does zygote reproduce sexually!?
100764
<No.A zygote (Greek: ζυγωτόν) is a cell that is the result of fertilization. That is, two haploid cells—usually (but not always) an ovum from a female and a sperm cell from a male—merge into a single diploid cell called the zygote (or zygocyte).\n\nAnimal zygotes undergo mitotic cell divisions to become an embryo. Other organisms may undergo meiotic cell division at this time (for more information refer to biological life cycles).\n\nTwins and multiple births can be monozygotic (identical) or dizygotic (fraternal).
550765
No, not sexually per se-but bacteria do exchange DNA, and use a long tube to do it...a suspiciously phallic thing.  It is called the "F pilus" (no, I'm serious here), and the process of exchange is called "conjugation".  But, it isnt reproduction, it's only DNA exchange.
990688
There are many hundreds of thousands of species of unicellular algae that reproduce sexually. \n\nWe have some fossils of brown algae that were in the process sexually reproducing dating back to well before the first multicellular life evolved. We know this because such alage produce silicons 'skeletons' that preserved their structure. \n\nSo we can be absolutely certain that the first sexually reproducing organisms weren't multicellualr.\n\nAs for which the first were, we really can not know. It's almost impossible to tell from fossils whether how a unicellular organism reproduced if it doesn't produce a solid skeleton, and solid skeletons evolved late.
392040
Hope this sheds some light on it jessica.\n\n\nREPRODUCTION\n\nMost fishes are egg-layers, but many bear living young. Live-bearing fishes may be ovoviviparous, in which the eggs essentially simply hatch within the female, or viviparous, in which the unborn young are supplied nourishment through the mother's tissues. In some ovoviviparous fishes the embryo develops in the egg while the egg is still within its follicular covering within the ovary, and ovulation (or release of the egg) and birth occur at the same time. In other ovoviviparous forms the eggs are released from the protective follicles into the cavity of the hollow ovary, where development continues. In some viviparous fishes the walls of the egg follicle are in intimate contact with the embryo, supplying it with nourishment. In the viviparous sharks, a part of the oviduct, or egg channel, is developed into a uterus, where the modified yolk sacs of the young are closely joined to pockets within the uterus.\n\nIn live-bearing fishes and in some egg-layers, fertilization occurs internally, and methods have been evolved for introducing the sperm into the female's body. In sharks the pelvic fins of the male are modified into intromittent organs called myxoptergia, and in the male topminnows the anal fin is modified into a similar-functioning intromittent organ called the gonopodium.\n\nAt least three modes of reproduction--heterosexual, hermaphroditic, and parthenogenetic--are found in fishes. In the most common form, heterosexual reproduction, there are separate male and female parents, but even here there is considerable variation. In some live-bearing fishes, the female is able to store sperm for up to 8 or even 10 months, and this sperm is used to fertilize new batches of eggs as they develop. In some cases, a female may carry sperm from several males at once.\n\nIn hermaphroditic reproduction, a single fish is both male and female, produces both eggs and sperm (either at the same time or at different times), and mates with other similar hermaphroditic fishes. External self-fertilization occurs in one hermaphroditic fish, which sheds egg and sperm simultaneously. In another, internal self-fertilization may occur. In certain fishes there is a time sequence of hermaphroditism, young fishes reversing their sex as they grow older.\n\nIn parthenogenetic reproduction, unfertilized eggs develop into embryos. This is known to exist in at least one fish species, Poecilia formosa, of the Amazon River; however, even though development proceeds without fertilization in some of these females, mating with a male is still required to stimulate egg development.\n\nParental care also shows great diversity. Some fishes, like the Atlantic herring, form huge schools of males and females and freely shed their eggs and sperm (milt), and then abandon the eggs. Other fishes build nests and care for both the eggs and newly hatched young. Others have evolved methods of carrying the eggs with them, commonly in their mouths, but also in gill cavities or in special pouches on the body.
