In this picture the Primary Consumer is a mouse. The mouse then eats the Producer, which is grass. The grass attains 10% of the Sun's energy so when the mouse eats the grass it only gets 1% of the energy from the grass. The Secondary Consumer, which is a snake then eats the mouse. When the snake eats the mouse it only obtains 0.1% of the sun's energy which is 10% of the energy the mouse obtained from the grass and 10% of the energy the grass got from the sun. Only 10% of energy is passed though each level of the food chain. Now when the Tertiary Consumer, the hawk comes along and eats the snake it only obtains 0.01% of the energy from the sun which is 10% of the energy the the snake got from the mouse and 10% of the energy the mouse got from the grass which is 10% of the energy the grass got from the sun. Now when the hawk dies organisms like ants and worms break down and decompose its body that's why they are called Decomposers. The ant and worm obtain 0.001 of the sun's energy. When the ant decomposes the hawk this in some way helps fertilizes the grass and the food chain starts all over again.