The point source pollution can be defined as the pollution whose source of origin can be traced back and the further pollution can be prevented. For example sewage drainage in the pond. The non-point source pollution is the one whose source of origin can be many and cannot be traced back to a single source. For example rain water causing surface runoff which is transferring pesticides, organic matter, sewage water in the water body.
The principle difference between point source and nonpoint source water pollution is the number of sources of pollution. In the point source pollution the number of sources of pollution can be determined and traced back whereas in the nonpoint source pollution number of sources of pollution remains undetermined.
natural selection is natural, selective breeding is not. Natural selection is when the best genes are passed down. Selective is when the best of an animal group are forced to mate