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18401.

Question : Describe the digestive system of cockroach.

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Solution :
1. The digestive system of cockroach consists of the alimentary canal and digestive glands.
2. The alimentary canal is present in the body cavity and is divided into three regions: foregut, midgut and hindgut.
3. The foregut includes pre-oral cavity, mouth, pharynx and oesophagus. This in turn opens into a sac like structure called the crop.which is used for storing food.
4. The crop is followed by the gizzard or proventriculus which has an OUTER layer of thick circular muscles and thick inner cuticle forming six highly chitinous plates called "teeth". Gizzard helps in the grinding of the food particles.
5. The midgut is a short and narrow tube behind the gizzard and is glandular in nature.
6. At the junctional region of the gizzard are eight fingers like tubular blind processes called the hapatic caecae or enteric caecae.
7. The hindgut is marked by the presence of 100 -150 yellow coloured thin filamentous malphigian tubules which are helpful in removal of the excretory PRODUCTS from the haemolymph. The hindgut is broader than the midgut and is differentiated into ileum, COLON, and rectum. The rectum opens out through the anus.
8. Digestive glands of cockroach consist of the salivary glands, the glandular cells and hepatic caecae. A pair of salivary glands is found on EITHER side of the crop in the thorax. The glandular cells of the midgut and hepatic or gastric caecae produce digestive juices.
Discussion
18402.

Question : Describe the digestive role of chymotrypsin. Which two other digestive enzymes of the same category are secreted by its source gland ?

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SOLUTION :CHYMOTRYPSIN CONVERTS protein peptones and PROTEASES into dipeptide.
Trypsinogen, procarboxy PEPTIDASE are other enzymes of that series.
Discussion
18403.

Question : Describe the digestive role of chymotrypsin.

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Solution :Chymotrypsin is a proteolytic enzyme PRESENT in PANCREATIC JUICE of pancreas. It hydrolyses the proteoses and peptones into PEPTIDES. Peptones and proteoses `OVERSET("Chymotrypsin")to` Peptides
Discussion
18404.

Question : Describe the digestion of fats in the human alimentary canal.

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Discussion
18405.

Question : Describe the concept of Phytochrome.

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Solution :PHYTOCHROME is a bluish biliprotein pigment responsible for the perception of light in photo physiological process. Butler et al., (1959) named this pigment and it exists in two interconvertible forms: (i) red light absorbing pigment which is designated as `P_r`and (ii) far red light absorbing pigment which is designated as `P_(fr)` The `P_r`form absorbs red light in 660 nm and changes to` P_r`. The `P_r`form absorbs far red light in 730 nm and changes to `P_r` . The` P_r`form is biologically inactive and it is stable whereas `P_(fr)`form is biologically active and it is very unstable. In short day plants, `P_r`promotes flowering and Pr inhibits the flowering whereas in long day plants flowering is promoted by `P_(fr)`and INHIBITED by` P_r`form. `P_(fr)`is always associated with hydrophobic area of membrane systems while `P_r`is found in diffused STATE in the cytoplasm. The interconversion of the two forms of phytochrome is mainly involved in flower induction and also additionally plays a role in seed germination and changes in membrane CONFORMATION.
Discussion
18406.

Question : What are non-competitive inhibitors?

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Solution :Competitive Inhibitor: Molecules that resemble the shape of the substrate and may compete to occupy the active site of ENZYME are known as competitive inhibitors. For example : the enzyme that CATALYSES the reaction between carbon dioxide and the `CO_(2)` acceptor molecule in photosynthesis, known as ribulose biphosphate carboxylase oxygenase (RUBISCO) is competitively inhibited by oxygen/carbon-di-oxide in the chloroplast. the competitive inhibitor is malonate for succinic dehydrogenase.

Non-competitive Inhibitors: There are certain inhibitors which may unlike the substrate molecule but still combines with the enzyme. this either blocks the attachment of the substrate to active site or change the shape so that it is unable to accept the substrate. for example the effect of the amino acids alanine on the enzyme pyruvate kinase in the final step of GLYCOLYSIS. Certain non-reversible/irreversible inhibitors bind tightly and PERMANENTLY to an enzyme and destroy its catalytic properties entirely. these could also be termed as poisons. example-cyanide ions which blocks cytochrome oxidase in terminal oxidation in cell aerobic respiration, the nerve gas sarin blocks a neurotransmitter in synapse transmission.
Discussion
18407.

Question : Describe the characteristic features of kingdom protista.

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Solution :All single celled eukaryotes are placed under Protista, but the boundaries of this kingdom are not well defined.
Habitat : MEMBERS of Protista are primarily aquatic.
This kingdom forms a link with the others dealing with plants, animals and fungi.
Structure : Being eukaryotes, the protistan cell body contains a well defined nucleus and other membrane - bound organelles.
Some have flagella or CILIA.
Reproduction : Protists reproduce asexually and sexually by a PROCESS involving cell fusion and zygote formations.
Member of Protista : Chrysophytes Dinoflagellates, EUGLENOIDS, Slime moulds and Protozoans are under protista.
Discussion
18408.

Question :Describe the changes and various phase seen during Meiosis - II with diagram.

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Solution :Meiosis II takes place in four SUB phase.
Meiosis II resembles a normal mitosis. The nuclear of chromosomes is maintained in its sub phase / stages :
(i) Prophase - II (ii) Metaphase - II (iii) Anaphase - II (iv) TELOPHASE - II are seen.
(i) Prophase-II: Meiosis-II is initiated immediately after cytokinesis. The nuclear membrane disappears by the end of prophase-II. The chromosomes again become compact.
(ii) Metaphase - II : The chromosomes align at the equator and microtubules from opposite of the spindle get attached to the kinetochores of sister chromatids.
(iii) Anaphase - II : It begins with the simultaneous SPLITTING of the centromere of each chromosome (which was HOLDING the sister chromatids TOGETHER) allowing them to move toward poles of the cell.
(iv) Telophase - II : Meiosis ends with telophase - II, in which the two groups of chromosomes once again get enclosed by a nuclear envelope. Cytokinesis follows resulting in the formation of tetrad of cells i.e., four haploid daughter cells.
Discussion
18409.

Question : Describe the changes occurring during synthesis phase.

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Solution :During this phase synthesis of DNA and replication of DNA take place and amount of DNA per cell doubles.
If the INITIAL amount of DNA is denoted as 2C then it increases to 4C. However, there is no increase in the chromosome number.
If the cell had diploid or 2n number of chromosomes at G, phase, EVEN after S-phase the number of chromosomes remains the same i.e. 2n.
Histone protein is synthesized.
In ANIMAL CELLS, during the S-phase, DNA replication begins in the nucleus and the centriole duplicates in the CYTOPLASM.
Discussion
18410.

Question : Name the components of nervous system.

