Biology Labs PDF

# Saved Photos ## 1. To Study the Microscope ### Introduction: - A microscope is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. - Microscopy is the science investigating small objects and structures using a microscope. - Microscopic means being invi...

# Saved Photos ## 1. To Study the Microscope ### Introduction: - A microscope is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. - Microscopy is the science investigating small objects and structures using a microscope. - Microscopic means being invisible to the eye unless aided by a microscope. ### Goal: - To study the microscope. ### Apparatus and Tools: - Microscope ### Theory: - It is one of the most important instruments in a biology laboratory. - It comes to be called as 'The primary instrument of the biologists'. - It helps to increase the resolving power of human eye which fails to recognize objects lying closer between 0.01 to 0.25 mm. - Resolving Power: Property to distinguish objects lying very close as separate bodies. ### Example: ### Procedure: 1. Show the various parts and components of microscope to students. 2. The microscope is built around a strong base and a vertical frame (arm). 3. The base supports the vertical frame. 4. A round, rectangular or square stage is fixed to the frame. 5. It is provided with mechanical clips to hold the slide in position. 6. Stage is vertically movable with the help of coarse and fine adjustment screws on the frame. 7. Coarse adjustment moves the stage rapidly. 8. Fine adjustment screw makes image clear. 9. Below the stage, an iris diaphragm and condenser lens are present. 10. Iris diaphragm, regulate the aperture, through which light rays reach the condenser and are passed to an object. 11. Condenser is a system of two or more lenses under the stage which receives parallel light rays from light source and converge them at the level of stage. 12. Below the condenser, a light source is present with a switch and brightness adjustment. 13. Body of the microscope is composed of a head. 14. At the upper end of the head, is an ocular (eye piece). 15. At the lower end of this tube is a revolving nose-piece with about three objectives viz. low power, high power and oil immersion. ### Anatomy of a Microscope - **Ocular Lens (Eyepiece)** - **Diopter Adjustment** - **Nose Piece** - **Mechanical Stage** - **Condenser** - **Illumination** - **Objective Lens** - **Head** - **Frame (Arm)** - **Stage Control** - **Coarse Adjustment** - **Brightness Adjustment** - **Fine Adjustment** - **Light Switch** - **Base** ### Magnification: - Apparent increase in image size. ### Resolution: - Ability to distinguish fine detail. ### Contrast: - Ability to distinguish objects, such as cells, from the background. ### Cytology: - Study of cells. ### Histology: - Study of tissues. ### Pathology: - Study of disease. ### Total Magnification: - Overall enlargement of the image of a specimen. - To calculate total magnification, multiply the magnification of the ocular lens (10X) with the magnification of the objective lens. ## 2. To Be Able to Differentiate Between Biological Molecules Practically. ### Introduction: - Biomolecule, also called biological molecule, are substances that are produced by cells and living organisms. - Biomolecules have a wide range of sizes and structures and perform a vast array of functions. - The four major types of biomolecules are carbohydrates, lipids, nucleic acids, and proteins. ### Goal: - To be able to differentiate between biological molecules practically. ### Apparatus and Tools: - Test tubes - Test tube holder - Test tube brushes - Pipettes - Water bath - UV spectrophotometer - Vortex - Different biological samples ### Chemical Required: - **Benedict's reagent:** - Prepared by adding 17.3 gm of sodium citrate, 10 gm of sodium carbonate and 17.3 gm of sodium pentahydrate to 100 ml of water in a beaker. - **Lugol's iodine:** - 5% elemental iodine is mixed with 10% potassium iodide to form the Lugol's iodine. - **Ethanol and water** - **Biuret reagent:** - 0.3 g of CuSO4 and 0.9 g of sodium-potassium tartrate are added to 50 ml of 0.2N NaOH. - To this, 0.5 g of KI added and the volume is made up to 100 ml by adding 0.2N NaOH. ### Theory: #### Benedict's Test for Reducing Sugars - Benedict's test is a biochemical test performed to distinguish reducing sugars (monosaccharides and some disaccharides) from non-reducing sugars. - A reducing agent has