The eyes in cockroach are large, sessile, paired, bean-shaped and present on either side of head. These are compound in nature. Each compound eye consists of a large number of visual elements called ommatidia.

Each ommatidium is composed of a diopteric region and reticular (receptor) region. It is capable of producing a separate image of a small part of object seen.

Thus, the image of the object viewed consists of several pieces and hence known as mosaic image. From the inner end of each ommatidium, fine nerve fibres arise, all of which combine to form one optic nerve connected to the brain.

Frog is a poikilotherm (cold blooded animal), i.e., it regulates its body temperature according to its environment. For withstanding very cold temperatures, it undergoes winter sleep (hibernation) and summer sleep in hot temperatures (aestivation). During this period, it lives in a dormant stage with very minimal vital body activities. Also, frog is capable of changing its body colour, though gradually, with the change in its surrounding and climatic conditions. This capability in frog is called as comouflage and lets it escape from the predators, an essential survival parameter for living.

(a) Nictitating Membrane It protects the eye from water and any other damaging matter by covering the eye ball of forg.

(b) Tympanum It is a present on each side of frog head and is involved in the hearing process.

(c) Copulatory Pad These pads are present in the limbs of the male frog and helps in copulation by holding the female during its sexual activity.

(a) Simple Columnar Epithelium This epithelium lines the stomach, intestine, gall bladder etc. It forms goustric and intestinal glands, where it has a secretory role and is called as glandular epithelium. In intestinal mucosa, this epithelium has microvilli which increase the absorptive surface area and is called brush bordered columnar epithelium.

(b) Stratified Epithelium These are made up of more than one layer of epithelial cells (also called compound epithelium). They are the only cells of the deepest layer and rest on the basement membrane they cover the surface where constant wear and tear take place. They mainly function as a protective epithelium.

(c) Connective Tissue It is the tissue which connects different tissues or organs and provides support to various structures of animal body. These tissues are mesodermal in origin and consist of living cells and extra cellular matrix, e.g., blood is a fluid or vascular connective tissue.

Segmentation is the serial repetition of similar body parts along with the length of an animal. The body of animals can be truely segmented or pseudo/false segmented. True segmentation is found in annelids, arthropods and some chordates. In this, there is a linear repetition of body parts and each repeated unit is called somite (metamere). In earthworms, the successive somites are essentially similar but they are dissimilar in different body regions of a crayfish or insect. Metamerism is conspicuous both externally and internally in annelids. Pseudosegmentation is seen when body is divided into number of pseudosegments which are independent of each other. Each segment is able to perform all the vital function of body. Body grows by the addition of new segments from the anterior end, e.g., tapeworm.