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Solution :Central neural system (CNS): The CNS includes the brain and the spinal cord, which are PROTECTED by the bones of the skull and vertebral column. During its embryonic development, CNS develops from the ectoderm.
Brain: The brain acts as the command and control system. It is the site of information processing. It is located in the cranial cavity and is covered by three cranial meninges. The outer thick layer is Duramater which lines the inner surface of the cranial cavity, the median thin layer is Arachnoid mater which is separated from the duramater by a narrow subdural space. The innermost layer is Piamater which is closely adhered to the brain but separated from the arachnoid mater by the subarachnoid space. The brain is divided into three major regions: Forebrain, Midbrain and Hindbrain.
Fore Brain: It comprises the following regions: Cerebrum and Diencephalon. Cerebrum is the 'seat of intelligence and FORMS the major part of the brain. The cerebrum consists of an outer cortex, inner medulla and basal nuclei. The superficial region of the cerebrum is called cerebral cortex, which looks grey due to the presence of unmyelinated nerve cells. Cerebral cortex consists of neuronal cell body, dendrites, associated glial and blood vessels. The surface of the cerebrum shows many convolutions (folds) and grooves. The folds are called gyri (singular gyrus), the shallow grooves between the gyri are called sulci (singular SULCUS) and deep grooves are called fissures. These sulci and gyri increase the surface AREA of the cerebral cortex. Several sulci divide the cerebrum into eight lobes: a pair of frontals, parietals, temporals and occipital lobes.
Mid brain: The mid brain is located between the diencephalon and the pons. The lower portion of the midbrain consists of a pair of longitudinal bands of nervous tissue called cerebral peduncles which relay impulses back and forth between cerebrum, cerebellum, pons and medulla. The dorsal portion of the midbrain consists of four rounded bodies called corpora QUADRIGEMINA which acts as a reflex centre for vision and hearing.
Hind brain: Rhombencephalon forms the hind brain. It comprises of cerebellum, pons varolii and medulla oblongata. Cerebellum is the second largest part of the brain. It consists of two cerebellar hemispheres and central worm shaped part, the vermis. The cerebellum controls and coordinates muscular movements and body equilibrium. Any damage to cerebellum often results in uncoordinated voluntary muscle movements.
Pons varoli: It lies infront of the cerebellum between the midbrain and the medulla oblongata. The nerve fibres in the pons varolii form a bridge between the two cerebellar hemispheres and connect the medulla oblongata with the other region of the brain. The respiratory nuclei found in the pons cooperate with the medulla to control respiration.
Medulla oblongata: It forms the posterior most part of the brain. It connects the spinal cord with various parts of the brain. It receives and integrates signals from spinal cord and sends it to the cerebellum and thalamus. Medulla contains vital centres that control cardio vascular reflexes, respiration and gastric secretions.
Discussion
18411.

Question : describe the arrangement of floral members in relation to their insertion on thalamus.

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Solution :For ANSWER SEE section-A, Q. No. 13( C ).
Discussion
18412.

Question : Describe the androecium of Liliaceae member by using technical terms.

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Solution :Androecium : STAMENS 6, arranged in two whords of three each, epitepalous , apostamenous /freeand opposite to tepals. ANTHERS dithecous, basifixed, introse, and DEHISCING longitudinally.
Discussion
18413.

Question : Describe the action of ATPase in skeletal muscle fibres.

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Solution :Types of skeletal muscle fibres:
Fast fibres and SLOW fibres:
1. Fibres containing myosin with high ATPase activity are classified as fast fibres and with lower ATPase activity are classified as slow fibres.
2. Fibres that contain numerous MITCHONDRIA and have a high CAPACITY for oxidative phosphorylation are classified as oxidative fibres. The oxidative fibres are termed as red muscl e fibres. Fibres that contain few mitochondria but possess a high concentration of glycolytic enzymes and large stores of glycogen are called gycolytic fibres. The lack of myoglobin gives pale colour to the fibres, so they are termed as white muscle fibres.
Skeletal muscle fibres are further classified into three types based on the above classification. They are slow- oxidative fibres, fast- oxidative fibres and fast- glycolytic fibres.
1. Slow- oxidative fibres have low rates of myosin ATP hydrolysis but have the ability to make large amounts of ATP. These fibres are used for prolonged, regular activity such as long distance swimming. Long- distance runners have a high proportion of these fibres in their leg muscles.
2. Fast- oxidative fibres have high myosin ATPase activity and can make large amounts of ATP. They are particularly suited for rapid actions.
3. Fast- glycolytic fibres have myosin ATPase activity but cannot make as much ATP as oxidative fibres, beacuse their source of ATP is glycolysis. These fibres are best suited for rapid, INTENSE actions, such as short sprint at maximum speed.
Discussion
18414.

Question : Describe structure of prokaryotic cell. OR In which organisms prokaryotic cells are found ? Give information about diversity of their shapes.

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Solution :The prokaryotic cells are represented by bacteria, blue-green algae, mycoplasma and PPLO.
They are generally smaller and multiply more rapidly than the eukaryotic cells. Thiey MAY vary greatly in SHAPE and size. The four basic shapes of bacteria are BACILLUS coccus, VIBRIO and spirillum.

The organisation of the prokaryotic cell is fundamentally smaller even though prokaryotes exhibit a wide variety of shapes and functions.
All prokaryotes have a cell wall surrounding the cell MEMBRANE.
The fluid matrix filling the cell is the cytoplasm.
There is no well-defined nucleus. The genetic material is naked not enveloped by a nuclear membrane.
Many bacteria have small circular DNA outside the genomic DNA. These are called plasmids.
The plasmid DNA confers certain unique phenotypic characters to such bacteria.
(i) Resistance to antibiotics.
(ii) Plasmid DNA is used to monitor bacterial transformation with foreign DNA.
Nuclear membrane is not found in it. Cell organelles, like CER, Golgi bodies, mitochondria are not present except Ribosomes.
A specialised differentiated form of cell membrane called mesosome is the characteristic of prokaryotes. They are essentially infoldings of cell membrane.
Discussion
18415.

Question : Describe structure of reproductive system of earthworm with diagram.

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Solution :Earthworm is a hermaphrodite, i.e., TESTES and ovaries are present in the same animal.There are two pairs of testes present in the 10th and 11th segments.Their vasa deferentia run up to the 18th segment when they join the prostatic duct.Two pairs of accessory glands are present i.e. one pair of each in the 17th and 19th segments.The common prostrate and spermatic duct opens to the exterior by a pair of male genital pores on the ventrolateral side of the 18th segment.Four pairs of spermathecae are located in 6th - 9th segments (one pair in each segment). They receive and store spermatozoa during copulation.

One pair of ovaries is attached at the INTER segmental septum of the 12lh and 13th segments. Ovarian funnels are present BENEATH the ovaries which continue into oviduct, join together and open on the ventral side as a single median female genital pore on the 14th segment. Mating : A mutual exchange of sperm occurs between two worms during mating. One worm has to find another worm and they mate juxtaposing opposite gonadal openings.The male genital pores of one comes in contact with pores of spermathecal of another earthworm. In this situations DUE to releasing of sperms, sperm cells enter in spermathecae of companion animal. Hence by doing exchange of sperm cells, companion animals separate from each other.

Formation of Cocoon : After sometime the glands of clitellum does secretion and make a white girdle like structure. Due to contraction, slowly girdle/ tube moves towards auterior end.The girdle moving towards anterior end when passes from spermathecae region, sperm cells stored in spermathecae enter in it. Now in this tube, egg cells of same animals and sperm cells of companion animal and nutrient FLUID are collected. Both the ends of tube/ girdle came out of the body are closed. This tube is closed cocoon. Fertilization takes place in it and egg cells result in a zygote. .After about 3 weeks, each cocoon produces two to twenty baby earthworms. The development of earthworm is direct. It means no larvae formation takes place during development.
Discussion
18416.

Question : Describe structure of chlorophyll a.

