Were invertebrates more common? Did most organisms live on land or in the sea?

Yes, invertebrates are common than vertebrates. Most organisms started off in the sea, then adapted to live on land.

Explanation:

In the past, the first animals were mostly invertebrates and lived in the water for a certain amount of time. Then, they developed the right body parts to be able to live on the land.

invertebrates are animals with no backbone.

this is true, assuming that the allele is completely recessive and incomplete dominance is not a factor.