Extinction of species reduces the number of different species in ecosystems, hence lowering the diversity of living things.
Sonar testing has caused whales to die in mass amounts.
plays the role in skeletal muscle movement
In eukaryotic cells the DNA can be found in the nucleus mainly. so DNA replication takes place in the nucleus during the S phase of the cell cycle.
Also in eukaryotic cells there are mitochondria and chloroplasts (plants) and these have circular DNA and they also get replicated (according to their own mechanism).
Prokaryotic cells don't contain a nucleus. They do not contain DNA in the cytoplasm and thus the DNA replication will take place here.
I really hope this helps!