Test Corrections

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Part 1:
1.  The type of succession that begins in an area where the natural community has been disturbed, removed, or 
      destroyed but in which the bottom soil or sediment remains is known as

      D) secondary

Explanation:  Secondary succession begins in habitats where communites are entirely or partially destroyed by some kind of damaging event.  For example, secondary succession begins in habitats damaged by fire, floods, insect devastations, overgrazing, and forest clear-cutting and in distrubed areas such as abandoned sgricultural fields, vacant lots, roadsides and construction sites.  Because these habitats previously supported life, secondary succession, unlike primary succession, begins on substrates that already contain soil.  In addition, the soil contains a native seed bank.

2.  Succession on a sand dune would follow which order?
      D)  Grass, shrubs, cottonwoods, pine and black oak, beech and maple

Explanation:  After grasses become established, which hold down loose sand, winds bring seeds of more complex plants (shrubs, alders, and willows) to the area.  In this open canopy sun, sun-requiring trees such as cottonwoods and some spruce become established.  Next, larter trees like pines, black oak, aspen, and birch begin to grow and dominate.  After shade develops from the first large trees, other types of trees, which are more shade resistant, begin to grow in the area.  What has now formed is called a broad-leaf forest.  The pines, aspens, and birches have grown rapidly, and sun required for their saplings to grow has been shut out.  New trees cannot grown in this shade.  As a result, the forest understory is conducive to shade-tolerant oak, tulip trees, beech, maple, ash, hemlock, and others.  Slowly the pines, aspens, and birches die out, leaving the climax forest.

Part 2:
1.  Which of the following cycles would be considered sedimentary?
     D)  Phosphorus cycle

Explanation:  The largest reservoir of phosphorus is sedimentary rock.  The phosphorus cycle originates with the introduction of phosphate into soils from the weathering of rocks.  Phosphate enters living ecosystems when plants take up phosphate ions from the soi.

2.  Which of the following is the root cause of habitat loss; especially in less developed nations?
     B)  poverty

Explanation:  Poverty is a force that drives many people to exploit the land they live on.  Farming, trade in animals, and building roads are all methods that people use to make money.