<Ul> <Li> Physiognomy: the apparent characteristics, outward features, or appearance of ecological communities or species . </Li> <Li> Biome: a grouping of terrestrial ecosystems on a given continent that are similar in vegetation structure, physiognomy, features of the environment and characteristics of their animal communities . </Li> <Li> Formation: a major kind of community of plants on a given continent . </Li> <Li> Biome - type: grouping of convergent biomes or formations of different continents, defined by physiognomy . </Li> <Li> Formation - type: a grouping of convergent formations . </Li> </Ul> <Li> Physiognomy: the apparent characteristics, outward features, or appearance of ecological communities or species . </Li> <Li> Biome: a grouping of terrestrial ecosystems on a given continent that are similar in vegetation structure, physiognomy, features of the environment and characteristics of their animal communities . </Li> <Li> Formation: a major kind of community of plants on a given continent . </Li>

What has to be present in biomes to make them similar