1 . You’ve probably heard of a hybrid(杂交物种)in films or books. The centaurs in the Harry Potter films are hybrids of human and horse.     1    

Hybridization occurs in both plants and animals.     2     What’s more, many plants that people eat, from strawberries to carrots, corn and potatoes, have been created by hybridization.

Cross-breeding(杂交)sometimes occurs when animals’ normal territory overlaps(部分重叠).     3     The grolar bear is a hybrid that happens when grizzly and polar bears mate. As the environment warms, grizzlies in Alaska and Canada wander further north, bringing them into contact with polar bears.

Artificial mixing often happens in zoos, where different species that don’t normally meet in the wild can be introduced to each other. Ligers(lion and tiger hybrids)are unlikely to occur in nature, because the only place that their habitats overlap is the Gir Forest in India.     4     Mixed species are more likely to be born with health issues than other animals. Most hybrids born in zoos are infertile, which means they are unable to have babies. However, many cross-breeds born in the wild, like the grolar bear, can have their own babies.

    5     “It’s part of the evolutionary process,” he says. Fertile hybrids can lead to the creation of a new species and increase the variety of living things.