Paper Code 29983 (03 hours) Total Marks: 100 (1) All questions are compulsory (2) Figures to the right indicate full marks (3) Draw diagrams wherever necessary

Q.1.A. Give 2 examples of each of the following: (07) i. Plant micronutrients - boron (B), copper (Cu), iron (Fe) manganese (Mn), molybdenum (Mo) and zinc (Zn), Chloride (Cl)

ii. Respiratory organs - nose, pharynx, larynx, trachea, bronchi, lungs

iii. Saprophytes - Rhizopus, yeast, mushroom

iv. Apical meristem - Shoot apical meristem and root apical meristem

v. Connective tissue - reticular connective tissue, adipose tissue, cartilage, bone, and blood.

vi. Animals with incomplete digestive system - coelenterates, planaria

vii. Grinding organ in birds - beak and gizzard

Q.1.B.State whether the following sentence is true or false: (06) i. Tarsal is a bone present in cranial cavity - False it is present in limbs ii. Conduction of water and minerals in plants is carried out by Xylem tissue - True iii. Human heart is divide into three chambers - False four chambers iv. Tendrils are present as a support in woody plants - False non woody plants v. Platelets help in clotting of blood - True vi. Erythrocytes are nucleated cells - False Non nucleated cells

Q.2.A. Answer Any One of the following: (10)

i. Explain using a flow chart all the types of Plant tissues. Explain any 2 with their structure and function in detail. Plant Tissue: Group # 1. Meristems Tissue: A meristematic tissue consists of a group of cells which remain in a continuous state of division or they retain their power of division.

The characteristic features of meristematic tissue are as follows:

1. They are composed of immature cells which are in a state of division and growth.

2. Usually the intercellular spaces are not found among these cells.

3. The cells may be rounded, oval or polygonal in shape; they are always living and thin- walled.

4. Each cell of meristematic tissue possesses abundant cytoplasm and one or more nuclei in it.

5. The vacuoles in the cells may be quite small or altogether absent.

Meristems and Growth of Plant Body: Beginning with the division of the oospore, the vascular plant generally produces new cells and forms new organs until it dies. In the beginning of the development of the plant embryo cell division occurs throughout the young organism.

But as soon as the embryo develops and converts into an independent plant the addition of new cells is gradually restricted to certain parts of the plant body, while the other parts of the remain concerned with activities other than growth.

This shows that the portions of embryonic tissue persists in the plant throughout its life, and the mature plant is a composite of adult and juvenile tissues. These juvenile tissues are known as the meristems. The presence of meristems remarkably differentiates the plant, from the animal.

In the growth resulting from meristematic activity is possible throughout the life of the organism, whereas in animal body the multiplication of the cells mostly ceases when the organism attains adult size and the number of organs is fixed.

The term meristem (Greek meristos, meaning divisible) emphasizes the cell-division activity characteristic of the tissue which bears this name. It is obvious that the synthesis of new living substance is a fundamental part of the process of the formation of new cells by division.

The living tissues other than the meristems may also produce new cells, but the meristems carry on such activity indefinitely, because they not only add cells to the plant body, but also perpetuate themselves, that is, some of the products of division in the meristems do not develop into adult cells but remain meristematic.

The meristems usually occur at the apices of all main and lateral shoots and roots and thus their number in a single plant becomes quite large. In addition, plants bearing secondary increase in thickness possess extensive meristems, the vascular and cork cambia, responsible for the secondary growth.

The combined activities of all these meristems give rise to a complex and large plant body. The primary growth, initiated in the apical meristems expands the plant body and produces the reproductive parts. On the other hand, the cambia, aid in maintenance of the expanding body by increasing the volume of the conducting system and forming supporting and protecting cells.

Plant Tissue: Group # 2. Permanent Tissues: The permanent tissues are those in which growth has stopped either completely or for the time being. Sometimes, they again become meristematic partially or wholly. The cells of these tissues may be living or dead and thin-walled or thick-walled. The thin-walled permanent tissues are generally living whereas the thick-walled tissues may be living or dead.

The permanent tissues may be simple or complex. A simple tissue is made up of one type of cells forming a uniform of homogeneous system of cells. The common simple tissues are – parenchyma, collenchyma and sclerenchyma.

A complex tissue is made up of more than one type of cells working together as a unit. The complex tissues consist of parenchymatous and sclerenchymatous cells; collenchymatous cells are not present in such tissues.

The common examples are:

The xylem and the phloem.

Simple Tissues: 1. Parenchyma:

The paren•chyma tissue is composed of living cells which are variable in their morphology and physiology, but generally having thin walls and a polyhedral shape, and concerned with vegetative activities of the plant. The individual cells are known as parenchyma cells.

The word parenchyma is derived from the Greek para, beside and enchein, to pour. This combination of words expresses the ancient concept of parenchyma as a semi- liquid substance poured beside other tissues which are formed earlier and are more solid.

Phylogenetically the parenchyma is a primitive tissue since the lower plants have given rise to the higher plants through specialization and since the single type or the few types of cells found in the lower plants have become by specialization the many and elaborates types of the higher plants.

The unspecialized meristematic tissue is parenchyma and is often called parenchyma thus it can be said that, ontogenetically parenchyma is a primitive tissue.

The parenchyma consists of isodiametric, thin-walled and equally expanded cells. The parenchyma cells are oval, rounded or polygonal in shape having well developed spaces among them. The cells are not greatly elongated in any direction. The cells of this tissue are living and contain sufficient amount of cytoplasm in them. Usually each cell possesses one or more nuclei.

Parenchyma makes up large parts of various organs in many plants. Pith, mesophyll of leaves, the pulp of fruits, endosperm of seeds, cortex of stems and roots, and other organs of plants consist mainly of parenchyma. The parenchyma cells also occur in xylem and phloem.

In the aquatic plants, the parenchyma cells in the cortex possess well developed air spaces (intercellular spaces) and such tissue is known as aerenchyma. Parenchyma may be specialized as water storage tissue in many succulent and xerophytic plants. In Aloe, Agave, Mesembryanthemum, Hakea and many other plants chlorophyll-free, thin-walled and water- turgid cells are found which represent water storage tissue.

When the parenchyma cells are exposed to light they develop chloroplasts in them, and such tissue is known as chlorenchyma. The chlorenchyma possesses well developed aerating system. Intercellular spaces are abundant in the photosynthetic parenchyma (chlorenchyma) of stems too.

Commonly the parenchyma cells have thin primary walls. Some such cells may have also thick primary walls. Some storage parenchyma develop remarkably thick walls and the carbohy•drates deposited in these walls, the hemicellulose, are regarded by some workers as reserve materials.

Thick walls occur, in the endosperm of Phoenix dactylifera, Diospyros, Asparagus and Coffea arabica. The walls of such endosperm become thinner during germination.

The turgid parenchyma cells help in giving rigidity to the plant body. Partial conduction of water is also maintained through parenchymatous cells. The parenchyma acts as special storage tissue to store food material in the form of starch grains, proteins, fats and oils. The parenchyma cells that contain chloroplasts in them make chlorenchymas which are responsible for photo•synthesis in green plants.

In water plants the aerenchyma keep up the buoyancy of the plants. Such air spaces also facilitate exchange of gases. In many succulent and xerophytic plants such tissues store water and known as water storage tissue. Vegetative propagation by cuttings takes place because of meristematic potentialities of the parenchyma cells which divide and develop into buds and adventitious roots.

2. Collenchyma:

Collenchyma is a living tissue composed of somewhat elongated cells with thick primary non-lignified walls. Important characteristics of this tissue are its early development and its adaptability to changes in the rapidly growing organ, especially those of increase in length.

When the collenchyma becomes functional, no other strongly supporting tissues have appeared. It gives support to the growing organs which do not develop much woody tissue. Morphologically, collenchyma is a simple tissue, for it consists of one type of cells.

Collenchyma is a typical supporting tissue of growing organs and of those mature herbaceous organs which are only slightly modified by secondary growth or lack such growth completely. It is the first supporting tissue in stems, leaves and floral parts. It is the main supporting tissue in many dicotyledonous leaves and some green stems. Collenchyma may occur in the root cortex, particularly, if the root is exposed to light.

It is not found in the leaves and stems of monocotyledons. Collenchyma chiefly occurs in the peripheral regions of stems and leaves. It is commonly found just beneath the epidermis. In stems and petioles with ridges, collenchyma is particularly well developed in the ridges. In leaves it may be differentiated on one or both sides of the veins and along the margins of the leaf blade.

The collenchyma consists of elongated cells, various in shape, with unevenly thickened walls, rectangular, oblique or tapering ends, and persistent protoplasts. The cells overlap and interlock, forming fibre-like strands. The cell walls consist of cellulose and pectin and have a high water content.

They are extensible, plastic and adapted to rapid growth. In the beginning the strands are of small diameter but they are added to, as growth continues, from surrounding meristematic tissue. The border cells of the strands may be transitional in structure, passing into the parenchyma type.

As regards the cell arrangement there are three types of collenchyma — angular, lamellar and tubular. In angular type the cells are irregularly arranged (e.g., Ficus, Vitis, Polygonum, Beta, Rumex, Boehmeria, Morus, Cannabis, Begonia); in lamellar type the cells lie in tangential rows (e.g., Sambucus, Rheum, Eupatorium) and in tubular type the intercellular spaces are present (e.g., Compositae, Salvia, Malva, Althaea).

The common typical condition is that with thickenings at the corners. The three forms of collenchyma have been named by Muller (1890) angular (Eckencollenchym), lamellar (Plattencolenchym), and tubular or lacunate (Luchencollenchym), respectively. The word lamellar has reference to the plate like arrangement of the thickenings; the lacunate (tubular) to the presence of intercellular spaces.

The walls of collenchyma are chiefly composed of cellulose and pectic compounds and contain much water (Majumdar and Preston, 1941). In some species collenchyma walls possess an alternation of layers rich in cellulose and poor in pectic compounds with layers that are rich in pectic compounds and poor in cellulose.

In many plants collenchyma is a compact tissue lacking intercellular spaces. Instead, the potential spaces are filled with intercellular material (Majumdar, 1941).

The mature collenchyma cells are living and contain protoplasts. Chloroplasts also occur in variable numbers. They are found abundantly in collenchyma which approaches parenchyma in form. Collenchyma consisting of long narrow cells contains only a few small chloroplasts or none. Tannins may be present in collenchyma cells.