370678
The first example would be "halpodiploidy" that occurs in bees, ants and wasps. In this form of asexual reproduction, females lay unfertilized eggs. The eggs can then hatch without fertilization, giving an asexually produced male, or they can be fertilized by a male, giving a sexually produced female.\n\nA second example would be "parthenogenesis" (Greek for "virgin birth"), seen in some fish, reptiles and amphibians. One commonly studied reptile species, the lizard Cnemidophorus neomexicanus, contains only females. All progeny contain the exact genetic information as its mother, essentially making it a clone. The females still engage in lesbian sexual behavior, which is thought to stimulate the laying of eggs. No genetic information, however, is transferred during this sexual act.\n\nThere are many other examples, and the previous answer touched on a few. I would add that anthrax is a bacterium, and therefore NOT a many-celled organism.
266090
Yes. You do understand how women get pregnant, don't you? It's about a sperm and an egg. That's all. It's not how you do it, when you do it, where you do it. It's just about a SINGLE, SOLITARY, swimming sperm cell that travels up the birth canal, past the cervix, and into the uterus, where it penetrates the outer cell wall of a SINGLE, SOLITARY egg. It doesn't matter HOW it gets there. And there are millions upon millions of sperm cells in every ejaculation.
511116
No. Once a fish egg is layed, that means it has formed a zygote, the fusion of sperm and egg. It has no characteristics of a seed and will not grow into a tree.
834627
meiosis ensures that each gamete is a haploid (i.e. has half, or n, chromosomes of a normal cell). when the gametes fuse the zygote becomes 2n like a normal cell. Mitosis produces daughter cells which both have 2n, and these cannot be present in the gametes or else the zygote would have 4n!
356272
when you have sexual intercourse and the egg is fertilized by the sperm.If anyone asks you didnt get it from me.
119623
In nature, living things evolve through changes in their DNA. In an animal like a chicken, DNA from a male sperm cell and a female ovum meet and combine to form a zygote -- the first cell of a new baby chicken. This first cell divides innumerable times to form all of the cells of the complete animal. In any animal, every cell contains exactly the same DNA, and that DNA comes from the zygote. \n\nChickens evolved from non-chickens through small changes caused by the mixing of male and female DNA or by mutations to the DNA that produced the zygote. These changes and mutations only have an effect at the point where a new zygote is created. That is, two non-chickens mated and the DNA in their new zygote contained the mutation(s) that produced the first true chicken. That one zygote cell divided to produce the first true chicken. \n\nPrior to that first true chicken zygote, there were only non-chickens. The zygote cell is the only place where DNA mutations could produce a new animal, and the zygote cell is housed in the chicken's egg. So, the egg must have come first.\n\nVirginia Kelly\n\nTo be ...
77951
There are many different types of "sex" practiced in the plant and animal kingdoms besides the type we humans are familiar with. There are species in which the fathers get pregnant (like seahorses). There are species where males will turn into females (or vice-versa) if it would help the species survive. There are lots of examples of parthenogensis (virgin birth). There are cases where a single individual (like a plant) will pollinate itself, but others where biology tries to prevent this, although the plant might be hermaphroditic. There are plants which have several different reproduction mechanisms; a piece of the root can produce a new individual, for example. Some organisms can engage in both sexual and asexual reproduction as well; earthworms, honeybees, and geckos can asexually reproduce. There are species with 3 or even more sexes (like the clam shrimp in the US, for example, which has 3 sexes, or possibly  the New Zealand lizard the tuatara, which appears to have 4 sexes. There are species where males just fertilize the eggs deposited by the female in some location (most fish). Bacteria and viruses reproduce in strange ways, by dividing, or by taking over the reproduction mechanism of some other organism. \n\nThe astounding variety of "sex" and/or reproduction just goes on and on and on. We are still learning about the amazing diversity of life on this planet. \n\nIf and when we ever discover life on other planets, you can be sure that they will have different ways to reproduce, that may or may not have anything to do with what we might recognize as sex, and probably using mechanisms we cannot even imagine.
