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International Baccalaureate: Biology

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  • Marked by Teachers essays 11
  • Peer Reviewed essays 1
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  1. Marked by a teacher

    Experiment to investigate the effect of different antibiotics on the bacteria Bacillus subtilis:

    4 star(s)

    Gram-positive organisms normally do not have the outer membrane, whereas Gram-negative organisms do. Gram-positive bacteria include many well -known genera like Streptococcus and Bacillus. Most pathogenic bacteria in humans are Gram-positive organisms and these are used to manufacture antibiotics. Bacillus subtilis, also known as the hay bacillus or grass bacillus is a Gram- positive bacterium, which is mostly found in soil. Bacillus subtilis is not a human pathogen and it can contaminate food but rarely causes food poisoning. Bacillus subtilis spores can survive the extreme heat during cooking and Bacillus subtilis is responsible for causing a sticky, stringy consistency in spoiled bread dough.

    • Word count: 748
  2. Marked by a teacher

    The Effect of Temperature on Enzymatic Activity. Aim To investigate enzyme activity of yeast on glucose at different temperatures

    3 star(s)

    � � 5 cm3 syringes x5 � � 10 cm3 of 10% yeast solution � � 15cm3 of 2% glucose solution � � 1 thermometer � � 2 hotplates � � Stopwatch � � Ice cubes x 6 � � 400mL water � � Observations chart & pen Method 1. 1. Place 6 ice cubes and 80 mL of water into Beaker A 2. 2. Measure and record the temperature (should be around 10�C) 3. 3. Fill 3cm3 of glucose solution into the syringe and then in the same syringe insert 2 cm3 of the yeast solution 4.

    • Word count: 862
  3. Marked by a teacher

    Investigating the relationship between cell size and rate of diffusion

    Variables: In this investigation, the variable I am manipulating, the independent variable are the dimensions of surface area to volume ratio of the agar cube. The variable I am observing/recording, the dependent variable, is the rate of diffusion (NaOH turns the agar cube pink as it disperses into it). The controlled variables will be keeping the concentrations of the Sodium Hydroxide constant, to use agar jelly from the same batch (so the type of agar jelly is exactly the same), and to keep the time even for all cubes so the NaOH has the same amount of time to disperse into the cube.

    • Word count: 751
  4. Enzyme Investigation. How does the concentration of hydrogen peroxide affect the amount of oxygen produced by the enzyme catalase?

    This means enzyme activity increases and the rate of reaction also increases. Independent and dependent variables Variable measured Method of measuring variable Independent variable Hydrogen peroxide concentration (%) The 5 values I will use for the concentration of substrate hydrogen peroxide would be 20%, 40%, 60%, 80% and 100%. These percentages will be calculated from the hydrogen peroxide to water concentration radio where water is used to dilute the hydrogen peroxide. The concentration percentage/ hydrogen peroxide to water ratio will be as follows: - 4ml: 16ml = 20% - 8ml: 12ml = 40% - 12ml: 8ml = 60% - 16ml: 4ml = 80% - 20ml: 0ml= 100% Dependent variable The volume of oxygen produced (cm3)

    • Word count: 873
  5. Research Question To what extent does watching different genres of movies affect our sympathetic and parasympathetic nervous systems, causing changes in heart rate?

    These neurons release the neurohormone acetylcholine, which inhibits heart rate. The slowing of heart rate is called bradycardia. Another major role playing hormone is adrenaline which causes an immediate hike in the heart rate. Hypothesis Different stimulus causes different changes in heart rate because of varied responses from the sympathetic and parasympathetic nervous systems. Watching horror and action movies should cause a greater increase in the heart rate, whereas, comedy and romance are more probable to cause a slight hike. On the other hand, watching a musical is expected to make the heart rate stable and almost near normal as the softness of the music used this case is supposed to make any living creature calm.