Ontogenetically collenchyma develop from elongate, pro-cambium like cells that appear very early in the differentiating meristem. In the beginning, small intercellular spaces are present among these cells, but they disappear in angular and lamellar types as the cells enlarge, either by the enlarging cells or filled by intercellular substance.

The chief primary function of the tissue is to give support to the plant body. Its supporting value is increased by its peripheral position in the parts of stems, petioles and leaf mid-ribs. When the chloroplasts are present in the tissue, they carry on photosynthesis.

3. Sclerenchyma:

The sclerenchyma (Greek, sclerous, hard; enchyma, an infusion) consists of thick walled cells, often lignified, whose main function is mechanical. This is a supporting tissue that withstands various strains which result from stretching and bending of plant organs without any damage to the thin-walled softer cells.

The individual cells of sclerenchyma are termed sclerenchyma cells. Collectively sclerenchyma cells make sclerenchyma tissue. Sclerenchyma cells do not possess living protoplasts at maturity. The walls of these cells are uniformly and strongly thickened. Most commonly, the sclerenchyma cells are grouped into fibres and sclereids.

Fibres:

The fibres are elongate sclerenchyma cells, usually with pointed ends. The walls of fibres are usually lignified. Sometimes, their walls are so much thickened that the lumen or cell cavity is reduced very much or altogether obliterated. The pits of fibres are always small, round or slit-like and often oblique.

The pits on the walls may be numerous or few in number. The middle lamella is conspicuous in the fibres. In most kinds of fibres, however, on maturation of cells the protoplast disappears and the permanent cell becomes dead and empty. Very rarely the fibres retain protoplasts in them.

The fibres are abundantly found in many plants. They may occur in patches, in continuous bands and sometimes singly among other cells. As already mentioned, they are dead and purely mechanical in function. They provide strength and rigidity to the various organs of the plants to enable them to withstand various strains caused by outer agencies. The average length of fibres is 1 to 3 mm. in angiosperms, but exceptions are there.

In Linum usitatissimum (flax), Cannabis sativa (hemp), Corchorus capsularis (jute), and Boehmeria nivea (ramie), the fibres are of excessive lengths ranging from 20 mm. to 550 mm. Such long, thick-walled and rigid cells constitute exceptionally good fibres of commercial importance.

In addition to these plants common long fibre yielding plants are Hibiscus cannabinus (Madras hemp), Agave sisalana (sisal hemp), Sansevieria and many others.

The fibres are divided into two large groups xylem fibres and extraxylary fibres. The xylem fibres develop from the same meristematic tissues as the other xylem cells and constitute an integral part of xylem. On the other hand, some of the extraxylary fibres are related to the phloem.

The fibres that form continuous cylinders in monocotyledonous stems arise in the ground tissue under the epidermis at variable distances. They are known as cortical fibres. The fibres forming sheaths around the vascular bundles in the monocotyledonous stems arise partly from the same procambium as the vascular cells, partly from the ground tissue.

The fibres present in the peripheral region of the vascular cylinder, often close to the phloem are known as pericyclic fibres. The extraxylary fibres are sometimes combined into a group termed bast fibres.

Generally the term extraxylary fibres is used for bast fibres, which are classified as follows — phloem fibres, fibres originating in primary or secondary phloem; cortical fibres, fibres originating in the cortex; perivascular fibres (Van Fleet, 1948), fibres found in the peripheral region of the vascular cylinder inside the innermost cortical layer but not originating in the phloem.

The extraxylary fibres may vary in length, and their ends are sometimes blunt, rather than tapering, and may be branched. The longest fibres (primary phloem fibres) measured Boehmeria nivea (ramie). The cell walls of extraxylary fibres are very thick. The pits are simple or slightly bordered. Some possess lignified walls, others non-lignified.

The fibres of Linuin usitatissimum are non-lignified, and their secondary walls consist of pure cellulose. On the other hand, the extraxylary fibres of the monocotyledons are strongly lignified. Concentric lamellations are found in extraxylary fibres. In the fibres of Linum usitatissimum the individual lamellae vary in thickness from 0.1µ to 0.2µ.

Xylem fibres typically possess lignified sec•ondary walls. They vary in size, shape, thickness of wall, and structure and abundance of pits.

Sclereids:

The sclereids are widely distributed in the plant body. They are usually not much longer than they are broad, occurring singly or in groups. Usually these cells are isodiametric but some are elongated too. They are commonly found in the cortex and pith of gymnosperms and dicotyledons, arranged singly or in groups. In many species of plants, the sclereids occur in the leaves.

The leaf sclereids may be few to abundant. In some leaves the mesophyll is completely permeated by sclereids. Sclereids are also common in fruits and seeds. In fruits they are disposed in the pulp singly or in groups (e.g., Pyrus). The hardness and strength of the seed coat is due to the presence of abundant sclereids.

The secondary walls of the sclereids are typically lignified and vary in thickness. In many sclereids the lumina are almost filled with massive wall deposits and the secondary wall shows prominent pits. Commonly the pits are simple and rarely bordered pits may also occur.

Xylem:

Xylem is a conducting tissue, which conducts water and mineral nutrients upward from the root to the leaves. The xylem is composed of different kinds of elements.

They are:

(a) Tracheids,

(b) Fibres and fibre-tracheids,

(c) Vessels or tracheae and

(d) Wood parenchyma.

The xylem is also meant for mechanical support to the plant body.

(a) Tracheids:

The tracheid is a fundamental cell type in xylem. It is an elongate tube like cell having tapering, rounded or oval ends and hard and lignified walls. The walls are not much thickened. It is without protoplast and non-living on maturity. In transverse section the tracheid is typically angular, though more or less rounded forms occur.

The tracheids of secondary xylem have fewer sides and are more sharply angular than the tracheids of primary xylem. The end of a tracheid of secondary xylem is somewhat chisel- like. They are dead empty cells. Their walls are provided with abundant, bordered pits arranged in rows or in other patterns.

The cell cavity or lumen of a tracheid is large and without any contents. The tracheids possess various kinds of thickenings in them and they may be distinguished as annular, spiral, scalariform, reticulate or pitted tracheids. Tracheids alone make the xylem of ferns and gymnosperms, while in the xylem of angiosperms they occur associated with the vessels and other xylary elements.

The tracheids are specially adapted to function of conduction. The thick and rigid walls of tracheids also aid in support and where there are no fibres or other supporting ceils, the tracheids play a prominent part in the support of an organ.

(b) Fibres and Fibre-tracheids:

In the phylogenetic development of the fibre, the thickness of the wall increases while the diameter of the lumen decreases. In most types the length of the cell also decreases and the number and size of the pits found on the walls also decrease. Sometimes the lumen of the cell becomes too much narrow or altogether obliterated and simultaneously pits become quite small in size.

At this stage it is assumed that either there is very little conduction of water or no conduction through such type of cells, typical fibres are formed. Between such cells (i.e., fibres) and normal tracheids there are many transi•tional forms which are neither typical fibres nor typical tracheids. These transitional types are designated as fibre-tracheids.

The pits of fibre- tracheids are smaller than those of vessels and typical tracheids. However, a line of demarcation cannot be drawn in between tracheids and fibre- tracheids and between fibre-tracheids and fibres. When the fibres possess very thick walls and reduced simple pits, they are known as libriform wood fibres because of their similarity to phloem fibres (liber = phloem fibres).

The libriform wood fibres chiefly occur in woody dicotyledons (e.g., in Leguminosae). The walls of fibre tracheids and fibres of many genera of different families possess gelatinous layers. The cells possessing such layers are known as gelatinous tracheids, fibre-tracheids and fibres. In certain fibre-tracheids the protoplast persists after the secondary wall is mature and may divide to produce two or more protoplasts.

These protoplasts are separated by thin transverse partition walls and remain enclosed within the original wall. Such fibre tracheids are called septate fibre-tracheids. In fact, they are not individual cells but rows of cells. Here, the transverse partitions are true walls, and each chamber has a protoplast with nucleus.

(c) Vessels:

In the phylogenetic development of the tracheid the diameter of the cell has increased and the wall has become perforated by large openings. Due to these adaptations and specia•lizations water can move from cell to cell without any resistance.

In the more primitive types of vessels, the general form of the tracheid is retained and increase in diameter is not much. In the most advanced types, increase in diameter is much and the cell becomes drum-shaped (e.g., Quercus alba).

The tracheid is sufficiently longer than the cambium cell from which it is derived. The primitive vessel is slightly longer than the cambium cell. The most advanced type of vessel retains the length of cambium cell or is somewhat shorter, with a diameter greater than its length (drum- shaped vessel).

The ends of the cells change in shape in the series from least to highest specialization. The angle formed by the tapering end wall becomes greater and greater until the end wall is at right angles to the side walls (as in drum-shaped vessel in Quercus alba). Some intermediate forms possess tail-like lips beyond the end wall.

Usually the diameter of vessels is much greater than that of tracheids and because of the presence of perforations in the partition walls they form long tubes through which water is being conducted from root to leaf.

The pits are often more numerous and smaller in size than are those of tracheids and cover the wall closely. When found in abundance they are either scattered or arranged in definite patterns on the walls of the vessels.

(d) Wood Parenchyma:

The parenchyma cells which frequently occur in the xylem of most plants. In secondary xylem such cells occur vertically more or less elongated and placed end to end, known as wood or xylem parenchyma. The radial transverse series of the cells form the wood rays and are known as wood or xylem ray parenchyma.

The xylem parenchyma cells may be as long as the fusiform initials or they may be several times shorter, if a fusiform derivative divides transversely before differentiation into parenchyma (wood parenchyma). The shorter type of xylem parenchyma cells is the more common.

The ray and the xylem parenchyma cells of the secondary xylem may or may not have secondary walls. If a secondary wall is present, the pit pairs between the parenchyma cells and the tracheary elements may be simple, half-bordered or bordered. In between, parenchyma cells only simple pit pairs occur.

The xylem parenchyma cells are noted for storage of food in the form of starch or fat. Tannins, crystals and various other substances also occur in xylem parenchyma cells. These cells assist directly or indirectly in the conduction of water upward through the vessels and tracheids.

Phloem:

The xylem and phloem have evolved along more or less on similar lines. In xylem a series of tracheids, structurally and functionally united, has become a vessel whereas in phloem a series of cells similarly united, forms a sieve tube.

The fundamental cell type of xylem is tracheid, whereas in phloem the basic cell type is the sieve element. There are two forms of sieve element the more primitive form is the sieve cell of gymnosperms and lower forms where series of united cells do not exist, the unit of a series, the sieve tube element.

