The Light Dependent Reactions of Photosynthesis

Overview Living things require energy to stay alive. The main energy source for autotrophs, a group of organisms that produce their own food, achieve this by gathering natural commodities such as water and sunlight. These sources of energy are converted through a series of biochemical l processes into substances that the autotroph can use to maintain its necessary functions. The sun is the starting point for the process of photosynthesis ("photo" refers to light sunlight). The sun emits many, many different wavelengths, including X-rays, UV rays, and a spectrum of light that is visible to us. The light used by photosynthesis is the spectra of visible light. The figure above shows the spectra of light which is absorbed by a plant. The sun is sometimes thought to emit simply a white light, but sunlight is actually reflected in a spectra similar to the one shown above. Plants appear to have a green color because this green light is not absorbed as much as other colors (with different wavelengths). As a result, this light is reflected by the plant, showing its green color. Another feature of the above graph is the inclusion of several pigments in the typical autotroph. Organisms that undergo photosynthesis contain a variety of colored pigments, which are organized on membranes within chloroplasts. These pigments include Chlorophyll a, Chlorophyll b, and various carotenoids.

  • Word count: 1328
  • Level: International Baccalaureate
  • Subject: Biology
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Biology Internal Assessment. How does exercise affect breathing rate?

BIOLOGY INTERNAL ASSESSMENT How does exercise effect breathing rate? ________________ Introduction Different activities have different effects on the breathing rate because of the difference in the amount of oxygen needed. This investigation will assess how breathing rate changes in three different state of humans’ body: at rest, after light exercise and after heavy exercise. Base on the result we can find out the way in which our body adapts to particular activities that need different amount of oxygen or in another word, how exercises affect breathing rate. Research question What effect does exercises’ intensity have on breathing rate? Hypothesis The increasing in the intensity of exercise results in the higher breathing rate. + At rest, breathing rate will maintain at normal speed to provide enough oxygen for cells to carry out aerobic respiration because at this state, body as well as muscle don’t need much energy. + After light exercise, breathing rate will increase slightly because during light exercises, small amount of lactic acid is generated and it needs to be broken down into energy. + After heavy exercise, breathing rate will increase sharply because during vigorous exercises, lung and heart are unable to get enough oxygen to muscle quickly enough, a large amount of lactic acid is generated and as a result the breathing rate must increase to get

  • Word count: 758
  • Level: International Baccalaureate
  • Subject: Biology
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Use of stem cells to treat Stargardts disease and one other named condition.

http://www.jimonlight.com/wp-content/uploads/2012/02/DURRESHAHWAR_STARGARDTS-DISEASE_19490101_13236.jpg Stargardt's macular dystrophy: The problem: Stargardt macular degeneration is a recessive genetic (inherited) eye disorder that causes progressive central vision loss, and eventually total blindness. Stargardt’s disease, with symptoms beginning in childhood, is the most common form of juvenile macular degeneration; affecting around one in 10,000 children. The mutation causes an active transport protein on photoreceptor cells to malfunction. These photoreceptor cells degenerate over time, which results in the production of a dysfunctional protein that cannot perform energy transport. The treatment: Embryonic stem cells are unique in that they have the potential to differentiate into any type of adult body cell (totipotent). Most embryonic stem cells are taken from embryos that have been fertilised in vitro in the laboratory (IVF), Under laboratory conditions, when embryonic stem cells are treated to divide and differentiate, retinal cells can be derived from embryonic stem cells. These retinal cells can then be injected into the retina of people with Stargardt's macular dystrophy. The retinal cells attach to the retina and become functional. Central vision improves as a result of more functional retinal cells. The future: This treatment is still in at the stage

  • Word count: 606
  • Level: International Baccalaureate
  • Subject: Biology
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How does the salinity of water affect the germination of mung been seeds as measured by the number of seeds that successfully germinate?

