The Nearctic ecozone covers North America, including northern Mexico and Greenland. Florida, though, sits outside this ecozone.
Although currently joined to South America for 180 million years the two continents where separated and therefore evolved very different plant and animal lineages.
A number of large animals, including horses, camels, mammoths, mastodonts, ground sloths, sabre-tooth cats, the giant short-faced bear, and the cheetah, became extinct in North America at the same time the first evidence of humans appeared. The American bison, brown bear or grizzly bear, and elk entered North America around the same time as the first humans, and expanded rapidly, filling ecological niches left empty by the newly-extinct North American megafauna.
Broadleaf forests are the dominant habitat of the UK and most of temperate northern Europe. There's little left of Britain's ancient wildwood, but isolated pockets of oak, beech and mixed deciduous and evergreen woodlands are scattered across the continent, and dictate its biodiversity.
Coastal cliffs are the rocky land edges that face the sea. These are complex and diverse habitats that lie above the water line, where exposure to salty spray, wind, sun and rain all play their part, as does the type of rock.
The coniferous forests of temperate regions undergo warm summers and cool winters, unlike their tropical counterparts. The species aren't exclusively conifers, there are usually a few broadleaf varieties too.
Desert and dry scrubland describes any area that receives less than 250mm of rainfall a year. Not just the endless, baking sand dunes of popular conception, it includes arid areas in temperate regions.
Mediterranean forest includes the fynbos of South Africa, the matorral of Chile and forests in parts of California. Hot, dry summers, contrast with much milder, wetter winters.
Polar regions, found at the planet's northern and southern extremes, are the icy wastes of the continental ice caps and the frozen pack ice of the ocean. The only 'plants' here are specialised forms of cold-loving algae that grow on the surface of snow.
The taiga is the largest land habitat - a northern zone of coniferous forests, stretching right round the planet from western Alaska to eastern Siberia. In the winter the temperature can drop to as low as -50 degrees Celsius and the taiga is blanketed in snow.
Temperate grasslands include the prairies of North America, the steppes of Russia and the pampas of Argentina. Summers here are mild to hot and the winters can sometimes be very cold – for instance, blizzards can blanket the great plains of the United States.
Tropical coniferous forests may sound like an odd concept to northern Europeans who associate conifers with cooler northern climes. However, their ability to conserve moisture is the perfect adaptation for certain areas of the tropics and subtropics where conditions are drier year round.
Tropical dry forests, in contrast to rainforest, have to survive a long dry season each year, so the predominantly deciduous trees shed their leaves to cope with it. Sunlight can then reach the ground, so the season that's bad for the trees is good for the forest floor.
Tropical grasslands include the savanna usually associated with Africa, and savanna-type grasslands found in India, Australia, Nepal and the Americas. They are characterised by drought-resistant shrubs and grasses, dotted with trees such as acacias or baobabs.
Tundra is the cold, treeless region around the poles that has permafrost as one of its defining features. Even at the height of summer, the soil a few centimetres under the surface remains frozen.
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