Q 1 (A). Fill in the Blanks (5) 1. to Provide Energy to Carry out Life Processes

Home , Holozoic nutrition, Saprotrophic nutrition

Exam: F.Y.BSc Semester – I Subject: Life Science Paper – II Date of Exam: 27th November 2017 Question Paper code: 12024

Q 1 (A). Fill in the blanks (5) 1. To provide energy to carry out life processes. 2. Autotropic 3. Nutritional Needs /Fuel for all cellular work/The organic raw materials for biosynthesis/Essential nutrients, substances such as vitamins that the animal cannot make for itself. 4. Glycogen 5. 20

Q 1 (B) Match the Columns (5) A B (1) femur (b) appendicular skeleton (2) Phloem (e) organic solute (3) blood (a) fluid connective tissue (4) Stomata (c) Transpiration (5) Hydra (f) water

Q 1 (C) Define 1. Anaerobic means without air.Sometimes there is not enough oxygen around for animals and plants to respire, but they still need energy to survive. Instead they carry out respiration in the absence of oxygen to produce the energy they require, this is called anaerobic Respiration

2. Urecotelism: Insects,land snails, and many reptiles including birds excrete nitrogenous waste product in the form of uric acid which is insoluble in water ,such organisms are called urecotelic organisms

3. Breathing roots found in plants growing in scanty oxygen levels 4. Book lungs : These are the respiratory organs and are always in pairs. Each comprising of 100-130 leaflets arranged like leaves of the book. They are present in scorpions.

5. Malpigian tubules : these are long ,filamentous, thread like yellow coloured structures attached at the junction of midgut and handgut in cockroach and serves as an excretory organs.

Q 1 (D) True or False 1. False 2. True 3. True 4. False 5. False

Q 2. (a) Answer any one: (10) 1. What is nutrition ? Explain Heterotrophic nutrition using suitable examples? Heterotrophic nutrition is nutrition obtained by digesting organic compounds. Animals, fungi, and protists are unable to synthesize organic compounds to use as food. They are known as heterotrophs. Heterotrophic organisms have to acquire and take in all the organic substances they need to survive. All heterotrophs (except blood and gut parasites) have to convert solid food into soluble compounds capable of being absorbed (digestion). When the soluble products of digestion a of the organism where complex materials (assimilation) are broken down for the release of energy (respiration). All heterotrophs depend on autotrophs for their nutrition. The three main types of heterotrophic nutrition are: Holozoic nutrition: the word holozoic is made from two words- holo= whole and zoikos= animals and literally means animals which eat their food whole. Complex food is taken into a specialist digestive system and broken down into small pieces to be absorbed. This consists of 5 stages, ingestion, digestion, absorption, assimilation and egestion. E.g.: human Saprobiontic /saprotrophic nutrition: Organisms feed on dead organic remains of other organisms. Eg.: decomposers Parasitic nutrition: Organisms obtain food from other living organisms (the host), with the host receiving no benefit from the parasite. When a parasite is present inside the body of the host, it is known as an endoparasite. Generally endoparasites attack and live in an intestine of an organism whereas parasites such as mites and leeches attach themselves to the outside the host’s body. They are known as ectoparasites. They suck and feed on the blood of the host. E.g.: tapeworms Symbiotic nutrition: Certain plants live in close association with other plants for long periods and share and shelter. E.g.: fungi and algae, rizobium and leguminous plants.

2. Explain the types of complex tissues in plants. Complex Tissues: The complex tissues are composed of different types of cells performing diverse functions. These are of two types:- xylem and phloem. (i) Xylem: Structurally, xylem consists of both living and nonliving cells. Xylem consists of four elements: tracheids, vessels, xylem fibers and xylem parenchyma.

Xylem A - Trachieds; B & C - Vessels

Tracheids: Tracheids are elongated or tube-like dead cell with hard, thick and lignified walls. Their ends are tapering, blunt or chisel-like. Their function is conduction of water and providing mechanical support to the plant. Vessels: Vessel is long cylindrical, tube like structure with lignified walls and a wide central lumen. The cells are dead as these do not have protoplast. The cells are arranged in longitudinal series in which the partitioned walls (transverse walls) are perforated, so the entire structure looks-like a water pipe. Their main function is transport of water and minerals. It also provides mechanical strength. Xylem fibers: These cells are elongated, lignified and pointed at both the ends. A xylem fiber helps in conduction of water and nutrients from root to the leaf and provides mechanical support to the plant.

3 Xylem Parenchyma: The cells are living and thin walled. The main function of xylem parenchyma is to store starch and fatty substances. (ii) Phloem: Phloem consists of four types of elements – sieve tubes, companion cells, and phloem parenchyma and phloem fibers.

