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Biology for Advanced Level Secondary Schools
which give birth to live young). have sound producing vocal sacs and
(f) They have two pairs of pentadactyl copulatory pads on the first digit of the
limbs for locomotion except cecilians. fore limbs, whereas in female frogs these
The forelimbs have less musculature, are absent. Moreover, the abdomen of the
while the hind limbs are webbed male frog is much slender than that of the
and long with powerful muscles for female frog.
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jumping.
(g) Most have long and protruding eyes Structure of Kihansi spray toad
for viewing preys widely and for The Kihansi spray toad is a tiny toad of just
avoiding enemies. about two centimetres in length, endemic
to a two hectare area of Kihansi Gorge,
(h) They have sticky tongue, which helps
them in capturing prey. of the Udzungwa Mountains, in southern-
central Tanzania. The toad is a highly
(i) Most undergo metamorphosis for specialised toad species, adapted to giving
development from larval to adult stage birth to a fully formed toadlet. Currently it
in their life cycle.
is one of the very few amphibian species
known to give birth to fully formed
Structure of a frog toadlets. The overall background colour
The body of the adult frog is divisible of Kihansi spray toad is golden yellowish,
into the head and trunk. The neck and tail with yellow and brown speckles on the
parts are absent. The head is blunt, and dorsal surface, or dark lateral bands with
the mouth is terminal, with two flexibly adjacent lighter striping (Figure 3.62b).
movable jaws. The head bears external Ventrally, the skin is translucent, whitish
nares, a pair of nostrils that lead into nasal near the throat and posterior, with the
passages. The eyes are large, bulged and liver, fat bodies, and intestines visible
covered by a nictitating membrane that through the ventral skin. Moreover, these
protects them while in water. Behind the toads have flaps over the nostrils that
eye, there is a circular patch, a tympanum may be a special adaptation for living in
or eardrum, which receives sound signals. the spray zone of waterfalls. On the feet,
toes are partially webbed, with no external
The trunk widens in the middle, but tympana.
tapers towards the end; four legs help in
swimming and jumping. The hind limbs Body systems of amphibians
end in five digits and are larger and more Amphibians have a number of body
muscular than the fore limbs that end in systems that enable them to perform various
four digits. In both, fore and hind limbs, physiological processes. Digestive and
the digits are webbed for swimming urinogenital systems of a frog or toad will
purpose (Figure 3.62a). Frogs exhibit be emphasised in this text.
sexual dimorphism in that male frogs
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