Phloem like xylem, is a complex tissue, and consists of the following elements:

(a) Sieve elements,

(b) Companion cells,

(c) Phloem fibres and

(d) Phloem parenchyma.

In the pteridophytes and gym•nosperms only sieve cells and phloem parenchyma are present. In some gymno•sperms, sieve cells, phloem parenchyma and phloem fibres are present. In angiosperms, sieve tubes, companion cells, phloem parenchyma, phloem fibres, sclereids and secretory cells are present.

(a) Sieve Elements:

The conducting elements of the phloem are collectively known as sieve elements. They may be segregated into the less specialized sieve cells and the more specialized sieve tubes or sieve tube elements. The morphologic specialization of sieve elements is expressed in the development of sieve areas on their walls and in the peculiar modifications of their protoplasts.

The sieve areas are depressed wall areas with clusters of perforations, through which the protoplasts of the adjacent sieve elements are interconnected by connecting strands. In a sieve area each connecting strand remains encased in a cylinder of substance called callose.

The wall in a sieve area is a double structure consisting of two layers of primary wall, one belonging to one cell and the other to another, cemented together by interce•llular substance.

Like the pits in the tracheary elements, the sieve areas occur in various numbers and are variously distributed in sieve elements of different plants. The wall parts bearing the highly specialized sieve areas are called sieve plates (Esau, 1950). If a sieve plate consists of a single sieve area, it is a simple sieve plate. (b) Companion Cells:

The companion cell is a specialized type of parenchyma cell which is closely associated in origin, position and function with sieve-tube elements. When seen in transverse section the companion cell is usually a small, triangular, rounded or rectangular cell beside a sieve-tube element.

These cells are living having abundant granular cytoplasm and a prominent elongated nucleus which is retained throughout the life of the cell. Usually the nuclei of the companion cells serve for the nuclei of sieve tubes as they lack them. The companion cells do not contain starch.

They live only so long as the sieve-tube element with which they are associated and they are crushed with those cells. The companion cells are formed by longitudinal division of the mother cell of the sieve tube element before specia•lization of this cell begins. One daughter cell becomes a companion cell and other a sieve tube element.

The companion cell initial may divide transversely several times producing a row of companion cells so that one to several companion cells may accompany each sieve-tube element. A companion cell or a row of companion cells formed by the transverse division of a single companion- cell initial may extend the full length of the sieve-tube element.

The number of companion cells accompanying a sieve-tube element is fairly constant for a particular species. The solitary and long companion cells occur in primary phloem of herbaceous plants whereas numerous companion cells occur in the secondary phloem of woody plants.

(c) Phloem Fibres:

In many flowering plants, fibres form a prominent part of both primary and secondary phloem. The phloem fibres are rarely found or absent in phloem of living pteridophytes. They are also not found in some gymnosperms and angiosperms. Only simple pits are found on the walls of phloem fibres. The walls may be lignified or non-lignified.

The Cannabis (hemp) fibres are lignifed, whereas fibres of Linum (flax) are of cellulose and without lignin. Because of the strength of strands of phloem fibres, they have been used for a long time in the manufacture of cords, ropes, mats and cloth. The fibre used in this way has been known since early times as bast or bass, and this way the phloem fibres are also known as bast fibres.

The sclereids are occasionally found in the primary phloem. The older secondary phloem of many trees also contains the sclereids. These cells develop from phloem parenchyma as the tissue ages and the sieve tubes cease to function.

(d) Phloem Parenchyma:

The phloem contains parenchyma cells that are concerned with many activities characteristic of living parenchyma cells, such as storage of starch, fat and other organic substances. The tannins and resins are also found in these cells. The parenchyma cells of primary phloem are elongated and are oriented, like the sieve elements. There are two systems of parenchyma found in the secondary phloem.

These systems are — vertical and the horizontal. The parenchyma of the vertical system is known as phloem parenchyma. The horizontal parenchyma is composed of phloem rays. In the active phloem, the phloem parenchyma and the ray cells have only primary un-lignified walls.

The walls of both kinds of parenchyma cells have numerous primary pit fields. The phloem parenchyma is not found in many or most of monocotyledons.

ii. Discuss with suitable examples three nutritional apparatus in animals

Heterotrophic nutrition: The word ‘heterotroph’ is derived from two Greek words—heteros (other) and trophe (nutrition). Unlike autotrophs, which manufacture their own food, heterotrophic organisms obtain food from other organisms. As heterotrophs depend on other organisms for their food, they are called consumers. All animals and non-green plants like fungi come under this category. Consumers which consume herbs and other plants are called herbivores, and those which consume animals are called carnivores. After taking complex organic materials as food, heterotrophs break them into simpler molecules with the help of biological catalysts, or enzymes, and utilize them for their own metabolism. Depending upon the mode of living and the mode of intake of food, heterotrophs may be parasitic, saprophytic or holozoic. Parasitic: Parasitic organisms, or parasites, live on or inside other living organisms, called hosts, and obtain their food from them. The host does not get any benefit from the parasite. Different parasites, like Cuscuta (akash-bel), Cassytha (amar-bel), hookworms, tapeworms, leeches, etc., have different modes of feeding, depending upon habit, habitat and modifications. Saprophytic: Saprophytic organisms, or saprophytes, derive their food from dead organisms. They secrete enzymes that are released on food material outside their body. These enzymes break down complex food into simple forms. Common examples of saprophytes are fungi (moulds, mushrooms, yeasts) and many bacteria. Holozoic: In holozoic nutrition complex organic substances are ingested (taken in) without their being degraded or decomposed. After intake, such food is digested by enzymes produced within the organism. Digested food is absorbed into the body and the undigested product is egested (expelled) from the body. This kind of nutrition is found mainly in non-parasitic animals— simple ones like Amoeba and complex ones like human beings. How Organisms Obtain Nutrition: Different organisms obtain food in different ways. Nutrition in unicellular organisms, like Amoeba, involves ingestion by the cell surface, digestion and egestion. Amoeba takes in complex organic matter as food. Amoeba first identifies its food. It then throws out a number of small pseudopodia (projections of cytoplasm, also called false feet). These pseudopodia enclose the food particle and prevent it from escaping. The food enclosed in the cell membrane forms a food vacuole. The complex food is broken down into simpler molecules with the help of digestive enzymes of the organelle called lysosome. The digested food is distributed in the cytoplasm and the undigested food is egested through the cell membrane.

In Paramecium, a unicellular organism with a specific shape, food is ingested through a special opening, the cytostome (cell mouth). Food is brought to this opening by the lashing movement of cilia that cover the entire surface of the cell.

Types of feeding mechanisms 1. Suspension Feeders and Filter Feeders Many aquatic animals are suspension feeders, which eat small organisms or food particles suspended in the water. For example, clams and oysters feed on tiny morsels of food in the water that passes over their gills; cilia sweep the food particles to the animal's mouth in a film of mucus. Filter feeders such as the humpback whale shown above move water through a filtering structure to obtain food. Attached to the whale's upper jaw are comblike plates called baleen, which strain small invertebrates and fish from enormous volumes of water. 2. Fluid Feeder Fluid feeders suck nutrientrich fluid from a living host. This mosquito has pierced the skin of its human host with hollow, needlelike mouthparts and is consuming a blood meal. Similarly, aphids are fluid feeders that tap the phloem sap of plants. In contrast to such parasites, some fluid feeders actually benefit their hosts. For example, hummingbirds and bees move pollen between flowers as they fluid-feed on nectar.

3. Substrate Feeders Substrate feeders are animals that live in or on their food source. This leaf miner caterpillar, the larva of a moth, is eating through the soft tissue of an oak leaf, leaving a dark trail of feces in its wake. Some other substrate feeders include maggots (fly larvae), which burrow into animal carcasses. 4. Bulk Feeders Most animals, including humans, are bulk feeders, which eat relatively large pieces of food. Their adaptations include tentacles, pincers, claws, poisonous fangs, jaws, and teeth that kill their prey or tear off pieces of meat or vegetation. In this amazing scene, a rock python is beginning to ingest a gazelle it has captured and killed. Snakes cannot chew their food into pieces and must swallow it whole—even if the prey is much bigger than the diameter of the snake. They can do so because the lower jaw is loosely hinged to the skull by an elastic ligament that permits the mouth and throat to open very wide. After swallowing its prey, which may take more than an hour, the python will spend two weeks or more digesting its meal.

Q.2.B. Answer Any Two of the following: (10) i. What are Macronutrients in plants? Give the functions of any 2 in detail Macronutrients are required by the plants in larger amounts. The most important Macronutrients in plants are: Nitrogen, Phosphorus and Potassium. Besides these, calcium, magnesium and sulphur are also considered to be macronutrients.

Functions of Nitrogen: (i) The most recognized role of nitrogen in the plant is its presence in the structure of protein molecule. (ii) It is the constituent of such important biomolecules like purines and pyrimidine’s which are found in DNA and RNA. (iii) Nitrogen is found in the structure of porphyrin molecules which are the percursors of chlorophyll pigments and cytochromes that are essential in photosynthesis and respiration. (iv) The coenzymes like NAD+, NADP+, FAD, etc., are essential to the function of many enzymes and nitrogen is a structural component of these coenzymes. (v) Other compounds in the plant such as some vitamins contain nitrogen. Phosphorus: Next to nitrogen, phosphorus is very often the limiting nutrient in soils. It is present in the soil in inorganic and organic forms.

Functions of Phosphorus: (i) It is a constituent of nucleic acids. Both DNA and RNA have a sugar-phosphate backbone in their structures. Triphosphate forms of nucleotides are precursors of nucleic acids. (ii) Phosphorus is a constituent of phospholipids or phosphoglycerides or glycerol phosphatides which along with proteins, are characteristic major components of cell membranes; only very small amounts of phosphoglycerides occur elsewhere in cells. The most abundant phosphoglycerides in higher plants are phosphatidyl ethanol amine and phosphatidyl choline (lecithin). (iii) Phosphorus is a constituent of the coenzymes NAD+ and NADP +, which take part in most of the cellular oxidation-reduction reactions involving hydrogen transfer. Most of the important metabolic processes like photosynthesis, respiration, nitrogen metabolism, carbohydrate metabolism, fatty-acid metabolism, etc., are dependent on the action of these coenzymes. (iv) Phosphorus is a constituent of ATP and other high energy compounds. (v) The intermediate of glycolysis between glucose and pyruvate are phosphorylated compounds.

