Aceasta metoda de reproducere a fost mai buna,mereu este tinut cei mai bun,mai simplu,ceva care poate sustine acel lucrur,fenomen mai mult timp.
Tu daca faci ceva si ai cateva optiuni la dispozitie,alegi pe aia mai buna corect? Pe aia mai buna,mai simpla,mai stiu si eu rapida,depinde de ce nevoi ai in situatia respectiva.
Viata este diversa,formele mai complexe necesita adaptari diferite.Un organism complex a trebuie sa i se atribuie o reproducere diferite de ce era in cazul cand organismele erau mai simple,asta pentru ca altfel aparea situatia ca organismul respectiv sa nu se poata sustine,mai simplu specia respectiva ar fi colapsat,s-ar fi dus de rapa.
Cum este sa faci un motor bun,puternic totu ok,dar ai un sistem de racire slab si ineficient,acel motor se va strica,deci cam asa cred ca au stat lucrurile si cu reproducerea asta sexuata, sau cum ii mai zice.
In cazul organismelor complexe colonarea sau inmultirea prin partenogeneza ar fi dus la aparitia de greseli, ar fi dus la aparitia de indivizi din ce in ce mai slabi si in final la moartea acelei specii.
Exemplu, sunt unele soparle care asa se reproduc, prin colonare cum zice Ray 
dar clonarea este cuvant atribuit unei operatii efectuate de un alt organism altui organism, asa cand un organism se reproduce singur, parca din cate imi amintesc se numeste partenogeneza.
In sf tot dracu ala e, deci in cazul animalelor lucru asta este daunator, duce la aparitia de greseli si in final specia se duce la fund
Asta este explicatia stiintei.Chestia naspa este ca nu avem cum proba daca un organism se reproduce prin clonare, folosim cuvantu lu Ray poate duce spre dezastru. Daca soparla aia se cloneaza fara absolut nici o problema si a supravietuit oricaror conditii, se pare ca lucrurile nu-s asa de clare pe cat se zice.
Situatia este mult mai complexa decat pare la prima vedere.Adica soparla aia a putut, alte animale nu.Pai de ce? Ai pus o intrebare buna poate ca nu pricepem noi explicatiile, tot ce se poate.Ray de exemplu stie tot, a priceput tot, dar stai ca acu ma duc sa il intreb de ce soparlele sau unele se cloneaza singure si nau nici pe dracu, iar un om, un alt animal nu poate sa o faca sa vezi ce raspuns da, o sa se ia de altceva, ca raspuns desigur nu are, el orice scrie aici este luat de la altii.
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Pai in prima faza celule doar se clonau, apoi o mutatie a dus la aparitia cromozomului y desi avem doua sexe cel feminim si masculin, dar nu uita ca exista animale care poseda ambele sexe, asta in epoca cambriana cand animalele au devenit complexe
https://ro.wikipedia.org/wiki/Cambrian
Cum a apărut actul sexual în procesul de evoluţie?
Algele includ unul dintre cele mai simple organisme de reproducere sexuală din lume, iar această provenienţă datează de acum două miliarde de ani. Algele o fac, plantele o fac, la fel ca şi insectele şi ciupercile. Acest proces se manifestă prin eliberarea spermatozoizilor în vânt sau apă pentru a putea fi transportaţi către cele mai apropiate ouă, bazându-se pe specii diferite pentru a transporta gameţii masculini către femele sau pentru a manevra două corpuri, astfel încât deschiderile de la nivelul organelor reproductive să fie apropiate pentru a avea loc schimbul de fluide.
https://www.descopera.ro/......distractiv
Nimeni nu stie. Cei care spun ca vai s-au clonat celulele si blablabla spun baliverne.Au fost ei acolo ca sa vada? Exista posibilitati infinite care au dus la aparitia vietii. Poate am fost creati de Dumnezeu conform religiei sau poate universul nostru este o plantatie a cuiva. Nimeni nu va stii niciodata adevarul.
