What are the three main layers of skin?

How does the molecular clock work? a. it analyzes the brain functionality of two different species.b. it examines and compares the physical characteristics of two different species.c. it illustrates relationships between two different species.d. it compares the number of mutations that exist in the dna of two different species.

What is true of sea slugs in these orders

How can an organ, such as the lungs, work for multiple body systems?