What is an explanation of why producers are always found at the lowest tropical level

Asap! how does the distance between two objects affect the force of gravity? how is the moon dependent on the sun?

Consider the classification levels of a human. eukarya ,animalia ,chordata ,mammalia ,primates, hominidae ,homo ,sapiens .which is the most specific taxonomic level in the classification system above? a sapiens b homo c hominidae d primates

They live on every continent except antarctica