Tasks for Biology - list
TASK 1: Proof of enzyme – amylase
Flush your mouth with water (saliva contains enzyme amylase, which splits starch into simple sugars), filtrate it using a funnel, wet filtration paper and beaker. Prepare six tubes. The first one will contain 1 ml of saliva (concentrated amylase), second to fifth tubes will contain 1 ml of decreasing concentrations (1/2, 1/4, 1/8, 1/16) of amylase prepared by diluting saliva with physiological solution (0.9 % NaCl). The sixth tube will be a control containing 1 ml of physiological solution. Add 2 ml of starch to each tube including the control tube. Incubate the tubes at 40°C in a water bath for 5 min. Add Lugol’s solution to the control tube to permanent blue color and add the same amount to all other tubes. Evaluate the color of all tubes and explain why the color changed.
TASK 2: Proof of starch
Press a piece of potato against a slide (or scrape off some juice from a cut half of potato), add a drop of water and cover with the cover glass. Observe starch grains consisting of concentric layers. Add Lugol’s solution (KI + I2 + H2O) and observe the blue color of the stained starch.
Fig.: Starch grains.
TASK 3: Proof of fat
Observe the orange-red lipid vacuoles inside the liver cells.
Fig.: Lipid vacuoles in liver cells.
TASK 4: Proof of DNA in the nucleus of onion
Put an internal epidermis of onion onto the slide, fix it with 1 % acetic acid for few minutes, then stain it with 1 % methyl-green dye for 5 minutes and cover it with the cover glass.
TASK 5: Proof of protein (after Heller)
Pour 2 ml of nitric acid into the tube and slowly add egg white (the two liquids must not mix). You can observe a white ring of denatured protein between both layers.
Fig.: Proof of protein (ater Heller).
TASK 1: Viruses
Draw some of the viruses.
Fig.: Some examples of viruses (deduction of viral names: filum=fiber, calix=cup, corona=ring, parvus=small, toga=coat).
Prokaryotes and immersion microscopy
TASK 1: Smear impression of human tongue mucosa
Take a clean slide (from a box labelled "otisk jazyka") and anneal it in a gas burner flame. Let it cool off and then impress the surface of your tongue (after roughing it with your teeth) on the slide. Let the slide dry and then fix it above the flame. Perform Giemsa-Romanowski staining for 10 min. Rinse the dye with distilled water and dry the slide gently using a filtration paper. Observe the stained epithelium cells (polygonal shape, nucleus) and bacteria under immersion objective with immersion oil and measure their size.
Fig.: Epithelium cells of tongue and bacteria.
TASK 2: Bacteriological smear
Sterilize the bacteriological loop using the gas burner flame and let the loop cool off (not to kill the bacteria). Take a colony of bacteria from the surface of the agar medium in a Petri dish with the bacteriological loop and make a thin smear in a droplet of water on a slide. Let it dry and fix it over the flame (three times).
- Apply the crystal violet (the primary stain) on the slide for 3 min.
- Rinse it with distilled water and apply the Lugol solution (iodine solution) for 2 min.
- Rinse it and add the ethanol (decolorizer) until the stain stops being washed out.
- Apply the carbolfuchsin (counterstain) for 1.5 min.
- Rinse it with distilled water and dry with filter paper.
Observe and draw G+ (purplish-blue) and G- (red) bacteria under immersion objective.
Fig.: Bacteriological smear: A – transfer of bacteria by bacteriological loop, B – homogenisation of bacteria with water, C – bacteriological smear.
TASK 3: Cyanobacteria
Observe the structure of cyanobacteria and compare it with cells of green algae or diatoms (frustules), which can be also present in the sample. Just by the preparing of the sample, you can observe oscillatory motion of cyanobacteria.
Fig.: Comparation of cyanobacteria with green algae and diatom.
Eukaryotes - Plant cell
TASK 1: Chloroplasts
Prepare NP from leaf and observe plant cells with cell wall and round green chloroplasts.
