The four principles of natural selection

1) Variation: there needs to be a difference in the individuals within a population

2) Inheritance: These variable traits must be able to be passed down genetically

3) Growth rate: There needs to be a growth rate that requires a struggle for resources

4) Survival rate: There needs to be a difference in survival rate for the different variation types... certain variations will live

the answer is d. chordata

answer; both surfaces of the membrane are nonpermeable