1077389
When two egg cells are fertilized by two sperm cells in the same period of time, fraternal twins are formed. So, if a woman’s ovaries release more than one egg during ovulation and the woman has contact with more than one man during her fertile period, it is possible that she will become pregnant with twins who have different fathers. This phenomenon is extremely rare, but possible.\n\nIn even rarer cases, fraternal twins from different fathers may result from mistakes made during assisted fertility procedures. For instance, if a woman is artificially inseminated with a mixture of two men’s sperm cells because the equipment was not properly cleaned after its last use, she may become pregnant with fraternal twins who have different biological fathers. Again, while possible, this occurrence is exceedingly rare.\n\nNote: Identical twins cannot have different fathers. Identical twins are formed when the zygote created from one egg cell and one sperm cell splits during its development. When a single zygote produces twins, one man is the father of both children.
293799
Yes- they do.  Women with DS are fertile. Men with DS have traditionally been considered sterile; however, there have been two documented cases of adult men with DS fathering children.
367063
The sperm and egg (1n) come from the gametophyte through mitosis. After fertilization, the zygote grows into a sporophyte (2n). The sporophyte creates spores (1n) by meiosis which grows into a gametophyte (1n). It's a cycle! Hope this helps!
145878
In nature, living things evolve through changes in their DNA. In an animal like a chicken, DNA from a male sperm cell and a female ovum meet and combine to form a zygote -- the first cell of a new baby chicken. This first cell divides innumerable times to form all of the cells of the complete animal. In any animal, every cell contains exactly the same DNA, and that DNA comes from the zygote. \n\nChickens evolved from non-chickens through small changes caused by the mixing of male and female DNA or by mutations to the DNA that produced the zygote. These changes and mutations only have an effect at the point where a new zygote is created. That is, two non-chickens mated and the DNA in their new zygote contained the mutation(s) that produced the first true chicken. That one zygote cell divided to produce the first true chicken. \n\nPrior to that first true chicken zygote, there were only non-chickens. The zygote cell is the only place where DNA mutations could produce a new animal, and the zygote cell is housed in the chicken's egg. So, the egg must have come first.
297470
It depends on the mode of fertilization. In the case of external fertilization, the male gametes do not enter the reproductive tract of the female.\nIn the case of semi-internal fertilization, by means of spermatophores, the male sperm is encased in a small "package" called spermatophore, which enters the outer part of the female reproductive tract. Fertilization occurs when the ova reach that sector. \nFor internal fertilization, males have some kind of copulatory organ. This organ may be derived from different structures: in cartilaginous fishes, from the pelvic fins; in some bony fishes, from the ana.l fin (although most bony fishes have external fertilization); in amniotes there's a derivation from the cloaca (penis or hemipenises). In spiders, sperm is transferred via the pedipalps. Squids use special tentacles... the list is enormous. \nIn any case, this copulatory structure enters the female body (or fits closely into her genital opening) and releases the sperm.
409310
Assuming we're talking about humans ...\n\nIn the female gamete (the ovum, or egg cell) the DNA in the nucleus is contained in 23 chromosomes.  One of these is the sex chromosome, but this is always an X chromosome.  Outside the nucleus are additional pieces of DNA ... most notably, DNA in the mitochondria of the cell, which will get passed intact to the offspring.\n\nIn a male gamete (spermatozoan or sperm cell) the DNA in the nucleus is also contained in 23 chromosomes.  One of these is the sex chromosome and is either a Y or an X chromosome.  This will determine the gender of the offspring.  Sperm cells also have DNA in their mitochondria, but these are discarded upon fertilization (so the offspring gets mitochondrial DNA exclusively from the mother).\n\nUpon fertilization, the two gametes make a zygote.  The 23 chromosomes from each (haploid) gamete produces a complement of 46 total chromosomes in the (diploid) zygote.  The pair of sex chromosomes determines the gender of the developing offspring ... XY is a boy, XX is a girl.