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Solution :`*`Chlorophyll a is MADE up of tetrapyrrolic ring (HEAD) with central CORE of magnesium and a phytol alcohol (tail).
`*`Chlorophyll a POSSESSES` -CH_2` (methyl) group.
Discussion
18417.

Question : Describe structure and types of Gynoeclum.

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Solution :Gynoecium : It is the female reproductive part of the flower and is MADE up of one or more carpels.
A carpel consists of three parts.
Ovary is the enlarged basal part, on which lies the ELONGATED tube.
The STYLE connects the ovary the stigma.
The stigma is usually at the tip of the style and is the receptive surface for pollen grains.
Each ovary bears one or more ovules attached to a flattened, cushion - like placenta.
Types of Gynoecium : When there is only one carpel in Gynoecium it is called monocarpellary e.g. PEAS.
When more than one carpels are present in Gynoecium it is called polycarpellary.
In polycarpellary Gynoecium if all carpels are free from each other then it is called Apocarpous e.g. LOTUS, rose.
If all carpels are fused it is termed as syncarpous. In such cases there is only one ovary e.g. Tomato, Mustard.
Carpel is considered as female structure.
Androecium and Gynoecium are necessary for sexual reproduction. Therefore they are called necessary whorls.
After ſertilisation, the ovules develop into seeds and the ovary matures into a fruit.
Discussion
18418.

Question : Describe structure and function of Chloroplasts.

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Solution :Majority of the chloroplasts of the GREEN plants are found in the mesophyll cells of the leaves.
These are lens-shaped, oval, spherical, discoid or even ribbon-like organelles .
They are having variable length (5-10 urn) and width (2-4 `mu`m).
Their number varies from 1 per cell of the Chlamydomonas, a green alga to 20-40 per cell in the mesophyll.

The chloroplasts are also double membrane bound. Of the two, the inner chloroplast membrane is relatively less permeable.
The space limited by the inner membrane of the chloroplast is called the stroma.
A number of organised flattened MEMBRANOUS sacs are called the thylakoids, are present in the stroma.
Thylakoids are arranged in stacks like the piles of coins called GRANA (singular: GRANUM) or the intergranal thylakoids.
There are flat membranous tubules called the stroma lamellae connecting the thylakoids of the different grana.
The membrane of the thylakoids enclose a space called a lumen.
The stroma of the chloroplast contains enzymes required for the synthesis of carbohydrates and proteins.
It also contains small, double-stranded circular DNA molecules and ribosomes.
The ribosomes of the chloroplasts are smaller (705) than the cytoplasmic ribosomes (80S).
Discussion
18419.

Question : Describe special inflorescence with example.

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Solution :Special Inflorescence:
The inflorescence other than racemose, cymose and mixed type are coming under special type of inflorescence.
Types:
(a) CYATHIUM:
1. Cyathium inflorescence consists of small unisexual flowers enclosed by a common involucre which mimics a single flower. Male flowers are organised in a scorpioid manner.

2. Female flower is solitary and centrally located on a long pedicel. Male flower is represented only by stamens and female flower is represented only by pistil.
3. Cyathium may be actinomorphic (Eg: Euphorbia) or zygomorphic (Eg: Pedilanthus). A nectar is present in involucre.
(b) Hypanthodium:
1. RECEPTACLE is a hollow, globose STRUCTURE consisting of unisexual flowers present on the inner wall of the receptacle.
2. Receptacle is closed except a small opening called ostiole which is COVERED by a series of bracts.
3. Male flowers are present nearer to the ostiole, female and natural flowers found in a mixed manner from middle below. Eg: FICUS sps.
(c) Coenanthium:
Circular disc like fleshy open receptacle that bears pistillate flowers at the center and staminate flowers at the periphery. Eg: Dorstenia.
Discussion
18420.

Question : Describe soil as reservoir of essential elements.

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Solution :The role of minerals in plant nutrition is referred as mineral nutrition. SOIL consists of a wide variety of nutrients.
Majority of the nutrients that are essential for the growth and development of plant become available to the roots due to weathering and BREAKDOWN of rocks.
These processes enrich the soil with dissolved ion and inorganic salts.
They are derived from the rock minerals.
Soil not only supplies minerals but also harbours nitrogen fixing bacteria, other microbes holds water, supplies air to the roots and acts as matrix that stabilizes the plant.
Since deficiency of essential minerals AFFECT the crop yield.
There is a OFTEN a need for supplying them through fertilizers.
Both MACRO nutrients (N, P, K, S etc) and micro nutrients (Cu,Zn,Fe,Mn etc) from components of fertilizers and are applied as per need.
Discussion
18421.

Question : Describe sexual reproduction in fungi.

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SOLUTION :(Plasmogamy, Karyogamy, Meiosis in zygote, Dikaryophase)
The STEPS are :
(i) Plasmogamy : fusion of protoplasm of TWO MOTILE or non-motile gametes.
(ii) Karyogamy : fusion of two nuclei.
(iii) Zygotic Meiosis to form haploid spores.
(iv) Dikaryophase in ascomycetes and basidiomycetes where before karyogamy two nuclei per cell (dikaryon) are found.
Discussion
18422.

Question : Describe ringing experimentwith diagram.

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Solution :The experiment involves the removal of all the tissue outside to vascular cambium ( bark, cortex, and phloem) in woody stems except xylem. Xylem is the only remaining tissue in the girdled area which connects upper and lower part of the plant. This setup is placed in a BEAKER of water. After some time, it is observed that a swelling on the upper part of the RING appears as a result of the accumulation of food material. If the experiment continues within days, the ROOTS die first. It is because, the supply of food material to the root is cut down by roots gradually die the upper part ( stem), which depends on root for the ASCENT of SAP, will ultimately die.
Discussion
18423.

Question : Describe respiratory system of cockroach

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Solution :The respiratory system consists of a network of trachea. They are main ELEMENTS of respiratory system. Many branches of trachea are spread in the whole body. Its end branches are CALLED tracheoles. It transports `O_(2)`in all parts of the body. Trachea possess direct contact with atmospheric air by spiracles. There are 10 PAIRS of spiracles present on the lateral side of the body. Among them two pairs in thorax region and eight pairs are located in abdomen region. The wall of spiracles is formed of FUNNEL like structures. Funnel like structures prevent dust like substances into respiratory system. Valve controls opening of spiracles. During respiration oxygen enters into trachea by spiracles and from there comes into contact with tissue FLUID through tracheoles and gets dissolved in it. Tissues of the body use this dissolved oxygen for procuring work energy. Carbon dioxide produced during it also gets dissolved in tissue fluid and comes out during exhalation.
Discussion
18424.

Question : Describe : RespiratoryQuotient.

