The radula is an anatomical structure used by mollusks for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the oesophagus. The radula is the toothed chitinous ribbon in the mouth of most molluscs. It can be compared with the tongue of human beings but, unlike our tongue, it is used for cutting and chewing food before it enters the esophagus. The radula is present in all molluscs except bivalves, and only in molluscs.

Balanoglossus is a deuterostome, and resembles the Ascidians or sea squirts, in that it possesses branchial openings, or "gill slits". It has notochord in the upper part of the body and has no nerve chord. It does have a stomochord, however, which is gut chord within the collar. Balanoglossus is an ocean-dwelling acorn worm (Enteropneusta) genus of great zoological interest because, being a Hemichordate, it is an "evolutionary link" between invertebrates and vertebrates. ... Hyman (1959), however, placed them near Echinodermata and gave Hemichordata a status of an independent phylum.

This is the most accepted system of classification. The five kingdoms are as follows:

1. Monera
2. Protista
3. Fungi
4. Plantae and
5. Animalia

The Solanales are an order of flowering plants, included in the asterid group of dicotyledons. Some older sources used the name Polemoniales for this order.

• Species is a group of organisms with similar morphological characters and are able to breed among themselves to produce fertile offsprings of their own kind.

• Genus is a group of species which are related and have less characters in common as compared to species.

• Family is represented by a group of related genera that are more similar to each other than with the genera of other families.

• Order is an assemblage of families resembling one another in a few characters.

• Class represents organisms of related orders.

• Phylum includes all organisms belonging to different classes having a few common characters.

• Kingdom includes all organisms who share a set of distinguishing common characters.

Solution: Growth is defined as a vital process which brings about an irreversible and permanent change in the shape, size, form, weight and volume of a cell, organ or whole organism, accompanied with increase in dry matter.

Lichens are the composite or dual organisms representing a symbiotic association between a fungus and alga. The fungal partner is called mycobiont whereas algal partner is called phycobiont. Algae prepares food for fungi and fungi provides shelter and absorbs mineral nutrient and water for its partner. Lichens grow on barren rocks, cooled volcanic lava and icy tundra soils. They can tolerate extreme dessication but not the polluted air. Depending upon the shape, the three morphological forms of lichens are :
(a) Crustose lichens : They are thin membranous forms of lichens attached to the substratum in the form of a crust, e.g., Khizocarpon, Haematoma etc.
(b) Foliose lichens : They have flat, lobed and leaf like body attached to the substratum by fungal hyphae called rhizines. e.g., Parmelia.
c) Fruticose lichens : They have branched and small bushy bodies, which is attached to the substratum by discs, e.g., Usnea and Cladonia etc.
Importance of lichens :
(a) Litmus used as pH indicator was prepared from lichen Rocella tinctorea.
(b) Scented incense or perfumes are obtained, from Ramalina and Evernia.
© Lichens acts as pollution indicators.
(d) Certain lichens are source of food for grazing animals.

Serum consists of plasma from which fibrinogens have been removed. It contains antibodies to counter act the effect to toxic substances of micro-organisms. It is the plasma without the clotting factors.

The heart is roughly cone shaped hollow organ. It is approximately the size of owner’s closed fist and weighs about 250-300 gm in female and 300-350gm in the male. The heart lies in the thoracic cavity in the space between the lungs (mediastinum) anterior to the vertebral column and posterior to the sternum. The heart consists of 4 chambers. At first, the heart is divided into the right and left side by the septum. Each side is further divided into 2 chambers each by the atrioventricular valve. The upper two chambers are called atrium and lower two are called ventricles. Atrium are thin-walled chamber separated by an interauricular septum

The right atrium receives impure blood from the body through the opening via superior and inferior vena cava. Ventricles are a thick-walled chamber. separated by the thick inter-ventricular septum.

The animal kingdom is also classified on the basis of the level of organization other than symmetry, germ layers, and body cavity.  Though the animals are multicellular, the level of organization varies from cellular and tissue level.

Cellular level: In this structural organization, each cell of the organism performs all life process e.g., Porifera.