Ciudata ideea ta ca ar trebui ca inmultirea sexuata sa apara la fiecare specie. Candva, a aparut ca o mutatie, la un organism unicelular eucariot; in culturile de organisme unicelulare apar mutatii foarte multe, datorita succesiunii rapide a generatiilor. Cum trasatura asta e foarte avantajoasa, caci mareste mult variatia individuala, facilitand selectia naturala, toate organismele complexe se trag din acel organism eucariot sexuat. Mamiferele au mostenit sexul de la anfibieni, acestia de la pesti, pestii de la cordate.
Sunt posibilități infinite, dar doar câteva au o logică și niște dovezi științifice.
"Pura intamplare." Necredinciosii pun pe seama purei intamplari totul si ei nu-si bat capul prea mult. Ei zic despre credinciosi ca "nu-si bat capul" dar nu se vad pe ei insisi. La ei se aplica "crede in pura intamplare si nu cerceta".
Ai fost tu acolo sa vezi ca am fost creati de Dumnezeu?
Stai... negi teoria evoluției dar susții parțial religia prin acel "poate"?!
Ești normal? S-a-ntâmplat ceva?
Da chiar am fost acolo, repetentule la biologie celulele se cloneaza si in prezent, cel mai usor este sa nu gandesti, ai auzit de divizare celulara? de faptul ca din doua celule un om devine ceea ce este da din doua spermatoizul si ovulul
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"Pura intamplare." Necredinciosii pun pe seama purei intamplari totul si ei nu-si bat capul prea mult. Ei zic despre credinciosi ca "nu-si bat capul" dar nu se vad pe ei insisi. La ei se aplica "crede in pura intamplare si nu cerceta".
iar minti mincinosule,ce castigi cu asta, evolutia nu este rodul intamplari exista selectie naturala,sexuala,mecanisme prin care viata a evoluat,ca tu habar nu ai e altceva ca categoric habar nu ai,un om care stie ce e evolutia nu scrie ca intamplari, evolutia e un fapt stiintific,doar indioti se indoiesc de asta,repetenti la biologie, logica,cine spune ma mincinosule sa nu cerceteze, am spus eu asa ceva,ma cat poti minti omule nu ti rusine ma, la varsta ta sa minti atata, logic sa cerceteze, si sa gandeasca singur ca are creier nu sa spuna dumnezeu e raspunsul la toate ca a gandi e greu bre, de asta suntem de rasul ue ca traim inca in evul mediu cu multi indioti si prosti
Cica intamplare Despre selectia naturala si teoria evolutiei https://www.youtube.com/watch?v=BiFr-YpKe4I
https://www.youtube.com/watch?v=CZobczeN3so
Ce rol sa aiba intamplarea? Scrii ''pura intamplare'' in ghilimele, parca ai cita pe cineva; de fapt te citezi pe tine. La numere mici vorbesti de intamplare, la miliarde de microorganisme, o mutatie foarte improbabila pentru un singur organism, va apare cu siguranta, chiar la cateva organisme. Asa ca orice mutatie posibila, apare in mai multe randuri, si cand e utila se poate transmite.
Man lasa'ne cu povestile astea ce zic uni altii,ce ic cercetatorii,tu vad vii si arati numa ce zic alti,dar tu, TU personal ce parere ai?
Uite sunt specii de soparle astazi nu acu milioane de ani, deci sunt care se coleaza singure, cum fac asta si mai ales cum de supravietuiesc?
Hai sa luam de bun faptul ca clonarea asta la animale ar duce la aparitia de greseli, dar la aceste soparle de ce nu apar greseli? La plante de ce nu apar greseli? De ce toate aceste specii cas animale cas vegetale nu dispar, ma refer daca clonarea asta sa te citez pe tine ar fi rea.Am citat doar cuvantu clonare,de fapt se numeste altfel dar zicem asa ca vorba ta e mai simplu.
Deci de ce sa arunc eu in vant seminte,spermatozoizi bla bla cand e mai simplu sa ma clonez
Ambele sexe exista si astazi la unele batriciene,sau cum le mai zice broaste,dar vorbeam de clonare.