a functional group that can be oxidized. A ketone or aldehyde functional group can act as a reducing agent. - In order to detect the reducing agent, Benedict reagent is used. - It appears deep blue in color. - It consists of copper sulfate mixed with sodium citrate and a weak alkali, sodium carbonate. - When reducing sugars are heated in the presence of alkali, they get converted to enediols, which are powerful reducing agents. - Enediols reduce the cupric ions (Cu2+) present in the benedict's reagent to cuprous ions (Cu+), which get precipitated as insoluble red-colored cuprous oxide. #### Starch: - A polysaccharide consisting of long chains of glucose. #### Amylase: - An enzyme found in saliva and pancreatic secretions that breaks down polysaccharides into smaller oligosaccharides and disaccharides such as maltose. - Stomach acids dramatically alter the pH of different parts of the digestive system. - pH affects the way enzymes such as amylase function. - Amylase is an enzyme that breaks down polysaccharides into smaller oligosaccharides, maltose, and with enough time eventually into glucose. #### Benedict Reagent - Light blue solution that tests for many types of simple sugars. - Benedict reagent goes through a series of color changes to indicate the amount of simple sugars present. - **Light blue (original color) = no simple sugars**. - The color then progresses through **green, yellow, orange, red, and brown** as the amount of simple sugars increase. **What is the best pH for amylase activity?** - Amylase works best at pH 7 but generates a little maltose at pH 2. ## 3. Iodine Test For Starch - Iodine test is based on the fact that polyiodide ions form colored adsorption complex with helical chains of glucose residue of amylase (blue-black), dextrin (black), or glycogen (reddish-brown). - Monosaccharides, disaccharides, and branched polysaccharides like cellulose remain colorless. - Amylopectin produces orange-yellow hue. #### Glucose: - A small, six-carbon sugar molecule found in starch and glycogen. - A common monosaccharide: One individual molecule of sugar; the building blocks of carbohydrates. #### Disaccharide: - A carbohydrate made up of two sugar molecules linked together. #### Maltose: - A disaccharide consisting of two glucose molecules bound together. #### Simple sugar: - Monosaccharides and disaccharides. #### Oligosaccharide: - A carbohydrate made up of more than two sugar molecules linked together. #### Polysaccharide: - A carbohydrate made up of hundreds to thousands of sugar molecules linked together. #### Starch: - A plant-based polysaccharide. #### Glycogen: - An animal-based polysaccharide. #### Iodine: - A solution that turns from brown to purple in the presence of starch. #### Positive control: - Any procedure that is known to produce the desired result. - A positive test result means what you are looking for is present. #### Negative control: - Any procedure that is known to NOT produce the desired result. - A negative test result means what you are looking for is NOT present. ## 4. Emulsion Test For Lipids. - This test is based on the fact that lipids dissolve in ethanol (due to hydrophobic interaction), but on the addition of water lipids spontaneously disperse to form micelles (small droplets). - These droplets form the top layer as they are less dense than water and ethanol, and also appear cloudy white as they diffract light. #### Lipid: - A macromolecule made up of dozens to hundreds of molecules of mostly carbon and hydrogen. #### Cholesterol: - A lipid with a structure containing over 20 carbon atoms configured into four rings. #### Phospholipid: - A lipid made up of a three-carbon glycerol molecule with a phosphate group and two fatty acids attached. #### Triglyceride: - A lipid made up of a three carbon glycerol molecule with three fatty acid chains attached to it. #### Fatty acids: - Long chains of carbon with hydrogen attached, making them nonpolar molecules #### Nonpolar: - A type of covalent bonding that produces a molecule without any charge. - This is common when many of the same or similar atoms are bonded. #### Polar: - A type of covalent or ionic bond that produces a molecule with electrical charges. - This is common when atoms that are very dissimilar are bonded. #### Saturated fatty acid: - A chain of carbon atoms using only single carbon-to-carbon bonds with hydrogen atoms attached to the carbon atoms. #### Unsaturated fatty acid: - A chain of carbon atoms that contain one (monounsaturated) or more (polyunsaturated) double bonds between carbons with hydrogen atoms attached to the carbon atoms. #### Emulsifier: - A substance that has a polar and nonpolar component that can disperse fat into smaller particles in water or other polar solutions. ## 5. Biuret Test for Proteins. - The biuret reagent contains sodium hydroxide, copper (II) sulfate, and potassium sodium tartrate. - Under alkaline conditions of the biuret reaction (pH 14), deprotonation of the amide nitrogen occurs, which leads to high electron density at the nitrogen atom. - Further, copper (II) ion complexes with four peptide nitrogen's to yield a tetradentate violet colored coordination complex. - At high pH, Cu2+ bonding with OH- ion leads to an insoluble precipitate, which is minimized by the addition of potassium sodium tartrate, which stabilizes the cupric ions. #### Proteins: - Polymers consisting of long chains of amino acid monomers. #### Monomer: - A substance that is the smallest unit of a category of substances. - For example, an amino acid is a monomer of a protein. #### Dipeptide: - When two amino acids fold to form a dipeptide. #### Polymer: - A substance made up of many units of a common chemical attached to each other. #### Biuret reagent: - A light blue reagent that tests for protein. - The Biuret reagent turns from light blue to pink if a low concentration of protein is present. Dark purple indicates a high protein concentration. ## 6. To Differentiate Between Prokaryotic and Eukaryotic Cells, in Addition to Plant and Animal Cells. ### Introduction: - A cell is defined as the smallest, basic unit of life that is responsible for all of life's processes. - Cells are the structural, functional, and biological units of all living beings. - A cell can replicate itself independently. - Hence, they are known as the building blocks of life. - Each cell contains a fluid called the cytoplasm, which is enclosed by a membrane. - In addition, present in the cytoplasm are several biomolecules like proteins, nucleic acids and lipids. - Moreover, cellular structures called cell organelles are suspended in the cytoplasm. ### Goal: - To differentiate between prokaryotic & eukaryotic cells, in addition to plant and animal cells. ### Apparatus and Tools: - Permanent Slides - Model of Prokaryotic and Eukaryotic cell - Microscope - Electron Micrograph ### Theory: - A cell is the structural and fundamental unit of life. - The study of cells from its basic structure to the functions of every cell organelle is called Cell Biology. - Robert Hooke was the first Biologist who discovered cells. - All organisms are made up of cells. - They may be made up of a single cell (unicellular), or many cells (multicellular). - Mycoplasmas are the smallest known cells. - Cells are the building blocks of all living beings. - They provide structure to the body and convert the nutrients taken from the food into energy. - Cells are the lowest level of organisation in every life form. - From organism to organism, the count of cells may vary. - Humans have more number of cells compared to that of bacteria. - Cells comprise several cell organelles that perform specialised functions to carry out life processes. - Every organelle has a specific structure. - The hereditary material of the organisms is also present in the cells. ### Example: - **Prokaryotic Cell:** Bacteria - **Eukaryotic Cell:** Plant, Animal, Fungi ### Procedure: - Observe the permanent slides and electron micrograph. ### Results: #### Prokaryotic Cell: Bacteria - **Observation:** 1. The first organisms to inhabit Earth were prokaryotes. 2. Most prokaryotes are unicellular. 3. Prokaryotic cells have a variety of shapes. 4. The outermost layer is the cell wall, which maintains cell shape and protects the cell. 5. Cell wall is made up of peptidoglycan. 6. Cell wall is followed by plasma membrane. 7. Ribosomes (70S) are present in the cytoplasm. 8. DNA is present in nucleoid, a region of cytoplasm that is not enclosed by a membrane. 