Both plants and animals of many sorts show
remarkable changes in form, structure, growth
habits, and even mode of reproduction in becom-
Line ing adapted to different climatic environment,
(5) types of food supply, or mode of living. This
divergence in response to evolution is commonly
expressed by altering the form and function of
some part or parts of the organism, the original
identity of which is clearly discernible. For
(10) example, the creeping foot of the snail is seen in
related marine pteropods to be modified into a
flapping organ useful for swimming, and is
changed into prehensile arms that bear suctorial
disks in the squids and other cephalopods. The
(15) limbs of various mammals are modified according
to several different modes of life—for swift run-
ning (cursorial) as in the horse and antelope, for
swinging in trees (arboreal) as in the monkeys, for
digging (fossorial) as in the moles and gophers,
(20) for flying (volant) as in the bats, for swimming
(aquatic) as in the seals, whales, and dolphins,
and for other adaptations. The structures or
organs that show main change in connection with
this adaptive divergence are commonly identified
(25) readily as homologous, in spite of great altera-
tions. Thus, the finger and wristbones of a bat and
whale, for instance, have virtually nothing in
common except that they are definitely equivalent
elements of the mammalian limb.
 

The author provides information that would answer which of the following questions（）
Ⅰ. What factors cause change in organisms
Ⅱ. What is the theory of evolution
Ⅲ. How are horses’ legs related to seals’ flippers