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Solution :During aerobic respiration, `O_(2)`is CONSUMED and `CO_(2)` is released.
The ratioof the volumeof `CO_(2)` evolved to the volume of `O_(2)`consumed in respiration is called the respiratoryquotient.
`RQ = ("Volume of " CO_(2) "evolved ")/("Volume of "O_(2) " consumed ")`
The respiratoryquotientdepends upon the TYPE of respiratory substrated usedduring respiration.
RQ of Carbohydrates : Whencarbohydrates are used as substrate and are completely oxidised,the RQ will be 1, because amountsof `CO_(2) and O_(2)` are evolved and consumed.
Equation : `C_(6) H_(12) O_(6) + 6O_(2) to 6CO_(2) + 6H_(2) O ` + Energy
`RQ = (6 CO_(2))/( 6O_(2)) = 1.0`
RQ of fat : When fats are used in respiration, the RQ used than 1. Calculation for a fatty acid, tripalmitin, if usedas a substrate is shown.
`2(C_(51) H_(98)O_(6)) + 145O_(2) to 102 CO_(2) + 98 H_(2) O` + Energy
`RQ = (102 CO_(2))/(145 O_(2))` = 0. 7
Protein : Whenproteins are respiratorysubstrates the ratio would be about 0.9.
When organic acid is used for respiration the RQ remain above 1.
e.g. equation for respiration of oxalic acid :
`2 (CO OH)_(2) +O_(2) to 4CO_(2) + 2H_(2) O` Energy
`RQ = (4 CO_(2))/( 1 O_(2))` = 4
NOTE : Inliving organismsrespiratory substrates are often more than one , pure proteins or fatsare never usedas respiratorysubstrates.
Discussion
18425.

Question : Describe reproductive system of female cockroach and process of fertilization with diagram

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Solution :Cockroaches are dioecious and both sexes have well developed reproductive organ.Reproductive system of male cockroach : Male reproductive system consists of a pair of testes, one lying on each lateral side in the `4^(th) - 6^(th)`abdominal segments. From each testis a thin vas deferens, which opens into ejaculatory duct through seminal vesicle. The ejaculatory duct opens into male gonopore situated ventrally to anus. A characteristic mushroom-shaped gland is present in the 6th - 7th abdominal segments which functions as an accessory reproductive gland. Other long and flat gland - conglobate gland is located on the ventral side of ejaculatory duct is an accessory reproductive gland. Its secretion makes hard coating around sperm cells bag. The EXTERNAL genitalia are represented by male gonapophysis or phallomere (chitinous asymmetrical structures, surrounding the male gonopore). The sperms are stored in the seminal vesicles and are glued together in the form of bundles called spermatophores which are discharged during copulation. (II) Female reproductive system :The female reproductive system consists of two large ovaries lying laterally in the 2nd - 6th abdominal segments.Each ovary is formed of a group of eight ovarian tubules or ovarioles containing a chain of developing ova. Oviducts of each ovary unite into a single median oviduct which opens into the genital chamber. A pair of spermatheca is present in the 6th segment which opens into the genital chamber.Egg cells enter into genital chamber during mating. They are fertilized by sperm cells.Collateral glands present in female cockroach possess secretion. Due to its secretion oothecae is formed.Fertilised egg cells are encased in capsules called oothecae. Oothecae is a dark reddish to blackish brown CAPSULE, about 3/8" (8 MM) long. They are dropped or glued to a suitable surface, usually in a crack or crevice of high relative humidity near a food source.On an average, females PRODUCE 9-10 oothecae, each containing 14-16 eggs.The development of P-americana is indirect.Means its development is done by nymphal stage.The nymph appears like adult insect only. The nymph grows by moulting about 13 times to reach the adult form. The next to last nymphal stage has wing pads but only in adult cockroaches.
Discussion
18426.

Question : Describe reproduction in living organisms.

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Solution :In multicellular organisms reproduction refers to the production of progeny possessing features more or LESS similar to those of parents
Fungi multiply and spread easily due to the millions of asexual spores produce by them.
Budding is observed in lower organisms like yeast and hydra.
 In Planaria (flat worms) regeneration is seen is a fragmented organism regenerates the lost part of its body and becomes a new organism.
FRAGMENTATION is seen in fungi, filamentous algae and the PROTONEMA of mosses.
Unicellular organisms like bacteria, unicellular algae or Amoeba, reproduction is synonymous with growth means increase in number of cells.
Growth can be define as equivalent to increase in cell number or mass.
Hence, in single-celled organisms it is not very clear about the usage of these two terms - growth and reproduction.
There are many organisms which do not reproduce like as Mules, sterile WORKER bees, infertile human couples etc.
Hence, reproduction cannot be considered as DEFINING characteristic of living organisms.
No non-living object is capable of reproducing of replicating by itself.
Discussion
18427.

Question : Describe primary, secondary and tertiary structure of proteins. OR Describe structure of proteins.

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Solution :Structure of molecules means different things in different contexts.
In inorganic chemistry, the structure invariably refers to the MOLECULAR formulae (e.g., NaCl, `MgCl_2`, etc.).
Organic chemistry always write a two DIMENSIONAL view of the molecules while representing the structure of the molecules (e.g., benzene, naphthalene, etc.).
Physicists conjure up the three dimensional views of molecular structures while biologists describe the protein structure at four levels.

(a)Primary Structure : The sequence of amino acids i.e., the positional information in a protein - which is the first amino acid, which is second, and so on - is called the primary structure.
(b) Secondary Structure : A protein is imagined as a line, the left end is represented by the first amino acid and the right end represented by the last amino acid.
The first amino acid is called as N-terminal amino acid. The last amino acid is called the C-terminal amino acid.
Protein thread is folded in the form of a helix, (similar to a revolving staircase)
In proteins, only right handed helices are observed. Other regions of the protein thread are folded into other forms in what is called the secondary structure.
( c) Tertiary Structure : The long protein chain is also folded upon itself like a hollow woolen ball, giving rise to tertiary structure. It gives us a 3-dimensional view of a protein.
Tertiary structure is absolutely necessary for the many biological activities of proteins.
( d) Quaternary Structure : Some proteins are an assembly of more than one polypeptide or subunits. These individual folded polypeptides are arranged with respect to each other (e.g. linear string of spheres, cubes etc.) it is the architecture of a protein called quaternary structure of a protein.

HAEMOGLOBIN : Human haemoglobin CONSISTS of 4 subunits. Two are identical to each other. Hence, two subunits are a TYPE and two subunits are (3) type.
Discussion
18428.

Question : Describe phylum platyhelminthes.

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Solution :Platyhelminthes have dorso-ventrally flattened body, hence are called flatworms.
These are mostly endoparasites found in animals including human beings.
Flatworms are bilaterally symmetrical, triploblastic and acoelomate animals with ORGAN level of organisation.
Hooks and suckers are present in the parasitic forms.
Some of them absorb NUTRIENTS from the host directly through their body surface.
Specialised cells called flame cells help in osmoregulation and excretion.
Sexes are not separate.
Fertilisation is internal and development is through MANY larval stages.
Some members like Planaria possess high regeneration capacity.
Examples : Taenia (TAPEWORM), FASCIOLA (Liver fluke).
Discussion
18429.

Question : Describe Phycomycetes.

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Solution :Habitats : Members of phycomycetes are found in aquatic habitats and on decaying wood in MOIST and damp PLACES or as obligate parasites on plants.
Body organisation : The mycelium is ASEPTATE and coenocytic.
Hyphal wall contains microfibrils of cellulose CHITIN or both.
Reproduction : Asexual reproduction takes place by Zoospores (motile) or by aplanospores (non-mutile).
These spores are endogenously produced in sporangium.
A zygospore is formed by FUSION of two gametes.
These gametes are similar in morphology (isogamous) or dissimilar (anisogamous or oogamous).
Discussion
18430.

Question : Describe photolysis of water.

Answer»

Solution :The electrons that were moved from photosystem - II have to be replaced.
This is achieved by electrons available due to spliting of water
Explanation of the process :
The splitting of water is associated with the PS-II, water is split into `H^(+)`, [O] and electrons.
`2H_(2)O rarr 4H^(+) + O_(2) 4e^(-)`
This creates oxygen, one of the net products of photosynthesis.
The electons NEEDED to replaced those REMOVED from photosytem - I are provided by photosystem - II.
Water splitting complex is associated with th PS II, which itself is physically located on the inner side of the MEMBRANE of the thylakoid.
Discussion
18431.

