Millions of kinds, most still unnamed
Scientists have named around one and a half million kinds of animal, and they describe something like fifteen thousand new species every year. One widely quoted study in 2011 estimated that the Earth holds about 8.7 million species of plants and animals in all, which would mean most living things have never been named. New mammals still turn up: in 2013 scientists named the olinguito, a small furry relative of the raccoon from the cloud forests of the Andes. One had lived in American zoos for years, mistaken for a similar animal.
The animals in this grid are the famous ones — the DOG and CAT, the LION, TIGER and ELEPHANT — but they are a tiny fraction of the whole. Around 97 per cent of animal species have no backbone: insects, worms, spiders, snails, jellyfish and their relatives.
Why scientists use Latin names
Common names cause confusion. A robin in Britain is a small red-breasted bird; an American robin is a much larger thrush that only shares the red breast. A buffalo in Africa and a buffalo in North America are different animals too. So every species also has a two-part scientific name, usually in Latin or Greek, used the same way in every language. The system was set out by the Swedish scientist Carl Linnaeus in the eighteenth century, and he included people in it: he named our own species Homo sapiens, meaning wise human, and placed us among the animals alongside the apes.
The TIGER is Panthera tigris, the WOLF is Canis lupus, and the pet DOG is usually treated as a kind of wolf. The first part of the name groups close relatives together, so a lion, Panthera leo, sits in the same group as the tiger.
The same shape, reached twice
A SHARK is a fish and a DOLPHIN is a mammal, yet they have the same streamlined shape, a fin on the back and a powerful tail, because they solved the same problem: moving fast through water. Evolution often lands on similar answers in unrelated animals, which scientists call convergent evolution. Bats and birds both evolved wings, and insects and the flying reptiles called pterosaurs had done so separately long before either, and the moles of Europe and a marsupial mole in Australia look strikingly alike without being close relatives.
The rest of the grid mixes pets and wild animals: the HORSE, RABBIT, HAMSTER, PARROT, GOLDFISH and TORTOISE; the GIRAFFE, ZEBRA, MONKEY, KANGAROO and CAMEL; the PENGUIN, OCTOPUS, WHALE and TURTLE; the SNAKE, FROG, EAGLE, OWL, FOX, BEAR and DEER. Each has its own family of puzzles, and our ecosystems page covers how they all depend on one another. Some are in trouble. About two in every five kinds of FROG and other amphibian are threatened with extinction, more than any other group of backboned animals. And WWF's Living Planet Index, which follows thousands of wildlife populations, found in 2024 that they had shrunk on average by about 73 per cent since 1970 — an average across populations, not a count of animals lost, but a clear warning all the same.