    • Word count: 804
  6. Chromatography of photosynthetic pigments. Aim: To determine the different photosynthetic pigments found in spinach and find their relative front values using paper chromatography.

    b (cm) Experimental Rf Standard Rf Carotene 5.7 6.2 0.91 0.98 Phaeophytin 3 6.2 0.48 0.53 Xanthophyll 2.4 6.2 0.38 0.3 Chlorophyll a 1.9 6.2 0.3 0.42 Chlorophyll b 1.2 6.2 0.19 0.34 Comparison of the Experimental and Standard Relative Fronts of Photosynthetic Pigments Evaluation Carotene travelled the furthest away from the loading line (5.7cm ) while chlorophyll a demonstrated the shortest distance travelled (1.2).

    • Word count: 552
  7. Lung Volume Measurement Biology Lab. My hypothesis is that the breathing rate and tidal volume increases after exercise.

    Put your mouthpiece into the hose opening of the spirometer. 4. Inhale normally. Put the mouthpiece in your mouth and exhale normally. Measure the volume and record as your tidal volume. Repeat this step 2 more times. Calculate the average tidal volume and record. 5. Inhale as deeply as possible, put the mouthpiece in your mouth and exhale as much air as possible. Measure the volume and record as your vital capacity. Repeat this step 2 more times. Calculate your average vital capacity and record.

    • Word count: 985
  8. The effect of varying temperature on the permeability of plasma membrane on beetroot.

    nucleus, mitochondrion.1 Beetroot has a betalain pigment, which makes it appear dark red or purple in colour. By putting beetroot cores into water with varying temperature, it affects the cell membrane. The cell membrane is made up of two layers of molecules, so it's called "bilayer" ("bi" means two). The molecules in this bilayer are called phospholipids. Each of these phospholipids has a head and a double tail. The head is hydrophilic.

    • Word count: 528
  9. Questions on RNA and DNA, bacteria and immunity.

    Step 1 * The DNA double helix is unwound and separated into strands by breaking the hydrogen bonds. * Helicase is the main enzyme involved. Step 2 * The single strand act as templates for new strands * Free nucleotides are present in large numbers around the replication fork * The bases of thee nucleotides form hydrogen bonds with the bases on the parent strand * The nucleotides are linked up to form the new strand * DNA polymerase is the main enzyme involved Step 3 * The daughter DNA molecules each rewind into a double helix (c)

    • Word count: 662
  10. The aim of this investigation is to examine the difference in the mass of potato after keeping the in sugar solutions of different concentrations for 24 hours. The water potential will also be calculated.

    - Paper towels - Plastic wrap Method: Step 1: Pour 100ML of sugar solution 250ML beaker. Step 2: Measure the mass of the potato cores together. Step 3: Put the potato cores into the beaker of sugar solution. Step 4: Cover the beaker with plastic wrap and allow it to stand for a 24-hour period. Step 5: After keeping the potato cores in the solution for 24 hours remove them from the beaker, blot with a paper towel, and measure the mass of the fore cores after soaking.

    • Word count: 920
  11. To stimulate the effect of acid rain on plant life, students to set up a lab experiment to compare the effect of varying levels of acidity on plant seed germination.

    Method for control Sunlight The lab's to be conducted after the curtains are drawn and the bags to be placed in a wooden drawer in a cupboard Purity of water The vessels to be cleaned properly before use so that the water oes not get contaminated and to test the pH of water before use so that water purity can be known. Amount of air in the zip bag Gently press the bags before zipping them and make sure that the max amount of air is lost.

    • Word count: 739
  12. Title: separation of pigments of photosynthesis using paper chromatography. Goal (main aim): Calculating the Rf of every single pigment, in order to distinguish it and identify its solubility.

    Volume & concentration of extraction The extraction sample will be taken using the same tweezers. Materials and procedure: Materials: 1- Chromatography Jar. 2- Plant. 3- Chromatography paper. 4- Solvent (organic). 5- Tweezers. 6- Pipette. 7- Mortar and Pestle. 8- Scissors. 9- Ruler. 10- Calculator. Procedure: * Preparation of the mixture: 1- Place a piece of the obtained plant leave into the pestle. 2- Add 5ml (approx.), of 90% isopropyl alcohol. * Preparation of the chromatogram: - Attain a chromatography paper. - Cut the paper, in order to have a triangular end. - Draw a line above the triangular end, with 1 cm, draw a point in the center of that line, the previous line is considered the start line.

    • Word count: 765
  13. Chromatography lab. Title: separation of pigments of photosynthesis using paper chromatography.

