Compare and contrast the physical properties of mars and earth?

Which list shows the levels of organization of an organism in hierarchical order from left to right, from the smallest to the most complex?

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 used to keep track of the gamates and possible offsprings combination