Why are there so many types of species? One reason is that the types of environments differ in different parts of the world.   Even in one region of a single continent, southern South America for example, there is a great diversity in natural environments.  One would not find the same species of plants and animals in the Andes,


the thorn forest-scrubland of the Chaco in Paraguay,


the coastal environments of Chile (with its colonies of comorants and sea lions),

sea lions

Brazilian rainforests,jungle

and Paraguayan subtropical rainforests.waterfall

The aquatic environments of the United States


have very different species than the those found in the aquatic environments in South America.

lily pads

    Throughout the world, there are classes of ecosystems referred to as biomes.  A biome is a major type of physical environment that is inhabited by characteristic plants and animals.  Temperature and annual precipitation determine the nature of many of these biomes.

a) deserts: Deserts actually contain a diversity of organisms.  Some are dormant until the rains come and others are nocturnal.

b) grasslands: In grasslands, the amount of rainfall is less than that needed to support trees. Herbivorous mammals and the insects they attract are important components of the animal life.

c) savanna: Savannas are extensive grasslands with occasional trees.  They are often tropical with rainy and dry seasons.

d) tropical rain forests: Tropical rainforests have high temperatures and a great amount of annual rainfall.   There is little seasonal change and, as a result, trees do not drop their leaves.  Because the trees do not drop their leaves and because insects and decomposers quickly make use of the organic matter on the forest floor, the soils are relatively poor with very few nutrients.  Tropical rainforests have an incredible biodiversity—an estimated half of all the plant and animal species on earth live here.  The following images are of a Brazilian rainforest (just south of Rio) and a subtropical rainforest in Paraguay (the national park Ybycui).


e) temperate deciduous forests: The dominant type of tree in temperate deciduous forests are the broad-leafed flowering plants which drop their leaves in colder seasons.  There is a lesser diversity of species than that found in tropical rainforests.


f) coniferous forests: Conifers have thin leaves (which we often call needles).  These needles allow them to lose less water which is especially an advantage in areas with harsh winters such as northern latitudes and higher altitudes


g) tundra: The tundra has a permanently frozen soil layer and short plants.  It can be found in polar regions and at high altitudes (such as in the Andes below).