Structure of Phloem

Sieve tube: These are elongated, tube-like slender cells placed end to end. The transverse walls at the ends are perforated and are known as sieve plates. The main function of sieve tubes is translocation of food, from leaves to the storage organs of the plants. Companion Cells: These are elongated cells attached to the lateral wall of the sieve tubes. These are mostly found in angiosperms. Phloem Parenchyma: The phloem parenchymas are living cells which have cytoplasm and nucleus. Their function is to store food materials. Phloem fibers or bast fibers: Sclerenchymatous cells associated with primary and secondary phloem are commonly called phloem fibers. These cells are elongated, lignified and provide mechanical strength to the plant body.

Q.2 (B) 1. Explain hormonal control of digestion? Hormonal control of digestion Gut hormones have a key role in controlling food intake and energy expenditure. The gut is the body’s largest hormone-producing organ, releasing more than 20 different peptide hormones, some of which target the brain to regulate appetite and influence the pleasure of eating.

Gut hormones The gut hormones work in association with the gut’s extensive nervous system (enteric nervous system) and play a co-ordinating role in the control of appetite, the digestion of food, the regulation of energy balance and the maintenance of blood glucose levels. The gut continuously sends information to the brain regarding the quality and quantity of the food that is consumed.

The role that some of these hormones play is:

Ghrelin is produced in the stomach, and its function is to tell the brain that the body has to be fed. It increases appetite.

Gastrin is produced in the stomach when it is stretched. It stimulates the release of gastric juice rich in pepsin and hydrochloric acid.

Secretin is produced in the duodenum and has the effect of stimulating the pancreas to produce alkaline secretions as well as slowing the emptying of the stomach.

Cholecystokinin (CCK) is produced in the duodenum. It reduces appetite, slows down the emptying of the stomach and stimulates the release of bile from the gall bladder. Peptide YY (PYY) is produced in the last part of the small intestine known as the ileum as well as parts of the large intestine. It plays a role in slowing down the passage of food along the gut, which increases the efficiency of digestion and nutrient absorption after meal.

Glucagon-like peptide 1 (GLP-1) is produced in the small intestine and colon and has multiple actions including inhibition of gastric emptying and appetite as well as the stimulation of insulin release.

2. What are insectivorous plants? Explain how they are adapted for the process of digestion. Insectivorous plants are plants that derive some of their nutrients from trapping and consumiing animals or protozoan. The benefit they derive from their catch varies considerably; in some species it might include a small part of their nutrient intake and in others it might be an indispensable source of nutrients. As a rule, however, such animal food, however valuable it might be as a source of certain critically important minerals, is not the plants' major source of energy, which they generally derive mainly from photosynthesis. Insectivorous plants might consume insects and other animal material trapped adventitiously, though most species to which such food represents an important part of their intake are specifically, often spectacularly, adapted to attract and secure adequate supplies. Their prey animals typically but not exclusively, comprise insects and other arthropods. Plants highly adapted to reliance on animal food use a variety of mechanisms to secure their prey, such as pitfalls, sticky surfaces, hair-trigger snaps, bladder-traps, entangling furriness, and lobster- pot trap mechanisms. Also known as carnivorous plants, they appear adapted to grow in places where the soil is thin or poor in nutrients, especially nitrogen, such as acidic bogs and rock outcroppings. Insectivorous plants include the Venus fly trap, several types of pitcher plants, butterworths, sundews, bladderworts, etc. They exploit the prey organisms mainly in a mutualistic relationship with other creatures, such as resident organisms that contribute to the digestion of prey. In particular animal prey organisms supply carnivorous plants with nitrogen, but they also are important sources of various 6 other soluble minerals, such as potassium and trace elements that are in short supply in environments where the plants flourish. This gives them a decisive advantage over other plants, whereas in nutrient-rich soils they tend to be out- competed by plants adapted to aggressive growth where nutrient supplies are not the major constraints. Technically these plants are not strictly insectivorous, as they consume any animal that they can secure and consume; the distinction is trivial, however, because not many primarily insectivorous organisms exclusively consume insects. Most of those that do have such a restrictive diet, such as certain parasitoids and hunting wasps are specialised to exploit particular species, not insects in general.

3. Distinguish between photosynthetic and chemosynthetic bacteria.

All living organisms obtain their energy in two different ways. The means by which organisms obtain their energy depends on the source from which they derive that energy. Some organisms obtain their energy from the sun by the process of photosynthesis. These organisms are known as phototrophs because they can make their own organic molecules using sunlight as a source of energy. Among the organisms that can use sunlight as a source of energy include plants, algae and some species of bacteria. The organic molecules produced by phototrophs are used by other organisms known as heterotrophs, which derive their energy from phototrophs, that is to say, they use the energy from the sun, indirectly, by feeding on them, producing the organic compounds for their subsistence. Heterotrophs include animals, humans, fungi, and some species of bacteria, such as those found in the human intestines. Chemosynthetic Bacteria Chemosynthetic bacteria are organisms that use inorganic molecules as a source of energy and convert them into organic substances. Chemosynthetic bacteria, unlike plants, obtain their energy from the oxidation of inorganic molecules, rather than photosynthesis. Chemosynthetic bacteria use inorganic molecules, such as ammonia, molecular hydrogen, sulfur, hydrogen sulfide and ferrous iron, to produce the organic compounds needed for their subsistence. Most chemosynthetic bacteria live in environments where sunlight is unable to penetrate and which are considered inhospitable to most known organisms. Chemosynthetic bacteria usually thrive in remote environments, including the Arctic and Antarctic polar regions, where they can be found deep into the ice; they are also

7 found many miles deep in the ocean where sunlight is unable to infiltrate or several meters deep into the Earth’s crust. Chemosynthetic bacteria are chemoautotrophs because they’re able to use the energy stored in inorganic molecules and convert them in organic compounds. They're primary producers because they produce their own food. An organism that produces organic molecules from organic carbon is classified as a chemoheterotroph. Chemoheterotrophs are at the second level in a food chain.

