Primary succession begins after
a?

Primary succession is one of two types of biological and ecological succession of plant life, occurring in an environment in which new substrate devoid of vegetation and other organisms usually lacking soil, such as a lava flow or area left from retreated glacier, is deposited.

a new volcanic rock

Explanation: Primary succession is a a type of ecological succession in which change in vegetation which occurs on previously unvegetated region. Examples of where primary succession may take place include the newly developed islands, new volcanic rock, and on land formed from glacial retreats.

sorry, but you do not have posted the diagram.

answer: grassland biomes are closer to the equator and receive more rain.

grasslands are biomes that are dominated by grasses rather shrubs and trees. savanna are biomes that exhibit grasses, shrubs and small tree as vegetation. grasslands are located near the equator of the earth. these are found in north america. savanna biomes are found in africa, south america, australia and india. grassland exhibit moderate climatic conditions, it receives   amount of rainfall higher than savanna.   therefore, savanna exhibit dry and hot climatic conditions.