Packed with poison!

In the ocean, a box jellyfish dangles tentacles covered with venom-filled stingers. The jellyfish uses its stingers to kill its prey. But its venom can also kill humans within minutes. The brightly colored poison dart frog is deadly to humans too. Just a speck of its poison can kill a person. These two creatures are among the most venomous and poisonous animals in the world. How do animals use their poisons? When are humans in danger?