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AS and A Level: Exchange, Transport & Reproduction

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Five tips on presenting and analysing data from core practicals

  1. 1 Raw data should be presented in a table with clear headings. All table column and row headings should contain units and readings should all be recorded to the same decimal place.
  2. 2 Raw data should be processed to provide descriptive statistics such as the mean and standard deviation.
  3. 3 Present data using the relevant graph type. Ensure that you add error bars showing either standard deviation or standard error.
  4. 4 When describing trends and patterns, manipulate data to calculate the size of key changes. For example, absorbance increases by 0.09 absorbance units between 10◦C and 40 ◦C. Preferably express the change as a percentage increase or decrease. Do not simply quote points, eg at 10 ◦C absorbance was 0.01 and at 40 ◦C it had gone up to 0.1 absorbance units.
  5. 5 Discuss each phase of the graph. For example if there is a slow increase, followed by a rapid increase, and then the graph levels off and shows a decrease, discuss these four key phases. Do not give detailed descriptions of each small fluctuation. The trends and patterns are the important things.

Meiosis and Mitosis facts

  1. 1 Meiosis generates gametes/sex cells, whereas mitosis is for growth/repair and generates daughter cells identical to the parent cell.
  2. 2 During Meiosis chromosome number is halved producing haploid gametes with a single copy of each chromosome. During Mitosis chromosome number is maintained producing diploid daughter cells with maternal and paternal copies of each chromosome, i.e. homologous chromosome pairs.
  3. 3 Before mitosis and meiosis all chromosomes are copied as part of interphase. At the end of interphase there are two identical copies of every maternal chromosome and every paternal chromosome, so chromosome number has doubled (i.e. at the end of interphase a human cell contains 46 x 2 = 92 chromosomes). The identical copies of chromosomes are referred to as sister chromatids and they are joined by a centromere.
  4. 4 In meiosis, genetic variation is generated by crossing over during prophase 1, and independent chromosome assortment at metaphase 1 and metaphase 2. During crossing over maternal and paternal chromosomes cross each other, and break at points known as chiasma. Maternal and paternal alleles below the chiasma change places so that the paternal chromosome contains maternal alleles and vice-versa. During metaphase 1 and 2, maternal and paternal chromosomes align randomly on one side of the equator. As the maternal and paternal chromosomes can align on either side, different potential chromosome combinations can occur.
  5. 5 The events in metaphase, anaphase and telophase are identical in both mitosis and meiosis 1 and 2. In mitosis a single division occurs, whereas in meiosis cells undergo 2 meiotic divisions.
    a) During meiosis 1, maternal and paternal sister chromatids are separated so that 1 cell contains both maternal sister chromatids of a pair and the other contains both paternal sister chromatids.
    b) During the second meiotic division, sister chromatids are separated. The gametes that result contain only 1 chromosome from each pair, i.e. they are haploid.

How to evaluate experimental methods

  1. 1 When evaluating the reliability of experimental methods, always consider whether all variables other than the independent variable have been adequately controlled. If a variable cannot be controlled has it been monitored to establish any effect it might have?
  2. 2 All experiments must be repeated to establish reliability. Has the experiment been repeated at least three times? Preferably you should repeat it more than 3 times.
  3. 3 What does the standard deviation suggest about the spread of the data? If the mean is 5, but the standard deviation is 3, readings vary from the mean considerably. This suggests that the mean does not represent the actual readings.
  4. 4 How precise are the measurements? If a balance used to measure change in mass only measures to 0.1 g then the reading could be 0.12 g, 0.15g, or 0.18g etc.
  5. 5 How accurate are the readings? If equipment is re-used for different repeats for example, cross contamination could affect the accuracy of subsequent readings. If tubes are shaken different amounts, different volumes of gas could be released. Consider all potential sources of error and discuss how the procedure could be improved to reduce these sources of inaccuracy.

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  1. Peer reviewed

    Infertility and Assisted Reproduction Technology.

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    grows outside the uterus. Other conditions that can occur are Ovulation problems are any condition (usually hormonal) that prevents the release of a mature egg from an ovary. Poor egg quality is when eggs that become damaged or develop chromosomal abnormalities cannot sustain a pregnancy. This problem is usually age-related. The egg quality declines significantly in the late 30s and early 40s. Polycystic ovary syndrome is when the patients whose ovaries contain many small cysts have hormone imbalances and do not ovulate regularly. Female tube blockages are blocked or damaged fallopian tubes prevent eggs from getting to the uterus and sperm from getting to the egg.

