Why are producers generally found at the beginning of a good chain?

Particle model to predict what will happen if a sharp object creates a hole in the soccer ball

State one important difference between a physical change and a chemical change?

Polar bears give birth and hunt on sea ice. which of the following would polar bears survive during the melting of arctic ice? growing another layer of fur during summer migrate inland to search for different food sources staying put until the ice refreezes sticking to the usual diet of seals