Student Writing Handbook Fifth+Edition

Classification / 73

brief periods in the cave for protection. Pack rats and cave crickets spend part of every day in

the cave and reproduce there, both of them using chemical trails to find their way to and from

their shelters. The most generally recognized cave animals, the bats, use the cave primarily for

hibernation, depending on the cold-air drafts from outside to slow their metabolism so that their

fat reserves will last through the winter.

Of greater interest to scientists, however, are the permanent cave dwellers, those animals

that can survive in the dark environment where lack of plant life severely limits the food chain.

Troglophiles can live outside the cave, but the environment outside the cave must be similar to

that inside. For instance, they can survive under rocks and undercut banks or under the tree

litter in the forest. Over the centuries, however, certain troglophiles have evolved so that those

that remained inside caves became a separate species, the troglobites. They have evolved for

survival, so they can detect minute food sources and use little energy for survival. For instance,

they have lost seeing eyes and any coloration. Because of the constant temperature and

humidity in the caves, the evolutionary process has given them large sensory structures which

can detect water movement or air movement, a sense which helps protect them from preda-

tors and obstacles and helps them locate prey. As a final evolutionary quirk, their reproduction

depends on the added food supply brought as a result of seasonal flooding. Because length of

daylight cannot trigger an annual biological calendar, the troglobites must be ready to repro-

duce quickly. As a result of these evolutionary changes, they are literally confined to the cave.

The permanent cave dwellers include beetles, spiders, millipedes, mites, springtails, bristle-

tails, fish, crayfish, shrimp, isopods, amphipods, and flatworms.

The animals at Mammoth Cave provide obvious examples for scientific study. Some animals

use the cave as only a part of their environment while others depend entirely upon the cave for

their survival. Evolutionary changes within the full-time cave residents provide curious exam-

ples for further investigation.

ANALYSIS of THE SAMPLE foR SCIENCE

The whole system of scientific identification is based on classification, and the pre-
ceding sample indicates the appropriateness of the classification method of develop-
ment for a science paper. The following comments point to the general success of the
approach:

• The topic sentence indicates that the classification of cave animals will be
  divided according to their dependency on the cave (means) and divided into
  two groups (number).


• Each of the two body paragraphs describes one of the groups.


• Details for each group separate one from the other, clearly establishing that one
  group is really a cave visitor while the other depends on the cave for survival.


• Within the second group, two subdivisions are identified, further evidence that
  classification is of particular benefit to the scientific paper.


• The writer maintains unity in each body paragraph and throughout the entire
  paper.