Biome

Biomes, also called ecosystems, are areas with specific height, light levels, vegetation, and types of blocks. There are 6 biomes currently in Pocket Edition: Desert, Tundra, Forest, Plains, Ocean, and Extreme Hills.

Desert, Beach, & Oasis
A desert is a infertile biome consisting mostly of sand, sandstone (on layer 3 & 4), and sand dunes. Sugarcane can be found also in the desert biome if next to an ocean or a river biome.

Water is occasionally found nearby deserts.
A beach is a biome like the desert but found near ocean biome. Cactus may occasionaly spawn in here.

An oasis are mostly part of the desert biome with small patches of sand and a water source.

Tundra_biome.jpg Types
Dirt, usually with snow on the top. Water sources have ice on the top.

Height
Tends to be quite mountainous. Rarely totally flat.

Vegetation
Spruce trees can only be found in this biome. Grass blocks are located underneath the snow.

Forest_biome.jpg Types
Mainly dirt and grass, with the somewhat rare patch of gravel.

Height
Rather close to sea level, but bumpy.

Vegetation
Oak and Birch trees, with sugar cane occasionally spawning near water. Mushrooms sometimes spawn underneath trees, where the light level is low enough.

Other notable features
Not safe to travel at night, because trees are very dense and can obstruct vision, but allow plenty of room for monsters to spawn. Creepers are especially a problem in this biome.

Clearing
A small to medium sized area devoid of trees.

Plains
=== Block Types===

Mostly Dirt and Grass, Gravel forms (Rarely) in patches.

Height
Mostly Flat, but small to medium sized hills tend to form.

Vegetation
Mushrooms and Flowers, the area is rather barren of trees.

Other Notable Features
Very flat and grassy, making it the most suitable location to build large structures, but rarely far from a forest.

Ocean
=== Block Types===

Oceans are extremely large areas of water, sometimes extending for one hundred blocks in all directions, and can be as much as 40 blocks deep. The bottom consists of either dirt, sand, or gravel, and clay can sometimes be found near the shore.

Height
Sea level and can extend from 15-25 blocks deep, though can be up to 40 blocks deep

Other notable features
If you can create a solid surface to build on, it is the absolute flattest biome in the game.

Lake
Smaller bodies of water, usually up to about 5-10 blocks deep.

Block Types
Dirt, stone, and grass.

Height
Extremely hilly, mountains rise very high and are incredibly steep.

Vegetation
There is very little vegetation due to the lack of available space. Trees can sometimes spawn, and mushrooms spawn underneath overhangs.

Other notable features
This is the most unusual biome, overhangs tend to form and extend for quite a ways. Another common oddity is "Floating Islands", Where part of the terrain is suspended midair, with no apparent connection to any cliff or the ground. These are hard to access, but, if it is big enough, are among the most interesting places to build your home.

Hills
Smaller mountains which are very common in most biomes.