9. Flagella may be present over the entire surface of the cell or concentrated at one or both ends. 10. Pili are appendages that pull two cells together prior to DNA transfer from one cell to the other. #### Eukaryotic Cell: Plant - **Observation:** - There are a large number of regularly shaped cells lying side by side and each cell has a distinct cell wall. - A distinct nucleus is present on the periphery of each cell. - Lightly stained cytoplasm is observed in each cell. #### Eukaryotic cell: Animal - **Observation:** - A large number of flat and irregular-shaped cells are observed. - The cells do not have a cell wall. - However, each cell has a thin cell membrane. - A deeply stained nucleus is observed at the centre of each cell. - No prominent vacuoles are observed in the cells. #### Micrograph: - A photograph taken through a microscope of a magnified specimen. #### Cell: - The smallest unit of life that can function independently. #### Prokaryotic cell: - A cell that lacks a nucleus. #### Eukaryotic cell: - A cell that contains a nucleus and other membrane-bounded organelles and that tends to be larger than a prokaryotic cell. #### Cytoplasm: - A fluid called cytosol plus all the cell contents between the nucleus (in eukaryotic cells) and the cell membrane. #### Cell membrane: - Lipid-rich bilayer that surrounds the cytoplasm and contents of a cell and forms a boundary between the cell interior and its environment. #### DNA (deoxyribonucleic acid): - Nucleic acid that serves as the genetic material in all cells by encoding the information for the production of proteins and RNA. #### RNA (ribonucleic acid): - Nucleic acid that is synthesized from DNA and is used at ribosomes to coordinate the synthesis of proteins. #### Ribosomes: - Structures composed of RNA and protein that are the sites of protein synthesis. #### Organelles: - Membrane-bounded compartments in eukaryotic cells that carry out specialized functions. #### Nucleus: - Organelle that contains the DNA and acts as the command center of the cell. #### Rough endoplasmic reticulum: - Organelle that is a network of membranes studded with ribosomes and that plays a role in protein synthesis. #### Smooth endoplasmic reticulum: - Organelle that is a network of membranes and is the site of lipid synthesis and the detoxification of certain drugs and poisons. #### Golgi apparatus: - Organelle that is a stack of flattened sacs where proteins are modified, processed, and packaged for different locations in the cell or for export. #### Mitochondria: - Organelle that carries out cellular respiration to produce ATP #### Chloroplast: - Organelle found in plant cells and some protist cells that carries out photosynthesis to produce sugars. #### Central vacuole: - Organelle found in plant cells that is a large, fluid-filled sac for storing water and metabolites. #### Centrioles: - Two short cylinders of proteins found in animal cells that help to organize microtubules. #### Cell wall: - Outer layer on prokaryotic, plant, fungi, and many protist cells that surrounds the cell membrane and provides support, shape, and strength to the cell. ## 7. To Reveal the Presence of Enzymes in Some Vegetables and Fruits ### Introduction: - An enzyme is a substance that acts as a catalyst in living organisms, regulating the rate at which chemical reactions proceed without itself being altered in the process. - Enzymic browning is an oxidation reaction that takes place in some foods, mostly fruit and vegetables, causing the food to turn brown. - There are thousands of enzymes are found in living cells where they act as catalysts or the thousands of chemical reactions which occur. - In addition to making life possible, many enzymes have numerous applications that affect our daily lives in other ways such as food processing, clinical diagnoses, sewage treatment, and the textile industry. - Most enzymes in the human body work best at around 37°C, which is the body's typical temperature. - At lower temperatures, they may still work but much more slowly. ### Goal: - To reveal the presence of enzymes in some vegetables and fruits. ### Apparatus and Tools: - **For Amylase:** - Starch-agar plates (0.2% soluble starch, 2% agar) - Wax pencil - Distilled water (in wash bottle) - Plant samples as in procedure. - **For Catalase:** - Test tubes (one for each material to be tested plus extra for control) - Hydrogen peroxide (H2O2) (3% solution) - Assorted living tissue: sliced raw potato, ground meat, liver, yeast cells, ground young leaves - Assorted non-living material: piece of baked potato or cooked liver, etc. (Use caution with rocks or sand, some will "bubble.") - **For Papain:** - Gelatin (Knox, Jello) - Beaker (150 ml) - Balance or teaspoon - Stirring rods (3) - Test tubes (2) - Test tube rack - Beaker of ice water - Hot plate - Distilled water (100 ml) ### Theory: - Enzyme experiments are ideal for "hands on" opportunities. - Since several factors affect the rate at which enzymatic reactions proceed, an enzyme experiment presents many opportunities in the biology laboratory. - The experiments presented are selected on the basis that they: - are simple to prepare, - use materials which are familiar to the student, and - can be used as a base from which to construct additional experiments. #### For Amylase: - Amylase is an enzyme that catalyses the hydrolysis of the polysaccharide starch (amylose) to the disaccharide maltose. - It is readily abundant in saliva, but somewhat unpleasant to obtain in large quantities. - It is widely distributed in plant tissues, but is most abundant in seeds, where it apparently functions in initiating the breakdown of stored starch to glucose which is needed in large amounts during germination. #### For Catalase: - Hydrogen peroxide (H2O2) is naturally formed in living organisms, however it is very harmful and is broken down immediately by several enzymes including catalase. - This enzyme catalyses the breakdown of hydrogen peroxide to water and oxygen. #### Enzymatic activity can be measured in two ways. - **Amount of substrate consumed** - **Amount of product produced** #### For Papain: - Papain, from the latex of the papaya plant, is one of a family of plant enzymes that includes bromelain (from pineapple) and ficin (from fig), all of which break down proteins. - This is why the directions on a box of Jello remind you never to use fresh or frozen pineapple in your gelatin, since gelatin is the protein responsible for the "gel." - A convenient source of papain is fresh pineapple juice or meat tenderizer. ## 8. To Study the Effect of Osmosis on Different Types of Cells Through Experiments on Plant and Animal Cells ### Introduction: - All cells are enclosed by a cell membrane. - This structure has two layers. - Each layer has two main components, phospholipids and proteins. - The phospholipid molecules are able to move around within the layers and give the cell membrane flexibility. - Protein molecules are found embedded in the two layers of phospholipids. - Membrane proteins have a wide variety of functions. - Some allow a cell to respond to specific chemical signals from other cells. - Others are enzymes. - Some proteins are involved in the transport of substances across the cell membrane. - The cell membrane is selectively permeable. - It lets some substances pass through readily and some substances pass through more slowly, but prevents other substances passing through it at all. - Some small molecules such as water, oxygen and carbon dioxide can pass directly through the phospholipids in the cell membrane. - Larger molecules such as glucose require a specific transport protein to facilitate their movement across the cell membrane. - Very large molecules such as glucose require a specific transport protein to facilitate their movement across the cell membrane. - Very large molecules such as proteins are too big to move through the cell membrane, which is said to be impermeable. ### Goal: - To study the effect of osmosis on different types of cells through experiments on plant and animal cells. ### Apparatus and Tools: - Blood Sample - Test tube - Glass slide - Coverslip - Microscope - Salt solution (0.85%) - Rhoeo leaf - Petriplates - Sugar solution (5%) - Microscope ### Theory: - Cells can gain or lose water by the process of osmosis. - This depends on the water concentration of the solution inside the cell compared to water concentration of the solution outside the cell. - The water concentration can be thought of as the proportion of a solution that is water. - Solutions with a high concentration of solute molecules, such as sugars or salts, have a low concentration of water molecules and vice versa. - The net movement of water from a region of high water concentration to a region of low water concentration through a selectively permeable membrane. #### There are 3 types of osmotic environments: isotonic, hypotonic, and hypertonic. - **Isotonic Environment** - Water enters and leaves cells at the same rate. - **Hypertonic environment** - A solution with a higher concentration of nonpermeable solutes in comparison to another solution. - **Hypotonic environment:** - A solution with a lower concentration of nonpermeable solutes in comparison to another solution #### Tonicity: - The ability of a solution to change the volume of a cell through osmosis. - **Isotonic:** A solution with the same concentration of nonpermeable solutes in comparison to another solution. ## 9a. To Study the Different Stages of Mitosis in Onion Root Tips ### Introduction: - Somatic growth in plants and animals takes place by the increase in the number of cells. - A cell divides mitotically to form two daughter cells wherein the number of chromosomes remains the same (i.e., unchanged) as in the mother cell. - In plants, such divisions rapidly take place in meristematic tissues of root and shoot apices, where the stages of mitosis can be easily observed. - In animals, mitotically dividing cells can be easily viewed in the bone marrow tissue of a vertebrate, epithelial cells from gills in fishes and the tail of growing tadpole larvae of frog. ### Goal: - Preparation and study of mitosis in onion root tips. ### Apparatus and Tools: - Onion bulbs - Wide mouth glass tubes/jar/bottle - Glacial acetic acid - Ethanol 2-4% acetocarmine/acetoorcein stain - N/10 HCl - Spirit lamp/hot plate - Slide - Cover slips - Blotting paper - Molten wax/nail polish - Compound microscope. ### Theory: - For entities to mature, grow, maintain tissues, repair and synthesize new cells, cell division is required. - Cell division is of two types: - Mitosis: - The nucleus of the eukaryotic cells divides into two, subsequently resulting in the splitting of the parent cells into two daughter cells. - Hence, every cell division involves two chief stages: - **Cytokinesis:** Cytoplasm division - **Karyokinesis:** Nucleus division - Meiosis: - A cell division process in eukaryotes that divides the genetic material into two identical daughter nuclei. - **Cytokinesis:** Division of the cytoplasm into daughter cells. - **Chromosome:** A molecule of DNA wrapped around proteins and contained in the nucleus of eukaryotic cells. - **Spindle:** A set of microtubule proteins that coordinate the movement and division of chromosomes during mitosis. - **Sister chromatids:** One of two identical copies of a chromosome produced by DNA replication and attached to each other at the centromere. - **Centromere:** Constriction where sister chromatids of a duplicated chromosome are held together. - **Centrosome:** Microtubule-organizing center in cells; in animals cells, it contains two, short cylinders of microtubules called centrioles. ### Procedure 1. Take a small piece of tender stem and hold it vertically. 2. Cut several thin sections using a blade. 3. Transfer the sections into a watch glass containing water. 4. Select a section which is complete, thin, and uniform, and transfer it onto a slide with a drop of water, using a brush. 5. Add one drop of safranin solution (stain) and leave it for 3 minutes. 6. Remove the excess stain by washing. 7. Add 2 drops of glycerin and put the cover slip, using needle. 8. Blot out extra glycerin and focus the slide, first under low power and then under high power. 9. Compare the slide with structure given in figure. ### Results: - Carefully observe the different type of plant tissues. ## 9b. To Study the Different Stages of Meiosis Using Permanent Slides ### Introduction: - Meiosis is a type of cell division in which the number of chromosomes is halved (from diploid to haploid) in the daughter cells, i.e., the gametes. - The division is completed in two phases, meiosis I and meiosis II. - Meiosis I is a reductional division in which the chromosomes of homologous pairs separate from each other. - Meiosis II is equational division resulting in the formation of four daughter cells. - Stages of meiosis can be observed in a cytological preparation of the cells of testis tubules or in the pollen mother cells of the anthers of flower buds. ### Goal: - To study the different stages of meiosis using permanent slides. ### Apparatus and Tools: - Permanent slides of meiosis and compound microscope. ### Theory: - Meiosis is the process in which a single cell divides twice to form four haploid daughter cells. - These cells are the gametes: sperms in males and eggs in females. - The process of meiosis is divided into two stages. - Each stage is subdivided into several phases. #### Meiosis I #### Meiosis II #### Homologous chromosomes: - Two chromosomes that share the same size, centromere position, and sequence of genes. #### Sister chromatids: - One of two identical copies of a chromosome produced