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    the heart

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    Main: The heart is a muscular organ that it part of the cardiovascular system. It is located between the lungs, behind the sternum and is approximately the size of a fist. The heart is protected by a membrane called the pericardium which surrounds the heart and secretes a fluid that reduces friction when the heart beats. The atria's job is to receive blood and the ventricles job is to be filled with blood and send it to everywhere in the body. There are three layers which make up the wall of the heart. The outer layer is epithelial tissue, the middle layer is cardiac muscle and the inner layer is connective tissue.

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    The Various Roles Played By Proteins

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    Intrinsic proteins lie across the whole membrane. They help ions and molecules which are water soluble to cross the membrane at this point, therefore controlling what goes into and what comes out of the cell. Another function of proteins in the cell membrane is to 'detect signals from the outside of cells and relay them to the inside' (Phillipallan,nov 1999); these are known as receptor proteins (sometimes with sugars attached) and their job is to alter a cells behaviour to enable signal molecules like hormones to bind specifically to their own receptor.

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    Effect of Caffeine on the Heart Rate of Daphnia

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    It is the most commonly used mind-altering drug in the world. When used in moderation, caffeine acts as a mild stimulant to the nervous system, blocking the neurotransmitter adenosine and resulting in a feeling of well-being and alertness. Also, it is found that caffeine binds to receptors on the surface of heart muscle cells which leads to an increase in the level of cAMP inside the cells (by blocking the enzyme that degrades cAMP), mimicking the effects of epinephrine (which binds to receptors on the cell that activate cAMP production). cAMP acts as a "second messenger," and activates a large number of protein kinase A (PKA; cAMP-dependent protein kinase).

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    Osmosis. Finding the water potential of potato tuber cells

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    I know form prior work, investigation and study that the water potential will be around 0.4M. So I have decided to use 6 different solutions that are on either side of this figure. Table 1 below shows which molarity's I will be using. Table 13 Molarity (mol dm3) Water Potential (kPa) 0.00 �0 0.05 -130 0.10 -260 0.15 -410 0.20 -540 0.25 -680 0.30 -860 0.35 -970 0.40 -1120 0.45 -1280 0.50 -1450 0.55 -1620 0.60 -1800 0.65 -1980 0.70 -2180 0.75 -2370 0.80 -2580 0.85 -2790 0.90 -3000 0.95 -3250 1.00 -3500 Making the solution Of these 7 solutions I will have to make myself form the 1 mole stock sucrose solution.

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    Types of diffusion

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    Plants use osmosis to take up water into their roots because they have a large surface area and the water coming through the permeable membrane generates the pressure needed to send the water up the plant to the vital areas. Simple diffusion is a process of diffusion which does not require a special protein channel, facilitated diffusion (or facilitated transport) is a process of diffusion, a form of passive transport, where molecules diffuse across membranes, with the assistance of transport proteins.

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  7. Free essay

    Movement of Nutrients in Plants

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    In some cases, the ions may enter the plant against a concentration gradient. The ions are selectively absorbed by active transport, therefore energy is used. Mineral ions are taken up by the root hairs and other surface cells in the young parts of the root. Active transport occurs across the plasma membranes of the root hairs and the cortex cells. The ions move inwards via the symplast, through plasmodesmata. Once inside the vessels and tracheids, the ions are carried up the stem, along with the water in the transpiration stream.

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  8. Investigate the functions and dysfunctions of the nervous system.

    (en.wikipedia.org/wiki/Parasympathetic_nervous_system, 16/01/12) The nervous system also contains the sense organs that detect stimuli, these are eyes, which contain light receptors, ears which contain sound and balance receptors, nose which contain smell receptors that are sensitive to chemical stimuli, the tongue which contains taste receptors and can detect chemical stimuli, such as salt, bitter, sweet, savory and sour. And the skin that is sensitive to pressure, temperature and touch. When responding to stimuli the body may need to respond quickly so may miss out the brain completely, this is called a reflex action and helps keep the body safer by preventing injury.

