Which branch of science was newly developed after the discoveries about dna?

You can't say it developed just one branch of science.
To name a few: Genomics, Genetics, Chemistry and The science of studying DNA itself. We can't forget about the uses in technology like DNA Nanotechnology.
But technically, the main branch of science developed after the discoveries about DNA was Molecular Biology.

I would say molecular biology most probably 

Although i don't know what is the simulated system, starfish are predators that eat mostly  microalgae,  snails, sponges, bivalves, mussels and other small marine animals. removing starfish from any system would definitely increase this animals that they prey.