What is conservation biology and why is it important

What is the law of conservation of matter in biology.
All matter, living and non-living, in the universe are made up of atoms.
According to the the law of Conservation of Matter, matter is neither created nor destroyed.
All matter is made up of atoms.
Biology calls this cycling of matter as nutrient cycling.

Within a certain degree, zoos can help endangered species become healthier and some off the list.
Many zoos have captive breeding programs.
These can help make a species healthier by getting greater of genes.
Or figuring out why one population is getting a disease another group isn't.