The big question when moving from OoT to ALttP is, "What in the heck happened to all the cool races of Hyrule?" In ALttP, all the maidens and their fathers appear to be human/Hylian, not Goron or Zora or anything else. Below is a blow by blow account of how the races of Hyrule fair in ALttP, as well as theories about what happened to them.
The Kokiri - In ALttP only a few of these ageless forest dwellers were still around, though not living in the Lost Woods. Perhaps with the death of the Deku Tree and the erosion of traditions, many Kokiri became bored with eternal life in the forest, and fed up with Mido's bossing, and left for adventure in Hyrule. Leaving the forest caused them to age, and as they mixed with the rest of the population they became indistinguishable from normal people. Some, however, still wore traditional Kokiri clothing to keep their heritage alive.
The Elf Brothers - These two look remarkably like Kokiri, due to their clothing and elfish appearance. They live near the Lost Woods and are chopping down a tree with that saw.
Flute Boy - He is dressed in a traditional Kokiri outfit (except for maybe the yellow vest) and plays the Ocarina, a Kokiri instrument. The Ocarina is mistakenly called a Flute, pointing out the eroding traditions of this time period.
Kakariko Blacksmiths - These two old, bearded elves must be Kokiri. Although they aren't dressed like Kokiri, the Kokiri were the only ones who might have grown this small with age.
The Gorons - The Gorons make no appearance at all in ALttP. Perhaps they hid themselves deep within Death Mountain, or maybe the entire race died out from starvation, war, and hard times. How did the Sage become human? I dunno - maybe Darunia's descendants passed on their powers to a human, or maybe Gorons and humans intermarried.
The Zora - This noble race reduced in numbers drastically by the time of ALttP, unless you count Zolas as Zoras. Either the Zora become hostile to the rest of Hyrule, and started calling themselves Zolas, or the entire Zora population (save Ruto and the King) was wiped out when Zora's Domain froze over. How did the descendant of Ruto become human? Maybe Link married Ruto after all...
Zolas - They look like a swamp monster from a B-grade movie, but these water creatures are the closest things to Zoras you will find in ALttP. Maybe they are Zoras...
Zora - One Zora, probably descended from the royal family due to his size, showed up in ALttP, calling himself by the name of Zora. He is either one of the last remaining Zoras or is King of the Zolas.
The Gerudo - The fate of this race is unknown. Probably with the demise of Ganondorf, many became disillusioned with their tribe culture and thieving lifestyle and started a new life with normal people. Although the Gerudo race consisted of only females, when they intermarried with normal people they started having boy and girl babies equally instead of just one boy every 100 years.
The matter of who is descended from who, as well as the fate of the races of Hyrule, remain complex mysteries. Consider the following quote, taken from the maiden in the Ice Palace in ALttP:
They say the Hylia people controlled mysterious powers, as did the seven wise men. But the blood of the Hylia has become thin over time. We who carry the blood of the seven wise men do not possess strong power any more, either.
Why did the blood of the Hylia become thin, and why did the power of the sages' descendants decrease over time? Following the pattern of all the theories I have presented, I would say that their powers were diluted because they intermarried with common folk. I am hard pressed to come up with any other explanation, other than the excuse that maybe ALttP didn't portray all the facts correctly. But if one aspect of the game is wrong, what does that do to the credibility of the rest of the game?