    Materials and procedure: Materials: 1- Chromatography Jar. 2- Plant. 3- Chromatography paper. 4- Solvent (organic). 5- Tweezers. 6- Pipette. 7- Mortar and Pestle. 8- Scissors. 9- Ruler. 10- Calculator. Procedure: * Preparation of the mixture: 1- Place a piece of the obtained plant leave into the pestle. 2- Add 5ml (approx.), of 90% isopropyl alcohol. * Preparation of the chromatogram: - Attain a chromatography paper. - Cut the paper, in order to have a triangular end. - Draw a line above the triangular end, with 1 cm, draw a point in the center of that line, the previous line is considered the start line.

    • Word count: 768
  14. Yeast lab. Question: how does the yeast concentration affect the rate of anaerobic respiration?? Measured by the concentration of released CO2.

    Controlled variables: Variable Why to control How to control Concentration of sucrose Because sucrose is the reactions substrate. It will be kept constant for all the trials. Temperature Higher temperature increases the rate of reaction The experiment will be initiated in room temperature away from air sources. Time 2 minutes for each trial Equipments and procedure: Equipments: - PASCO GLX with (CO2 sensor). - 200 ml, 3 % sucrose solution. - Variety of yeast solutions (g/ml) (2%,4%,6%,8% and 10%). - Cylinder. - Beaker (200 ml). - Plastic cover. Procedure: - Prepare at least 5 different concentrations of yeast (2%, 4%, 6%, 8% and 10%)

    • Word count: 844
  15. Investigation Question: How does Body Mass Index affect heart rate with respect to exercise?

    After jumping jacks, immediately take subject's heart rate by counting pulse for exactly one minute 5) Record value in data table 6) Calculate % increase of heart rate using the formula provided below. Record value in data table 7) Repeat process for multiple trials (20 total) Formula for calculating percent increase of heart rate: (Heart rate after jumping jacks) - (resting heart rate) % Increase= __________________________________________________________________ X 100 (resting heart rate) Trial Body Mass Index Resting Heart Rate Heart Rate after jumping 1 20 66 127 2 19 60 129 3 22 72 118 4 26 66 93 5 21 84 126 6 29 84 140 7 24 78 120 8 22 96 98 9 22

    • Word count: 964
  16. Laboratory work on a theme The dependence of the rate of photosynthesis on light intensity

    Aim Determine intensity of photosynthesis on allocation of ?2, depending on the light exposure. Variables Independent variable is the level of the illumination level, which I changed. Dependent variable is oxygen allocation, which depends on the illumination level. MATERIALS AND METHODS Materials Punch, cups, a solution of baking soda 0.5%, medical syringes with the cylinder 10 ml, glass tubes, the lamp of 100 W, a box, the leaves of plants (Chlorophytum). Chlorophytum Method 1)

    • Word count: 513
  17. Osmosis in potato experiment

    Processed Data: - The average final weight is obtained using the following rule: - The percentage change is obtained using the following rule: table (2): percentage change of potato cubes weight in different sucrose solutions: Percentage change in the mass of potato cubes Difference between final and initial weights in (g) (�0.1) g Average final weight (gram) (�0.05) g Sucrose solution Molarities (mol/L) 33.3 % 0.20 0.80 0.1 18.2 % 0.20 1.30 0.2 14.2 % 0.10 0.80 0.3 00.0 % 0.00 0.90 0.4 -14.1 % -0.24 1.46 0.5 -12.7 %

    • Word count: 614
  18. All animals and plants are attacked by parasites and pathogens; evolution is the results of an arm race between the parasite and the host

    Evolution occurs faster in pathogens than they do in humans (mammals). This is due to factors such as: the changing life span and generations of pathogens occur faster than those of humans. There are much higher populations of pathogens this allows more evolutionary changes to occur. Pathogens are smaller organisms; this means that there are fewer functions, less complexity and fewer physical aspects that need evolving, making mutation much easier. Pathogens are also simpler organisms and so a fewer changes in them will have much more of an effect than it would in a more complex organism like a mammal.

    • Word count: 949
  19. Investitigation of Veins and arteries. Research topic: the elasticity of cows vein and aorta hung with different masses.