Potassium: After nitrogen and phosphorus, soils are usually most deficient in potassium. For that reason, commercial mixed fertilizers usually contain these three elements (N, P and K). Functions of Potassium: Relatively high amounts of potassium is required by the plants for normal growth, but this situation does not correlate with the observed functions of potassium. It does not enter into the composition of any organic compound in the plant. This element seems to function mostly as a catalytic agent in several enzymatic reactions. Its probable role is to provide the necessary ionic environment for preserving the proper three- dimensional structure of enzymes for optimal activity. (a) Physiological Functions: (i) Potassium has been shown to be linked with carbohydrate metabolism. (ii) It is essential for translocation of sugar. Spanner, proposed a mechanism of potassium circulation around the sieve plate for increasing translocation of sugar in sieve tubes. Circulation of potassium establishes a potential difference across the sieve plate which actually favours sugar translocation. So, any factor that increases potassium transport could alter the electro osmotic potential between sieve tubes and influences sugar translocation. (iii) Stomatal opening in higher plants requires potassium. It has been estimated by the X-ray electron probe micro-analyser, that the guard cells of opened stomata contains a relatively high concentration of potassium as compared to the closed stomata. There is an influx of potassium ions (K+) into the guard cells during stomatal opening at the expense of ATP. Potassium accumulation in the guard-cell vacuole results in osmotic swelling of guard cell and stomatal opening. (iv) Potassium has a general role in the regulation of water in plant cells. Under water- stress conditions potassium being absorbed selectively prevents the plant from losing water. (b) Biochemical Functions: (i) The reactions, involved in the phosphorylation of carboxyl groups and inter-conversions of enol-keto intermediates are activated by potassium. (ii) Potassium is required by the enzyme acetic thiokinase from spinach leaves for maximal activity. (iii) Potassium might act as a regulator of the enzyme pyruvate kinase through repression of synthesis of the enzyme. (iv) Folic acid metabolism has been shown to require potassium. (v) γ-glutamylcysteine synthesis specifically requires potassium. (vi) Potassium is required by the enzyme succinyl-CoA synthetase isolated from tobacco for maximal activity. (vii) Nitrate reductase formation in rice seedlings specifically requires potassium. (viii) There is an absolute requirement for potassium by starch synthetase isolated from sweet com. (ix) Potassium, through its role in ATPase activity, may be involved in ion transport across biological membranes.

Calcium: Calcium is present adequately in most soils for favourable plant growth. It is absorbed as divalent Ca2+.

Functions of Calcium: Ca2+ functions both as a structural component and as a cofactor for certain enzymes. (a) Structural Functions: Calcium has been associated with the cell wall structure. It is required to bind pectate polysaccharides that form a new middle lamella in the cell plate that arises between daughter cells. Ethylenediamineteracetic acid (EDTA), a chelating agent, stimulates growth of the Avena coleoptile through increased plasticity caused by the partial removal of pectate-bound calcium. Protein as well as calcium are involved in binding cell walls together. Calcium in the cell wall remains bonded with ionized carboxyl groups of cellulosic fraction. Low pH has been found to mimic IAA induced cell elongation. The possible explanation might be that an increase in hydrogen ions within cell walls would decrease ionization of carboxyl grouping of cellulose, which in turn decreases the amount of bonding of calcium between associated carboxyl’s. Cell wall extension induced by CO2 and low pH is reduced when calcium is added in the experimental solution, supporting the hypothesis that calcium influences cell wall rigidity through its effect on ionic bridging between cellular molecules. (b) Membrane and Ion Regulation: (i) Calcium is involved in spatially three dimensional arrangement of the membranes. Calcium salt of lecithin, a lipid compound, is involved in the formation or organization of cell membranes. EDTA stimulated Avena coleoptile growth may also be caused by an increase in cell permeability through the removal of calcium. (ii) All organisms maintain low concentrations of free Ca2+ in their cytosol. This is also true even though calcium is abundant in many plants. Mostly calcium remains in vacuoles and bound in cell walls to pectate polysaccharides. Calcium is frequently stored in vacuoles as insoluble crystals of oxalates, carbonates, phosphates or sulfates. Low concentrations of calcium in cytosol must be maintained partly to prevent formation of insoluble calcium salts of ATP and other organic phosphates, and calcium inhibition of the action of many enzymes present in the cytosol. (iii) Calcium ions can serve a protective function. It protects plants from the injurious effects of hydrogen ions, high salt concentration in the environment, and toxic effects of other ions in the environment. (c) Physiological and Biochemical Functions: (i) Relatively high concentration of calcium is required for nodulation and successful symbiotic nitrogen fixation. (ii) Much calcium within the cytosol becomes reversibly bound to a small, soluble protein called Calmodulin. Calmodulin is activated by calcium binding in such a way that it then activates several enzymes. So an enzyme activating role of Ca2+ exists mainly when the ion is bound to calmodulin or closely related proteins. (iii) Ca2+ is required for the barley a-amylase activity. (iv) Adenine triphosphatases (ATPases) found in different plant tissues show a varied response to calcium. (v) Phospholipase D from cabbage and carrot is activated by Ca2 +. (vi) Calcium may also be an activator for the enzymes arginine kinase, adenylkinase and potato apyrase. (vii) The mitochondrial number in wheat roots is reduced under calcium-deficiency condition. (viii) Increased levels of carbohydrates in the leaves and decreased levels in the stems and roots of cotton plants result from calcium deficiency. This is interpreted as decrease in carbohydrate translocation owing to calcium deficiency, an effect similar to that found in boron deficiency. (d) Cytological Functions: (i) Calcium in small amounts is necessary for normal mitosis, because Ca2+ is needed to form microtubules of the spindle apparatus. (ii) Calcium is also involved in chromatin organization, it is suggested that nucleoprotein particles are held together by Ca2+. So calcium deficiency results in abnormal mitosis and thus chromosomal aberration.

Magnesium: Like calcium, magnesium is also an exchangeable cation. It is present in the soil in water soluble, exchangeable, and fixed form.

Functions of Magnesium: Magnesium, like calcium, also serves as a structural component and is involved as a cofactor in many enzymatic reactions. (a) Structural Functions: (i) Magnesium is a component of the chlorophyll structure. (ii) Magnesium is required to maintain ribosome integrity. (iii) Magnesium is necessary to maintain the structural integrity of chromatin fibre. It is involved in coiling of 110Å thick DNA histone protein fibre to form a 300Å thick chromatin fibre. (b) Physiological and Biochemical Functions: (i) Magnesium plays two very important roles in plant in photosynthesis and carbohydrate metabolism. Almost all the phosphorylating enzymes involved in carbohydrate metabolism require Mg2+ as an activator for maximal activity. Generally ATP is involved in these reactions. It has been suggested that Mg2 + forms a chelated complex with the phosphate groups, establishing the configuration that allows maximal activity. (ii) The release of energy in the hydrolysis of high energy compounds like ATP is greatly influenced by Mg2+. It complexes with ATP, ADP and AMP with differing affinities, resulting in hydrolysis of these compounds. Magnesium through complex formation with phosphate groups, exerts a controlling power on the steady state concentrations of high energy phosphates and influences the rate and extent of the phosphate-transfer reactions. (iii) Mg2+ has also a direct role on potassium-sodium stimulated ATPase activity. 2+ (iv) Mg is necessary for full activity of the two principal CO2 fixing enzymes, PEP carboxylase and RuBisCO. (v) Mg2 + is also an activator for DNA and RNA polymerases involved in DNA and RNA synthesis from nucleotide triphosphates. Thus Mg2 + helps in protein synthesis by activating enzymes of nucleic acid synthesis and forming imitation complexes with mRNA, ribosome and fMet initiator tRNA.

Sulphur: 2- Sulphur is taken up by the plants from the soil as divalent sulphate anions (SO4 ), which is enzymatically converted into an activated form before it can be incorporated into organic compounds.

