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International Baccalaureate: Biology
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- Marked by Teachers essays 11
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Neurology and Behaviour. Focus question: Is there an increase in the perception and rating of disgust in females rather than males?5 star(s)
These signals are then combined by the different receptors in order to create what individuals perceive as smell. Olfactory receptor neurons in the nose are different to other neurons due to their short lifespan however regenerate on a regular basis. (Moran, 2007) Vision however is the ability of the eye to focus and detect light using the photoreceptors located on the retina of each eye. The photoreceptors sense and encode the patterns created by light found in the individuals surroundings. These photoreceptors are sensory neurons and the axons of particular retinal ganglion cells start from the back of the eyeball in the individual's optic nerves and then following the central nervous system to reach the brain where the information is then processed.
- Word count: 4552
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
to the area of lower water concentration (potato cell). However, as the duration given for osmosis to occur increases, the volume of fluid in the cell will increase as water continually enters the cell, increasing its turgidity (when pressure inside the cell increases as the volume of its contents increases). Eventually, the cell wall will be stretched to the maximum, achieving full turgor, which will then force water back out of the cell due to the high pressure within the cell.
- Word count: 2612
seeds are placed in a hot environment, then their germination will be positively affected compared to cress seeds grown in a normal light environment because seeds Variables The independent variables in this experiment were the light and the temperature. We put some of the cress seeds under a bright light and others in a dark cupboard. As for the temperature, we put some cress seeds in a stove and others in a fridge. The dependent variable in this experiment is the germination.
- Word count: 1944
After adding in iodine, when amylase breaking down starch, less and less starch will be present and the color of this solution will become lighter and lighter. Equipments � 0.1% Amylase 0.5 ml � 1% Starch 5ml � 10 Test tubes and rack � Iodine solution � Syringes � Marker pen � Electronic water bath set at 20, 30, 40, 50, 60 and 70�C with thermometers � Dropper � Thermometer � Beakers � Spot-plates � Stopwatch Controlled variables � Same temperature of amylase and starch solution This can ensure that amylase can react with starch solution in the same temperature,
- Word count: 1232
The Effect of Temperature on Enzymatic Activity. Aim To investigate enzyme activity of yeast on glucose at different temperatures3 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
* 4% Hydrogen Peroxide Solution (5cm3) * 3% Hydrogen Peroxide Solution (5cm3) * 2% Hydrogen Peroxide Solution (5cm3) * 1% Hydrogen Peroxide Solution (5cm3) * 0.5% Hydrogen Peroxide Solution (5cm3) * Coloured Liquid * Distilled Water * 3x 20cm3 Syringes * 1x U-Shaped Tube (manometer) * 1x Stopwatch * 1x Retort Stand with clamps * 1x Rubber Bung * 1x Tube * 1x Forceps * 1x Scalpel * 1x Ruler * 1x White tile * 4x Plastic Containers * 1x Safety Goggles * 1 pair of gloves Procedure 1. The chicken liver was cut into pieces each measuring approximately 1cm by 1cm by 1cm.
- Word count: 1206
As far as it is known every living thing uses ATP as its primary source of energy, from bacteria to plants. At any instant in time a cell in the human body can contain about one billion ATP molecules, but this amount is used up quite quickly and is normally recycled straight away in the mitochondria where chemiosmotic phosphorylation occurs. One way that ATP is used is for muscle contractions, when you are running, walking, even me typing this essay, your body is using ATP to move muscles for movement, but not only movement, but it isn't only used for
- Word count: 1166
The cups used for the solutes must be completely dry before adding the solutes in. The same potato must be used to obtain all potato chips, in order to keep the water potential of the potato. The experiment must occur at room temperature. The same balance must be used, to achieve accuracy in measuring the mass. Equipment List: - Stop Watch - Electronic Scale - 1 whole potato - Cork Borer - 1 Piece of paper towel (cut into 5 pieces)
- Word count: 1975
Enzyme Coursework. Investigation to find the effect of substrate concentration on the rate of an enzyme controlled reaction5 star(s)
The rate of an enzyme controlled reaction are mainly affected by: temperature, substrate concentration, enzyme concentration and pH. By increasing the substrate concentration, there is a higher chance of a substrate colliding with an enzyme and subsequently reacting (as there is simply more substrate moving around in the solution). Increasing the substrate concentration further will cause the rate of reaction to plateau when all of the enzymes' active sites are constantly in use - at which point the enzyme concentration can be considered a limiting factor.
- Word count: 1640