Do you know how many kinds of plants and animals there are in the world? Experts believe there are between eight and fourteen million, but right now w

Do you know how many kinds of plants and animals there are in the world? Experts believe there are between eight and fourteen million, but right now we only know about 1.8 million. Scientists are slowly finding new kinds all of the time—and that’s good news for us.
In 2009, a university professor named Christopher Austin and his graduate student Eric Rittmeyer discovered a new kind of animal. They were in Papua New Guinea, studying the wide variety of life on the island. One day, the researchers were listening to the sounds frogs make at night. Suddenly they started to hear some very unusual, high-pitched calls. At first, they couldn’t tell where the calls were coming from, but after some time they realized they were coming from the ground.
They started to look carefully among the leaves. They were expecting to find an insect, but what they found surprised them. It was an incredibly tiny frog—just seven millimeters long! “This frog has a call that doesn’t sound like a frog at all. It sounds like an insect,” said Austin. The frog they discovered was the smallest frog in the world.
Researchers believe that frogs and bugs are very important. They help to keep our environment clean. We can also use them to make new medicines. Researchers all over the world are working very hard to find new plants and animals every day. However, their jobs are getting more and more difficult. This is because forests like the ones these animals live in are quickly disappearing, and the animals are, too
Questions:
How many kinds of plants and animals haven’t been found yet?
Where did the researchers find new frogs?
What does “them” refer to?