Question : Describe photorespiration.

Answer»

Solution :The respiration which occurs in presence of light and in chlroplast is called photorespiration.
To understand photorespiration we have to know a little bit more about the first step of the Calvin - pathway.
In this reation RUBP combines with `CO_(2)` to form 2 molecules of 3PGA, that is catalysed by RuBisCO.
`RuBP + CO_(2)overset("RuBisCO)rarr2xx3PGA`
RuBisCO : That is the most abundant enzyme in the world.
Characteristic : It is CHARACTERISED by the fact that its active site can BIND to both `CO_(2) and O_(2)` - hence the name.
Specially : RuBisCO has a much greater affinty for `CO_(2)` than for `O_(2)`.
Base : It is the relative concentration of `O_(2) and CO_(2)` that determines which of the twowill bind to the enzyme.
In `C_(3)` plants some `O_(2)` does bind to RuBisCO and hence `CO_(2)` fixation is decreased.
Here the RuBP instead of being converted to 2 molecules of PGA binds with `O_(2)` to from molecule of phosphoglycerate and phosphoglycolate in a pathway called photorespiration.

In the photorespiratory pathway, there is neither SYNTHESIS of sugars, nor of ATP
Rather it results in the release of `CO_(2)` with the utilisation of ATP.
In the photorespiratory pathway there is no synthesis of ATP or NADPH.
THEREFORE, photorespiration is a wasteful process.
Discussion
18432.

Question : Describe parts of frult with diagram .

Answer»

Solution : The fruit is a mature or ripened ovary , developed after FERTILISATION . If a fruit is FORMED without fertilisation of the ovary. It is called a parthenocarpic fruit. Generally, the fruit consists of a wall or pericarp and seed. Seed is enclosed by pericarp in a fruit.
Pericarp may be dry or fleshy . When pericarp is thick and fleshy , it is differentiated into the OUTER epicarp, the middle mesocarp and the inner endocarp.
More Infortnition :
Types of fruits : On the basis of origin and development there are three types offruits : (a) Simple Fruit (b) Aggregate Fruit (c) Composite Fruit.
(a) Simple Fruit : The fruit which develops monocarpellary ovary or polycarpellary ovary . Such fruits are dry or fleshy. (i) Pericarp of simple dry fruit are dry . It has two types
(1) Dehiscent and (2) Indehiscent
When pericarp of dry dehiscent fruit becomes mature, it releases seed by exploding in various types.
On the basis of explosion Dehiscence it can be classified in various types. Like (1) FOLLICLE (2) Legumes and Capsule and Siliqua
Simple indehiscent dry fruit : No explosion of wall of mature fruit occurs. Pericarp naturally degenerates and releases seed.
Their development occurs from monocarpellary or fused polycarpellary which is one chambered or one ovuled e.g. caryopsis, achene, cypsela, nut and samara are types of Indehiscent fruits.
Fleshy Fruit : In fleshy fruits pericarp is fleshy. There are three types of it. (i) Drupe, (ii) Berry and (III) Sebia
Drupe : In mango and coconut, the fruit is known as a drupe. They develop from monocarpellary superior ovaries and are one seeded.
In mango the pericarp is well differentiated into an outer thin epicarp, middle fleshy edible mesocarp and an inner stony hard endocarp.
In coconut which is also a dipe, the mesocarp is fibrous.
Discussion
18433.

Question : Describe pharynx, oesophagus and external structure of stomach of digestive track of human beings.

Answer»

Solution :(a) Pharynx : The oesophagus and the trachea open into pharynx.
Pharynx is located BEHIND Nose, MOUTH and larynx. It is divided into three parts.
(i) NASOPHARYNX
(ii) Oral pharynx
(iii) Laryngeal pharynx
Function : It helps to swallow food. It sends food in oesophagus.
A cartilaginous flap called epiglottis prevents the entry of food into the glottis.
(b) Oesophagus : Oesophagus is a thin, long tube. It is behind trachea and in the front of vertebral column. It extends POSTERIORLY passing through the neck, thorax and diaphragm and leads to .J. shaped bag like structure called stomach.
A muscular sphincter regulates the opening of oesophagus into the stomach.
Function : It sends food into stomach.
(c) Stomach : The most enlarged part of digestive tract is stomach. The stomach is located in the upper left portion of the abdominal cavity. It has three parts:
(i) Cardiac Stomach : Oesophagus OPENS into it.
(ii) Fundus : It is the main part of stomach.
(iii) Pyloric Stomach : It is a transverse part of stomach. Stomach is connected to duodenum by oesophagus and pyloric stomach through cardiae stomach. It opens into first part of small intestine.
Function : Stores food temporarily, food gets churned and converts into chyme.
Discussion
18434.

Question : Describe parts of a typical flower.

Answer»

Solution :(A)Parts of flower in Anglosperms :
Flower is the reproductive unit in the angiosperms.
It is meant for sexual reproduction.
It has mid axis. It is called STALK or pedicel.
The swollen end of stalk or pedicel is called thalamus . Four different kinds of whorls are arranged successively on it.
These are calyx , corolla , androecium and gynoecium.
Calyx and corolla are accessory organs , while androecium and gynoecium are reproductive organs.
( i ) Calyx : Calyx is the outer most whorl of the flower . It is made up of sepals . Sepals are green and leaf like in APPEARANCE and protects the plant in bud stage . Calyx can be Gamosepalous or polysepalous.
(ii) Corolla : Corolla is located inside the calyx . They are of different shape and colour and attractive . Corolla can be Polypetalous or Gamopetalous , Petals attract insects for pollination.
There is a variety of shape and colour of corolla in plants , Corolla can be tube shaped , bell shaped , funnel shaped or wheel - shaped.
In some plants Androccium and Gynoecium , both are present . It is called bisexual flower.
A flower having either only slamens or only carpels is called unisexual flower.

(B) Parts of flower on the basis of symmetry :
On the basis of flower symmetry , the flower may be of 3 types , (i) actinomorphic or radial symmetry (ii) zygomorphic (bilateral symmetry) (iii) asymmetric.
(i) Actinomorphic or radial flower : When a flower can be DIVIDED into two equal radial halves in any radial plane passing through the centre , it is said to be actinomorphic , e.g. , mustard , datura , chilli.
(ii) Zygomorphic : The flower can be divided into two similar halves only in one particular vertical plane . It is zygomorphic , e.g. pea , gulmohur , bean , cassia.
(iii) Asymmetric : A flower is asymmetric if it cannot be divided into two similar halves by any vertical plane passing through the centre , as in canna.
A flower may be trimerous , tetramerous and pentamerous when the floral appendages are in multiple of 3 , 4 or 5.
Flowers with bracts , reduced leaf found at the base of the pedicel are called bracteate and those without bracteate , ebracteate.
(C) Parts of flowers on the basis of position of ovary : There are 3 types of flowers on the basis of position of ovary.
Based on the position of calyx , corolla and androecium in RESPECT of the ovary on thalamus , the flowers are described as hypogynous , perigynous and epigynous.
(i) Hypogynous : In the hypogynous flower the gynoecium occupies the highest position while the other parts are situated below it . The ovary in such flowers is said to be superior, e.g., mustard, china rose and brinjal etc.
(ii) Perigynous : If gynoecium is situated in the centre and other parts of the flower are located on the rim of the thalamus almost at the same level , it is called perigynous . The ovary here is said to be half inferior , e.g. plum , rose , peach.
(iii) Epigynous : In epigynous flowers, the margin of thalamus grows UPWARD enclosing the ovary completely and getting fused with it, the other parts of flower arise above the ovary. Hence , the ovary is said to be inferior as in flowers of guava and cucumber, and the ray florets of sunflower.
Discussion
18435.

