230 ❯ STEP 4. Review the Knowledge You Need to Score Highgiven trophic level. These pyramids tend to vary from one ecosystem to another. Like
energy pyramids, the base of the biomass pyramid represents the primary producers and
tends to be the largest.
There is also the pyramid of numbers,which is based on the numberof individuals at
each level of the biomass chain. Each box in this pyramid represents the number of mem-
bers of that level. The highest consumers in the chain tend to be quite large, resulting in a
smaller number of those individuals spread out over an area.
Two more terms to cover before moving on to the biomes are food chainsandfood
webs.Afood chainis a hierarchical list of who snacks on who. For example, bugs are eaten
by spiders, who are eaten by birds, who are eaten by cats. A food webprovides more infor-
mation than a food chain—it is not so cut and dry. Food webs recognize that, for example,
bugs are eaten by more than only spiders. Food webs can be regarded as overlapping food
chains that show all the various dietary relationships.Biomes
The various geographic regions of the earth that serve as hosts for ecosystems are known as
biomes.Read through the following list so that you will be able to sprinkle some biome
knowledge into an essay on ecological principles.- Deserts.The driest land biome of the group, desertsexperience a wide range of temper-
ature from day to night and exist on nearly every continent. Deserts that do not receive
adequate rainfall will not have any vegetative life. However, plants such as cacti seem
to have adjusted to desert life and have done quite nicely in this biome, given enough
water. Much of the wildlife found in deserts is nocturnal and conserves energy and
water during the heat of the day. This biome shows the greatest daily fluctuation in
temperature due to the fact that water moderates temperature. - Savanna.Savannagrasslands, which contain a spattering of trees, are found throughout
South America, Australia, and Africa. Savanna soil tends to be low in nutrients, while
temperatures tend to run high. Many of the grazing species of this planet (herbivores)
make savannas their home. - Taiga.This biome, characterized by lengthy cold and wet winters, is found in Canada
and has gymnosperms as its prominent plant life. Taigascontain coniferous forests
(pine and other needle-bearing trees). - Temperate deciduous forests.A biome that is found in regions that experience cold win-
ters where plant life is dormant, alternating with warm summers that provide enough
moisture to keep large trees alive. Temperate deciduous forestscan be seen in the
northeastern United States, much of Europe, and eastern Asia. - Temperate grasslands.Temperate grasslandsare found in regions with cold winters.
The soil of this biome is considered to be among the most fertile of all. This biome
receives less water than tropical savannas. - Tropical forests.Found all over the planet in South America, Africa, Australia, and Asia,
tropical forestscome in many shapes and sizes. Near the equator, they can be rainforests,
whereas in lowland areas that have dry seasons, they tend to be dry forests. Rainforests
consist primarily of tall trees that form a thick cover, which blocks the light from reach-
ing the floor of the forest (where there is little growth). Tropical rainforests are known for
their rapid recycling of nutrients and contain the greatest diversity of species. - Tundras.Thetundrabiome experiences extremely cold winters during which the
ground freezes completely. The upper layer of the ground is able to thaw during the
summer months, but the land directly underneath, called the permafrost,remains
BIG IDEA 4.A.6
Interactions among
organisms and with
their environment
result in movement
of matter and
energy.
BIG IDEA 4.B.4
Distribution of local
and global ecosys-
tems changes over
time.