There are suggestions that the Uruk-hai were the result of crossbreeding Orcs and Men. There were other creatures in Saruman's armies, and under his command in the Shire, that appear to have been hybrids. "Half-orcs" were as tall as Men and are never described simply as Orcs, as the Uruk-hai frequently are.
The Uruk-hai are simple crossbreeds of human and orc, equivalent to a corrupted version of half-elves. There are two subspecies: Morgul Uruk-hai, bred by Morgoth and Sauron, similar to orcs but much larger and stronger.
If you're referring to Saruman's scene, then it works this way. First, you breed a Orc with a human, creating a tiny baby. Then, you take said baby and throw him into what's basically an incubator, forcing him to grow rapidly by foul arts into an Uruk Hai. In short, they're not made from mud, they're incubated in mud.
In the movies Uruk-hai are described as a crossbreed between "Orcs and Goblin-men". This is a reference to the creatures mentioned by Gamling in the novel that blend the traits of Orcs and Men. These Uruks are sent after the Fellowship, and their initial captain is Lurtz, a movie-only character.
Uruk-Hai were bred by Saruman in Isengard and were speculated to be the crossbreeding of Orcs and Men. That said, while he was shown to have a more hands-on approach with the Uruk-hai, he merely added to what was already created by Sauron.
Allegedly, Tolkien originally toyed with the idea of making the Nazgûl afraid of the river as a result of being barred from crossing running water, which is an idea borrowed from classic folklore where evil things are unable to go across running water.
Mordor Orcs refer to the Orcs that Sauron bred for his own army. The first Dark Lord Melkor took hostage some Elves from Cuiviénen. He tortured them, beat them, and broke their bodies into the first deformed and twisted beings known as Orcs.
Aragorn is not half Elf, although he is a descendant of Elros, who is half Elf (and the brother of Elrond, the half-Elf who raised him), which explains why Aragorn's life span is unusually long.
Uruk-hai, however, were bred by Saruman in the Third Age in order to create a stronger army for Sauron in the War of the Ring. There are hints that Uruk-hai are the result of crossing men and orcs, to create a new breed that did not have the weaknesses of the Orcs.
No, he's an Orc. That's why he's known as the Pale Orc and not the Pale Uruk-Hai. He's just as mean as an Uruk-Hai and far more intelligent than the average Orc as I understand it and also bigger than the average orc, but he's still just an Orc. The Uruk-Hai, if you remember, were bred by Sauruman to be fearless.
Since Tolkien said that Orcs were generally just seen as soldiers, then any female Orcs could have been soldiers as well. Much in the same way that female Dwarves aren't seen in The Lord of the Rings, but it is known that they still exist, the same could be true for Orc women.
Especially in Tolkien's The Lord of the Rings, orcs appear as a brutish, aggressive, ugly, and malevolent race of monsters, contrasting with the benevolent Elves. They are a corrupted race of elves, either bred that way by Morgoth, or turned savage in that manner, according to the Silmarillion.
In the movie adaptations, they appear to be created by only Saruman, in the name of creating a superior foot soldier for mass use in Sauron's armies. They were also meant to supplant the Orcs, and had nothing but contempt for their cousins, along with everything else.
"Uruk" means "orc", and "hai" means "human". The Uruk-Hai are a cross between orc and man, and orcs are corrupted Elves. He already had the orcs on hand, and was going to win with them anyway. He didn't need the Uruk-Hai.
In The Book of Lost Tales, it is said that Orcs were "bred from the heats and slimes of the earth" through the sorcery of Morgoth. Again, Tolkien later changed this, as Morgoth could not create life on his own. This led to the most popular theory that Orcs were created from corrupted Elves.
The Uruks in the service of Barad-dûr used the symbol of the red Eye of Sauron, which was also painted on their shields. Uruk-hai were later bred by the wizard Saruman the White late in the Third Age by his dark arts in the pits of Isengard.
As such, the Orcs were literally born in the dark, fighting and thriving in the black of night. When the sun rose over Middle-earth for the first time years after their initial creation, the light traumatized the Orcs, burning and blinding them after so many years shrouded in darkness.
Forget Sauron, probably the most lethal character in The Hobbit and Lord Of The Rings franchises was a blonde elf called Legolas. The lean, mean orc-slaying machine – played by Orlando Bloom – was taking down bad guys left, right and centre, and now someone has made a video detailing every one of his kills.
Yes, female orcs do exist in Middle-earth.
“There must have been orc-women,” Tolkien wrote. “But in stories that seldom, if ever, see the Orcs except as soldiers of armies in the service of the evil lords, we naturally would not learn much about their lives.
While the date of Legolas's birth is unknown, he was likely born sometime after his grandfather was killed and his father took over the rule of the Woodland Realm. Like all Elves, Legolas is immortal. Elves do not die by natural causes; however, they can be killed in battle.
Character. Although he lived among them, Legolas was not fully of the Silvan Elves. As a son of the Elven-king Thranduil, who had originally come from Doriath, Legolas was at least half Sindar; his mother's identity is completely unknown.
Long story short, this means that Legolas, as the son of Thranduil, would be a Sindar Elf by blood. However, he (along with the rest of the Fellowship) seems to consider himself a Wood-elf (one of the Silvan Elves), as they are his people.
After Sauron's defeat, Aragorn and his army killed the remaining Orcs in Mordor. It can be assumed that any Orcs in the Lonely Mountain would have also escaped once they got to know about their master's downfall.
Some people (including me) have discussed whether Orcs might have raped and cross-bred with Elf-women. In fact Tolkien himself wrote at one stage that the Orcs raped Elf-women but he did not retain this explicit language throughout his later writings.
What happened to the Orcs after the War of the Ring? They fled and hid in the mountains, just as they did after the Battle of Five Armies. But they weren't wiped out. Over the centuries, they disappeared, just as the Elves, Dwarves, Dragons, and so on did.