Biology Internal Assessment DCP and CE “Effect of Salinity on Germination” 2014 Research Question How does the salinity of water affect the germination of mung been seeds as measured by the number of seeds that successfully germinate? Raw Data table 1 showing the effect changing the salinity of water added to ten ungerminated Vigna radiate (mung bean) seeds has on the seeds ability to begin germination as shown by a cracked testa four days after solution was added to the seeds? Salinity of Water (mol L-1) Number of mung bean seeds with a cracked testa four days after being exposed to the solution ±1 seed Trials 1 2 3 4 5 0.0 0 6 8 9 9 0.2 2 3 6 8 6 0.3 3 3 2 2 4 0.4 2 2 4 6 2 0.5 2 0 2 1 1 Key Colour used to indicate the raw data used to calculate example mean Colour used to indicate the raw data used to calculate example standard deviation Raw Data table 2 showing the effect changing the salinity of water added to ten ungerminated Vigna radiate (mung bean) seeds has on the seeds ability to successfully germinate as determined by the visible presence of a radicle seven days after the solution was added to the seeds? Salinity of Water (mol L-1) Number of mung bean seeds successfully germinated as determined by the visible presence of a radicle seven days after being exposed to the solution ±1 seed Trials 1 2 3 4

  • Word count: 2947
  • Level: International Baccalaureate
  • Subject: Biology
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Biology Internal Assessment - investigate whether the Window and Notching caterpillar share the same ecological niche.

Biology Internal Assessment DCP and CE “Ecological Niches of Caterpillars” 2013 Design Aim To investigate whether the Window and Notching caterpillar share the same ecological niche. Research Question How does the shape of the feeding bite as measured by the distance from the midrib of the cabbage tree leaf to the nearest point of the feeding site indicate whether the Window and the Notching caterpillar share the same ecological niche? Variables Independent Variable – Shape of feeding site Range: Window or Notch Dependant Variable The distance from the midrib of the cabbage tree leaf to the nearest point of the feeding site. Results Raw Data Table showing the distance from the midrib of the cabbage tree leaf to the nearest point of the feeding site (mm) of 50 samples from notched and window shaped feeding sites on cabbage tree leaves. Shape of Feeding site The distance from the midrib of the cabbage tree leaf to the nearest point of the feeding site. (mm) (±1mm) Notch 7 9 8 12 12 6 12 10 11 10 9 6 11 4 5 Notch 7 6 8 11 11 6 7 8 9 6 8 7 8 7 6 Notch 4 13 5 9 6 12 7 14 10 13 10 10 12 8 6 Notch 9 5 7 11 9 Window 5 10 8 7 6 3 2 5 10 5 10 1 5 5 7 Window 6 2 11 5 1 3 10 11 3 5 5 7 6 5 3 Window 5 7 4 6 8 3 2 8 3 9 5 5 10 4 6 Window 9 4 3 1 10 Key

  • Word count: 2843
  • Level: International Baccalaureate
  • Subject: Biology
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How does mowing or not mowing effect the petiole heights of white clover as measured by the height of the petiole of individual clover heights on a School field?

Biology IA Petiole Heights of White Clover 2013 Design Aim To investigate the effect of regular mowing on the petiole height of white clover. Research Question How does mowing or not mowing effect the petiole heights of white clover as measured by the height of the petiole of individual clover heights on a Kristin field? Variables Independent Variable – Mowed or Unmowed Dependant Variable Height of Petiole Results Raw Data Table showing petiole heights (cm) of 50 white clover samples from unmown and mown areas. Unmown 30 87 48 92 54 33 135 60 81 139 90 78 125 174 167 Mown 83 70 32 61 70 45 28 34 37 20 25 30 31 35 80 Unmown 184 80 125 163 197 116 236 42 93 330 132 136 70 80 80 Mown 22 62 35 25 44 30 12 53 45 40 33 52 34 30 25 Unmown 70 75 63 90 86 100 278 26 20 110 120 10 55 75 80 Mown 34 45 24 21 57 42 33 24 43 26 20 30 45 190 40 Unmown 100 40 70 80 140 Mown 52 51 43 21 26 Processed Data Table showing mean petiole heights of 50 white clover samples from unmown and mown areas. Mean (cm) Standard Deviation Unmown 103 63 Mown 42 27 Note: Processed data was put to the same number of decimal places as raw data Calculations: Mean From: http://easycalculation.com/statistics/standard-deviation.php Standard deviation From:

  • Word count: 1870
  • Level: International Baccalaureate
  • Subject: Biology
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How does changing the percentage of sucrose added to yeast affect the rate of respiration of yeast as measured by the height of gas bubbles (froth) ?