Tissue level: In this structural organization, a tissue is made up of group similar type of cells that perform same functions and group of the same type of tissues forms organs. Such organs perform a specific function for the body.

• The name Cnidaria is derived from the cnidoblasts or cnidocytes , which contain the stinging capsules or nematocytes present on the tentacles and the body.
• Cnidarians exhibit tissue level of organisation and are diploblastic, digestion is extracellular and intracellular, and have a central gastro-vascular cavity with a single opening, hypostome.
• Cnidarians like corals have a skeleton composed of calcium carbonate and exhibit two basic body forms called polyp and medusa, polyp is sessile and cylindrical form like Hydra, whereas, the latter is umbrella-shaped and free-swimming like Aurelia.
• Cnidarian which exist in both polyp and medusa forms exhibit alternation of generation called as
• Polyps produce medusae asexually and medusae form the polyps sexually (e.g., Obelia).
• Examples- Physalia (Portuguese man-of-war), Adamsia (Sea anemone).

DISORDERS OF RESPIRATORY SYSTEM

• Asthma is a difficulty in breathing causing wheezing due to inflammation of bronchi and bronchioles.
• Emphysema is a chronic disorder in which alveolar walls are damaged due to which respiratory surface is decreased.
• Occupational respiratory disorders include lung damage due to inflammation, which ultimately leads to fibrosis.

Secondary or intermediate host - An organism in or on which a parasite develops to an adult but not sexually mature stage.

It is an organism that harbors the sexually immature parasite and is required by the parasite to undergo development and complete its life cycle.

This type of regeneration has little growth and depends upon tissues repatterning. For eg., Hydra grows by loss of cells from its end and by budding. When cut into two, the upper part develops into foot while the lower part develops into the head. The formation of nearby heads is inhibited by the head region.

Answer: Metagenesis is the phenomenon in which one generation of certain plants and animals reproduce asexually, followed by the sexually reproducing generation. ... Coelenterates exhibits metagenesis (e.g., Obelia) where polyp form alternates with medusa in its life cycle.

The nervous system has two main parts: The central nervous system is made up of the brain and spinal cord. The peripheral nervous system is made up of nerves that branch off from the spinal cord and extend to all parts of the body. The diffuse nervous system is the most primitive nervous system. In diffuse systems nerve cells are distributed throughout the organism, usually beneath the outer epidermal layer.

The leaves of ferns are often called fronds. Fronds are usually composed of a leafy blade and petiole (leaf stalk). Leaf shape, size, texture and degree of complexity vary considerably from species to species. A fern leaf or frond. They have vascular tissue with leaf blades and a stalk, which runs from the base of the frond to the tip. Their primary roles are in photosynthesis and reproduction as well as providing many other uses for ferns.

A flagellum (/fləˈdʒɛləm/; plural: flagella) is a lash-like appendage that protrudes from the cell body of certain bacteria and eukaryotic cells termed as flagellates. A flagellate can have one or several flagella. Flagella are key structures concerned with bacterial motility. Nevertheless, bacteria that lack flagella may still be motile. A type of gliding motility can be achieved by the flexible movement of the whole cell. This is mainly observed on solid media, whereas flagellar motion is common to liquid environments. The primary purpose of cilia in mammalian cells is to move fluid, mucous, or cells over their surface. Cilia and flagella have the same internal structure. The major difference is in their length. Cilia and flagella move because of the interactions of a set of microtubules inside.

.Four Kingdom Classification System
The four kingdom classification system included Monera in addition to Protista, Plantae and Animalia. Studies with electron microscope made it clear that bacteria and related organisms have a different nuclear structure as compared to others. They are* prokaryotes, thus kingdom-Monera was created by Copeland (1956). Fungi continued to remain with Plantae in this system.

The ordering of organisms into groups on the basis of non-evolutionary features (e.g. the grouping together of plants according to the number and situation of their stamens, styles, and stigmas rather than their evolutionary relationships). An artificial system of classification is based upon one or a few easily observable characteristics, and is devised and used for a limited purpose where convenience and speed are important. It conveys little information.