Complex sentence: In the 1970s traditional views on the moral standing of animals were challenged by Richard Ryder and Peter Singer, who introduced the notion of speciesism, which is defined as discrimination on the basis of species for what some consider morally irrelevant reasons.
Split into simpler sentences: In the 1970s traditional views on the moral standing of animals were challenged by Richard Ryder and Peter Singer, who introduced the notion of speciesism. This is defined as discrimination on the basis of species for what might be considered morally irrelevant reasons.