Chemosynthetic Bacteria are commonly found in Hydrothermal Vents Hydrothermal vents are fissures in the deep ocean crust where super-heated lava and magma seep, releasing dissolved chemicals when coming in contact with the deep ocean’s cold water and are located very deep into the ocean where sunlight is unable to penetrate; therefore, the organisms that live at hydrothermal vents obtain their energy from the chemicals ejected out from the ocean crust.

Ecosystems depend upon the ability of some organisms to convert inorganic compounds into food that other organisms can then exploit (or eat!). In most cases, primary food production occurs in a process called photosynthesis, which is powered by sunlight. In a few environments, primary production happens though a process called chemosynthesis, which runs on chemical energy. Together, photosynthesis and chemosynthesis fuel all life on Earth.

Photosynthesis occurs in plants and some bacteria, wherever there is sufficient sunlight – on land, in shallow water, even inside and below clear ice. All photosynthetic organisms use solar energy to turn carbon dioxide and water into sugar and oxygen. There is only one photosynthetic formula: CO2 + 6H2O -> C6H12O6 + 6O2.

Chemosynthesis is the use of energy released by inorganic chemical reactions to produce food. Chemosynthesis is at the heart of deep-sea communities, sustaining life in absolute darkness, where sunlight does not penetrate. All chemosynthetic organisms use the energy released by chemical reactions to make a sugar, but different species use different pathways.

4. Using a flow chart classify animal tissues and explain any two in detail.

Epithelial There are three principal cell shapes associated with epithelial cells; Squamous , cuboidal and columnar. There are three ways of describing the layering of epithelium: simple, stratified, and pseudostratified. Pseudostratified epithelium possesses fine hair-like extensions called cilia and unicellular glands called goblet cells that secrete mucus. This epithelium is described as ciliated pseudostratified epithelium.

Stratified epithelium differs from simple epithelium in that it is multilayered. It is therefore found where body linings have to withstand mechanical or chemical injury. In Keratinised epithelia, the most apical layers (exterior) of cells are dead and contain a tough, resistant protein called keratin. An example of this is found in mammalian skin that makes the epithelium waterproof.

Transitional epithelia are found in tissues such as the urinary bladder where there is a change in the shape of the cell due to stretching.

Connective Tissue

Connective tissue is divided into four main categories:

Connective proper

Cartilage

Bone

Blood

Connective tissue proper has two subclasses: loose and dense. Loose connective tissue is divided into 1) areolar, 2) adipose, 3) reticular. Dense connective tissue is divided into 1) dense regular, 2) dense irregular, 3) elastic.

Areolar Connective Tissue

These tissues are widely distributed and serve as a universal packing material between other tissues. The functions of areolar connective tissue include the support and binding of other tissues.

Adipose Tissue or Body Fat

This is loose connective tissue composed of adipocytes. It is technically composed of roughly only 80% fat. Its main role is to store energy in the form of lipids, although it also cushions and insulates the body.

10 The two types of adipose tissue are white adipose tissue (WAT) and brown adipose tissue (BAT). Adipose tissue is found in specific locations, referred to as adipose depots.

Reticular Connective Tissue

This tissue resembles areolar connective tissue, but the only fibres in its matrix are the reticular fibres, which form a delicate network. The reticular tissue is limited to certain sites in the body, such as internal frameworks that can support lymph nodes, spleen, and bone marrow.

Dense Regular Connective Tissue

This consists of closely packed bundles of collagen fibers running in the same direction. These collagen fibers are slightly wavy and can stretch a little bit. With the tensile strength of collagen, this tissue forms tendons and ligaments. This tissue forms the fascia, which is a fibrous membrane that wraps around the muscles, blood vessels, and nerves.

Dense Irregular Tissue

This has the same structural elements as dense regular tissue, but the bundles of collagen fibers are much thicker and arranged irregularly. This tissue is found in areas where tension is exerted from many different directions. It is part of the skin dermis area and in the joint capsules of the limbs.

Elastic Connective Tissue

The main fibers that form this tissue are elastic in nature. These fibers allow the tissues to recoil after stretching. This is especially seen in the arterial blood vessels and walls of the bronchial tubes.

Cartilage

This is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes, and the intervertebral discs.

