Consider the following statements and choose the correct answer:
1. The biogeographical realms are regions made up of whole continents, or of large parts of a continent, separated by major geographic barriers and characterized by the presence of certain unique animals and plants
2. In each biome the kind of climax vegetation is uniform - grasses, conifers, deciduous trees but the particular species of plant may vary in different parts of the biome
3. There is usually a sharp line of demarcation between adjacent biomes
4. The definition of biome includes not only the actual climax community of a region but also the several intermediate communities that precede the climax community