Functions of Sulphur: (i) Sulphur is a constituent of certain amino acids like cystine, cysteine and methionine. Thus -2 sulphur participates in protein structure. The absorbed SO4 is converted subsequently into an activated form, which is then reduced and incorporated into cystine, cysteine, and methionine, and finally into the protein structure. Sulphur forms cross-links in the protein molecule and thus stabilizes the tertiary structure of protein. (ii) Sulphur is a constituent of biotin, thiamine, coenzyme A and lipoic acid which are involved in cellular metabolism. (iii) Sulphur along with iron forms Fe-S centres of many enzymes, which are important electron carriers in photosynthesis, respiration, nitrogen metabolism, etc. (iv) Sulphur is a component of S-adenosyl-methionine, which is involved in lignin and sterol biosynthesis. (v) It is a constituent of volatile oils which give characteristic pungent odours to cruciferous plants, onion, garlic, etc. ii. Briefly explain the organs with their functions of Digestive system in humans Digestion begins with chewing in the mouth where large pieces of food are broken up into smaller particles that we can swallow. Saliva, secreted by three pairs of exocrine salivary glands located in the head, drains into the mouth through a series of short ducts. Saliva, which contains mucus, moistens and lubricates the food particles before swallowing. It also contains the enzyme amylase, which partially digests polysaccharides (complex sugars). A third function of saliva is to dissolve some of the food molecules. Only in the dissolved state can these molecules react with chemoreceptors in the mouth, giving rise to the sensation of taste. Finally, saliva has antibacterial properties. The next segments of the tract, the pharynx and esophagus , do not contribute to digestion but provide the pathway for ingested materials to reach the stomach. The muscles in the walls of these segments control swallowing. The stomach is a saclike organ located between the esophagus and the small intestine. Its functions are to store, dissolve, and partially digest the macromolecules in food and to regulate the rate at which the contents of the stomach empty into the small intestine. The acidic environment in the gastric (adjective for “stomach”) lumen alters the ionization of polar molecules, leading to denaturation of protein. This exposes more sites for digestive enzymes to break down the proteins, and disrupts the extracellular network of connective-tissue proteins that form the structural framework of the tissues in food. The low pH also kills most of the bacteria that enter along with food. The digestive actions of the stomach reduce food particles to a solution known as chyme , which contains molecular fragments of proteins and polysaccharides; droplets of fat; and salt, water, and various other small molecules ingested in the food. Virtually none of these molecules, except water, can cross the epithelium of the gastric wall, and thus little absorption of organic nutrients occurs in the stomach. Most absorption and digestion occur in the next section of the tract, the small intestine , a tube about 2.4 cm in diameter and 3 m in length, which leads from the stomach to the large intestine . Hydrolytic enzymes in the small intestine break down molecules of intact or partially digested carbohydrates, fats, proteins, and nucleic acids into monosaccharides, fatty acids, amino acids, and nucleotides. Some of these enzymes are on the luminal surface of the intestinal lining cells, whereas others are secreted by the pancreas and enter the intestinal lumen. The products of digestion are absorbed across the epithelial cells and enter the blood and/or lymph. Vitamins, minerals, and water, which do not require enzymatic digestion, are also absorbed in the small intestine. The small intestine is divided into three segments: An initial short segment, the duodenum, is followed by the jejunum and then by the longest segment, the ileum. Normally, most of the chyme entering from the stomach is digested and absorbed in the first quarter of the small intestine in the duodenum and jejunum. Therefore, the small intestine has a very large reserve for the absorption of most nutrients; removal of portions of the small intestine as a treatment for disease does not necessarily result in nutritional deficiencies, depending on which part of the intestine is removed. Two major organs—the pancreas and liver—secrete substances that flow via ducts into the duodenum. The gall bladder stores and concentrates bile between meals. Pancreas have the following functions: Secretion of enzymes and bicarbonate; also has nondigestive endocrine functions, Digest carbohydrates, fats, proteins, and nucleic acids, Neutralize HCl entering small intestine from stomach. The liver is concerned with the following functions Secretion of bile, Solubilize water-insoluble fats, Neutralize HCl entering small intestine from stomach, Elimination in feces. iii. Explain the process of food digestion in Ruminants The cow's digestive tract consists of the mouth, esophagus, a complex four-compartment stomach, small intestine and large intestine . The stomach includes the rumen or paunch, reticulum or "honeycomb," the omasum or "manyplies," and the abomasum or "true stomach." The rumen. The rumen (on the left side of the animal) is the largest of four compartments and is divided into several sacs. It can hold 25 gallons or more of material, depending on the size of the cow. Because of its size, the rumen acts as a storage or holding vat for feed. It is also a fermentation vat. A microbial population in the rumen digests or ferments feed eaten by the animal. Conditions within the rumen favor the growth of microbes. The rumen absorbs most of the volatile fatty acids produced from fermentation of feedstuffs by rumen microbes. Absorption of volatile fatty acids and some other products of digestion is enhanced by a good blood supply to the walls of the rumen. Tiny projections called papillae increase the surface area and the absorption capacity of the rumen. The reticulum. The reticulum is a pouch-like structure in the forward area of the body cavity. The tissues are arranged in a network resembling a honeycomb. A small fold of tissue lies between the reticulum and the rumen, but the two are not actually separate compartments. Collectively they are called the rumino-reticulum. Heavy or dense feed and metal objects eaten by the cow drop into this compartment. The reticulum lies close to the heart. The omasum. This globe-shaped structure (also called the "manyplies") contains leaves of tissue (like pages in a book). The omasum absorbs water and other substances from digestive contents. Feed material (ingesta) between the leaves will be drier than that found in the other compartments. The abomasum. This is the only compartment (also called the true stomach) with a glandular lining. Hydrochloric acid and digestive enzymes, needed for the breakdown of feeds, are secreted into the abomasum. The abomasum is comparable to the stomach of the non-ruminant. The small intestine. The small intestine measures about 20 times the length of the animal. It is composed of three sections: the duodenum, jejunum, and ileum. The small intestine receives the secretions of the pancreas and the gallbladder, which aid digestion. Most of the digestive process is completed here, and many nutrients are absorbed through the villi (small finger-like projections) into the blood and lymphatic systems. Cecum. The cecum is the large area located at the junction of the small and large intestine, where some previously undigested fiber may be broken down. The exact significance of the cecum has not been established. Large intestine. This is the last segment of the tract through which undigested feedstuffs pass. Some bacterial digestion of undigested feed occurs, but absorption of water is the primary digestive activity occurring in the large intestine.

Function of the Digestive Tract Eructation (belching). Large quantities of gas, mostly carbon dioxide and methane, are produced in the rumen. Production amounts to 30 to 50 quarts per hour and must be removed; otherwise bloating occurs. Under normal conditions, distension from gas formation causes the cow to belch and eliminate the gas. Rumination. A cow may spend as much as 35 to 40 percent of each day ruminating (cud chewing). The actual amount of time spent ruminating varies from very little (when grain or finely ground rations are fed) to several hours (when long hay is fed). Mature cattle spend little time chewing when eating. During rest periods, feed boluses (cud) are regurgitated for rechewing to reduce particle size and for resalivation. Feed is more readily digested by rumen microbes as particle size is reduced. Motility of the rumen and reticulum. The rumen is always contracting and moving. Healthy cows will have one to two rumen contractions per minute. The contractions mix the rumen contents, bring microbes in contact with new feedstuffs, reduce flotation of solids, and move materials out of the rumen. Lack of or a decrease in frequency of rumen movements is one way of diagnosing sick animals. Saliva production. As much as 50 to 80 quarts of saliva can be produced by salivary glands and added to the rumen each day. Saliva provides liquid for the microbial population, recirculates nitrogen and minerals, and buffers the rumen. Saliva is the major buffer for helping to maintain a rumen pH between 6.2 and 6.8 for optimum digestion of forages and feedstuffs.

iv. Explain what is Ascent of sap in plants The water after being absorbed by the roots is distributed to all parts of the plant (excess of which is lost through transpiration). In order to reach the topmost parts of the plant, the water has to move upward through the stem. This upward movement of water is called as Ascent of Sap. Theories of Ascent of SAP: (A) Vital Theories: Supporters of vital theories think that the ascent of sap is under the control of vital activities in the stem. Two such theories are common but they are not very convincing: (1) According to Godlewski (1884) ascent of sap takes place due to the pumping activity of the cells of xylem parenchyma which are living. The cells of the medullary rays which are also living, in some way change their O.P. When their O.P. becomes high they draw water from the lower vessel and their O.P. becomes low. Now due to the low O.P., water from the cells of xylem parenchyma is pumped into the above vessel. This process is repeated again and again and water rises upward in the xylem. This theory seemed only hypothetical, and was further discarded by the experiments of Strasburger. (1891, 1893) who demonstrated that ascent of sap continues even in the stems in which living cells have been killed by the uptake of poisons. (2) According to Bose (1923) upward translocation of water takes plate due to the pulsatory activity of living cells of inner most cortical layer just outside the endodermis. This theory was also rejected because many workers could not repeat his experiment and many others found no correlation between pulsatory activity and the ascent of sap.

(Bose, in his experiment used an electric probe which was connected to a galvanometer. When the needle of the electric probe was inserted into the stem slowly and slowly, the needle of the galvanometer showed some oscillations but when the electric probe needle reached the innermost layer of cortex, the needle of galvanometer showed violent oscillations. He attributed this to the pulsating activity of these cells.)

(B) Root Pressure Theory: Although, root pressure which is developed in the xylem of the roots can raise water to a certain height but it does not seem to be an effective force in ascent of sap due to the following reasons: (i) Magnitude of root pressure is very low (about 2 atms).

(ii) Even in the absence of root pressure, absent of sap continues. For example, when a leafy twig is cut under water and placed in a beaker full of water it remains fresh and green for sufficient long time.

(iii) In gymnosperms root pressure has rarely been observed.

(C) Physical Force Theories: Various physical forces may be involved in the ascent of sap:— (1) Atmospheric Pressure: This does not seem to be convincing because: (i) It cannot act on water present in xylem in roots,

(ii) In case it is working, then also it will not be able to raise water beyond 34′.

(2) Imbibition: Sachs (1878) supported the view that ascent of sap could take place by imbibition through the walls of xylem. Now it is well known that imbibitional force is insignificant in the ascent of sap because it takes place through the lumen of xylem elements and not through walls.

(A leafy twig is cut under water and the cut end is dipped in melted paraffin wax for some time. A thin section of stem near cut end is removed to expose the cell walls. The twig is transferred to a beaker containing water. The twig soon wilts because the lumens of xylem elements have been plugged by wax).

(3) Capillary Force: In plants the xylem vessels are placed one above the other forming a sort of continuous channel which can be compared with long capillary tubes and it was thought that as water rises in capillary tube due to capillary force, in the same manner ascent of sap takes place in xylem.

There are many objections to this theory: (i) For capillarity a free surface is required.

(ii) The magnitude of capillary force is low.

(iii) In spring when there is more requirement of water due to the development of new leaves, the wood consists of broader elements. While in autumn, when water supply decreases, the wood consists of narrow elements. This is against capillarity.

(iv) In Gymnosperms usually the vessels are absent. Other xylem elements do not form continuous channels.

(D) Transpiration Pull and Cohesion of Water Theory: This theory was originally proposed by Dixon and Joly (1894) and greatly supported and elaborated by Dixon (1914, 1924). This theory is very convincing and has now been widely supported by many workers.

It is based on the following features: (i) Cohesive and Adhesive properties of water molecules to form a continuous water column in the xylem.

(ii) Transpiration pull exerted on this water column.

Water molecules remain joined to each other due H-bonds between water molecules, to the presence of H-bonds between them. (Whenever a H-atom comes between two electro-negative atoms a bond is established between the two which is called as H bond and is represented by dotted lines. In case of water, the electropositive H-atoms of one water molecule are connected with electronegative O-atoms of other water molecules by H-bonds).

Although H-bond is very weak (containing about 5k. cal. energy) but when they are present in enormous numbers as in case of water, a very strong mutual force of attraction or cohesive force develops between water molecules and hence they remain in the form of a continuous water column in the xylem. The magnitude of this force is very high (sometimes up to 350 atmos.), therefore the continuous water column in the xylem cannot be broken easily due to the force of gravity or other obstructions offered by the internal tissues in the upward movement of water.

The adhesive properties of water i.e. the attraction between the water molecules and the container’s walls (here the walls of xylem) further ensure the continuity of water column in xylem.

When transpiration takes place in leaves at the upper parts of the plant, water evaporates from the intercellular spaces of the leaves to the outer atmosphere through the stomata. More water is released into the intercellular spaces from the mesophyll cells. In turn, the mesophyll cells draw water from the xylem of the leaf.

Due to all this, a tension is created in water in the xylem elements of the leaves. This tension is transmitted downward to water in xylem elements of the roots through the xylem of petiole and stem and the water is pulled upward in the form of continuous unbroken water column to reach the transpiring surfaces—up to the top of the plants.