Cartilage is composed of specialized cells called chondroblasts and, unlike other connective tissues, cartilage does not contain blood vessels. Cartilage is classified in three types: 1) elastic cartilage, 2) hyaline cartilage, and 3) fibrocartilage, which differ in the relative amounts of these three main components. 11

Elastic Cartilage

This is similar to hyaline cartilage but is more elastic in nature. Its function is to maintain the shape of the structure while allowing flexibility. It is found in the external ear (known as an auricle) and in the epiglottis.

Hyaline Cartilage

This is the most abundant of all cartilage in the body. Its matrix appears transparent or glassy when viewed under a microscope. It provides strong support while providing pads for shock absorption. It is a major part of the embryonic skeleton, the costal cartilages of the ribs, and the cartilage of the nose, trachea, and larynx.

Fibrocartilage

This is a blend of hyaline cartilage and dense regular connective tissue. Because it is compressible and resists tension well, fibrocartilage is found where strong support and the ability to withstand heavy pressure are required. It is found in the intervertebral discs of the bony vertebra and knee meniscus.

Bone tissue is also called the osseous tissue. The osseous tissue is relatively hard and lightweight in nature. It is mostly formed of calcium phosphate, which gives bones their rigidity. It has relatively high compressive strength, but poor tensile strength, and very low shear stress strength.

The hard outer layer of bones is composed of compact bone tissue, so-called due to its minimal gaps and spaces. Its porosity is 5–30%. This tissue gives bones their smooth, white, and solid appearance, and accounts for 80% of the total bone mass of an adult skeleton.

Blood

This is considered a specialized form of connective tissue. Blood is a bodily fluid in animals that delivers necessary substances, such as nutrients and oxygen, to the cells and transports metabolic waste products away from those same cells.

It is an atypical connective tissue since it does not bind, connect, or network with any body cells. It is made up of blood cells and is surrounded by a nonliving fluid called plasma.

Connective Tissues

Muscle

There are three kinds of muscle tissue: skeletal, smooth, and cardiac.

Skeletal is striated, multinucleate, and involuntary.

Smooth is spindle shaped, non-striated, and involuntary.

Cardiac is striated, has intercalated discs, and is involuntary.

Skeletal Muscle

Skeletal muscles are highly organized with cells lying parallel to each other. Skeletal muscles are voluntary and striated in nature that allows movement oof an organism by the deliberate generation of force.

Skeletal muscle fibers are the longest muscle fibers and have stripes on their surface. These stripes are called striations. These muscle fibers are cylindrical, multinucleate in nature. Their function is to produce locomotion that is voluntary in nature. They are also responsible for many facial expressions.

The skeletal muscle striations are large enough to align the nuclei to the sides of the fibers, which are known as peripherally located nuclei. The banding pattern of the striations reflects the alignment of the myofilament fibers. Skeletal muscle is striated, multinucleate, and involuntary.

Smooth Muscle

Smooth muscle is named because it does not have any striations. The individual smooth muscle fibers are spindle shaped and contain a centrally located nucleus.

13 Smooth muscle is found in the walls of the hollow organs. As an involuntary muscle, it propels substances along the internal passageways. By alternating contraction and relaxation, it helps in the movement of food substances, urine, blood, and at the time of birth.

Cardiac Muscle

Cardiac muscle is found in the walls of the heart. Although cardiac muscle is involuntary in nature, it is structurally different from smooth muscle. It is generally uninucleate, but is striated.

The striations are fitted together with unique junctions called intercalated disks, specialized junctions that help in the transmission of electricaal impulses so the heart can beat in a steady rhythm.

The involuntary contraction of cardiac muscle is coordinated by the intercalated disks, so the entire heart beats in a controlled, uniform manner, ensuring that blood is efficiently pumped from the chambers.

Nervous

Nervous tissue is composed of neurons and supporting cells called neuroglia, or "glial Cells"

There are six types of neuroglia. Four are found in the Central Nervous system, while two are found in the peripheral. 14 The four types of neuroglia found in the central nervous system are astrocytes, , microglial cells, ependymal cells, and oligodendrocytes.

The two types of neuroglia found in the peripheral nervous system are satellite cells and Schwann Cells.

Neurons are the other the other type of cell that comprise nervous tissue. Neurons have cell bodies, dendrites, and axons.

Q.3 A 1. Distinguish between axial and appendicular skeleton • A vertebrate endoskeleton is divided into an axial and an appendiculaar skeleton.

• The axial skeleton’s bones form the axis of the body and support and protect the organs of the head, neck, and chest.

• The appendicular skeleton’s bones include the bones of the limbs, and the pectoral and pelvic girdles that attach them to the axial skeleton.

• The bones of the skeletal system support and protect the body, and serve as levers for the forces produced by contraction of skeletal muscles.

• Blood cells form within the bone marrow, and the calcified matrix of bones acts as a reservoir fofor calcium and phosphate ions.

15 On the basis of the position of the skeletal structures in the body the endoskeleton is divisible into two parts.

1. Axial skeleton:

It consists of bones that lie around the axis: skull, vertebral column, sternum(breast bone) ,Hyoid bone (U-shaped bone in the neck which supports the tongue)and ribs.