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  9. Liver Transplant. This report will analyse how a liver transplant cures permanently damaged liver and what complications can occur.

    neutralising and destroying drugs and toxins * manufacturing bile * storing iron, vitamins and other essential chemicals * breaking down food and turning it into energy * manufacturing, breaking down and regulating numerous hormones including sex hormones * making enzymes and proteins which are responsible for most chemical reactions in the body, for example those involved in blood clotting and repair of damaged tissues. [1] What is Liver disease? The liver is a very tough and resilient organ which can exclusively regenerate itself.

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  10. Development of the human embryo

    At the moment of conception the gender is decided. From that point on it can not change. All of the time there is 50% chance of getting a girl versus a boy baby. The number of X and Y chromosome sperms are equal (Cole,2003). The moment of fertilization, an adventure begins. Along with it, the first trimester of pregnancy. Twelve hours after fertilization the first cell division takes place. Over the next several days these cells continue to divide at intervals of 12-15 hours. On the third day the ovum travels out of the fallopian tube and into the uterus (http://www.med.upenn.edu/).

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  11. Why is water a good transport medium?

    These bonds are called hydrogen bonds and means water molecules stick together making them cohesive. This is good in organisms because it means when water is transported though the body molecules will stick together. Water molecules are also adhesive, meaning they are attracted to other polar molecules and solid surfaces. Due to the interaction of the forces of adhesion and cohesion, water exhibits capillary action. Water rises into a narrow tube against the force of gravity. Water sticks to the inside wall of the tube and surface tension then straightens the surface causing a surface rise and more water is pulled up through cohesion.

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  12. The problem of rising deaths due to Malaria in Mumbai, India

    Despite efforts to eradicate and control malaria, it is increasing in Mumbai. Factors contributing to this worsening situation includes: - changes in population immunity - climate change - population movements - increasing resistance to available drugs (2) - increasing influx of migrants (8) - lack of effective pesticides available The Mumbai Health Service is struggling to cope with the increased numbers, and as a result the Brihanmumbai Municipal Corporation (BMC) have erected temporary sheds outside in which to treat the patients, due to lack of space.

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  13. Water diuresis

    Complete the data tables on the next two pages. There should be one table completed for each subject in your group. One subject will have data for urine osmolality but not ion concentrations. The other subjects will have data for urine ion concentrations but not osmolality. If there were only 3 subjects in your group write 'no subject available' across the last data table. 5) For the subjects in your group plot graphs showing the effects of the various treatments on: (a)

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  14. Role of blood in the body and experiment. The aim of this experiment is to either prove or disprove the hypothesis that altitude training increases the bloods efficiency of carrying oxygen around the body.

    they carry deoxygenated blood so therefore their walls are thin and made mostly of collagen. they have developed a large lumen so that resistance to flow is reduced. the exception is the pulmonary vein which carries oxygenated blood from the lungs back to the heart where it can be pumped around the body. What is the function and structure of blood? The function of blood is to carry substances around the body (see table below). Blood is the substance that is being investigated, it consists of: * Plasma - this makes up 55% of the blood and is the liquid part of the blood.

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  15. Structure of the Alimentary Canal in relation to digestion and absorption

    Submucosa- This is a layer of connective tissue that contains nerves, blood vessels and lymph vessels together with elastic fibres and collagen. 3. Muscularis Externa- This is made up of circular and longitudinal layers of smooth muscle fibres which control the shape and movement of the gut. 4. Serosa- This is the outermost layer and is made up of loose connective tissue which provides protection from friction against other organs. Different parts of the alimentary canal play a role in the journey of food from when it enters the mouth to when the leaves the body as waste: 1.

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  16. Enzyme Concentration

    Equipment * Milk powder solution * Test tubes * Test tube holder * Stop clock * Standard protease solution 1% * 5cm? pipettes * Glassware for diluting enzymes Safety All enzymes are potential allergens. Handle with care to minimize skin contact and inhalation. Also wear safety gear such as goggles and aprons.

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  17. Internal and External Fertilisation

    Environment for zygote Zygote usually develops externally in a watery environment which is vulnerable to environmental and predation, infection and rapid dispersal from the area. During external fertilisation, many gametes are released into the water by each sex at the same time and place. This type of fertilisation requires water because animal sperm must swim to the eggs. Water also protects the gametes from drying out. Species, which have external fertilisation, are either aquatic or return to water for reproduction.