Faptu ca toti ar arata identic ar dauna cu ceva oare? Nu stiu dar este o chestie curioasa totusi. Evolutia asta se pare ca sa complicat,sau poate ca nu,doar ca nu stim noi de ce a ales drumul asta cu sexe pentru reproducere. Poate voia sa se simta si organismul bine cine stie tu ce parere ai? Vorbesc aici de parerea ta nu veni cu linkuri si rahaturi spuse de altii, vina cu ceva rahat de la tine nu e nimic rau daca spui ceva, chiar daca e gresit, cel putin incercam sa mai gandim si noi nu? Nu trebuie sa ne lasam tot timpul la mana altora, ca asa zic aia, aia se ocupa studiaza bla bla.Lasa ca studiaza aia, uneori lumea nu e cinstita, sa nu zic de cele mai multe ori
Știința nu poate explica asta, deoarece nu are niciun sens.
EPrimul animal (unicelular) care a prins viața (prin circumstanțe încă inexplicabile) si care prin minune este capabil sa se si reproducă (altfel ar fi apărut degeaba) si care începe să evolueze... nu are niciun motiv sa renunțe la jumătate din funcția de reproducere.
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Tot "pura intamplare" se numeste pentru ca premisa se bazeaza pe "pura intamplare".
doar un indiot poate considera evolutia o pura intamplare
Parerea mea este ca viata a evoluat prin microevolutie =mici schimbari si macro evolutie =mari schimbari care se fac in timp, e vezi tu micro evolutia o putem vedea cu toti, de exemplu adaptarea microbilor la plastic =ceva facut de om,macroevolutia este in timp,necesita mai mult timp relian,dar asta nu inseamna ca evolutia e credinta nu si ca are ca baza mai multe lucruri care odovedesc
adn =genetica,toate animalele sunt indrudite genetic inclusiv omul,desi toate au acelasi stramos comun
fosile= sunt destule descoperite
prin anatomie,embriologie,socializarea si comportamentul animalelor,omul daca il studiezi vezi ca este ca orice alt animal,desi dovezi sunt,cine respinge evolutia? cei care habar nu au de ia,eu unu nu am cunoscut un om care sa o cunoasca si sa spuna nu cred,in fapt gasesti oameni care cred ca caini se transforma in pisici sau cimpanzei in oameni,isi dai seama ca nu are logica,dar asa vad ei evolutia,de pilda caini =cate rase a facut omul artificial,dar gandeste-te natura ce a putut face in sute de milioane de ani de evolutie, selectia sexuala,naturala nimeni nu o poate nega ia functioneaza inclusiv la om,inca ceva aparitia altor speci acum este mult mai complicata ca in trecut,cu cat un animal este mai complex, evoluat cu atat ca doua speci sa se reproduca sansele sunt mai mici, deci acum multe milioane de ani erau multe animale hibride, de exemplu noi genul nostru homo puteam face sex intre noi dar am ramas singuri doar noi din pacate cu cimpanzei numai putem face pui ca si ei si noi suntem prea evoluati, nu uita ca conteaza si oxigenul asta a determinat de ce dinozauri erau asa mari, vezi tu multe conteaza in jocul evolutiei
Pai nu a fost pura intamplare bre, asta au descoperit savanti inclusiv darwin, selectia naturala, sexuala nu sunt intamplari, daca din 5 copii, 3 mor din cauza unui mor si alti 2 supravetuiesc nu e pura intamplare, e semn ca ceva lea protejat ghici sistemul imunitar, uitate la rasele de caini cat de diferite sunt, asta intr-un secol dar in milioane de ani, vezi ca nu e pura intamplare, vorbim de stiinta, tehnologia de care te folosesti e pura intamplare?
Big bang nu a fost o intamplare ceva a cauzat asta si mutatia aia ceva a cauzat, totul are o cauza, absolut totul
https://en.wikipedia.org/wiki/Y_chromosome
Before Y chromosome
Many ectothermic vertebrates have no sex chromosomes. If they have different sexes, sex is determined environmentally rather than genetically. For some of them, especially reptiles, sex depends on the incubation temperature; others are hermaphroditic (meaning they contain both male and female gametes in the same individual).