2. Appendicular skeleton: It is situated at the lateral sides which actually extend outwards from the principal axis. It consists of free appendages, which are the upper and lowerlimbs,pectoral and pelvic girdles that connect the limbs to the axial skeleton.

2. Explain the role of proton pumps in plants

17 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 intercellular 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

18 protein then rotates and releases the molecule inside the cell, e.g., water channels – made up of eight different types of aquaporins.

Passive symports annd 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 prroteins 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.

20 Q 3 (B) 1. Explain circulation in hydra Animals without a circulatory system: eg hydra

• 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 (figure a). • 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

2. Give the role of Excersice in cardiac health Effects of diet and exercise on the Cardiac health 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.

3. What is upward translocation of solutes in plants? Explain PHLOEM TRANSPORT: FLOW FROM SOURCE TO SINK Food, primarily sucrose, is transported by the vascular tissue phloem from a source to a sink. Usually the source is understood to be that part of the plant which synthesises the food, i.e., the leaf, and sink, the part that needs or stores the food. But, the source and sink may be reversed depending on the season, or the plant’s needs. Sugar stored in roots may be mobilised to become a source of food in the early spring when the buds of trees, act as sink; they need energy for growth and development of the photosynthetic apparatus. Since the source-sink relationship is variable, the direction of movement in the phloem can be upwards or downwards, i.e., bi-directional. This contrasts with that of the xylem where the movement is always unidirectional, i.e., upwards. Hence, unlike one-way flow of water in transpiration, food in phloem sap can be transported in any required direction so long as there is a source of sugar and a sink able to use, store or remove the sugar. Phloem sap is mainly water and sucrose, but other sugars, hormones and amino acids are also transported or translocated through phloem The Pressure Flow or Mass Flow Hypothesis The accepted mechanism used for the translocation of sugars from source to sink is called the pressure flow hypothesis. (see Figure 11.10). As glucose is prepared at the source (by photosynthesis) it is converted to sucrose (a dissacharide). The sugar is then moved in the form of sucrose into the companion cells and then into the living phloem sieve tube cells by active transport. This process of loading at the source produces a hypertonic condition in the phloem. Water in the adjacent xylem moves into the phloem by osmosis. As osmotic pressure builds up the phloem sap will move to areas of lower pressure. At the sink osmotic pressure must be reduced. Again active transport is necessary to move the sucrose out of the phloem sap and into the cells which will use the sugar – converting it into energy, starch, or cellulose. As sugars are removed, the osmotic pressure decreases and water moves out of the phloem. To summarise, the movement of sugars in the phloem begins at the source, where sugars are loaded (actively 22 transported) into a sieve tube. Loading of the phloem sets up a water potential gradient that facilitates the mass movement in the phloem. Phloem tissue is composed of sieve tube cells, which form long columns with holes in their end walls called sieve plates. Cytoplasmic strands pass through the holes in the sieve plates, so forming continuous filaments. As hydrostatic pressure in the phloem sieve tube increases, pressure flow begins, and the sap moves through the phloem. Meanwhile, at the sink, incoming sugars are actively transported out of the phloem and removed

4. Explain locomotion in Earthworm? . Locomotion in earthworms 1. Hydrostatic skeletons are found primarily in soft-bodied terrestrial invertebrates, such as earthworms and slugs, and soft-bodied aquatic invertebrates, such as jellyfish, and squids. 2. In these animals a fluid-filled central cavity is encompassed by two sets of muscles in the body wall: circular muscles that are repeated in segments and run the length of the body, and longitudinal muscles that oppose the action of the circular muscles

3. Muscles act on the fluid in the body’s central space, which represents the hydrostatic skeleton.

4. As locomotion begins the anterior circular muscles contract, pressing on the inner fluid, and forcing the front of the body to become thin as the body wall in this region extends forward.

5. On the underside of a worm’s body are short, bristle-like structures called chaetae.

6. When circular muscles act, the chaetae of that region are pulled up close to the body and lose contact with the ground.

7. Circular-muscle activity is passed backward, segment by segment, to create a backward wave of contraction.

8. As this wave continues, the anterior circular muscles now relax, and the longitudinal muscles take over, thickening the front end of the worm and allowing the chaetae to protrude and regain contact with the ground.

9. The chaetae now prevent that body section from slipping backward.

10. This locomotion process proceeds as waves of circular muscle contraction arefollowed by waves of longitudinal muscle effects

Locomotion in earthworms: The hydrostatic skeleton of the earthworm uses muscles to move fluid within the segmented body cavity, changing the shape of the animal. When circular muscles contract the pressure in the fluid rises. At the same time the longitudinal muscles relax, and the body becomes longer and thinner. When the longitudinal muscles contract and the circular muscles relax, the chaetae of the worm’s lower surface extend to prevent backsliding. A wave of circular followed by longitudinal muscle contractions down the body produces forward movement.