    In this experiment, I will examine the elasticity of these blood vessels. Materials and apparatus: * Cow's vein * Cow's aorta * 1 Stand and clamp * 1 Paper clips * 1 Ruler (+/-0.5mm) * 10 Weights of 100 grams each Method: 1. Cut out a ring of 3mm from the aorta and another from vena cava 2.

    • Word count: 506
  20. Hair Lab Report - investigate the force needed to break down a hair and to investigate if characteristics found in different hairs make a change in the strength these have.

    Choose a hair, and tight it to the force meter apparatus. You should already have the first weight (100g) hanging from this apparatus. 4. Be aware that the hair is correctly tightened up, if it does, start adding more weight. First the cylinder weighing 100 g and afterwards the 10g weights. 5. When the hair breaks, record the amount of weight that it was put. 6. Repeat steps 3, 4 and 5 with all of the other hairs. Results: Name Color and type Treatment Length (cm)

    • Word count: 648
  21. Examine how the concentration of hydrogen peroxide affects the rate of reaction of the enzyme catalase.

    * Controlled variable: Temperature Materials: * Yeast Catalase * Hydrogen Peroxide * Test tubes * Beakers * Test tube rack * Stop watch * Pipette * Distilled Water * Pipette filler * Gas syringe * Stand Method: 1. Add 100% of hydrogen peroxide into the beaker. Connect this, to the gas syringe and measure the volume of oxygen produced every 30 seconds. 2. Every 30 seconds shake the beaker twice and then clean it. 3. Add 80% of hydrogen peroxide and 20% of distilled water into the beaker.

    • Word count: 775
  22. Stomach Cancer

    There are two main forms of stomach cancer, diffuse and intestinal, with the diffuse type affecting more of the non typical individuals, eg females and younger (see risk factors below). Diffuse and intestinal stomach cancers differ both in location and causative factors. 90% of stomach cancers are adenocarcinomas derived form the glandular tissue. Risk Factors As stomach cancer is multifactorial there are no causative factors as such, rather risk factors and predisposing factors, the most significant of which is Helicobacter pylori infection.

    • Word count: 939
  23. Digestion Lab. The specific purpose of this lab (activity 4) was to investigate fat digestion by pancreatic lipase and the action of bile, and to recognize whether fat digestion is ongoing or completed (2).

    Methods: The experiment was carried out by placing 6 test tubes, labeled 1 to 6, on the test tube holders in the incubation unit. Each test tube holds different solutions: test tube 1 contains lipase, vegetable oil, bile salts, and pH 7.0 buffer; test tube 2 contains lipase, vegetable oil, deionized water, and pH 7.0 buffer; test tube 3 contains lipase, deionized water, bile salts, and pH 9.0 buffer; test tube 4 contains deionized water, vegetable oil, bile salts, and pH 7.0 buffer; test tube 5 contains lipase, vegetable oil, bile salts, and pH 2.0 buffer; test tube 6 contains lipase, vegetable oil, bile salts, and pH 9.0 buffer.

    • Word count: 929
  24. This experiment was conducted to determine food preference of planaria. Planaria are freshwater creatures. They live in lakes, streams, and other freshwater bodies.

    Gather materials. 2. Label the choice chambers A, B, C, D, and E 3. Fill all of the choice chambers with 100mL of water 4. Place on type of food in each of the choice chambers, completely in one of the chambers (excluding the last choice chamber, which will have no food) 5. Add five planaria to each chamber that does not have food in it 6. Allow the planaria to move as they please for fifteen minutes 7.

    • Word count: 593

IB Biology is the study of living organisms. The four basic concepts which run through the course are: evolution, equilibrium within systems, universality versus diversity, and structure and function. These concepts give the student a strong foundation upon which other detailed knowledge can be built. You will also be completing a significant amount of practical work and an experimental approach is strongly emphasised.

Assessment is both externally and internally organised. The external examinations are a mixture of multiple-choice, short answer and extended answer tests.The extended answer examinations require you express yourself in a concise and scientific manner and some great examples of these IB Biology essays can be found on Marked by Teachers. Science can bring enormous benefits to societies and you will be encouraged to become a responsible and ethically minded scientist.


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