B2 Revision

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B2 Revision

• Topics 1-4

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DNA -

• Genes are made of a chemical called DNA. In DNA
  there 4 bases called Adenine, Cytosine, Thymine
  and Guanine
• DNA contains instructions for making the cell and
  telling it what to do.
• DNA gives order of amino acids, only one side
  acts as a code for making proteins (Coding
  Strand)
• Plants and animals have a similar structure. They
  have a nucleus which holds DNA as a set of
  chromosomes. Each gene contains information to
  make one protein.

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Fermentation -

•  A micro-organism is a living thing that is so
  tiny it can only be seen through a microscope.
  Scientists cultivate, or grow, microorganisms in
  a liquid that contains nutrients  - called
  culture medium.
• Scientists have to control the growth carefully
  otherwise they will produce very quickly. As they
  grow the microorganisms use up the nutrients in
  the culture medium and produce waste products and
  other substances. this process is called
  FERMENTATION
• We use fermentation for making wine and bear by
  using yeast. The yeasts uses sugar as a nutrient
  and as energy. The sugar is broken down to leave
  two waste products, carbon dioxide and alcohol
  (ethanol). When making beer or wine, alcohol is
  the product wanted, however, fermentation by
  microorganisms can be used to produce many other
  useful products. To do this, the microorganisms
  are cultivated in tanks called FERMENTERS.
• Microorganisms are grown in fermenters to
  produce products. Such as yoghurt, cheese,
  vinegar and soy sauce. They are also used to make
  a range of different enzymes needed in industrial
  processes. Moulds and bacteria are used to make
  antibiotics such as penicillin. These are all
  examples of fermentation.
• Bacteria and other microorganisms contain DNA.
  They use the same genetic code as humans.
  Scientists can make the bacteria produce new
  products by changing their DNA. First they have
  to identify the protein that is needed as a
  medicine, such as insulin, which is needed to
  control diabetes. Then the cut out the section of
  the human DNA that is used for making insulin.
  They then add that that DNA to the bacteria. The
  bacteria now contain the gene for making insulin.
  If they are cultivated in a fermenter, this will
  grow massive numbers of bacteria and will produce
  lots of insulin.

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Protein synthesis -

• To make proteins two things must happen
• The instructions from the code must be carried
  from the DNA in the nucleus top the ribosomes.
  TRANSCRIPTION.
•  Amino acids must be bought to the ribosomes to
  be build up into a protein. TRANSLATION.
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• Transcription
• It takes place in the nucleus. The DNA unzips and
  the mRNA enters and copies from the coding strand
  of the DNA. (But U replaces T). After coping the
  code the mRNA leaves the nucleus through the
  'nucleur pore'.
• Translation
• The mRNA goes to the ribosomes in the cytoplasm
  and the tRNAs bring appropriate amino acids to
  translate the mRNA. The amino acids join together
  to form a polypethide and many polypethides make
  up a protein.

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Protein synthesis -

• Transcription

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Protein synthesis -

• Translation

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Respiration -

• Respiration is the process of breaking down
  glucose to release energy which takes place in
  every cell in your body. All living things
  respire.
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Aerobic Respiration This is using oxygen-
remember 'air'obic. It's the most efficient way
to release energy from glucose. Glucose Oxygen
-gt Carbon Dioxoide Water ( Energy)
Anaerobic Respiration This is without oxygen when
there is not enough available. It's not the most
efficient way. Glucose -gt Lactic Acid (Energy)
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Growth - 