Origin
The X and Y chromosomes are thought to have evolved from a pair of identical chromosomes,[14][15] termed autosomes, when an ancestral animal developed an allelic variation, a so-called "sex locus" – simply possessing this allele caused the organism to be male.[16] The chromosome with this allele became the Y chromosome, while the other member of the pair became the X chromosome. Over time, genes that were beneficial for males and harmful to (or had no effect on) females either developed on the Y chromosome or were acquired through the process of translocation.[17]
Until recently, the X and Y chromosomes were thought to have diverged around 300 million years ago.[18] However, research published in 2010, [19] and particularly research published in 2008 documenting the sequencing of the platypus genome,[12] has suggested that the XY sex-determination system would not have been present more than 166 million years ago, at the split of the monotremes from other mammals.[13] This re-estimation of the age of the therian XY system is based on the finding that sequences that are on the X chromosomes of marsupials and eutherian mammals are present on the autosomes of platypus and birds.[13] The older estimate was based on erroneous reports that the platypus X chromosomes contained these sequences.[11][20]
Recombination inhibition
Recombination between the X and Y chromosomes proved harmful—it resulted in males without necessary genes formerly found on the Y chromosome, and females with unnecessary or even harmful genes previously only found on the Y chromosome. As a result, genes beneficial to males accumulated near the sex-determining genes, and recombination in this region was suppressed in order to preserve this male specific region.[16] Over time, the Y chromosome changed in such a way as to inhibit the areas around the sex determining genes from recombining at all with the X chromosome. As a result of this process, 95% of the human Y chromosome is unable to recombine. Only the tips of the Y and X chromosomes recombine. The tips of the Y chromosome that could recombine with the X chromosome are referred to as the pseudoautosomal region. The rest of the Y chromosome is passed on to the next generation intact. It is because of this disregard for the rules that the Y chromosome is such a superb tool for investigating recent human evolution.
Https://www.sciencedaily.com/releases/2009/04/090416125209.htm
Move over, Y chromosome – it's time X got some attention.
In the first evolutionary study of the chromosome associated with being female, University of California, Berkeley, biologist Doris Bachtrog and her colleagues show that the history of the X chromosome is every bit as interesting as the much-studied, male-determining Y chromosome, and offers important clues to the origins and benefits of sexual reproduction.
"Contrary to the traditional view of being a passive player, the X chromosome has a very active role in the evolutionary process of sex chromosome differentiation," said Bachtrog, an assistant professor of integrative biology and a member of UC Berkeley's Center for Theoretical Evolutionary Genomics.
Bachtrog, UC Berkeley post-doctoral fellow Jeffrey D. Jensen and former UC San Diego post-doc Zhi Zhang, now at the University of Munich, detail their findings in this week's edition of the open-access journal PLoS Biology.
"In our manuscript, we demonstrate for the first time the flip side of the sex chromosome evolution puzzle: The X chromosome undergoes periods of intense adaptation in the evolutionary process of creating new sections of the genome that govern sexual differentiation in many species, including our own," she said.
Not all animals and plants employ genes to determine if an embryo becomes male or female. Many reptiles, for example, rely on environmental cues such as temperature to specify male or female.
But in life forms that do set aside a pair of chromosomes to specify sex – from fruit flies to mammals and some plants – the two X chromosomes inherited by females look nearly identical to the other non-sex chromosomes, so-called autosomes, Bachtrog said. The Y chromosome, however, which is inherited by males in concert with one X chromosome, is a withered version of the X, having lost many genes since it stopped recombining with the X chromosome.
In mammals, that probably took place about 150 million years ago, while in the fruit fly Drosophila melanogaster, a laboratory favorite, the sex chromosomes arose independently about 100 million years ago. In both humans and fruit flies, the Y chromosome has dwindled from a few thousand genes to a few dozen.