Fig.: Plant cells with cell wall and chloroplasts.
TASK 2: Vacuoles
Cut the berry and impress it on the slide glass, cover with cover glass and observe the violet coloured vacuoles and green chloroplasts. Then add a drop of NaOH (alkaline solution) to the one edge of glass and drop of acetic acid (acidic solution) to the second one. How does the color of vacuoles change according to different pH?
Fig.: Vacuoles and chloroplast in berries of Ligustrum vulgare
TASK 3: Crystalline inclusions of calcium oxalate
Observe styloids (prismatic crystals) in outer peel of onion, druses in fluid from Begonia stalk and raphids (needle-like crystals) in fluid from Pothos stalk.
Fig.: Crystalline inclusions of calcium oxalate
TASK 4: Pollen grains
Observe the various shapes of pollen grains from different plant species. Pollen grains vary in contrast; it is difficult to find them, and it is helpful to adjust the light to lower intensity.
Fig.: Pollen grains
Eukaryotes - animal cells and protozoa
TASK 1: Nerve cells (neurons)
Find the neurons in the so-called grey matter in the ventral spinal horns. Observe the large (particularly in the pig), intensively pink-stained neurons with nuclei and projections (dendrits).
fig.: A – cross-section of spinal cord, B – composition of the neuron.
TASK 2: Shape and number of nuclei
Using small magnification, find a place with a higher density of leucocytes (violet dots scattered among more numerous pink erythrocytes) and observe the shapes of the nuclei: round in lymphocytes, kidney- or bean-like in monocytes, lobular, segmented or polymorphic in mature forms of granulocytes, s-shaped and band shaped in younger forms. Using a meandering movement, find a pink-stained ciliate protozoan Spirostomum with a bead-shaped nucleus. Observe violet coloured macronucleus (large nucleus, vegetative nucleus) and micronucleus (small nucleus, generative nucleus) in ciliate protozoan Paramecium. Observe the numerous purple-stained nuclei within the greenish cytoplasm of protozoan Opalina ranarum (polynuclear cell) living as a commensal in the cloaca of frogs.
Fig.: Different shapes and numbers of nuclei.
TASK 3: Cell organelles - Golgi apparatus, mitochondria
Find an intact villus projecting into the lumen (interior) of the intestine. Find the layer of cylindric epithelial cells (enterocytes) on its surface. Note the violet elongated nuclei in the basal part of enterocytes and the Golgi apparatus in the apical (peripheral, luminal) part of enterocytes (above the nuclei). It is a round-shaped cluster of brown-black dots (silver stain) or is pale-colored. Observe occasional cells with two nuclei in the liver and mitochondria as tiny blue-black points (like powder) inside the liver cells (hepatocytes).
Fig.: A – cross section of intestine with villus, B – enterocyte with Golgi apparatus (GA) and nucleus.
Fig.: Mitochondria in liver cells (stained after Heidenhain).
TASK 4: Pigment inclusions
Observe the melanin pigment granules inside the cells (melanophores) with numerous branching projections. Melanophores or, more generally, chromatophores (Greek phorein = to carry), are responsible for coloration in animals (e.g. frogs) and sometimes enable color changes (in animals such as chameleons).
Fig.: Melanophores of frog containing pigment melanin.
TASK 1: Brownian motion
Place a drop of ferric oxide suspension onto a slide and cover it. Observe one small moving particle and draw trajectory of its movement. What is the principle of this movement?
TASK 2: Amoeboid movement
Observe movement of amoeba from the hay infusion. First, they are irritated and round, after some time they start to show protrusions (pseudopodia) and move. Pseudopodia are homogenous, cytoplasm is granulated. What is the principle of this movement?
TASK 3: Flagellar movement
Observe the flagellar movement of sperm (movement forward and rotation around axis) or movement of flagellar protozoans from hay infusion. If you want to slow them down, suck off water from the space between the two glasses using a filter paper.