Q .4 (A)

1. Give a comparative account of the respiratory organs of lower animals

Gas exchange in small animals (across surface) and cutaneous respiration in frogs,Gaseous exchange in invertebrates – trachea in insects, boook lungs in scorpion

2. Define Osmoregulation and give the structure and the role of kidney in humans?

Osmoregulation means the phhysiological processes that an organism uses to maintain water baalance; that is, to compensate fofor water loss, avoid excess water gain, annd maintain the proper osmotic concentration (osmolarity) of the body fluids.

● Our excretory system consists of kidneys, blood vessels that join them, ureters, urinary bladder and urethra.

● They help produce and excrete urine.

24 ● There are two beean-shaped kidneys that lie in the abdominal cavity

● 10 cm long and weighs about 150 g

● The kidneys produce s urine to filter out the waste products, like urea and uric acid, from the blood.

● A renal artery brings blood into the kidney, along with nitrogenous waste materials.

● After filtration in the kidney, the purified blood leaves the kidney through a renal vein.

● Urine leaves each kidney through a tube called ureters.

● Thee ureters from both the kidneys are connected to the urinary bladder that collects and stores urine.

● The urethra is a canal that carries urine from the bladder and expels it outside the body.

● Each kidney is enclosed in a thin, fibrous covering called the capsule

● The mammalian kidney has two distinct regions: an outer renal cortex and an inner renal medulla

● The hollow space from where the ureter leaves the kidney is called the pelvis

● Each kidney is made up of numerous (about one million) coiled excretory tubules, known as nephrons,and collecting ducts associated with tiny blood vessels.

(B)

1. Explain the difference between aerobic and anaerobic respiration

25 ● Aerobic means “with air”. This type of respiration needs oxygen for it to occur so it is called aerobic respiration. The word equation for aerobic respiration is:

● Glucose + Oxygen ———-> Carbon dioxide + Water + Energy

● In the above equations we see that glucose is broken down by oxygen to release energy with carbon dioxide and water being produced as by-products of the reaction.

● Approximately 2900 kJ of energy is released when one mole of glucose is broken down. The released energy is used to make a special energy molecule called Adenosine triphosphate (ATP). ATP is where the energy is stored for use later on by the body.

● Aerobic respiration occurs in plants as well as animals.

● Anaerobic means without air.Sometimes there is not enough oxygen around for animals and plants to respire, but they still need energy to survive.

● Instead they carry out respiration in the absence of oxygen to produce the energy they require, this is called anaerobic respiration.

2. Explain ultrafiltration and selective reabsorption

● UltraFiltration of blood occurs under high pressure in the nephrons of the kidney. Blood enters the glomerulus through the afferent arteriole (with a wider lumen) and leaves through the efferent arteriole (with a narrow lumen). Therefore, blood passes through the glomerulus under pressure. This results in filtration of blood.

● Water and small molecules are forced out of the walls of the capillaries of the glomerulus and Bowman’s capsule and enter the tubule of the nephron. Large molecules remain in the blood of the glomerulus. The filtrate contains water, glucose, salts, urea, vitamins, etc. It is called the glomerular filtrate.

● Some molecules of the glomerular filtrate are selectively reabsorbed into the blood.

● It contains many useful substances such as glucose, amino acids and salts.

● These are reabsorbed by a process, which requires energy. Without reabsorption, these nutrients could have been lost with the urine. The filtrate now contains urea, some salts and water. Reabsorption of solutes into the blood increases the water concentration of the filtrate(hypo).

● Then water is reabsorbed into the blood by the process of osmosis, and the osmotic balance is restored. The amount of water reabsorbed depends on the amount of excess water in the body and that of the dissolved waste to be excreted.

● This reabsorption of water from the filtrate to maintain the water balance of the body fluid is known as osmoregulation. In this way the kidneys serve as water-conserving organs. After reabsorption from 180 L of filtrate in the kidney, only 1-2 L of urine is produced.

3. Explain the role of book lungs in scorpio

The book lungs are respiratory organs and are always in pair.

Each book lung is comprised of numerous (100-130) leaflets arranged like leaves of the book.

Each leaflet is divided into compartments –

1. blood spaces through partitions of blood vessels.

2. The leaflets are separated from each other through air spaces.

The leaflets remain enclosed in a closed chamber, which is divided byy the leaflets into an upper pulmonary chamber and a lower atrial chamber. The atrial chamber communicaates outside through stigmata or stigma. Air enterrs the atrial chamber through stigma and afteer aerating the leaflets goes out through pulmonary chamber. Thus, oxygenation of blood takes place.

4. Write a note on cutaneous respiration in frogs

The skin of many frogs is thin and highly vascular to allow for gas exchange. Because of their thin skin, frogs must live in moist environments and secrete mucous from their skin to avoid desiccation. Cutaneous respiration also allows for the frog to remain almost completely submerged under water for long periods of time, while still oxygenating their blood. Frogs use their entire outer skin as a respiratory surface.