According to some workers, the main objection against this theory is that certain air bubbles present in the conducting channels will break the continuity of the water column. This has been counteracted by others who say that there are no air bubbles and if at all are present, they will not break the water column which will remain continuous through other elements of the xylem

(10 Q.3.A. Answer Any One of the following ) i. Explain the structure of human heart

The human heart is pinkish about the size of a fist and weighs approx. 300 gms, the weight in females being about 25% lesser than the males. It is a hollow, highly muscular, cone-shaped structure located in the thoracic cavity above the diaphragm in between the two lungs. It is protected by rib cage. The narrow end of the triangular heart is pointed to the left side, during working this end gives a feeling of the heart being on the left side. Location of heart: Heart is right in the centre between the two lungs and above the diaphragm in the ribcage. The narrow end of the roughly triangular heart is pointed to the left side and during working the contraction of the heart is most powerful at this end giving a feeling of the heart being on the left side. External Structure: The heart is surrounded by two layered tissue membrane called pericardium. The space between the two layers is filled with fluid called pericardial fluid. This fluid protects the heart from external pressure, push, shock and reduces friction during the heart beat and facilitates free heart contraction.

Internal Structure: The heart is composed of outer pericardial, middle myocardial and inner endocardial layers, which correspond to tunica adventitia, tunica media and tunica internal respectively of the blood vessels layers. The heart consists of four chambers. The two

thin walled auricles which are upper chambers (right and left). Right and left auricles are separated from each other by an inter-auricular septum. Right auricle receives deoxygenated blood from the body parts by anterior and posterior vena cava. The two thick walled lower chamber (right and left) are called ventricles. Right and left ventricles are separated by an inter-ventricular septum. The walls of left ventricle are much thicker as it supplies blood to large distance and up to the brain against gravity. The left ventricle has chordae tendinae and papillary muscles which prevent tricuspid and bicuspid valves from being pushed into auricles at the time of ventricular contraction.

Blood Vessels Entering and Leaving the Heart: 1. (a) Superior vena cava: It brings deoxygenated blood from anterior body parts (head, neck, chest and arms) to the right auricle. (b) Posterior vena cava: It brings deoxygenated blood from posterior or lower body parts i.e. abdomen and legs to the right auricle.lt is the largest vein

2. Pulmonary artery: It arises from right ventricles and carries deoxygenated blood to the lungs for oxygenation. 3. Pulmonary vein: It arises from each lung and brings oxygenated blood from lungs to left auricle. 4. Aorta: It arises from left ventricles and carries oxygenated blood to supply it to all body parts. Abdominal aorta is the largest artery. 5. Coronary arteries: There are two coronary arteries right and left, arising from the base of aorta and supply blood to heart muscles, (blockage at these arteries result a myocardial infraction or heart attack). Valves in the Heart: 1. Right atrio-ventricular valve (Tricuspid valve)-Located at the opening between right auricle and right ventricle. 2. Left atrio-ventricular valve (Mitral or bicuspid valve)-Located at the similar way between left auricle and left ventricle. 3. Pulmonary semi-lunar valve: Present at the opening of right ventricle into pulmonary artery. 4. Aortic Semi-Lunar Valve: Located at the point of origin of aorta from left ventricle. Pacemaker tissues of the Heart: Certain tissues in the heart, concerned with the initiation (generation of impulse) and propagation (conduction) of the heart beat, are called Pace- Maker tissue. ii. Explain the role of proton pump in transport in plants. MEANS OF TRANSPORT - Diffusion Movement by diffusion is passive, and may be from one part of the cell to the other, or from cell to cell, or over short distances, say, from the inter- cellular spaces of the leaf to the outside. No energy expenditure takes place. In diffusion, molecules move in a random fashion, the net result being substances moving from regions of higher concentration to regions of lower concentration. Diffusion is a slow process and is not dependent on a ‘living system’. Diffusion is obvious in gases and liquids, but diffusion in solids rather than of solids is more likely. Diffusion is very important to plants since it is the only means for gaseous movement within the plant body. Diffusion rates are affected by the gradient of concentration, the permeability of the membrane separating them, temperature and pressure. Facilitated Diffusion As pointed out earlier, a gradient must already be present for diffusion to occur. The diffusion rate depends on the size of the substances; obviously smaller substances diffuse faster. The diffusion of any substance across a membrane also depends on its solubility in lipids, the major constituent of the membrane. Substances soluble in lipids diffuse through the membrane faster. Substances that have a hydrophilic moiety, find it difficult to pass through the membrane; their movement has to be facilitated. Membrane proteins provide sites at which such molecules cross the membrane. They do not set up a concentration gradient: a concentration gradient must already be present for molecules to diffuse even if facilitated by the proteins. This process is called facilitated diffusion. In facilitated diffusion special proteins help move substances across membranes without expenditure of ATP energy. Facilitated diffusion cannot cause net transport of molecules from a low to a high concentration – this would require input of energy. Transport rate reaches a maximum when all of the protein transporters are being used (saturation). Facilitated diffusion is very specific:

it allows cell to select substances for uptake. It is sensitive to inhibitors which react with protein side chains. The proteins form channels in the membrane for molecules to pass through. Some channels are always open; others can be controlled. Some are large, allowing a variety of molecules to cross. The porins are proteins that form huge pores in the outer membranes of the plastids, mitochondria and some bacteria allowing molecules up to the size of small proteins to pass through. Figure 11.1 shows an extracellular molecule bound to the transport protein; the transport protein then rotates and releases the molecule inside the cell, e.g., water channels – made up of eight different types of aquaporins.

Passive symports and antiports Some carrier or transport proteins allow diffusion only if two types of molecules move together. In a symport, both molecules cross the membrane in the same direction; in an antiport, they move in opposite directions (Figure 11.2). When a molecule moves across a membrane independent of other molecules, the process is called uniport.

Active Transport Active transport uses energy to pump molecules against a concentration gradient. Active transport is carried out by membrane-proteins. Hence different proteins in the membrane play a major role in both active as well as passive transport. Pumps are proteins that use energy to carry substances across the cell membrane. These pumps can transport substances from a low concentration to a high concentration (‘uphill’ transport). Transport rate reaches a maximum when all the protein transporters are being used or are saturated. Like enzymes the carrier protein is very specific in what it carries across the membrane. These proteins are sensitive to inhibitors that react with protein side chains. Comparison of Different Transport Processes Table 11.1 gives a comparison of the different transport mechanisms. Proteins in the membrane are responsible for facilitated diffusion and active transport and hence show common characterstics of being highly selective; they are liable to saturate, respond to inhibitors and are under hormonal regulation. But diffusion whether facilitated or not – take place only along a gradient and do not use energy.

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Q.3.B. Answer Any Two of the following: (10) i. Write a note on transpiration Transpiration is the evaporative loss of water by plants. It occurs mainly through the stomata in the leaves. Besides the loss of water vapour in transpiration, exchange of oxygen and carbon dioxide in the leaf also occurs through pores called stomata (sing. : stoma). Normally stomata are open in the day time and close during the night. The immediate cause of the opening or closing of the stomata is a change in the turgidity of the guard cells. The inner wall of each guard cell, towards the pore or stomatal aperture, is thick and elastic. When turgidity increases within the two guard cells flanking each stomatal aperture or pore, the thin outer walls bulge out and force the inner walls into a crescent shape. The opening of the stoma is also aided due to the orientation of the microfibrils in the cell walls of the guard cells. Cellulose microfibrils are oriented radially rather than longitudinally making it easier for the stoma to open. When the guard cells lose turgor, due to water loss (or water stress) the elastic inner walls regain their original shape, the guard cells become flaccid and the stoma closes. Usually the lower surface of a dorsiventral (often dicotyledonous) leaf has a greater number of stomata while in an isobilateral (often monocotyledonous) leaf they are about equal on both surfaces.he transpiration driven ascent of xylem sap depends mainly on the following physical

ii. Schematically represent Double circulation

iii. Explain the pathway of circulation in hydra / jelly fish.

The circulatory system varies from simple systems in invertebrates to more complex systems in vertebrates. The simplest animals, such as the sponges (Porifera), do not need a circulatory system because diffusion allows adequate exchange of water, nutrients, and waste, as well as dissolved gases. Sponges and most cnidarians utilize water from the environment as a circulatory fluid. Sponges pass water through a series of channels in their bodies, and Hydra and other cnidarians circulate water through a gastrovascular cavity. Organisms that are more complex, but still have only two layers of cells in their body plan, such as jellies (Cnidaria) and comb jellies (Ctenophora), each cell layer is in direct contact with either the external environment or the gastrovascular cavity. Both their internal and external tissues are bathed in an aqueous environment and exchange fluids by diffusion on both sides (figure b). Exchange of fluids is assisted by the pulsing of the jellyfish body. Sponges do not have a separate circulatory system. They circulate water using many incurrent pores and one excurrent pore. The gastrovascular cavity of a Jelly fish serves as both a digestive and a circulatory system, delivering nutrients directly to the tissue cells by diffusion from the digestive cavity

iv. Sketch and Label the Sugar & Water conducting cells. The vascular tissues include xylem, which conducts water and minerals from the roots upward and throughout the plant, and phloem, which transports dissolved nutrients in all directions within the plant. The main conducting vessels of xylem are the tracheids and the vessels. Tracheids are long, thin tubes found in most vascular plants, while vessels are large tubes found predominantly in angiosperms. The tracheids and vessels form pipelines that have pores and perforated ends that allow water and minerals to be conducted from one tube to the next and out to the surrounding tissues. Tracheids and vessels also help support the plant body. The main conducting cells of phloem are sieve cells and sieve tube members. Both cell types have numerous pores through which substances are exchanged with adjacent cells. Sieve tube members occur in angiosperms, while sieve cells are found in other vascular plants. In angiosperms, small cells called companion cells assist the sieve tube members in their functions.