by DNA replication and attached to each other at the centromere. #### Diploid: - Cell condition in which two chromosomes of each type are present. #### Haploid: - Cell condition in which only one of each type of chromosome is present; gametes, such as sperm and eggs, are haploid. #### Germ-line cells: - Specialized cells that undergo meiosis to give rise to gametes. #### Zygote: - Diploid cell formed by the union of two gametes during fertilization. #### Oocyte: - Cell in an ovary that will undergo meiosis to form an ovum (egg). #### Spermatocyte: - Cell in a testis that will undergo meiosis to form a sperm cell. #### Gametes: - Haploid cells produced by meiosis that unite during fertilization as part of sexual reproduction; gametes contain half the number of chromosomes as body cells and are often called eggs and sperm. ### Example: #### Leptotene: - The nuclear membrane and nucleolus are not distinctly observable. - Fine network of thin threads are seen uniformly distributed in the nucleus. - These are chromatin threads, which may be observed as more prominent structures in the later stages. #### Zygotene: - This stage is characterized by the pairing of the homologous chromosomes, which can be seen as paired chromatin threads. #### Pachytene: - The chromatin threads get condensed and appear shortened and thick. - Pairs of homologous chromosomes can be seen. - Each chromosome has two chromatids and thus each bivalent consists of four chromatids. - This configuration is called tetrad. #### Diplotene: - The homologous chromosomes (each made up of two chromatids) show distinct separation from each other except at few regions where attachments are seen (figure). - These are chiasmata (sing. chiasma) representing the site of exchange of the parts between two homologous chromosomes. #### Diakinesis: - The homologous pair of chromosomes appear more shortened, thick and prominent. - Chiasmata can be still observed. - All the homologous pairs appear scattered in the cell. #### Metaphase I: - Homologous chromosomes are still in pairs and are arranged along the equatorial plane of the cell. - At this stage, the number of bivalents can be counted. - Chiasmata may still be seen in a few bivalents. #### Anaphase I: - Homologous chromosomes appear to have moved towards the two opposite poles of the cell. - At the later stage, the anaphase I may show the assembly of chromosomes at two poles. - This results into the reduction of number of chromosomes to half. - This stage can be identified by the presence of two chromatids in each chromosome. #### Telophase I: - The chromosomes present at the two poles appear decondensed and form two distinct nuclei. - The chromosomes are completely pulled apart and new nuclear envelope forms. #### Meiosis II #### Prophase II: - Distinct thread- like chromatin fibres or rod- shaped chromosome are seen. #### Metaphase II: - The chromosomes having two chromatids attached at the centromere are observed arranged at the equatorial plane of the cell. - Each chromosome of metaphase II has two chromatid whereas in metaphase I these are paired homologous chromosomes each having two chromatids thus forming tetrad. - In the metaphase I of meiosis, a few chiasmata are observed, whereas no chiasmata are observed during metaphase II. #### Anaphase II: - The two chromatids of each chromosome after separation appear to lie at the two poles of the cell. #### Telophase II: - The separated chromosomes appear decondensed and form nuclei. ## 10. Investigating Anaerobic Respiration in Seeds ### Introduction: - One of the basic and fundamental life processes that are carried out by living entities is respiration. - It is a catabolic process wherein complex organic molecules are broken down into simpler molecules. - The process releases energy either in the absence or presence of oxygen, and hence respiration can be of two kinds: #### Aerobic Respiration: - This kind of respiration takes place in the presence of oxygen, hence it results in the complete glucose oxidation with the release of energy. - It includes three stages namely, Krebs cycle, ETS and Glycolysis. - All events relating to ETS take place inside mitochondria while stages connected with glycolysis take place in the cytoplasm. #### Anaerobic Respiration: - In this type of respiration, oxidation of food takes place in an environment lacking oxygen supply. - Less energy is released as a result of incomplete oxidation