NAME: LIM WEI LING
STUDENT ID: 19164548 6 MAY 2004
LAB SESSION: WEDNESDAY, 9-12 A.M. LAB 8

VERTEBRATE STRUCTURE AND FUNCTION
DISSSECTION OF THE FROG
INTRODUCTION
The vertebrates are part of a phylogenetic branch of the animal kingdom. Mammals, birds, snakes, turtles, amphibians and various classes of fishes are all examples of vertebrates. In this experiment, the representative vertebrate used for dissection is the frog. Frogs belong to the Class Amphibia, order Anura. Adult frogs lack tail and caudal (tail) vertebrate are fused into a rodlike structure called urostyle. Most amphibians divides their lives between fresh water and land, thus are abundant in damp habitats such as swamps and rainforests. Hence, their body systems show adaptation to both aquatic and terrestrial environment. They rely heavily on their moist skin to carry out gas exchange with the environment. Besides that, the skin of frog functions in temperature regulation and absorption and regulation of water. On land, frogs use heir powerful hindlegs to hop along the terrain. It nabs its prey by flicking out its sticky tongue, which is attached to the front of the mouth. Besides that, frog also displays a wide variety of adaptations that help them avoid being eaten by larger predators. The skin gland of frog secretes poisonous mucus. Many poisonous frog species have bright colouration that apparently warns predators. Many frogs also exhibit colour patterns that camouflage (Campbell & Reece, 2002; Harley & Miller, 1992). With reference to the metamorphosis of frogs, amphibians indicate two lives. The larvae stage of a frog is a tadpole. The tadpole is usually an aquatic herbivore with gills, a lateral line system resembling that of fishes and well-developed tail. The tadpole thus lacks legs and swims. As the tadpole develops, the gills and the lateral system disappear and the legs develop. In the adult frog, air-breathing lungs, pairs of external eardrums, and a digestive system are developed to adapt to the terrestrial environment (Campbell & Reece, 2002). Frogs generally lay their eggs in ponds and swamps or at least in moist environments. Amphibian eggs lack shells and dehydrate quickly in dry air. Hence, reproduction of frog is tied to the water. Frogs reproduce through external fertilisation, with the male grasping the female and spiling the sperm over the eggs as the female sheds them. There are also some ovoviviparous and viviparous species that retain the eggs in the female reproduction tract, where embryos can develop without drying out (Campbell & Reece, 2002). In this experiment, the digestive system and the nervous system of the frog is examined to understand he vertebrate structure and function. Frogs although are amphibians posses all the essential features of vertebrates. Hence, frog is used for dissection to observe and understand the vertebrate structure and function.

AIM
To understand and develop the skills in the techniques and terms associated with dissection of a vertebrate, give a frog as a representative
To identify the anatomical structures and understand their relationship
To relate the structures and function of the body system in verterbrate

MATERIALS female frog - scissors wax dissecting tray - scalpel dissecting pins - forceps

EXPERIMENTAL PROCEDURES
Examination of External Features The skin colour and texture of the frog provided was observed. The parotid glands were located. The external nares (nostrils) were observed and the eyes were located laterally on the head. The eyelids were gently opened with a probe to locate the nictitating membrane. Laterally n the head, and slightly posterior to the eyes, the tympanic membrane, which was the external detector of the frog hearing system was located and observed. The hindlegs and forelegs of the frog were examined. The length and musculature of each was compared and their functions were