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Q.4.A. Answer Any One of the following: (10) i. Mention an account of gaseous exchange in mammals. How is it different with that of fish? The chief organ in mammalian respiration is the lungs. The lungs are actively ventilated via a suction-pump mechanism of inhalation and exhalation. Breathing is dependent upon the rib muscles and the diaphragm, a structure shaped like a dome-shaped floor just beneath the lungs. Inhalation happens when the rib cage opens up and the diaphragm flattens and moves downward. The lungs expand into the larger space, causing the air pressure inside to de- crease. The drop in air pressure inside the lung makes the outside air rush in. Exhalation is the opposite process. The diaphragm and the rib muscles relax to their neutral state, causing the lungs to contract. The squashing of the lungs increases their air pressure and forces the air

! to flow out.A diagram of ventilation in most mammals. The left image shows inhalation with a flattened diaphragm. The right side shows the dome-shaped diaphragm forcing the air out during exhalation.Most mammals are nose breathers. Inhaling through the nose warms and moistens the air. The air is filtered by cilia and mucus membranes, which trap dust and pathogens. Air then reaches the epiglottis, the tiny leaf-shaped flap at the back of the throat. The epiglottis regulates air going into the windpipe and closes upon swallowing to prevent food from being inhaled. It’s the gatekeeper to the lungs.

! The trachea is a long structure of soft tissue surrounded by c-shaped rings of cartilage. In humans, the trachea splits into two bronchi branches that lead to each lung. Each bronchi di- vides into increasingly smaller branches, until they form a massive tree of tubes. The smallest branches are called the bronchioles, and each bronchiole ends with a tiny air sac (no larger than a grain of sand) called an alveolus. The tiny alveoli (plural of alveolus) are crucial be- cause they increase the surface area used for gas exchange. If the lungs were just empty sacs, then only area available for gas exchange would be the walls of the lungs. In humans, that comes out to an area of approximately 0.01 m2. The alveoli, though, provide a whopping 75m2 of surface area where oxygen absorption can take place. That’s the size of half a vol- leyball court and it's all inside of you. As discussed above, gas exchange takes place in the capillaries, so the alveoli have a close working relationship with the network of capillaries. This brings the blood-carrying waste products close enough to the fresh air for diffusion to take place. The waste is removed and the oxygen is taken up by the blood. The hemoglobin in blood attaches oxygen molecules, kind of like a bus carrying passengers. Each hemoglobin protein can carry four passengers of oxygen at one time. Oxygen is delivered to the cells and carbon dioxide is removed. Water vapor and carbon dioxide are exhaled, and the process begins again with inhalation.Just as the heart beats on its own, breathing is done without conscious effort. There are sections of the brain, called the medulla and pons that regulate respiration. They control the rate of respi- ration by monitoring carbon dioxide levels in the blood. In times of excitement or during ex- ercise, the cells require more oxygen than normal and respiration speeds up. Tidal volume is the amount of air breathed in or out during a respiratory cycle. The tidal vol- ume and respiratory frequency, or the number of inhalations over a period of time (such as breaths per minute), vary amongst species, and it’s affected by age, pregnancy, exercise, ex- citement, temperature, and body size. For instance, horses have an average respiration of 12 times per minute, but pigs breathe an average of 40 times per minute.Marine mammals breathe oxygen with lungs just like their terrestrial brethren, but with a few differences. To prevent water from getting into their airway, they have adapted muscles or cartilaginous flaps to seal their tracheas when under the water. We wish our cartilaginous flaps did that, but our ancestors skipped out on a couple million years of pruning up in the ocean, so we're out of luck. Marine mammals also exchange up to 90% of their gases in a single breath, which helps them gather as much oxygen and expel as much waste as possible. A sperm whale can last for 138 minutes on a single breath. In fish, respiration takes place in the gills. Gills collect dissolved oxygen from the water and release carbon dioxide. Gills are much more complex than just a slit in the cheeks of a fish. Gills are comprised of gill arches with hundreds of gill filaments extending from them. Each filament is lined with rows of lamellae, and the gas exchange takes place as water flows through them. The frills and flaps increase the surface area to allow more gas exchange to take place, just as the alveoli do in the lungs.Fish utilize a countercurrent exchange pathway, which means that their arteries are arranged so that blood flows in the opposite direction of water movement against the gills. By having their respiration pathway in this orientation, maximum gas exchange can take place. If the blood and the water were moving in the same direction, the blood would always be next to the same bit of water which would soon be de- pleted of oxygen. By setting up a countercurrent pathway, the blood is always passing water that is still oxygenated. This allows the blood to gather as much oxygen as possible.Since wa- ter must be flowing over the gills to provide a continual source of oxygen, fish have devel- oped several ways to keep them ventilated. Some fish swim with their mouths open almost all of the time. Other fish have a special flap called an operculum, which is used to force water across the gills. Like all good rules, there’s an exception. While all fish have gills, one fish also has lungs. The lungfish can survive when its water habitat dries up from seasonal drought. What an aptly named fish. There’s also certain land crabs that have both lungs and gills, and can breathe both under the sea and on land.The lungfish is a unique animal which has gills and lungs. ii. Describe various types of respiratory pigments. Explain in detail about Hemoglobin as a respiratory pigment. The following points highlight the four main types of pigments found in the blood of animals. The types are: 1. Haemoglobin 2. Haemocyanin 3. Chlorocruorin 4. Haemerythrin. Type # 1. Haemoglobin: A haemoglobin (Hb) molecule is a conjugated protein, because it consists of a simple protein and with a non-protein part. The non-protein part is called prosthetic group. The protein part of the haemoglobin is called globin (96%) and a porphyrin ring with an iron atom at its centre, called haem or haematin (4%). The globin part consists of 4 polypeptide chains-two alpha (α) chains and two beta (β) chains. Porphyrins are heterocyclic ring structure containing haem or magnesium. The heterocyclic ring structure is composed of four pyrrole rings which are linket by methine bridges. The globin part helps to prevent oxygen from binding tightly to haem; when globin is present, oxygen binds reversibly to haem and can be released to the tissues. In respiratory organs the haemoglobin combines with O2 which form Oxyhaemoglobin at normal temperature and pressures. At the low pressure the oxyhaemoglobin dissociates as oxygen and haemoglobin (HbO2 ↔ Hb + O2)- Haemoglobin is involved in vertebrates in the transport of respiratory CO2 (about 10% of the total) as carbamino-haemoglobin in which CO2 is bound to the globin protein. The molecular weight of a haemoglobin molecule is 64,500 daltons. The oxygenated form of haemoglobin is scarlet and deoxygenated form is bluish-red. The haemoglobin is present in the erythrocytes in almost all vertebrates except a few Antarctic fish. In the invertebrates they are found in the plasma, coelomic fluid and haemoglobin- containing cells. In Annelida, the pigment is found in polychaeta (different kinds of respiratory pigments), in Oligochaeta (e.g., Pheretima, Lumbricus, Tubifex etc.), and in Hirudinea (e.g., Hirudo, Hirudinaria, etc.) In Mollusca the haemoglobin is found in the plasma of Gastropods (e.g., Planorbis), and in Bivalvia (e.g., Solen, Area, etc.). In Chiton and in some prosobranchs the haemoglobin is present in the muscles of radula as Myoglobin. In Crustacea the pigment is present in small- sized animals (e.g., Artemia, Daphnia, Triops, etc.). Type # 2. Haemocyanin: A blue-green copper containing respiratory pigments found in some crustaceans, xiphosurans, myriapodes, and in some gastropods, bivalves and cephalopods. Haemo-cyanin is always found in dissolved condition in plasma. It occurs in two forms— oxidized and reduced forms, and in reduced forms the prism-shaped or needle-shaped crystals are soluble in water. The oxygen carrying capacity of haemocyanin is lesser than haemoglobin. The mol. weight is variable in different groups of animals. In some crustaceans the mol. weight is about 4,00,000 daltons and in some gastropods it is 13,00,00,000. Haemocyanin binds a molecule of oxygen between a pair of copper atoms linked to amino acid side chains. In oxygenated condition the haemocyanin is bluish- green but it is colourless in deoxygenated state. Type # 3. Chlorocruorin: It is a green coloured respiratory pigment containing iron found in the plasma of some polychaetes (e.g., Serpulid, spirorbid, sabellid fanworms). It is also found in oxy-genated and reduced forms. The metalloprotein of chlorocruorin is similar to haemoglobin except one vinyl group (CH2 = CH—) is replaced by formyl (HCO—) group. The mol. weight is 30,00,000 daltons and generally it functions as oxygen carrier. Type # 4. Haemerythrin (Haemo-erythrin): It is an iron containing respiratory pigment found in the blood corpuscles of some invertebrates (e.g., Sipunculans, Priapulids and inarticulate Brachiopods). It is pink or violet coloured in oxygenated state and colourless in deoxygenated state. The mol. weight varies from 40,000 to 108,000 daltons and plays the role of oxygen storage. A few other less common respiratory pigments are: (i) Pinnaglobin—a brown coloured manganese containing pigment found in the plasma of Pinna (Lamellibranchs). (ii) Vanadium—It is a green coloured vanadium containing pigment found in the vanadocytes of some sea squirts (Ascidians).

Q.4. B. Answer Any Two of the following: (10)

i. Describe Partial Pressure and its role in respiration. it's the individual pressure exerted independently by a particular gas within a mixture of gasses. The air we breath is a mixture of gasses: primarily nitrogen, oxygen, & carbon dioxide. So, the air you blow into a balloon creates pressure that causes the balloon to expand (& this pressure is generated as all the molecules of nitrogen, oxygen, & carbon dioxide move about & collide with the walls of the balloon). However, the total pressure generated by the air is due in part to nitrogen, in part to oxygen, & in part to carbon dioxide. That part of the total pressure generated by oxygen is the 'partial pressure' of oxygen, while that generated by carbon dioxide is the 'partial pressure' of carbon dioxide. A gas's partial pressure, therefore, is a measure of how much of that gas is present (e.g., in the blood or alveoli). the partial pressure exerted by each gas in a mixture equals the total pressure times the fractional composition of the gas in the mixture. So, given that total atmospheric pressure (at sea level) is about 760 mm Hg and, further, that air is about 21% oxygen, then the partial pressure of oxygen in the air is 0.21 times 760 mm Hg or 160 mm Hg

ii. What are Pneumatophores? Describe its significance in marshy areas. Some lateral roots of mangroves become specialized as pneumatophores in saline mud flats; pneumatophores are lateral roots that grow upward (negative geotropism) for varying distances and function as the site of oxygen intake.They project some centimetres above the low-tide level. They have small openings (lenticels) in their bark so that air can reach the rest of the plants root system. An aerial root may be defined as a root which, for part of the day at least, is exposed to the air. The mangrove mud is rather anaerobic (oxygen poor) and unstable and different plants have root adaptations to cope with these conditions. Pneumatophore is a type Of breathing root (in mangroves and other swamp plants) an aerial root specialized for gaseous exchange

iii. Describe briefly “Water and salt regulation in stressed plants”. A xerophyte (xero meaning dry, phyte meaning plant) is a plant which is able to survive in an environment with little availability of water or moisture. Plants like the cacti and other succulents are typically found in deserts where low rainfall is the normal phenomena, but few xerophytes can also be found in moist habitats such as tropical forests, exploiting niches where water supplies are limited or too intermittent for mesophytic plants. Similarly Agricultural productivity is severely affected by high soil salinity and is responsible for decline in soil fertility. Some plants grow and complete their life cycle in the habitats with a high salt content. They are known as salt plants or halophytes. Plants inhabiting coastal low lying marshes, inland desserts, intertidal regions have to face high soil salinity. Glycophytes are very sensitive to salt injury.

