Yes it is, an example is a group of animals not treated with it died, but the animals that were survived--
Varieties of plants in which self-fertilization produces offspring that are identical to the parents are referred to as true-breeding. In this process the parents will pass down specific phenotypic trait of their offspring. True bred organisms will have pure genotype (genetic make up of an organism) and will therefore produce certain phenotype.
Kingdom, class or division.
It only allows certain things through, such as water. One way to remember it is to think about how you wouldn’t eat just anything, and the cell doesn’t let just anything in. I hope this helps