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Free CLEP Science and Mathematics Exam Braindumps (page: 16)

Page 15 of 128
PDF with 494 Questions

Lichens are hardy organisms that can be found growing on rocks or trees in relatively unpolluted environments. They are often the first colonizers of landscapes that have been destroyed by fire or other natural disasters. Lichens are made up of two symbiotic organisms. They are

  1. a fungus and an algae
  2. a fungus and a bacterium
  3. a bacterium and an algae
  4. two different species of algae
  5. two different species of fungus

Answer(s): A

Explanation:

Lichens are, in fact, a fungus and an algae that cohabit. The algae supplies sugar and other organic molecules to the relationship, while the fungus absorbs water and nutrients directly from the rocks, soil, or trees that the lichen lives on.



Organisms that display radial symmetry as adults, possess stinging cells, and tentacles would be found in the animal phylum

  1. Porifera
  2. Cnidaria
  3. Platyhelminthes
  4. Aschelminthes
  5. Annelida

Answer(s): B

Explanation:

The cnidarians include jellyfish, corals, hydra, and other stinging, tentacled animal life. Porifera are sponges, Platy-and Aschelminthes include the flatworms, roundworms, and rotifers; and, annelids are earthworms.



The soil of tropical rainforests is extremely nutrient-poor with little nitrogen. Despite this, the rainforests of the world are home to 75% of the world's species, including huge numbers of plants and trees.

What may account for this apparent contradiction?

  1. Frequent volcanic eruptions enrich the soil with nutrients.
  2. There are so many organisms living and dying in the rainforests at any one time that a great deal of organic matter continuously exists to be cycled through the soil.
  3. Nitrogen compounds necessary for growth can be synthesized from scratch, without nitrogen from the atmosphere, by bacteria living in the soil.
  4. The soil is able to hold a great deal of water which cycles back into forest vegetation.
  5. The soil is nitrogen-poor because many of the rainforest plants are able to use nitrogen directly from the air, so that it does not

Answer(s): B

Explanation:

Plants cannot absorb nitrogen directly from the air, nor can nitrogen compounds be synthesized de novo by soil bacteria. The reason that tropical rainforests can hold so much biodiversity and richness despite the poor soil is that there are so many living creatures that are continually dying and supplying the soil with organic nutrients. Therefore, the soil may not hold onto any nutrients for a long time because the rate of nutrient cycling is so great, but there are plentiful nutrients to be recycled at any one time.



Natural disasters that wipe out large portions of a population, resulting in the formation of a new population that possesses only a small proportion of the original population's genetic diversity, cause what is known as

  1. a founder effect
  2. a bottleneck effect
  3. gene flow
  4. allopolyploidy
  5. speciation

Answer(s): B

Explanation:

A bottleneck occurs when a population is suddenly reduced in number drastically enough that much of the genetic diversity that had been present in the population has been erased. This can result from natural disasters such as flooding, volcanism, and forest fires, or from overhunting and habitat destruction.






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