaleyo ndlela akhiphe umbungu.
Ngokuqondene nezimbali zesilisa, lezi zakha izigaxa zesilisa ezizungeze i-axis yezimbali. Zinesilinganiso kanye ne-microsporangia ezimbili noma impova lapho zigcina zenze amangqamuzana omama abuye abangele izinhlamvu zempova ezidumile. Ngaphakathi kwazo kunengqikithi yama-gametes amabili abesilisa, abizwa nangokuthi ama-anterozoid. Futhi aqukethe amasaka omoya amabili asiza ekuhlakazweni aze afinyelele embalini yesifazane. Kulokhu ngicabanga ukuthi kuzoba kuhle futhi ukuchaza imiqondo ethile:
- I-Microsporangia: Ziyizakhiwo ezikhiqizayo futhi zinezinhlamvu. Lezi imizimba emincane ngokuyisisekelo injongo yayo kuwukuhlakazeka futhi iphile isikhathi eside.
- Ama-Antherozoids: Ngokuyisisekelo i-gamete yesilisa, engalingana nesidoda sethu.
Ukuvundiswa kwezitshalo ze-gymnosperm
Ukwazi okuncane mayelana nezakhiwo zezimbali zesilisa nezinsikazi zama-gymnosperms, manje sizophawula ukuthi lokhu kukhulelwa kusebenza kanjani. Kufanele kuqashelwe ukuthi okusanhlamvu kwempova kungathatha isikhathi esingangonyaka ukuze kuqhume, lapho imbali yesifazane isifinyelelwe. Lapho lokhu kwenzeka, ishubhu lempova livuleka kancane kakhulu kulokho okubizwa ngokuthi i-nucellus yeqanda. Lapho ifika ku-gametophyte yesifazane, umsebenzi wayo olandelayo ukunqamula intamo ye-archegonium bese ingena ku-oosphere. lapho ulanda khona konke okuqukethwe kwakho. Kungalesi sikhathi lapho ukuvundiswa kwezitshalo ze-gymnosperm kwenzeka.
Phakathi nale nqubo, enye yama-gametes igcina ihlangene ne-nucleus yaleyo osphere eyenzeka kuyo. Ngenxa yalokho, i-zygote iyakhiwa, okuyiseli lapho umbungu wakheka khona futhi uthuthuke. Ngokuphathelene ne-nucleus yezitshalo, amanye amangqamuzana e-archegonium namanye ama-gamete wesilisa, wonke ayawohloka. Phakathi naleso sikhathi, i-endosperm, eyakhiwe amangqamuzana agciniwe, izungeza umbungu, ovikelwe yi- integument yeqanda, elibuye libe lignified. I-embryo ibhekwa njengevuthwe ngokugcwele lapho imbewu ikhishwa. Le nqubo ingathatha kalula iminyaka emibili kusukela ngesikhathi kuvela izimbali.
Endabeni yembewu evela kuphayini, ijazi lembewu yi-diploid futhi ikhiqizwa yi-sporophyte kamama. Ngokuphathelene ne-endosperm eyinhloko noma izicubu ezigciniwe, lena i-haploid njengoba iyingxenye ye-gametophyte yesifazane. Ngemva kokukhulelwa, umbungu we-diploid uyakhiwa, okuyi-sporophyte entsha.
Ama-angiosperms
Sesivele sazi ukuthi ama-gymnosperms ayini nokuthi asebenza kanjani, kodwa kuthiwani ngama-angiosperms? Ngaphambi kokuchaza ukuvundiswa kwalezi zitshalo, Okokuqala kufanele sicacise imiqondo ethile Ukuze uqonde kangcono inqubo:
- Carpels: Lawa amahlamvu aguquliwe okuthi, esewonke, akhe ingxenye yokuzala yowesifazane embali yezitshalo ze-angiosperm. Isethi yawo wonke ama-carpels embali ibizwa ngokuthi i-gynoecium.
- Ukucwaswa: Yileyo ngxenye ye-gynoecium ethola impova lapho kwenziwa impova.
- I-Micropyle: Eyaziwa nangokuthi i-micropyle, iyimbobo noma imbobo etholakala engxenyeni ye-apical ye-seminal rudiments noma ama-ovules.
- Ama-Synergists: Amaseli ane-nucleus etholakala ekugcineni kwe-embryo sac yezitshalo ze-angiosperm. Isikhwama sombungu ngasinye sinezimbili zazo. Ama-synergids amabili ndawonye akha i-filiform apparatus noma i-filar apparatus. Kumele kuqashelwe ukuthi zisiza i-oosphere ngesikhathi sokukhulelwa.
- i-polar nuclei: Lawa ma-nuclei amaseli atholakala ngaphakathi kwe-embryo sac, i-gametophyte yesifazane noma i-ovary. Bangenelela ekuvundiseni imifino.
Kufanele kushiwo ukuthi isikhwama sombungu ngasinye sinezinhlobo ezahlukene zamaseli, okuyiwona ezivundile yizimbobo ze-polar kanye ne-ovule. Kodwa-ke, lezo eziyinyumba, okungaba yi-antipodal kanye ne-synergistic, nazo ziyasebenzisana ngesikhathi sokuvundisa.
ukukhulelwa kwezitshalo ze-angiosperm
Ukuqeda ngendaba yokuvundiswa ezitshalweni, sizokhuluma ngokusebenza kwama-angiosperms. Lapho impova ye-carpel seyenzekile, uketshezi olunoshukela, olwakhiwe ikakhulukazi i-sucrose futhi olukhiqizwa ukucwaswa okuvuthiwe, ivuselela ukuhluma kwezinhlamvu zempova. Kolunye lwalezi zinhlamvu kuvela ishubhu lempova elinjongo yalo iwukudala indlela ngesitayela ize ifike ku-gametophyte yesifazane noma isaka lombungu lezitshalo ze-angiosperm. Lesi saki sombungu sitholakala ngaphakathi kweqanda.
Ama-gametes abesilisa noma ama-nuclei akhiqizayo ahamba ngeshubhu lempova aze afike ku-micropyle. I-pollen tube idlula kulesi sakhiwo futhi ikhipha konke okukuyo esikhwameni sombungu, eduze neyodwa yama-synergids amabili. Ngemuva kwale nqubo, i-nuclei ekhiqizayo ihlangana ne-oosphere kanye ne-polar nuclei, yingakho ibizwa ngokuthi "ukuvundiswa kabili".
Kunezinhlamvu eziningi ze-pollen ezivame ukufinyelela ukucwaswa futhi, ngenxa yalokho, zihlume. Noma kunjalo, eyodwa kuphela kuzo ezoveza ukukhulelwa. Uma i-ovary isivundisiwe, iqala ukukhula ibe yisithelo. Kulezo zithelo ezinothile imbewu, kukhona nezinhlamvu eziningana zempova ezidingekayo ukuze zihlangane neqanda ngalinye.
Kuyahlekisa ukuthi imvelo ihlele kanjani yonke into ukuze izinhlobo ezahlukene zemifino zizalane, akunjalo? Ngaphandle kokungabaza, leli zwe ligcwele indalo emangalisayo namakhono okuzalanisa.