I believe one of the jobs is Excrete impurities
Answer:
A. Commensalism because the flatworm benefits while the horseshoe crab doesn't but isn't affected.
B. Predator-prey since the shark is the predator and the seal is the prey.
C. Competition because the two males are fighting for the female.
Hope this helps :)
Phenotype is the set of observable characteristics of an individual resulting from the interaction of its genotype with the environment. Genotype is the genetic constitution of an individual organism. Allele is one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.