Mother are generally the ones responsible for caring for their children. There isn’t any        (differ) in the animal kingdom. Mothers in the wild bear similar responsibilities         mothers in the city. They bring us into the world, nurture us, love us, teach us the skills we need to survive and protect us from harm, until we are ready       (go) off on our own. Here we can cite the dolphin (海豚) as an example.
When baby dolphins are born, they imitate (模仿)      their mother does, such as following her every move and         (learn) the skills to live. Using echo(回音) location, the mother teaches her baby        most basic and necessary skill: finding food. But the dolphin mother still has some other special hunting        (trick).
Some years ago, researchers       (discover) something strange on the mouth of a dolphin in Shark Bay, Western Australia. It was first believed to be a tumor (肿瘤) ,but after analyzing the strange object, they realized it was (actual) a marine sponge (海绵状物). In fact, the sea-sponge is used as a hunting technique, passed on from mothers to their daughters,       originated in a single female. This finding is also the first evidence of a culture of tool- use in marine mammals.