Hence the intense interest in why and how the Y chromosome lost genes once it stopped interacting with the X. Scientists have found that, as the only chromosome pair that doesn't break and recombine every time a cell divides, the XY pair in males is unable to take advantage of the main way deleterious genetic mutations are eliminated. The XX pair in females does recombine, but for the Y, the only way to get rid of a bad mutation in a gene is to inactivate or delete the entire gene. Over millions of years, inactive genes are lost, and the Y shrinks.
"If you have no recombination, natural selection is less effective at removing detrimental genes," said Bachtrog. "Y is an asexual chromosome, and it pays a price for that: It keeps losing genes."
Bachtrog, whose career has revolved mostly around the study of the degeneration of the Y chromosome, decided to focus on the X chromosome several years ago and went about searching for sex chromosome pairs that have arisen more recently – and thus might be in the process of adapting to their new role. Her paper centers around study of the three sex chromosomes in a rare western fruit fly, Drosophila miranda, a darker-colored cousin of D. melanogaster. (Many creatures have more than one pair of sex chromosomes; the platypus, for example, has five pairs, all inherited together.)
While one of D. miranda's sex chromosomes is descended from the original sex chromosome that appeared in Drosophila nearly 100 million years ago, a second originated perhaps 10 million years ago, and the third about a million years ago. The older two look much alike, Bachtrog said: The Y chromosome in each pair has lost genes to become a shadow of its former self, while the two X chromosomes are indistinguishable from each other.
The third and youngest sex chromosome is different. The Y is not yet shriveled, though it contains many non-functional genes – about half the total – that will eventually be lost. The X, which is dubbed neo-X, is undergoing rapid change, however, with about 10 times the normal amount of adaptation seen in the autosomes, according to the researchers.
By adaptation, Bachtrog means that the gene sequences in the X chromosome are becoming fixed as random mutations have finally settled on a few beneficial changes that accommodate the increasingly irrelevant Y chromosome. Between 10 and 15 percent of neo-X genes show adaptation, compared to only 1-3 percent of autosome genes.
"In hindsight, that is not surprising," Bachtrog said. "Neo-X is facing a much more challenging situation than the autosomes because its pair, the Y chromosome, is degenerating. Its genes are no longer producing proteins, so neo-X has to compensate by up-regulating its genes. We find a lot of genes on the X chromosome are involved in dosage compensation."
In humans, for example, all genes on the X chromosome are twice as active to account for the lack of genes on the Y. Women accommodate this by inactivating one entire X chromosome so as not to produce too much protein, Bachtrog said.
Another change in neo-X that Bachtrog suspects is taking place is the elimination of genes that are harmful to females. Biologists have realized recently that some genes have opposite effects in males and females, and evolution is a tug of war between males jettisoning genes that they find detrimental only to have females put them back, and vice versa.
"A good place to put sexually antagonistic genes that are beneficial to one sex but detrimental to the other is on the sex chromosomes," she said. The Y always ends up in the male, she said, so genes on the Y chromosome won't affect females.
"Conversely, the X chromosome becomes feminized with genes that are good for the female but detrimental to the male," said Bachtrog, adding that the X also becomes demasculinized, losing genes that are of use only in the male.
In search of more insights into the evolution of the X chromosome, Bachtrog said she is looking for fruit fly species with older and younger sex chromosomes "to study sex chromosome evolution in action." She said evidence suggests that adaptation to being a sex chromosome is most intense between 1 and 10 million years after it starts. Bachtrog also is completing assembly of the genome sequence for D. miranda, which is not among the 12 species of Drosophila currently targeted by the genome sequencing community. She hopes that the fly will become a model system like D. melanogaster.
"Now, finally, we are within reach of studying model systems like D. miranda that we couldn't think of several years ago," she said, predicting that "whole genome comparisons will revolutionize evolutionary biology, ecology and many other fields."
The research was funded by the National Institutes of Health, an Alfred P. Sloan Faculty Research Fellowship in Molecular and Computational Biology and a David and Lucile Packard Foundation Fellowship.
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