Nucleated RBCs are present in frog. In fishes, amphibians, reptiles and birds, erythrocytes or RBCs are usually nucleated, oval and biconvex, but in mammals they are non-nucleated and biconcave.

Mantle, foot and shell are characteristics of a mollusc. Nautilus is a mollusc, it is a tetrabranch cephalopod. The shell is external and coiled over the head. Nauctilus is always active at night and rests on bottom during day.

Pepsin is inactivated at pH above 5. Pepsin is a proteolytic or protein splitting enzyme. The pH optimum of pepsin is about 2 and the enzyme, therefore, works well in the acidic gastric juice while it is inactivated in the basic medium.

Inner lining of blood vessels is formed by squamous epithelium. It consists of a layer of thin, flat, scale- like cells with prominent nuclei. The cells have irregular boundaries that fit closely into those of neighbouring cells.

Ciliated epithelium is found in the respiratory tract and in the fallopian tubes of women. It helps in the movement of particles out of the body using hair like structures, cilia.

Cuboidal epithelium is found in organs that are specialized for secretion such as salivary glands and thyroid follicles.

Columnar epithelium is uni- layered. It is found in lining of most of the digestive tract such as stomach, small intestine and large intestine.

Noctiluca is a marine and pelagic dinoflagellate which shows bio-luminescence. At night, it produces the effect of burning of sea. The luminescence is caused by a bio-luminescent luciferin,which under the influence of an
enzyme luciferase emits light.

The main excretory organs of prawn are paired green glands. They are located within the second antennae, which are the second pair of appendages, attached to the anterior part of the body. Each green gland consists of on endsac, labyrinth and a bladder.

Flame cell is a specialized excretory cell found in the simplest freshwater invertebrates, including flatworms, rotifers and nemerteans. It functions like a kidney, removing wate material.

The Malphigian tubule system is a type of excretory and osmoregulatory system found in some insects, myriapods, arachnids and tardigrades. It consist of branching tubules extending from the alimentary canal that absorbs solutes, water and wates from surrounding hemolymph.

Nephridium is an invertebrate organ which occurs in pairs and performs a function similar to the vertebrate kidney.

Moulting hormone (ecdysone) is secreted by prothoracic gland. These glands are paired, bilateral sheet of cells in the thorax. In Periplaneta, this endocrine gland is X-shaped. This gland is stimulated by prothoracicotropic hormone. Ecdysone, by causing transformation from larval to pupal stage, initiates post embryonic growth in insects.

A five kingdom division of organisms was proposed by Whittaker. Protista is one of that division. It is a kingdom of unicellular, eukaryotic organism. Many of them are photosynthetic autotrophs, unicellular algae and diatoms. Some protists are heterotrophic, e.g. Protozoa.

Insulin affects liver, muscle and adipose tissue. In the muscular tissue, it acts to promote carbohydrate metabolism and storage of glycogen. In liver cells, it favours glycongenesis, glycolysis and increases lipogenesis. In adipose tissue, in enhances the membrane transfer of glucose and promotes lipogenesis.

The flow of gastric juice is regulated partly by a nervous mechanism and partly by the action of the hormone gastrin, which is produced in the mucosa cells of the stomach. It induces the secretion of gastric juice by gastric glands.