of glucose. ### Goal: - Study of Anaerobic Respiration in Germinating seeds. ### Apparatus and Tools: - Germinating seeds (gram/urad/moong), flower buds, a small test tube/ glass vial, petridish, a plastic tray slightly bigger than the size of petridish, mercury, forceps, KOH pellets, burrette stand with clamp. ### Theory: - Breakdown of food substances to yield energy in the absence of oxygen is called anaerobic respiration. - It is observed in several soil anaerobic microorganisms, yeast and certain types of tissues in human body. - Anaerobic respiration yields much less energy per mole of glucose as compared with aerobic respiration. - Glucose (C6H12O6) → CO2 + C6H5OH ### Example: ### Procedure: 1. Take a test tube and completely fill it with mercury. Invert it over a petridish which is also filled with mercury. There must be a continuous column of mercury in the test tube. 2. Tilt the test tube slightly and with the help of forceps introduce 3-4 healthy germinating gram seeds. 3. Gently tap the test tube with your finger nail/forceps so that the seeds move upwards in the mercury column. 4. With a clamp fix the test tube to a stand and keep the setup undisturbed for two hours. ## 11 To Investigate the Different Types of Plant Tissue ### Introduction: - Plants are immobile and hence have been provided with tissues made up of dead cells, which provide structural strength. - They must endure unfavorable environmental situations like strong winds, storms, floods etc. - A tissue is a cluster of cells, that are alike in configuration and work together to attain a specific function. ### Goal: - To study the different types of plant tissue. ### Apparatus and Tools: - Blade - Tender stems of any plant - Glass slides - Cover slips - Safranin - Glycerine - Dissecting needle - Brush - Blotting paper - Watch glass - Compound microscope ### Theory: - A group of cells of the same size and shape, or of a mixed type, having a common origin and performing an identical function is called tissue. - Plant tissues are of two types-meristematic and permanent. - Meristematic tissue cells are capable of dividing, while permanent tissue cells are not. - Parenchyma, collenchyma, and sclerenchyma are the three types of simple permanent tissues. ### Example: ### Procedure: 1. Take a small piece of tender stem and hold it vertically. 2. Cut several thin sections using a blade. 3. Transfer the sections into a watch glass containing water. 4. Select a section which is complete, thin, and uniform, and transfer it onto a slide with a drop of water, using a brush. 5. Add one drop of safranin solution (stain) and leave it for 3 minutes. 6. Remove the excess stain by washing. 7. Add 2 drops of glycerin and put the cover slip, using needle. 8. Blot out extra glycerin and focus the slide, first under low power and then under high power. 9. Compare the slide with structure given in figure. ### Results: - Carefully observe the different type of plant tissues. ## 12. To Study the Different Types of Animal Tissues ### Introduction: - A tissue can be defined as a group of structurally similar cells performing a specific function or functions. - The study of the structure and function of the tissues is known as histology. - An organ is a structural and functional unit of a living body composed of different tissues. - Essentially the various organs of animals are composed of different types of tissues. - In this lab, students will be studying the structure of different types of animal tissues from the prepared slides and know about their function. ### Goal: - To investigate the different types of animal tissue. ### Apparatus and Tools: - Permanent slides of muscles, epithelial, connective and nerve fibres, and compound microscope. ### Theory: - A tissue is a group of connected cells that have a similar function within an organism. - There are four basic types of tissue in the body of all animals, including the human body. - These make up all the organs, structures and other contents of the body. #### Example of each tissue type: - **Epithelial tissue:** - Made up of layers of tightly packed cells that line the surfaces of the body for protection, secretion, and absorption. - Examples of epithelial tissue include the skin, the lining of the mouth and nose, and the lining of the digestive system. - **Muscle tissue:** - Made up of cells contain contractile filaments that move past each other and change the size of the cell