What is the process called for an ecosystem to recover over time?

How does pregnancy begin? a) a placenta forms in the uterus b) a sperm reaches an egg in the fallopian tubec) the blastocyst differentiates into two cell types d) contractions begin in the uterine wallapex

Which kind of worm has a closed circulatory system? a planarian b fluke c pinworm d an earthworm

What is required in the genotype of an individual to show a recessive trait? a. two recessive alleles b. at least one recessive allele c. no recessive alleles