Biology Internal Assessment DCP and CE “Frothy Yeast” 2014 Research Question How does changing the percentage of sucrose added to yeast affect the rate of respiration of yeast as measured by the height of gas bubbles (froth) achieved above the yeast-sucrose suspension in 360 seconds? Raw Data table showing the effect changing the percentage of sucrose added to yeast has on the rate of respiration of yeast as measured by the height of gas bubbles (froth) achieved above the yeast-sucrose suspension in 360 seconds. Percentage of sucrose added to the yeast (%) ±1% Rate of respiration of yeast as measured by the height of gas bubbles (froth) achieved above the yeast-sucrose suspension in 360 seconds (mm) ±1mm Trials 1 2 3 4 5 6 0 0 0 0 0 0 - 5 16 24 38 16 17 - 10 20 21 24 19 18 - 15 20 17 19 18 20 - 20 17 3 17 14 16 16 Key Colour used to indicate the raw data used to calculate example rate Because this value varies so greatly from the other values in the trials I shall omit it from my calculated results in my processed data table to try and maintain the integrity of my results. Observations * The temperature of our water bath was 42 not 40 as programed * When pouring the yeast into the tall test tubes it smeared the sides * The cylinders rested in the water bath at an angle * The height of the froth was uneven at

  • Word count: 3428
  • Level: International Baccalaureate
  • Subject: Biology
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investigating the water potential of potato cells

Internal assignment: Measure water potential of a potato's cells Research question: how is water potential of potato cells differ in different sucrose concentration? Background information: Investigate the water potential of a potato's cells in different sucrose concentrations. The concentrations will be: 0.8M, 0.4M, 0.2M, 0.15M, 0.075M and 0.00M. Terminologies used in this experiment: * Hypertonic solution: solution that has higher osmosis pressure (or has more solutes) than another solution to which it is compared. * Hypotonic solution: a solution that contains less solute (more water) compared to the cytoplasm of the cell. * Isotonic solution: Solutions of equal solute concentration1 * Diffusion: the spread of particles through random motion from regions of higher concentration to regions of lower concentration. * Osmosis: movement of solvent molecules through a selectively-permeable membrane into a region of higher solute concentration, aiming to equalize the solute concentrations on the two sides. It may also be used to describe a physical process in which any solvent moves, without input of energy, across a semi-permeable membrane (permeable to the solvent, but not the solute) separating two solutions of different concentrations * Water potential: potential energy of water per unit volume relative to pure water in reference conditions. Water potential

  • Word count: 1858
  • Level: International Baccalaureate
  • Subject: Biology
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Investigating Variation in Leaf Size

Investigating Variation in Leaf Size Aim: How much variation will we observe between species in terms of leaf area? How will this compare with variation within species (or between leaves of the same individual)? Description: The leaves of plants are adapted to maximize photosynthesis. They are also adapted to water availability and humidity. The size, shape and number of leaves on a given plant will reflect the conditions of its native habitat. Method: - Firstly, form a group of two to three people - Then go outside into the garden area and collect a pair of four different types of leaves. Try to collect a variation in leaf size. - After that place the leaves on a piece of squared paper (4mm²) and draw around them with a pencil. Next count all the individual squares and record the numbers in a chart. - Take the number of the squares for each leaf and multiply that number by 4. (For example: 132 is the number of counted squares and multiplied by 4 it equals 528). - After calculating the area of each leaf, record the results in a table. - By adding the numbers together and then dividing that number by two, you will be able to calculate the mean of each leaf type. - Then using a ruler measure the length of each leaf but try to make it a fair test by either including or not including the small stem of each leaf. Make sure that the measurements of length are

  • Word count: 563
  • Level: International Baccalaureate
  • Subject: Biology
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The greenhouse effect

THE GREENHOUSE EFFECT Between the main purposes of the present writing are the establishment of a basic idea on the subject known as "Greenhouse effect"- its pro's and con's, its causes and consequences - and to present my personal opinion on the issue. But before entering the sea of facts I'd like to clarify the term greenhouse. Greenhouses are used to grow plants, especially in the winter; they work by trapping heat from the sun. The glass panels of the greenhouse let in light but keep heat from escaping. Certain gases in the atmosphere behave much like the glass panes in a greenhouse. Based on the previous comparison, scientists define the greenhouse effect as the capacity of certain gases in the atmosphere to trap heat and infrared radiation emitted from Earth's surface, thereby insulating and warming the planet. In order to be more descriptive, let's follow the main steps in the process. When the Sun's radiation reaches Earth's atmosphere, some 25 percent of the energy is reflected back into space by clouds and other atmospheric particles. About 20 percent is absorbed in the atmosphere. About 50 percent of the Sun's energy, largely in the form of visible light, passes through the atmosphere to reach Earth's surface. Soils, plants, and oceans on Earth's surface absorb about 85 percent of this heat energy, while the rest is reflected back into the atmosphere where

  • Word count: 1243
  • Level: International Baccalaureate
  • Subject: Biology
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