Question : Describe other means of recording descriptions.

Answer»

Solution :Flora, manuals, monographs and catalogues are some other means of recording descriptions.
They ALSO help in correct identification.
Flora contains the actual account of habitat and distribution of PLANTS of a given AREA.
These provide the INDEX to the plant species found in a particular area.
Manuals are useful in a providing information for identification of names of species found in a an area.
Monographs CONTAIN information on any one taxon.
Discussion
18436.

Question : Describe nitrogen cycle.

Answer»

SOLUTION :Apart from CARBON ,hydrogen and oxygen. Nitrogen is the most prevalent element in living organism.
Nitrogen: Nitrogen is a CONSTITUENT of amino acids, proteins, hormones, chlorophylls and many of the vitamins.
Plants compete with microbes for the limited nitrogen that is available in soil.
Thus, nitrogen is a limiting nutrient for both natural and agricultural eco-systems.
Nitrogen exists as two nitrogen atoms joined be a very strong triple covalent bond (N=N)
The PROCESS of conversion of nitrogen `(N_2)` to ammonia is termed as nitrogen fixation.
IN nature, lightning and ultraviolet radiation provide enough energy to convert nitrogen to nitrogen oxides `(NO,NO_2,N_2O)` Industrial combustions, forest fires, automobile exhausts and power generating stations are also sources of atmospheric nitrogen oxides.
Decomposition of organic nitrogen of dead plants and animals into ammonia is called ammonification.
Some of this ammonia volatilises and re-enters the ATMOSPHERE.
But most of it is converted into nitrate by soil bacteria in the following steps:
`2NH_3+3O_2 to 2NO_2^(-) +2H^(+) +2H_2O`..........(i)
`2NO_2^(-)+O_2 to 2NO_3^(-)`........(ii)

Ammonia is first oxidised to nitrite by the bacteria Nitrosomans and /or Nitrococcus.
The nitrite is further oxidised to nitrate with the help of the bacterium Nitrobacter.
These steps are called nitrification.
`Ammonia to^(Oxidation) Nitrite`
`Nitrite to_(Oxidation)^(Nitrobacter) Nitrate`
These nitrifying bacteria are chemoautotrophs.
The nitrate thus formed is absorbed by plants is transported to the leaves.
In leaves it is reduced to form ammonia
`Nitrate to leaves to^(REduction ) Ammonia to Amino acid`
It is finally forms the amine group of amino acids. Nitrate present in the soil is also reduced to nitrogen by the process of denitrification.
`Nitrate to^(Denitrification) Nitrogen`
Pseudomonas+Thiobacillus bacteria
Discussion
18437.

Question : Describe nervous system of earthworm

Answer»

Solution :The NERVOUS system of earthworm is ganglionated. Nerve cells unite to FORM gaglia.The pair of GANGLIA is located on the ventral side in the posterior PART of third segment.It is known as sub pharyngeal ganglionA pair of ganglia is located on ventral side in each segment after 5th segment. It is known as ventral nerve cord.

On the dorsal side of pharynx a pair of ganglia is located in 3rd segment so it is known as super pharyngeal Ganglion. These ganglia are connected to subpharyngeal ganglia through circumpharyngeal connective. This pair of CIRCUM pharyngeal is connected with subphryngeal ganglia and suprapharyngeal ganglia form a Nerve ring. The cerebral ganglia along with other nerves in the ring integrate sensory input as well as command muscular responses of the body.
Discussion
18438.

Question : Describe modifications of stem with suitable examples.

Answer»

SOLUTION :For ANSWER SEE section-A, Q. No. 6
Discussion
18439.

Question :Describe modifications of stem for specific functions.

Answer»

SOLUTION :Stem performs some extra functions in addition to its normal functions. It gets modified for these functions.
(A) Modification of stems for food Storage :
(i) RHIZOME : Ginger, Turmeric, Zaminkand, Colocasla are underground stems. They store food and become an irregularly shaped node. It possesses nodes, internodes, scaly leaves and adventitious roots .
(ii) Tuber : In potato, scaly leaves located on underground stem, arise from axil of branches at top store food and forms round or oval structure. It is called tuber. There are craters on the surface of potato, it is called eye. It has bud. That performs vegetative propagations.
(iii) Corm : Amorphophalus is a condensed form of Rhizome.

(B) Modifications of Stem for Climbing :
Stem tendrils : In Passion Flower, Cucurbit, Bitter Gourd, Gourd, CUCUMBER stem tendrils develop as axillary buds are slender and spirally colled and help plants to climb. Such plants are called tendullar plants.

(c) Modifications of Stem for Protection :Stem Thorns : Sometimes axillary buds of stems may get modified into woody, straight and pointed thorns. They protect plant from browsng animal e.g. lemon, citrus, bougainvillea etc.

more information:
modification of stem for protection :
(D) Modifications of Stem for Photosynthesis : Phylloclade : The stems of some plants of dry region get converted pointed and fleshy. Like Opuntia and Euphorbia. They possess chlorophyll and CAPABLE of photosynthesis. It is called phylloclade. Eg. Opuntia and Muehlenubackia.

(E)Modifications of Stem for vegetative Propagations : In some plants from lower nodes of soil long, slender, straight and weak branches develop as stem.
more information : (i) Runner :It is a creeping stem with long internodes, running horizontally on the soil surface. Runner arises from an axillary bud. e.g. Grass, Oxails, Hydrocotyle.

(ii) Offset : In aquatic plants like Pistia and Eichornia, there is a lateral branch with short internodes and each node bearing a rosette of leaves and a tuft of roots.
(iii) Sucker : In plants like mint a slender lateral branch arises from the base of main axis, spread to new niches. When underground stems of older parts die, new plants are formed, mint is a sucker.
(iv) Stolon : In plants like strawberry and Jasmine a slender lateral branch arises from the base of the main axis and after growing aerially for some time, arch downwards to touch the ground it is called stolon.
(v) Leafy Shoot : In banana, pineapple and chrysanthemums the lateral branches originate from the basal and underground portion of the main stem, grow horizontally beneath the soil and then come out obliquely UPWARD giving rise to leafy shoots.
Discussion
18440.

Question : Describe modifications of root specific functions.

Answer»

Solution :Some plants perform some specific FUNCTIONS in ADDITION to their main functions.
For these functions their shape and structure are changed . Such functions are called specific functions and for that the changes that take place in their structure are called MODIFICATIONS.
They are modified for support , storage of food and respiration.
Modifications of plants for food storage :
( a ) Food storage in Tap root : Food is stored in tap root of carrot and it becomes cone shaped . Food is stored in Raddish and becomes spindle shaped . Food is stored in beet root and Turnip and becomes top shaped.
( b ) Food storage in Adventitious root : Food is stored in adventitious root of sweet potato and get swollen . So it is called simple Tuberous root.
In Asparagus and Dahlia food STORING root clusters are formed . They are called Fasciculated tuberous root.

