Red blood cells and white blood cells. Muscle cells and some others
When tiny ice crystals in clouds stick together to form snowflakes, the result is snow. If enough crystals form a clump, they'll become heavy enough to fall to the ground. When temperatures are cold and moisture in the form of tiny ice crystals exists in the atmosphere, snow forms.
Limiting factors such as loss of food sources can cause competition by forcing animals to fight over food resources.