TYPES OF XEROPHYTIC PLANTS: They are classified into four categories on the basis of their morphology and life cycle pattern: a. Ephemeral Annuals: These plants are also called as drought escapers. They are annuals and complete their life cycle within a very short period of 4 to 6 weeks.They do not withstand dry seasons but actually avoid them. They occur in semi arid regions. b. drought Evaders: They are extremely small in size. They have restricted growth and require very low amount of water for growth and development. They conserve what ever low amount of water they have. c. Succulent: These plants grow in habitats with less or no water. They store water whenever it is available typically in stems or leaves. They have succulent and fleshy organs like stems, leaves and roots which serve as water storage organs and accumulate large amounts of water during the brief rainy seasons. Eg: Opuntia. d. Non-Succulent Perennials: These are drought resistant or Endurers and called as true xerophytes. They possess a number of morphological, anatomical and physiological characteristics which enable them to withstand critical dry conditions. Eg: Acacia HALOPHYTIC PLANTS: When plants are under salt stress, flow of water into the plant is reversed and it causes ion imbalance. Plant dies as water is drawn out of the cell and accumulation of excess sodium (Na+) and chloride (Cl–) ions in the cytoplasm takes place. Many have toxic effects on the functioning of cells by affecting , altered Metabolism, damage to membranes, change in the pattern of protein synthesis, enzyme functions and poor rate of photosynthesis, toxicity etc iv. Explain Uricotelism with a suitable example. Depending upon the excretory product, animals show five types of nitrogenous excre-tion in which ammonotelism, ureotelism and uricotelism are major types and aminotelism and guanotelism are minor types. Nitrogenous waste substances such as ammonia, urea or uric acid are produced during protein metabolism according to the species. Excretion of uric acid is known as uricotelism and the animals which excrete uric acid are called uricotelic. Animals which live in dry conditions have to conserve water in their bodies. Therefore, they synthesize crystals of uric acid from their ammonia. Uric acid crystals are non-toxic and almost insoluble in water. Hence, these can be retained in the body for a considerable time. Uricotelic animals include most insects, (e.g., cockroach) some land crustaceans (e.g., Oniscus commonly known as “wood louse”), land snails (e.g., Helix commonly known as “land snail”), land reptiles (e.g., lizards and snakes) and birds. The concentration of uric acid is so high in guano (waste matter dropped by sea birds, used as fertilizer) that uric acid is commercially extracted from guano which is collected from uninhabited marine or littoral (part of country which is along the coast) islands. Primates including man also excrete some uric acid which is formed in their body by the breakdown of nucleic acids.

Q.5. Answer Any Four of the following: (20) i. Nervous system control in digestion The gastrointestinal tract has its own local nervous system, a division of the autonomic nervous system known as the enteric nervous system . The cells in this system form two networks or plexuses of neurons, the myenteric plexus and the submucosal plexus. These neurons either synapse with other neurons within a given plexus or end near smooth muscles, glands, and epithelial cells. Many axons leave the myenteric plexus and synapse with neurons in the submucosal plexus, and vice versa, so that neural activity in one plexus influences the activity in the other. Moreover, stimulation at one point in the plexus can lead to impulses that are conducted both up and down the tract. For example, stimuli in the upper part of the small intestine may affect smooth muscle and gland activity in the stomach as well as in the lower part of the intestinal tract. In general, the myenteric plexus influences smooth muscle activity whereas the submucosal plexus influences secretory activity. The enteric nervous system contains adrenergic and cholinergic neurons as well as neurons that release other neurotransmitters, such as nitric oxide, several neuropeptides, and ATP. The effectors mentioned earlier—muscle cells and exocrine glands—are supplied by neurons that are part of the enteric nervous system. This permits neural reflexes that are completely within the tract—that is, independent of the CNS. In addition, nerve fibers from both the sympathetic and parasympathetic branches of the autonomic nervous system enter the intestinal tract and synapse with neurons in both plexuses. Via these pathways, the CNS can influence the motility and secretory activity of the gastrointestinal tract. Thus, two types of neural-reflex arcs exist (1) short reflexes from receptors through the nerve plexuses to effector cells; and (2) long reflexes from receptors in the tract to the CNS by way of afferent nerves, and back to the nerve plexuses and effector cells by way of autonomic nerve fibers. Finally, it should be noted that not all neural reflexes are initiated by signals within the tract. Hunger, the sight or smell of food, and the emotional state of an individual can have significant effects on the gastrointestinal tract, effects that are mediated by the CNS via autonomic neurons. ii. Explain Five Kingdom classification with one example of each Kingdom Monera • Smallest and simplest lifeforms • Unicellular (one-celled) • Prokaryotes • no nucleus and other cell organelles • Bacteria and cyanobacteria Kingdom Protista • Diverse group of eukaryotic organisms • Most protists are unicellular. • Protist groups are predominately organized by feeding method plus other unique characteristics • Mostly non motile; some are photosynthetic • Plasmodium, algae, paramecium Kingom Fungii  Fungi are multicellular,with a cell wall, organelles including a nucleus, but no chloroplasts. They have no mechanisms for locomotion.  Fungi range in size from microscopic to very large ( such as mushrooms).  Nutrients are acquired by absorption.  For the most part, fungi acquire nutrients from decaying material.  Mushroom, yeast Kingdom Plantae  Plants are multicellular and most don't move, although gametes of some plants move using cilia or flagella. Organelles including nucleus, chloroplasts are present, and cell walls are present. Nutrients are acquired by photosynthesis (they all require sunlight).  Vascular or Nonvascular  Moss, Ferns, Horsetails, Gymnosperms, and Angiosperms Kingdom Anamalia • All multicellular • Heterotrophic nutrition by ingestion • Diploid adult • Reproduction is usually sexual • Embryonic development often used to taxonomically classify animal groups • 9 phyla • Humans, reptiles, fish etc.

iii. Write a note o role of exercise in cardiac health Effects of diet and exercise on the circulatory system Diet:A diet high in saturated fats increases blood pressure and the risk of atherosclerosis (or hardening of the arteries). Salt in the diet also raises blood pressure by increasing thirst and water intake. Exercise: •Exercise stimulates a temporary increase in heart rate and blood pressure. •It strengthens the heart and promotes healthy blood vessel •When we exercise our muscles get bigger & stronger this is the same for our heart . •Exercise improves circulation and reduces body weight •Most beneficial exercise is aerobic exercise e.g. Walking, jogging, running, swimming and Dancing so get your feet moving.

iv. Discuss Stomatal movements in plants. Each stoma is surrounded by two guard cells. The kidney-shaped guard cells contain chloroplasts. A respiratory cavity or chamber is found under each stoma. The mechanism of the closing and opening of the stomata depends upon the presence of sugar and starch in the guard cells. During day time or in the presence of light, the guard cells of the stomata contain sugar synthesized by their chloroplasts. The sugar is soluble and increases the concentration of the sap of guard cells. Due to higher concentration of the cytoplasm of guard cells, the water comes to them from the neighbouring cells by osmosis and they become turgid. With the result the stomata remain open. In the night or in the absence of light the sugar present in guard cells converts into the starch. The starch is insoluble, and this way the cell sap of the guard cells remains of much lower concentration than those of neighbouring cells, and the neighbouring cells take out the water from the guard cells by osmosis making them flaccid and the stomata closed. The conversion of sugar into starch during night and vice-versa in day time depends upon the acidity (pH) and alkalinity of the cell sap of guard cells. During night there is no photosyn- thesis and the carbon dioxide accumulates in the guard cells, converting the cell sap into weak acidic starch. During day time the carbon dioxide is used in the process of photosynthesis, the cell sap be- comes alkaline and the starch converts into sugar.

v. Osmoregulation in animals Osmoregulation is the active regulation of the osmotic pressure of an organism's body fluids, detected by osmoreceptors, to maintain the homeostasis of the organism's water content; that is, it maintains the fluid balance and the concentration of electrolytes (salts in solution) to keep the fluids from becoming too diluted or concentrated. Osmotic pressure is a measure of the tendency of water to move into one solution from another by osmosis. The higher the osmotic pressure of a solution, the more water tends to move into it. Pressure must be exerted on the hypertonic side of a selectively permeable membrane to prevent diffusion of water by osmosis from the side containing pure water. Organisms in aquatic and terrestrial environments must maintain the right concentration of solutes and amount of water in their body fluids; this involves excretion (getting rid of metabolic nitrogen wastes and other substances such as hormones that would be toxic if allowed to accumulate in the blood) through organs such as the skin and the kidneys. Two major types of osmoregulation are osmoconformers and osmoregulators. Osmoconformers match their body osmolarity to their environment actively or passively. Most marine invertebrates are osmoconformers, although their ionic composition may be different from that of seawater. Osmoregulators tightly regulate their body osmolarity, maintaining constant internal conditions. They are more common in the animal kingdom. Osmoregulators actively control salt concentrations despite the salt concentrations in the environment. An example is freshwater fish

vi. Complex tissues in plants

The vascular tissues include xylem, which conducts water and minerals from the roots upward and throughout the plant, and phloem, which transports dissolved nutrients in all directions within the plant. The main conducting vessels of xylem are the tracheids and the vessels. Tracheids are long, thin tubes found in most vascular plants, while vessels are large tubes found predominantly in angiosperms. The tracheids and vessels form pipelines that have pores and perforated ends that allow water and minerals to be conducted from one tube to the next and out to the surrounding tissues. Tracheids and vessels also help support the plant body. The main conducting cells of phloem are sieve cells and sieve tube members. Both cell types have numerous pores through which substances are exchanged with adjacent cells. Sieve tube members occur in angiosperms, while sieve cells are found in other vascular plants. In angiosperms, small cells called companion cells assist the sieve tube members in their functions.

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