Q.5 1. Explain the process of digestion in a ruminant stomach. Ruminants are mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. The process typically requires the fermented ingesta (known as cud) to be regurgitated and chewed again. The process of rechewing the cud to further break down plant matter and stimulate digestion is called rumination. The word "ruminant" comes from the Latin ruminare, which means "to chew over again". Rumination is a specialized digestion process found in most hoofed mammals with an even number of toes-such as cattle, sheep, goats, deer, antelope, camels, buffalo, giraffes, etc. All of these plant-eating animals lack the enzyme cellulase, which is capable of breaking down the tough cellulose in plant cell walls. The stomach of these grazing herbivores consists of four chambers—the rumen, the reticulum, the omasum, and the abomasum—each playing different roles in the digestion process. The ruminant animal swallows its food rapidly without chewing, and later regurgitates it (brings it back up into the mouth), then masticates it (chews), and finally re-swallows it. When grazing, ruminants swallow their food rapidly, they send large amounts into the largest chamber of the stomach, the rumen, where it is stored and partly digested before regurgitation and chewing when the animal is resting. Rumination is an adaption by which herbivores can spend as little time as possible feeding (when they are most vulnerable to predation) and then later digest their food in safer surroundings. Muscular contractions of the stomach move food back and forth between the rumen and the second stomach chamber, the reticulum, which is often called the honeycomb due to the complex appearance of its inner lining. Bacteria and microorganisms in the rumen (which can digest cellulose) begin the digestion of the plant fibers. Fine fibers are broken down, so providing protein, vitamins, and organic acids which are then absorbed into the bloodstream of the animal. Coarser plant fibers are passed from the rumen to the reticulum, where further bacterial

28 fermentation takes place, and the food is formed into soft chunks called the cud. The cud is regurgitated and ground thoroughly between the molars with an almost circular motion of the lower jaw. During the chewing process, called chewing the cud, copious quantities of highly alkaline saliva aid in breaking down the fibers, and the food is re-swallowed, this time bypassing the rumen and entering the smallest chamber, the omasum, or thirrd stomach. Here, water and essential acids are reabsorbed. It is the third stomach of a bullock which is eaten as tripe. Muscular contraction by the walls of the omasum mashes and compacts the food still further, passing it directly into the fourth stomach, the abomasum, where gastric secretions further digest the foood before it moves into the intestine. Large amounts of two gases, carbon dioxide and methane, form during bacterial fermentation in the first two chambers—the reticulorumen. Here, frothing occurs as part of the digestive process. Often, however, excessive frothhing caused by certain foods traps gas normally eliminated by belching, and bloating occurs. Certain cows are particularly susceptible to this, and farmers often lose animals unless these gases are released. Anti-foaming medications sometimes help, as does an invasive procedure that punctures the stomach wall and allows gases to escape. The methane produced by the digestive systems of the billions of domestic ruminants in the world is considered by some to be a major factoor in the destruction of the ozone layer in the upper atmmosphere.

Ruminant Stomach of Cow

2. Explain the process of nitrogeen fixation.

29 Nitrogen fixation is a process in which nitrogen (N2) in the Earth's atmosphere is converted into ammonia. Atmospheric nitrogen is relatively inert: it does not easily react with other chemicals to form new compounds. The fixation process frees nitrogen atoms from their triply bonded diatomic form N≡N, to be used in other ways. Nitrogen fixation, is essential for all forms of life because nitrogen is required to synthesize the basic building blocks of plants, animals and other life forms, e.g., nucleotides for DNA and RNA, the coenzyme nicotinamide adinine dinucleotide for its role in metabolism (transferring electrons between molecules), and amino acids for proteins. Also as part of the nitrogen cycle, it is essential for agriculture and is also useful in the manufacture of fertilizers. It is also an important process in the manufacture of explosives, e.g. - gunpowder, dynamite etc. Nitrogen fixation occurs naturally in the soil by nitrogen fixing bacteria associated with some plants (for example, Azobacter and legumes). Some nitrogen- fixing bacteria have very close relationships with plants, referred to as symbiotic nitrogen fixation. Some relationships between nitrogen-fixing bacteria and plants are often referred to as associative or non-symbiotic, as seen in nitrogen fixation occurring on rice roots. It also occurs naturally in the air by means of lightening. All biological nitrogen fixation is done by way of nitrogenase enzymes which contain iron, molybdeum or vanadium. Microorganisms that can fix nitrogen are prokaryotes like bacteria and archae.