Fig.: Types of movements: A – Brownian movement, B – amoeboid movement, C – flagellar movement.
TASK 4: Ciliary movement
Observe ciliary movement of unicellular ciliates from hay infusion or ciliary movement on the surface of some multicellular organisms (flatworm) from aquarium. What is the principle of a ciliary movement?
TASK 5: Cells with cilia
Observe and draw cells of cylindrical or conical shape with visible nucleus and with cilia localized at the wider base of the cell.
TASK 6: Structure of striated muscle
Observe the striated muscle. Striation is caused by different staining of muscle fibers. What is the principle of a muscle contraction?
Fig.: A – cell with cilia, B – striated muscle of insect.
TASK 1: Chemotaxis in ciliates
Put two drops of hay infusion onto the slide (do not cover). Connect both drops using skewer to form a thin bridge. Then add several crystals of salt (NaCl) to one of the drops. Observe negative chemotaxis.
TASK 2: Oxygenotaxis in ciliates
Cover a drop of hay infusion with cover glass and form air bubbles under it. You can observe positive oxygenotaxis. The same effect can be observed at the edges of cover glass.
Transport of substances, osmosis
TASK 1: Simple plasmolysis (plant cell in hypertonic solution)
Put the inner epidermis of an onion onto the slide and stain it with 1 % neutral red. Add 1M KNO3 and observe the plasmolysis. Draw your observation and write a conclusion.
TASK 2: Deplasmolysis
Add distilled water to the specimen from the previous task and observe the reverse process (cytoplasm and vacuoles increase their volume). Some cells are irreversibly damaged.
Fig.: Osmosis in epidermis of onion – simple plasmolysis
TASK 3: Spasm plasmolysis (plant cell in hypertonic solution)
Stain the epidermis of an onion with 1 % of neutral red; add 1 % CaCl2 and 1M KNO3. Observe the unequal separation of the cytoplasmic membrane from the cell wall caused by the increased cohesion of cytoplasmic membrane.
Fig.: Osmosis in epidermis of onion – spasm plasmolysis
TASK 4: Turgor (plant cell in hypotonic solution)
Put pollen grains on the slide and observe them using microscope. Then add water, cover with a cover glass and observe again. Write your observation.
Fig.: Osmosis: A – pollen grain in isotonic solution, B – pollen grain in hypotonic solution.
TASK 5: Macroscopic observation of osmotic haemolysis (blood in hypotonic solution)
Take two tubes and add 1 ml of blood into each of them. Then add 3 ml of physiological solution into one of them and 3 ml of water into the second one. Gently mix and compare both tubes. Perform the "reading test". Write down the result of your observation.
TASK 6: Microscopic observation of osmotic haemolysis
Put a small drop of blood on the slide and cover with a cover glass. Add water to one edge of the cover glass and let it suck in the part of the specimen. Then immediately suck the water off using a filter paper. Water causes haemolysis (rupture of erythrocytes) observed on interface of water and blood.
TASK 7: Plasmorhisis (animal cell in hypertonic solution)
Put a drop of blood on the slide, add 1M KNO3 and cover with a cover glass. You can observe shrunk erythrocytes (star-shaped) because of water escaping from them. Draw them and write a conclusion.
Fig.: Osmosis. A – haemolysis of erythrocytes, B – plasmorhisis of erythrocytes.
TASK 8: Phagocytosis
Find and draw leucocytes with phagocyted particles. You can count phagocytic activity (PA): PA = number of phagocytic cells / total number of cells.
Fig.: Leucocytes with phagocyted particles.
Mitosis in plant cell
TASK 1: Mitóza v buňkách kořínku cibule
Compress an onion rootlet under a cover glass with your finger (compression preparation) and observe the particular mitotic phases.
