What is the lac operon. Thorough explanation please :)

The lac operon of E. coli contains genes involved in lactose metabolism. ... It normally blocks transcription of the operon, but stops acting as a repressor when lactose is present. The lac repressor senses lactose indirectly, through its isomer allolactose. Catabolite activator protein (CAP) acts as a glucose sensor.

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.

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.