Dogs shown in this picture belongs to the secondary consumer trophic level which consumes primary consumer herbivores. These primary consumer herbivores are dependent on grass for food which is a primary producer. If all dogs die, the population of primary consumer herbivores will increase. This increase will lead to decrease in grass at a drastic rate. Therefore, primary producers (grass) will be affected.
An atom is stable because of a balanced nucleus that does not contain surplus energy. If the forces between the protons and the neutrons in the nucleus are unbalanced, then the atom is unstable. Stable atoms retain their form for ever, while unstable atoms undergo radioactive decay.