A View Of life 1

Modern biology examines the world of in all its details and interactions. An organism's ability to reproduce itself essential to the continuity of life. DNA, the hereditary material of life, is shown in (a) a computer
drawn simulation of the colored plastic space~filling molecular models used by
biologists. The balls represent the different atoms that make up DNA:
dark blue, carbon; , oxygen; white, hydrogen; blue, nitrogen; yellow, phospho-
rus. (b) A genetically engineered Escherichia coli bacterium (magnified 68,000
times). its hereditary material has been modified so that the bacterium produces
large quantities of the hormone human insulin. Individuals with the disease
diabetes mellitus have insufficient amounts of this hormone, which is necessary
for the normal metabolism of sugar. Since the bacterium itself has no use for
the insulin, and has no way of excreting it, instead the hormone accumulates in
an “inclusion bod)/’ within the bacterial cell. The insulin can be harvested by
destroying the bacterium. (c) An angelfish guarding a section of coral reef. BiolOgists are concerned with the physical characteristics of the fish, how its body
functions, its behavior, and its interaction with other living things in its environment, (d) Biologists also study the effects of human activities on the envi
ronment. Because human populations are expanding rapidly in the world’s
tropical areas, rainforests are being cleared to provide more land for agriculture.
Unfortunately, tropical soils are infertile and can produce crops for only a few
years. The cleared areas of rain forests may never recover from this destruction,
and many species of plants and animals may become extinct as a result.