Why can’t non-permeable or fully permeable membrane support life?

Which element provides strength to the exoskeleton of clams and oysters

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.

How does secondary succession differ from primary succession?