3. Explain what do you understand by ascent of sap We know that the roots absorb most of the water that goes into plants; obviously that is why we apply water to the soil and not on the leaves. The responsibility of absorption of water and minerals is more specifically the function of the root hairs that are present in millions at the tips of the roots. Root hairs are thin-walled slender extensions of root epidermal cells that greatly increase the surface area for absorption. Water is absorbed along with mineral solutes, by the root hairs, purely by diffusion. Once water is absorbed by the root hairs, it can move deeper into root layers by two distinct pathways: • apoplast pathway • symplast pathway

The apoplast is the system of adjacent cell walls that is continuous throughout the plant, except at the casparian strips of the endodermis in the roots (Figure 11.6). The apoplastic movement of water occurs exclusively through the intercellular spaces and the walls of the cells. Movement through the apoplast does not involve crossing the cell membrane. This movement is dependent on the gradient. The apoplast does not provide any barrier to water movement and water movement is through mass flow. As

30 water evaporates into the intercellular spaces or atmosphere, tension develop in continuous stream of water in the apoplast, hence mass flow of water occurs due to the adhesive and cohesive properties of water. The symplastic system is the system of interconnected protoplasts. Neighbouring cells are connected through cytoplasmic strands that extend through plasmodesmata. During symplastic movement, the water travels through the cells – their cytoplasm; intercellular movement is through the plasmodesmata. Water has to enter the cells through the cell membrane, hence the movement is relatively slower. Movement is again down a potential gradient. Symplastic movement may be aided by cytoplasmic streaming. You may have observed cytoplasmic streaming in cells of the Hydrilla leaf; the movement of chloroplast due to streaming is easily visible. Most of the water flow in the roots occurs via the apoplast since the cortical cells are loosely packed, and hence offer no resistance to water movement. However, the inner boundary of the cortex, the endodermis, is impervious to water because of a band of suberised matrix called the casparian strip. Water molecules are unable to penetrate the layer, so they are directed to wall regions that are not suberised, into the cells proper through the membranes. The water then moves through the symplast and again crosses a membrane to reach the cells of the xylem. The movement of water through the root layers is ultimately symplastic in the endodermis. This is the only way water and other solutes can enter the vascular cylinder. Once inside the xylem, water is again free to move between cells as well as through them. In young roots, water enters directly into the xylem vessels and/or tracheids. These are non-living conduits and so are parts of the apoplast. The path of water and mineral ions into the root vascular system is summarised .Some plants have additional structures associated with them that help in water (and mineral) absorption. A mycorrhiza is a symbiotic association of a fungus with a root system. The fungal filaments form a network around the young root or they penetrate the root cells. The hyphae have a very large surface area that absorb mineral ions and water from the soil from a much larger volume of soil that perhaps a root cannot do. The fungus provides minerals and water to the roots, in turn the roots provide sugars and N-containing compounds to the mycorrhizae. Some plants have an obligate association with the mycorrhizae. For example, Pinus seeds cannot germinate and establish without the presence of mycorrhizae.

4. Explain the role of root epidermis The apoplast is the system of adjacent cell walls that is continuous throughout the plant, except at the casparian strips of the endodermis in the roots. The apoplastic movement of water occurs exclusively through the intercellular spaces and the walls

31 of the cells. Movement through the apoplast does not involve crossing the cell membrane. This movement is dependent on the gradient.

5. Write a note on gaseous balance

6. Explain water and salt regulation under normal and stressed condition in plants. 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 annd 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 wateer wheneveer it is available typically in stems or leaves. They have to salt injury.

32 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

CHARACTERISTICS ADAPTATIONS OF XEROPHYTES: a.Roots: Root system is very well developed with extensive branching and often longer than shoot system. Root hairs and root caps are very well developed. b.Stems: Mostly they are stunted, woody hard and covered with thick bark. In somexerophytes stem becomes underground. In some plants stem becomes fleshy, green, leaf-like phylloclades covered with spines, Eg: Opuntia. Stems are usually covered by hairs some xerophytes have tiny hairs on their surface to provide a wind break and trap a layer of moisture hence reduce air flow thereby reducing the rate of evaporation. Stems usually have waxy coatings which may serve to reflect sunlight and reduce evaporation. c.Leaves: Leaves are very much reduced small scale like and sometimes modified in to spines to reduce the rate of transpiration. Lamina may be long narrow needle-like or divided into many leaflets as Eg: Acacia. Leaf surfaces are shiny glazed to reflect light and heat. Stomata are generally confined to lower epidermis of leaves called hypostomatous or Stomata are present in pits called sunken stomata. They are lined with hairs d. Molecular level adaptations: The stressed plants exhibit striking responses by producing plant hormone abscisic acid (ABA), which plays an important role in tolerance against drought. Abscisic acid can induce the expression of stress relieving genes. Presence of hydrophilic substances in the protoplasm like high molecular weight proteins, some carbohydrates (e.g., alginic acid).

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

33 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.

CHARACTERISTICS ADAPTATIONS OF HALOPHYTES:

Halophyte group of plants can survive high saline conditions and continue to thrive by maintaining their internal osmotic status.

In addition to the accumulation of osmo- protectant compounds, a large set of plant genes are expressed and accumulate new set of proteins under salt-stressed-condition. Eg Osmotin , Proline for ensuring endosmosis.

Some halophytes excrete salt with the help of specialized glands on their leaf surfaces.

Accumulation of sodium in different parts of the plant body is a highly selective process in most of the plants. Accumulation is highly preferred in older leaves than accommodating in younger sensitive meristem tissues. Transportation of sodium into the vacuole requires input of energy and is executed against concentration gradient.