In an ecosystem, which is not a density-dependent limiting factor?
a. predation
b. parasitism
c. competition
d. natural disaster

The correct answer is D. Natural disaster

The density dependent factors are those whose impact on the population growth is different with varying population density.

In the given options, A. Predation  B. Parasitism  C. Competition are density dependent limiting factor. This is because they all are dependent on population density. For instance, competition for food and other resources is high when there is large population in a particular area.

On the contrary, Natural disaster is not a density-dependent limiting factor. This is because its impact is not dependent on the number of individuals. For example- Earthquake is a natural disaster, which causes damage to all the life forms irrespective of the population size.

Thus, in an ecosystem, Natural disaster is not a density-dependent limiting factor.

answer; both surfaces of the membrane are nonpermeable