Biology Experiments PDF

# BIOLOGY ## Experiments ### Experiment No. 1: To prepare a temporary mount of a leaf peel to show its stomata. **Requirements:** Any Mesophytic dicot leaf, microscope, glass slides, distilled water, dropper, glycerol, coverslips, forceps etc. **Theory:** - **Leaf:** It is a flat green part of...

# BIOLOGY ## Experiments ### Experiment No. 1: To prepare a temporary mount of a leaf peel to show its stomata. **Requirements:** Any Mesophytic dicot leaf, microscope, glass slides, distilled water, dropper, glycerol, coverslips, forceps etc. **Theory:** - **Leaf:** It is a flat green part of plant. Leaf has leaf base, leaf stalk and leaf lamina. Leaf lamina has a network of veins and veinlets. - **Stomata:** Stomata in a leaf is a structure meant for gaseous exchange. Two guard cells outline the stomata and are surrounded by subsidiary cells of epidermis. Stomata open in light and closes in dark in most land plants and are usually present on lower surface of leaves. - During opening, guard cells absorb water from subsidiary cells and become turgid or swollen; during closing, guard cells become flaccid or shrunken by the loss of water to surrounding cells. - **Stomatal distribution can be of following types:** 1. **Hypostomatous:** Stomata are present only on lower surface of leaf e.g. Most dicots. 2. **Amphistomatous:** Stomata are present on both the surfaces of leaf but more on lower side. e.g. Most monocots (oat). 3. **Epistomatous:** Stomata are present on upper surface only e.g., water lily. **Procedure:** 1. Take a leaf and observe its parts. In case of small leaf, place it on glass slide and put a drop of glycerine and cover it with the coverslip. Observe this temporary mount of leaf under dissection microscope. 2. For observing stomata, select a plant and keep it exposed to sunlight for a few hours. 3. Take a turgid leaf of such mesophytic plant (for dicot-take Petunia, Dianthus and Solanum, for monocot-take lily, maize and grass). 4. Tear the leaf tangentially from its lower surface so that a thin peel can be obtained. (alternatively tear the peel horizontally with a sharp blade.) **Observations:** - **Structure of Stomata (in dicot leaf)**: Stomata after exposing to sunlight becomes open. Oblong or oval pores can be seen in kidney shaped guard cells. - **Structure of stomata (in monocot leaf)**: When stomata are observed after keeping the mount in darkness, they are found because guard cells lose turgidity in darkness. **Precautions:** 1. Select turgid leaf only. 2. Carefully remove the peel from lower epidermis only. 3. Mount the peel with outer epidermal surface towards objective lens of microscope. 4. Lower epidermis of leaf should be kept wet before use. 5. Do not breath over the peel. ### Experiment No. 2: To show that carbon dioxide is produced during respiration. **Requirements:** A conical flask, beaker, test tube, KOH Pellets, a glass tube bent at right angles, cork, thread, presoaked gram seeds, coloured water. **Theory:** - **Respiration:** Respiration is a vital process occurring in all living cells in which organic compounds are oxidised with the release of energy and CO2 in the presence or absence of oxygen, so respiration is a process of releasing energy from food for life processes. - **Chemical Equation:** $C_6H_{12}O_6 + 6O_2 \longrightarrow 6CO_2 + 6H_2O + Energy$ (Glucose) - **Types of respiration:** 1. **Aerobic respiration:** Free oxygen is used for complete oxidation of substrates forming CO2 and water and releases energy as ATP (Adenosine triphosphate). 2. **Anaerobic respiration (Fermentation):** It is incomplete oxidation of substrates without utilising free oxygen so that end products are carbon dioxide and ethyl alcohol. e.g. yeast, skeletal muscles. - **Chemical Reaction:** $Ca(OH)_2 + CO_2 \longrightarrow CaCO_3 + H_2O$ (Lime water) (White ppt.) **Procedure:** 1. Soak gram seeds overnight in water and germinate seeds by placing them in moist cotton wool for 3-4 days. 2. Place moist germinating seeds in a conical flask so that respiration may continue for longer time. 3. Suspend a test tube containing KOH pellets. 4. Fit a single hole cork in conical flask to close its mouth. 5. In hole of cork, place a glass tube bent twice at right angle. 6. Keep the connections air tight. 7. Dip the free end of bent tube in a beaker containing water. (Colour can be added in water for better observation.) Mark the initial level of water. 