The base of onion is sunk in water to let roots grow. When roots start to grow, their ends (about 2-3 mm) are cut and fixed in acetic acid and 96 % ethanol (in ratio 1:3) for 20 min. Then roots are macerated in hydrochloric acid and ethanol (in ratio 1:1) for 10 min., washed in distilled water for 10 min. and finally stained with acetorcein for 10 min.
Fig.: Mitosis in onion rootlet cells.
TASK 2: Mitotic phases in permanent preparation
Observe 30 mitotic figures (cells in mitosis) and determine mitotic phases. Which of them is the most frequent and why?
TASK 3: Defects of mitosis
Prepare compression preparation of the onion rootlet and observe defects of mitosis.
Fig.: Defects of mitosis: A – chromosome fragmentation in prophase, B – anaphase bridge, C –defective anaphase in cell with damaged chromosomes.
Mitosis in animal cell
TASK 1: Mitotic index
Observe the cells in five visual fields; count how many cells undergo mitosis and how many of them are in interphase and calculate mitotic index. In this specimen, you can also find monaster (cell in metaphase) and the anaphase bridge.
MITOTIC INDEX determines frequency of mitosis in plant or animal tissues (or in cell cultures).
MI (%) = M/N x 100 where M = number of mitotic cells, N = total number of cells.
TASK 2: Mitosis in histologic section of small intestine
Observe the cross-section of the small intestine under small and then use a higher magnification. In the intestinal villi you can find mitotic dividing cells.
Fig.: Mitosis in intestinal villi of small intestine.
TASK 3: Mitosis in histologic section of uterus
Observe the cross-section of the uterus under small and then higher magnification. Mitotic dividing cells can be found in uterine mucosa.
Fig.: Mitosis in mucosa of uterus.
TASK 4: Mitosis in histological section of testes
Observe the specimen under small and then larger magnification. Mitotic dividing cells are inside the seminiferous tubules on the periphery. Note: do not mistake mitotic cells for those dividing by meiosis.
Fig.: Mitosis in seminiferous tubules of testes.
Reproduction and development
TASK 1: Budding yeast
Prepare a native preparation of yeast and observe the buds on the surfaces of some of the cells.
Fig.: Budding yeast.
TASK 2: Cytological changes in vaginal mucosa during estral cycle
Observe and draw a specimens from four different phases of estral cycle. Each phase has its typical finding: proestrus (large epithelial cells with dark nuclei), estrus (corneous cells without nuclei), metestrus (cells with large nuclei, mucus), diestrus (mucus and leukocytes).
Fig.: Phases of estral cycle with typical findings in vaginal mucosa.
TASK 3: Cleavage of rabbit egg
Observe permanent preparations and photographs.
Fig.: Rabbit egg: A – surrounded by follicular cells, B – with two polocytes, C – consisting of two blastomeres, D – consisting of eight blastomeres.
TASK 4: Ontogenic development of different animal species
Fig.: Ontogenic development of different animal species: A – chicken louse Menacanthus stramineus (egg, 3 nymphs, imago), B – gypsy moth Lymantria dispar (egg, larva, pupa in cocoon, imago), C – common trout Salmo trutta (egg, embryo, hatched larva with yolk sac (=alevin), adult fish), D – common frog Rana temporaria (egg, tadpole, frog with tail, frog), E – domestic fowl Gallus gallus (egg, embryo, chicken after hatching, adult), F – brown rat Rattus norvegicus (uterus in early and late stage of gravidity, fetus and adult of rat).
TASK 1: Spermiogenesis
Observe specimen of rat testes and find seminiferous tubules, where spermiogenesis takes place (different stages). When you start from periphery, there are spermatogonia, small cells with nucleus rich in chromatin. More centripetally you can find primary spermatocytes (spermatocytes of I. order) and secondary spermatocytes (spermatocytes of II. order), that differ in size and in nucleus structure. Close to the centre of seminiferous tubule, there are small spermatids and mature sperm cells.
Fig.: Spermiogenesis in rat testes: A – rat testes with seminiferous tubules, B – seminiferous tubule with different spermiogenesis phases, C - developmental stages of spermiogenesis.
