Page 208 - Biology_F5

Comparative studies of natural groups of organisms

receives branches from the first and Activity 3.15: Dissection of a frog/toad
third nerve to form the brachial plexus) to display the visceral or general view
and other 3rd to 10th spinal nerves. (in situ) and digestive system.

(w) Trace the sympathetic cords on
either side of the aorta, notice the Materials
sympathetic ganglia and identify the Fresh male or female frog or toad,
FOR ONLINE READING ONLY
rami communicanes between the dissecting kit, dissecting tray or board,
spinal nerves and the sympathetic a piece of thread, chloroform, water, a
ganglia. pair of gloves, and cotton wool
(x) Cut the flesh of the pelvic girdles Procedure
through both thighs and trace the sciatic (a) Dissect the frog or toad in a usual
plexus (formed as an interconnection
of the seventh, eighth, ninth and tenth) way, open up the body cavity and
and the sciatic nerve (which passes pin aside the body wall to display the
down the leg close to the femur, and visceral (general) view of the animal
composed of the mainly joined eighth in an undisturbed condition.
and ninth nerves). (b) Deflect the alimentary canal to your
right hand side; which is the left hand
Safety precautions side of the animal and pin it to fully

1. Care should be taken when working and display the digestive system.
with live specimens such as frogs Questions
or toads, also chemicals like 1. Describe the following as seen in a
chloroform, as well as apparatus and dissected specimen:
equipment including the dissection (a) Visceral or general view.
kit tools.
(b) Digestive system.
2. The working area, equipment and
instruments used must be thoroughly (c) Compare what you have seen
cleaned after use using appropriate with that of Figure 3.63 and
methods. Good hygiene practices Figure 3.69.
should be observed at all times; 2. Explain the significance of
keep hands away from the mouth, ligaturing and flooding the
nose, eyes and face during and specimen with water.
after dissection; and wash hands 3. State the role(s) of each part of the
thoroughly using an antiseptic or digestive system.
soap immediately after conducting a 4. Classify a frog to class level.
dissection practical session.
3. All other laboratory safety rules and
regulations should be adhered to Task 3.17
under the supervision of a teacher Watch videos or simulations showing
or laboratory technician whenever dissection of a frog or a toad to display
working in the laboratory. the urinogenital system.

Form Five Student’s Book
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