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  18. Enzymes in medicine

    Streptokinase is a bacterial product so the body will build up an immunity to it. It is recommended that this medication should not be used again after four days from the first administration, as it may not be as effective and can also cause an allergic reaction. For this reason, it is usually given only for a person's first heart attack.

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  19. Free essay

    The Effect of Caffeine on heart rate. I think that the amount of caffeine in the blood will determine the heart rate of the daphnia.

    Using a pipette, transfer one large water flea to a cavity slide. Remove the water from around the water flea using filter paper, then add one or two drops of distilled water. 4. Use as much water as you can and do not use a cover slip. 5. Together these precautions will help maintain sufficient oxygen supply to the flea. A cavity slide filled with iced water and placed under the slide will act as a heat sink. 6. View the water flea under low power. Focus on its heart which can be seen through it translucent body. 7.

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  20. Fundamental human anatomy and physiology.

    Reference: http://training.seer.cancer.gov/module_anatomy/unit2_1_cell_functions_1.html# Viewed on 25/ 2/ 2008 Cytoplasmic Organelles Cytoplasmic organelles are little organs that are suspended within the cytoplasm of the cell therefore each type of organelle has to define a structure of a specific role in the function of the cell an example of this would be mitochondrion, ribosome, endoplasmic reticulum, Golgi apparatus, Lysosomes, Reference: http://training.seer.cancer.gov/module_anatomy/unit2_1_cell_functions_1.html# Viewed on 25/ 2/ 2008 Mitochondria Mitochondria is the second largest Organelle, with a single genetic structure which has a double layer of the outer membrane with inner fold known as a cristae this then controls the level of the water and the other materials within the cell therefore the Mitochondria gets rid of (disposes)

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  21. Heart Disease

    Your Blood pressure fluctuates and one suffers from either high blood pressure or low blood pressure. Those suffering from congenital heart disease are faced with the prospect of death due to a heart attack. Plaque formation on the arterial walls is a common cause of coronary heart disease. The blood vessels get blocked causing damage to various organs of the body. Another type of heart disease is peripheral vascular disease, which is due to blocked arteries in the arms and legs. It presents the mobility of the arms and legs, causing physical disability. A woman with congenital heart disease can consider pregnancy but has to undergo tests and evaluation to understand the risk factors involved.

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  22. Transport In Plants

    increases rate of transpiration Wind speed - still air saturated with water vapour - wind 'sweeps' water vapour away - this increases water potential gradient between leaf and air - increase in wind speed increases rate of transpiration Humidity - humid air saturated with water vapour - shallow gradient between air and leaf - increase in humidity decreases rate of transpiration Xylem Vessel - structure and function Hollow with no cell content lessressistance to water Large Lumen lessressistance to water

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  23. Atherosderosis. This is a disease where plaque builds up on the insides of the arteries. Multiple sclerosis. MS is a disease that affects the neurones in your brain and spinal cord causing problems in the vision muscle control and balance.

    What causes it? The exact causes of atherosderosis aren't known exactly but studies show that this can be a slow and complex disease that can start from childhood. But can develop faster as you age and also if you smoke, have high cholesterol, have high amounts of certain fats in the blood, high blood pressure and insulin resistance (diabetes) causing high amount of sugar in the blood. All of these factors can damage the inner layers of the artery, when this happens your body starts a healing process, where fatty tissues excrete compounds that promote healing.

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  24. Kidney Failure

    High B.P can damage glomeruli. Blood in glomeruli is already under high pressure but capillaries can be damaged if blood pressure gets too high.

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  25. Why has europe been dominant in history

    He transformed the Kingdom of England into the most efficient military power in Europe. However, he did start the Hundred Year's War, which was a big mistake. However, the war with France helped to create a sense of national unity that carried on after the war, which kept England strongly united. He vastly improved the Parliament and divided it into the House of Commons and Lords, which was very successful. 3) Charles Martel Charles was a Frankish military and political leader who lived between 688 and 741. Why I believe he is important to Modern European History is he led the Franks to a decisive victory over the Moors, halting their westward expansion.

    • Word count: 950

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