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READING COMPREHENSION

Lichens, of which more than twenty thousand species have been named, are complex
associations between certain fungi and certain algae. The lichen itself is not a organism; rather it
is the morphological and biochemical product of the association. Neither a fungus no an alga
alone can produce a lichen.
The intimate relationship between these two living components of a lichen was once
erroneously thought to represent mutualism. In mutualistic relationships, both participants
benefit. With lichens, however, it appears the fungus actually parasitizes the algae. This is one of
the conclusions drawn from experiments in which the two components of lichens were separated
and grown apart.
In nature, lichen fungi may encounter and grow around several kinds of algae. Some types of
algae the fungi may kill; other types it may reject. Lichen algae are autotrophic, meaning they
make their own food through photosynthesis. Lichen fungi are heterotrophic, meaning they
depend upon the algae within the lichen to supply their food. Up to ninety percent of the food
made by the green algal cells is transferred to the fungus. What, if anything, the fungus
contributes to the association is not well understood.
Lichen is hardy. They grow in many habitats and are often pioneers in hostile environments
where few other organisms can flourish. They have been known to grow endolithically, having
been discovered thriving inside of rocks in Antarctica. Lichens help reduce erosion by stabilizing
soil. Several kinds of insects’ glue lichens to their exoskeletons for camouflage. Many species of
birds use lichens as building materials for nests. Humans have used lichens for dyes and
antibiotics.

1. Which of the following best describes the lichens association?
A. Simple plant made of two different autotrophic organisms
B. A mutualistic association between a fungus and an alga
C. A parasitic association between two fungi, one autotrophic, the second heterotrophic
D. A union between a parasitic fungus and an autotrophic alga

2. The word “hardy” in line 16 is closest in meaning to …
A. tender
B. durable
C. armed
D. beneficial

3. In biology, mutualism occurs when two different organisms live close together and
A. one organism parasitizes the other
B. both organism benefit from the association
C. both organisms are harmed by the association
D. one organism benefits while the other does not or is harmed by the association

4. In line 7, the word “intimate” is nearest in meaning to …
A. living
B. extraordinary
C. biological
D. close

5. Lichens serve as camouflage for which of the following?
A. Insects

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