TASK 2: Different shape and size of sperm
Observe sperm of different animal species and compare the shape of sperm head, the size of acrosome (structure on the top of head containing enzymes important for penetrating the egg) and size and number of sperm tails.
Fig.: Sperm of different animal species.
TASK 3: Oogenesis
Observe the specimen of a rat ovary and find the primary follicle (oocyte surrounded by follicular cells) and mature follicle (Graafian follicle) with multiplied follicle cells and cavities filled with fluid.
Fig.: Oogenesis in rat ovary.
TASK 4: Reproduction of chromosome number during meiosis
Observe several sections of testes and try to find individual phases of meiosis (especially phases of first prophase).
Fig.: Meiosis in longitudinal section of testes of beetle Blaps mortisaga.
Influence of surroundings onto the bioplasm
TASK 1: Photodynamy
Prepare two slides, one with one drop of hay infusion, the other with two drops. Add eosin to one of the two drops on one slide (experiment) and to the single drop on the other slide (control). Expose the slide with two drops to light and place the other slide into dark. Observe specimen after 3 min. intervals and compare it to controls. The photodynamy causes excitation of the ciliates and their rapid movement, followed by inhibition and death.
TASK 2: The effect of ionizing irradiation on the testes of rat and fowl
Observe the testes under small and then larger magnification and compare the normal tissue with the tissue after irradiation. You can find damaged tubules and space around them. It is difficult to differentiate individual stages of spermatogenesis inside the tubules, because cells are damaged. In fowl, you can observe signs of reparation eight days after irradiation.
Fig.: The effect of ionizing irradiation on the testes of rat: A – normal tissue (small and large magnification), B – tissue after irradiation (small and large magnification).
TASK 3: Oligodynamic action (the effect of heavy metal ions dissolved in water solution (water upon mercury) on a survival of Protozoa
Put a drop of hay infusion and a drop of water upon the mercury on the slide. Observe a specimen in 3 min. interval and compare it with control (only hay infusion). You can observe excitation of ciliates and their rapid movement, followed by inhibition and death.
TASK 4: The effect of CdCl2 (cadmium chloride) on the testes of rat
Observe the testes of a rat that was fed with CdCl2 (under small and large magnification) and compare it with normal testes. Focus on the seminiferous tubules (their number and structure) and spermatogenesis.
TASK 5: The effect of phytoncides on survival of Protozoa
Cut an onion into small pieces and then crush it using sea sand and a mortar. Drop hay infusion on the slide and observe the presence of protozoa. Then put the specimen into the Petri dish and place crushed onion under it (see the picture). Control reactions and movement of the protozoa in 3-5 min. intervals and compare it with control (hay infusion without the effect of phytoncides). Note the time of protozoa’s death.
Research methods in biology - Cell and tissue cultures
TASK 1: Tissue culture
Observe and draw rabbit kidney tissue cells.
Fig.: Cells from tissue culture in different phases of mitosis or in interphase.
TASK 2: Work with inversion microscope
Observe adherent cells in cell culture growing in monolayer. Then pour off the medium from the bottle and rinse the cells with phosphate buffered saline and add 2 ml of trypsin. After the trypsinization you can observe loose cells, sometimes in clusters. Gentle shaking the bottle or gentle heating can help to release the cells from the bottom of the cultivation vessel. Add the medium with serum that inhibits the effect of trypsin to protect the cells. Transfer cells floating in the medium to a beaker and observe them under a light inversion microscope. What is the shape of cells now?
- Chemical composition
- Non-cellular life
- Prokaryotes and immersion microscopy
- Movement and irritation
- Transport of substances, osmosis
- Reproduction and development
- Influence of surroundings onto the bioplasm
- Research methods in biology
- Model organism
- Polymorphic genes
- Gene interactions
- Inheritance and sex
- Genetic linkage
- Population genetics
- Quantitative genetics
- Nonmendelian inheritance