Modifications of root for support : Prop roots and stilt roots are modifications for support.
( a ) Stilt Roots : The stems of maize and sugarcane have supporting roots coming out of the lower nodes of the stem . These are called stilt roots . e.g. Maize , Sugarcane , Pandanus etc.
( b ) Prop Root : The hanging structures that support a tree are called prop roots . e.g. Prop roots of banyan tree.

(c) Pneumatophores : The plant group developing in swampy and humid areas of salt water at seashore is called Mangrove.
Many roots of these plants develop towards opposite direction of gravity and longitudinally from soil directly.
Such root are porous and unbranched . It helps to get oxygen for respiration . They are called Pneumatophores or RESPIRATORY root.
Discussion
18441.

Question :Describe modification of leaves for specific functions with example.

Answer»

Solution :Modifications of Leaves for SPECIFIC functions : (a)Modifications for support and climbing : In some PLANTS with weak stems, leaves get converted into tendrils for climbing as in peas.
(b) Modifications of leaves for protection : Some plants have modification of leaves into spines for defense as in CACTI.

(c)Modification of leaves for food storage : Some plants have fleshy leaves for food storage. Eg. Onion and garlic.
.

Australian acacia : Leaves are small and short-lived. The petioles in these plants expand, become green and synthesise food.
Insectivorous : Leaves of certain insectivorous plants such as pitcher plant, venus-fly trap are also MODIFIED leaves.
Discussion
18442.

Question : Describe micro structure of cilia and flagella.

Answer»

Solution :Cilia and flagella are hair-like outgrowths of the cell membrane.
Cilia are small structures which work like oars, causing the MOVEMENT of either the cell or the surrounding fluid.
Flagella are comparatively longer and responsible for cell movement. The prokaryotic bacteria also possess flagella, but these are structurally DIFFERENT from that of the eukaryotic flagella.

The electron microscopic study of a cilium or the flagellum show that they are covered with plasma membrane. Their core is called the axoneme, possesses a NUMBER of microtubules running parallel to the LONG axis.
The axoneme usually has nine pairs of doublets of radially arranged peripheral microtubules, and a pair of centrally located microtubules. Such an arrangement of axonemal microtubules is referred to as the 9 + 2 ARRAY.
The central tubules are connected by to one of the tubules of each peripheral doublets by a radial spoke. Thus, there are nine radial spokes.
The peripheral doublets are also interconnected by linkers.
Discussion
18443.

Question : Describemetabolic processesof respiratorypathway.

Answer»

Solution :Glucose is the favoured substratefor respiration.
All carbohydrates are usually first converted into glucose before theyare used for respiration.
Othersubstrates can also be respired, but then they do not enter the RESPIRATORY pathwayat the first step .

As per shownin FIGURE, Fatswould NEED to be broken down into glycerol and fatty acids first.
If fattyacids were to be respired they would first be degraded to acetyl CoAand enter thepathway.
Glycerol would enterthe pathway after being converted to PGAL.
The proteinwould be degraded by proteases ad the individual amino acids depending on their would enter thepathway at some stagewithin the Krebs. cycle or even as pyruvate of acetyl CoA .
Since respiration breakdownof substrates,the respiratory process has traditionallybeen considered a catabolicprocess and the respiratory pathway as a catabolic pathway.
Hence fatty acids would be broken down to acetyl CoA beforeentering the respiratorypathway when it is used as substate.
These VARY compounds thatwould be withdrawn from the respiratory pathwayfor thesynthesisof the said substrates.
When the organism needsto synthesize fatty acid acetyl CoA would be withdrawnfrom the respiratory pathway for it
Hence, the respiratorypathway comes into the pictureboth during breakdown and synthesisor fatty acids.
Similarly during breakdownand synthesisof protein too, respiratoryintermediates forthe link.
Breaking down processes withinthe living organism is CATABOLISM and synthesis is anabolism .
Because the respiratory pathway is involved in bothanabolism andcatabolism.
It wouldhence be better to consider therespiratorypathway an an amphibolic pathwayratherthenas a catabolic one.
Discussion
18444.

Question : Describe Metaphase - I, Anaphase - I and Telophase - I of Meiosis - I.

Answer»

Solution :Metaphase - I:
The bivalent chromosomes ALIGN on the equatorial plate. The microtubules from the opposite poles of the spindle attach to the pair of HOMOLOGOUS chromosomes.
AnapbaseI: The homologous chromosomes separate, while SISTER chromatids remain associated at their centromeres.
Telophase - I: The nuclear membrane and nucleolus reappear. Cytokinesis follows and this is called as Dyad of CELLS.
The stage between the two meiotic divisions is called interkinesis and is GENERALLY short lived.
Discussion
18445.

Question : Describe mechanism of hearing briefly.

Answer»

SOLUTION :The external ear receives SOUND waves and directs them to the ear drum. The ear drum vibrates in response to the sound waves and these vibrations are transmitted through the ear OSSICLES (malleus, incus and stapes) to the oval window.
The vibrations are PASSED through the oval window on to the FLUID of the cochlea, where they generate waves in the lymphs.
The waves in the lymphs induce a ripple in the basilar membrane.
These movements of the basilar membrane bend the hair cells, pressing them against the tectorial membrane.
As a result, nerve impulses are generated in the associated afferent neurons. These impulses are transmitted by the afferent fibres via auditory nerves to the auditory cortex of the brain, where the impulses are analysed and the sound is recognised.
Discussion
18446.

Question : Describe mechanism of steroid and peoptide hormone with diagram.

Answer»

Solution :
Hormones preduce their effects on target tissues by binding to specific proteins called hormone receptors located in the target tissues only.
Hormone receptors present on the cell membrane of the target CELLS are celled membrane bound receptors and the receptors present inside the target cell are called intracellular receptors, mostly nuclear receptors. Binding of a hormone to its RECEPTOR leads to the formation of a hormone receptor complex.
Each receptor is specific to one hormone only and hence receptors are specific.
Hormone receptor complex formation leads to certain biochemical changes in the target tissue.
Target tissue metabolism and hence physiological functions are regulated by hormones.
On the basis of their chemical nature, hormones can be divided into :
(i) Peptide, polypeptide, protein hormones (e.g., insulin, glucagon, pituitary hormones, hypothalamic hormones, ETC.)
(ii) Steroids (e.g., cortisol, testosterone, estradiol and progesterone)
(iii) Iodothyronines (thyroid hormones)
(iv) Amino - acid derivatives (e.g., epinephrine).
Hormones which interact with membrane - bound receptors normally do not enter the target cell, but GENERATE second messengers (e.g., cyclic AMP,`"IP"_(3)"Ca"^("++)` etc.) which in turn REGULATE cellularmetabolism.
Hormones which interact with intracellular receptors (steroid, iodothyronines, etc.) mostly regulate gene expression or chromosome function by the interaction of hormone - receptor complex with the genome.
Cumulative biochemical actions result in physiological and developmental effects.
Discussion
18447.

Question : Describe Lundegardh'sCytochrome Pump Theory .