8. Keep the set up undisturbed for 15 minutes and mark the final level of water. 9. Note down the observations. **Observations:** KOH will absorb CO2. Thus water level in bent tube rises. **Precautions:** 1. Carefully hang the test tube containing KOH pellets. 2. KOH should be handled carefully, as it is corrosive. 3. Connections should be made air tight with molten wax. ### Experiment No. 3: To study binary fission in Amoeba or Paramaecium, budding (in yeast) with the help of prepared slides. **Requirements:** Compound Microscope, prepared slides of binary fission. **Theory:** - **Binary fission:** Binary fission is a method of asexual reproduction specially in protozoans. Binary means two and fission means splitting. - **In Binary fission:** a living organism divides in two e.g. in Bacteria, Amoeba, Paramecium etc. - Parent cell elongates and its nuclear body starts dividing into two followed by splitting, so that two new equal sized cells are formed. These new cells are called daughter cells. These daughter cells separate and redivide after maturity. It can be observed well in prepared slides. **Procedure:** 1. Select prepared slides of Amoeba (binary fission), yeast (budding) and Hydra (budding). **Observations:** - **Binary fission in Amoeba:** 1. Parent cell becomes elongated. 2. Nuclear body duplicates, elongates becomes oblong and ready to split. 3. At point of fission a cleavage or furrow can be observed. 4. Two small daughter cells are formed. - **Budding in Yeast:** 1. A small protuberance grows on upper part of yeast cell. 2. Nucleus divides amitotically. 3. Newly divided nucleus moves in to bud. 4. Repeated budding forms the chain of cells. - **Budding in Hydra:** 1. An outgrowth is observed on the body of Hydra. 2. Protuberance is large enough and is multicellular. 3. Bud bears separate mouth and tentacles. 4. Bud may detach to form new individual. **Procedure:** 2. Set up a light microscope. Look through eye piece and adjust mirror and diaphragm. 3. Observe the slides first under low power and then under high power and note down the observations. **Precautions:** 1. First, focus the slide under low power then observe under high power. 2. Whole mount of Hydra can be observed under dissecting microscope. ### Experiment No. 4: To identify different parts of an embryo of a dicot seed (Pea, Gram or Red kidney bean). **Requirements:** Petri-dish, cotton wool, germinating seeds, forcep, needle, filter paper **Theory:** - **Embryo:** Embryo has an axis with a downward pointing radicle including a root apex. Radicle penetrates seed coat, seed generating branches profusely and becomes primary root system. - **Epicotyl with plumule:** is present on top of embryonal axis here anatomy changes from root type to stem type. Shoot apex is formed to bear stem and leaves. - **Cotyledons:** The embryonal axis has two appendages in dicot seeds. The part of axis where cotyledons are attached is called a node. Cotyledons store food. - **In plants:** integument of ovule becomes seed coat. Zygote grows and becomes a true embryo inside integument. - **Seed germination:** Seeds are normally in a dormant condition when seeds resume their growth or development it is called seed germination. **Procedure:** **For seed germination:** 1. Take a petri dish and put some dry gram/bean seeds in it. 2. Soak the dicot seeds in plain water and allow it to germinate over night. 3. Drain the excess water and cover soaked seeds with wet cotton cloth and leave for a day. 4. Observe the structure of a seed. 5. Open the two cotyledons with a forcep and needle. 6. Also observe the embryonal axis with a magnifying glass and label its parts. **Observations:** **Structure of seed** | Part | Description | |----------------------------|-----------------------------------------------------------------------------------------------------| | Cotyledons | Food storage organs that serve as first seeds leaves in Bean seed. | | Plumule | Terminal part of embryo axis forms shoot. | | Epicotyl | Part of embryonal axis above cotyledon makes future shoot. | | Hypocotyl | Part below attachment point, makes structure, a part of future root. | | Radicle | Part of embryonal axis developing into a root. | | Micropyle | Aperture meant for absorption of water. | **Precautions:** 1. Conditions for the seed germination should be optimum. i.e. warmth, moisture and air. 2. Care should be taken to separate two cotyledons so that the embryonal axis is intact. 3. Do not use glycerine to germinate seeds.