For question 2:
Nitrogen-fixing bacteria convert
atmospheric N2 to ammonium, a process called nitrogen
fixation<span>.</span>
Answer:
An ecoregion (ecological region) or ecozone (ecological zone) is an ecologically and geographically defined area that is smaller than a bioregion, which in turn is smaller than a biogeographic realm. Ecoregions cover relatively large areas of land or water, and contain characteristic, geographically distinct assemblages of natural communities and species. The biodiversity of flora, fauna and ecosystems that characterise an ecoregion tends to be distinct from that of other ecoregions. In theory, biodiversity or conservation ecoregions are relatively large areas of land or water where the probability of encountering different species and communities at any given point remains relatively constant, within an acceptable range of variation (largely undefined at this point).

A map of the Amazon rainforest ecoregions. The yellow line encloses the ecoregions per the World Wide Fund for Nature.

A map of North America's bioregions
Three caveats are appropriate for all bio-geographic mapping approaches. Firstly, no single bio-geographic framework is optimal for all taxa. Ecoregions reflect the best compromise for as many taxa as possible. Secondly, ecoregion boundaries rarely form abrupt edges; rather, ecotones and mosaic habitats bound them. Thirdly, most ecoregions contain habitats that differ from their assigned biome. Biogeographic provinces may originate due to various barriers, including physical (plate tectonics, topographic highs), climatic (latitudinal variation, seasonal range) and ocean chemical related (salinity, oxygen levels).
When the acidic level of human blood increases bicarbonate (HCO 3-) accepts H + ions and forms carbonic acid and this is how the balance of hydrogen ions (H+) is restored.
Answer:
<em>Hi There The correct answer to this is Energy from the sun helped power the water cycle and Earth's gravity kept water in the atmosphere from leaving the planet. The oceans hold about 97 percent of the water on Earth. About 1.7 percent of Earth's water is stored in polar ice caps and glaciers. Rivers, lakes, and soil hold approximately 1.7 percent.</em>
<em>Hope it helps!</em>