Answer»

SOLUTION :Lundegardh'sCytochrome Pump Theory:
Lundegardh and Burstrom (1933) observed a correlation between respiration and anion absorption. When a plant is transferred from water to a salt solution the rate of respiration increases which is called as anion respiration or salt respiration. Based on this observation Lundegardh (1950 and 1954) proposed cytochrome pump theory which is based on the following assumptions:
i. The mechanism of anion and cation absorption are different.
ii. Anions are absorbed through cytochrome chain by an active process, cations are absorbed passively.
iii. An oxygen gradient responsible for oxidation at the outer surface of the membrane and reduction at the INNER surface.
According to this theory, the enzyme dehydrogenase on inner surface is responsible for the FORMATION of protons `(H^(+))` and electrons `(e^(-))`. As electrons pass outward through electron TRANSPORT chain there is a corresponding inward passage of anions. Anions are picked up by oxidized cytochrome oxidase and are transferred to other members of chain as they transfer the electron to the next component.
The theory assumes that cations `(C^(+))` move passively along the electrical gradient created by the ACCUMULATION of anions `(A^(-))` at the inner surface of the membrane.
Main defects of the above theory are:
(i) Cations also induce respiration.
(ii) Fails to explain the selectiveuptake of ions.
(iii) It explains absorption of anions only.
Discussion
18448.

Question : Describe internal structure of monocot (Maize) root.

Answer»

Solution :Internal structure of Monocotyledonous Root (Maize) : Maize is a dicot plant. While taking section of maize root under microscope following three layers are seen clearly, (1) Epidermis (2) Cortex (3) Stele.
Epidermis : This is the outermost PROTECTIVE layer of root. From the cells of this layer thin walled tube like appendages are produced. They are called root hairs. The cells of this layer do not possess cuticle layer because its FUNCTION is to absorb water and salts from the soil.
Cortex : In cortex, outer cortex, inner cortex and endodermis are included.
(i) Exodermis: This layer is located immediately below epidermis. Its cells are large, suberised thick walls. It protects inside tissues due to loss of epidermis.
(ii) Hypodermis : A region of 3-4 layers located below exodermis is called hypodermis. The wall of cells of these of these layers is lignified and becomes strong. This region is made up of collenchyma.
(iii) Inner Cortex : The region located inside the cortex is called inner cortex. This region is made up of parenchyma cells. They have thin wall and are round in shape.
(iv) Endodermis : The innermost layer of cortex is called Endodermis. The cells of this layer are connected tightly with each other. The radial wall and inner wall is stained with LIGNIN and suberin. This stain appears like horizontal .C.. Some of the cells in this layer stay with stain. They are called passage cells. These cells are exactly opposite to protoxylem and alive.
Stele: In stele pericycle vascular, bundle, conjunctive tissues and pith are included.
The NUMBER of group of xylem and phloem tissue is more than 8. So such stele s called polyarch.
(i) Pericycle : Pericycle is a one layered covering located inside of endodermis. The cells of this layer are alive, thin walled and parenchymatic.
Lateral roots produced by cells of this layer are located opposite to protoxylem. Thus they originate of their own.
(ii) Vascular Bundles : Here Vascular Bundles are of radial type. The Vascular Bundles of xylem and phloem are arranged at different radii. The development of xylem is exoarch as protoxylem are outside while metaxylem are located inside.
Phloem tissue is made up of sieve tube and companion cells which seem as small group between protoxylem.
(iii) Conjuctive Tissue : The tissue connecting xylem and phloem and having location with pericycle and pith is known as conjuctive tissue. INITIALLY they are made up of parenchyma. Later on they become of collenchyma.
(iv) Pith: The cells of pith are parenchymatic and they are more in number,
Inter cellular spaces can be seem between cells.
Discussion
18449.

Question : Describe Kingdom - Fungi.

Answer»

Solution :The Kingdom-Fungi or Mycota constitute a unique kingdom of heterotrophic organisms.
They show a great diversity in morphology and habitat.
Mycology is the branch of science that deals with the study of various fungi.
A scientist having specialisation in the study of fungi is called mycologist.
Examples of fungi :
(1) When your bread develops a mould or your orange rots it is because of fungi.
(2) The common mushroom you eat and TOADSTOOLS are also fungi.
(3) White spots seen on mustard leaves are due to a parasitic fungus.
(4) Some unicellular fungi, e.g. yeast are used to make bread and beer.
(5) Other fungi cause diseases in plant and animals, wheat rust. causing puccinia is an important example.
(6) Some are the source of antibiotics e.g. Penicillium.
Habitat : Fungi are cosmopolitan and occur in air, water, soil and on animals and plants.
They PREFER to grow in warm and humid places.
Body organisation : With the exception of yeasts which are unicellular, fungi are filamentous.
Their bodies consists of long, slender thread - like structure.
Fungal hyphae are thin tubular transparent threads or filaments filled with protoplasm are covered by WALL.
The network of hyphae is known as mycelium.
Some hyphae are continuous tubes filled with multinucleated cytoplasm - these are coenocytic hyphae.
Other have septate or cross wall in their hyphae.
The hyphae are of following types found in fungi :
(i) Aseptate hyphae : In aseptate hyphae cross walls or septa are not formed at the time of nuclear division.
Such hyphae are multinucleate.
It is called coenocytic, if mycelium contain aseptate and multinucleate hyphae.
(ii) Septate hyphae : In this type, cross walls or septa form after the nuclear division.
The cells may have one, two or many nuclei.
These have septal pores or cross walls in their hyphae, which allow movement of substances between adjacent cells.
Fungal tissue : In fungi, fungal tissue is formed by interweaving of fungal hyphae called as PLECTENCHYMA.
Fungal cells : Fungi are eukaryotic cell
A cell wall is present on the outside, made of chitin and polysaccharide.
They posses all the eukaryotic cell organelles except plastids.
Nutrition : Most fungi are heterotrophic and absorb soluble organic matter from dead substrates and hence are called saprophytes.
Those that depend on living plants and animals are called parasites.
They can also live as symbionts in association with algae as lichens and with roots of higher plants as mycorrhiza.
Reproduction : Reproduction in fungi can take place by vegetative means - fragmentation, fission and budding.
Asexual reproduction is by spores called conidia or sporangiospores or zoospores and sexual reproduction is by OOSPORES and basidiospores. The various spores are produced in distinct structures called fruiting bodies.
The sexual cycle involves the following three steps:
(i) Fusion of protoplasms between two motile or non-motile gametes called plasmogamy.
(ii) Fusion of two nuclei called Karyogamy.
(iii) Meiosis in zygote resulting in haploid spores.
When a fungus reproduces sexually, two haploid hyphae of compatible mating types come together and fuse.
In some fungi the fusion of two haploid cells immediately result in diploid cells (2n).
In other fungi (ascomycetes and basidiomycetes) an intervening dikaryotic stage (`n + n`, i.e. two nuclei per cell) occurs, such a condition is called dikaryon and the phase is called dikaryophase of fungus.
Later, the parental nuclei fuse and the cells become diploid.
The fungi form fruiting bodies in which reduction division occurs, leading to formation of haploid spores.
Discussion
18450.

Question : Describe Key as taxonomical aid.

Answer»

Solution :Key is taxonomical aid used for identification of plants and ANIMALS based on the similarities and dissimilarities.
The keys are based on the contrasting CHARACTERS generally in a pair called couplet.
It represents the choice made between two OPPOSITE options.
This results in acceptance of only one and REJECTION of the other.
Each statement in the key is called a lead.
Separate taxonomic keys are required for each taxonomic category such as family, genus and species for identification purposes.
Keys are generally ANALYTICAL in nature.
Discussion