Evolution doesn't work according to any plan or change in any particular direction. Sometimes it leads to the rise of more complex organisms, but usually it leads nowhere and an organism dies out. We call a species that dies out extinct. Most of the organisms that have evolved in the past are now extinct. Extinctions take place when the environment changes and one or more species cannot adapt. Sometimes the environment changes because a better-suited organism arrives to compete. Sometimes climates change. Parts of North Africa, now covered in desert, were once home to rivers, lakes and plants. Parts of Antarctica now buried in ice once grew tropical plants. Evidence suggests that giant meteors have crashed into the Earth at various times in history, causing mass extinctions. It is believed that such a crash 70 million years ago made the dinosaurs extinct. Which of the following is a false statement? A Some deserts we know today once had rivers and lakes. B Mass extinctions may have been caused by meteors. C Very few species have ever gone extinct. D Sometimes, species evolve to be more complex.