•  Cell division results in growth
•  Growth is a permanent increase in the size or
  mass of an organism.  All growth results from the
  production of new calls by Mitosis  the bigger
  the organism, the more cells it contains.
• Plants have a special way of growing, when new
  cells are formed around root and stem tips, their
  cell walls are still soft.  The cells absorb
  water into their vacuoles and get longer.  This
  process is called elongation as the cells get
  longer the roots or shoots get longer.  The cell
  wall hardens and the cell keeps its new shape.  
• There are different ways of measuring growth. One
  way is to simply weigh the organism.  Body cells
  contain a large amount of water so most of this
  weight will be water this is called the wet
  weight.  The amount of water can vary so the
  results may be inaccurate.
• Another, more accurate method is to dry out the
  body first.  This is called the dry weight.  This
  method kills the organism, so it if often only
  used to compare growth in plants.
• Another way is to look at size and length. 
  Plants can be measured from the shoot tip to
  ground level to give their height.  Measuring
  across the widest part of the plant is called
  its spread.  Height and spread are used by
  garden centers and plant catalogues so customers
  know big a plant will grow.
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Cell Division -

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Stem Cell -

•  Stem cells are found in all multi-cellular
  organisms. They are characterized by the ability
  to be able to renew themselves through mitotic
  cell division and differentiating in a large
  range of specialized cell types. In a developing
  embryo, stem cells can differentiate into all of
  the specialized embryonic tissues. In adult
  organisms, stem cells and progenitor cells act as
  a repair system for the body, replenishing
  specialized cells, but also maintain the normal
  turnover of regenerative organs, such as blood,
  skin, or intestinal tissues.
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• Self-renewal - the ability to go through numerous
  cycles of cell division while maintaining the
  undifferentiated state.
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• Potency - the capacity to differentiate into
  specialized cell types.

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Tough Decisions -

•  Termination The legal limit for abortion is
  23 weeks. This is because after 23 weeks the
  child is developed enough to be born alive and
  survive independent of its mothers womb.
• There are many people who disagree with the
  legalization of abortions and believe its
  against human rights. However, as you can see
  from below, more people support it than not.
• A 2009 poll by MORI surveyed women's attitudes to
  abortion. Asking if all women should have the
  right of access abortion
• 37 Strongly agree
• 20 Tend to agree
• 12 Neither agree nor disagree
• 7 Tend to disagree
• 12 Strongly disagree
• 3 Don't know
• 9 preferred not to answer

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Performance enhancing drugs   Lean mass
builders - used to amplify the growth of muscle
and lean body mass, and sometimes to reduce body
fat. E.g. anabolic steroids, beta-2 agonists and
various human hormones. Stimulants - used by
athletes to stimulate their bodies and perform at
optimum level, usually to increase alertness,
decrease fatigue, and/or increase aggressiveness.
E.g. caffeine and amphetamines. Painkillers -
mask athletes' pain so they can continue to
compete and perform beyond their usual pain
thresholds. Blood pressure is increased causing
the cells in the muscles to be better supplied
with oxygen. Sedatives - used by athletes in
sports like archery which require steady hands
and precise aim, and also by athletes attempting
to overcome nervousness. Alcohol and marijuana
are examples. Diuretics - remove water from
athletes' bodies. They are often used by athletes
who need to meet weight restrictions. Masking
drugs - used to stop detection of other drugs. An
example is the use of epitestosterone, it
restores the testosterone to normal levels after
anabolic steroid supplementation.
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Plant hormones -

• Auxin - needed for plant growth. It controls the
  growth of roots and shoots. Auxin is stored in
  the tips of new shoots and roots, and causes
  growth by diffusion.
•     If you cut the tip off a shoot, the shoot
  will stop growing. If the tip is replaced, it
  starts to grow again. However, auxin stops
  sideward growth, so if the tip is removed, the
  shoot will grow sideways.
•     There is a different effect of auxin in
  roots. It prevents growth vertically. This means
  the root will grow toward moisture, not downward
  with gravity. This causes a build-up of auxin on
  the bottom edge of the root.
•     If there is a build up of auxin on one part
  of a root or shoot, it causes only the top side
  to grow, making the shoot/root bend
  upward/downward respectively.

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Plant hormones -

• Gibberellin - promotes cell division and
  elongation. It also helps seeds to sprout.
• Cytokinin - also promotes cell division. High
  levels of this hormone are found in areas of the
  plant that require the most growth, such as
  roots, young leaves and developing fruits and
  seeds.
• Abscisic acid - slows down the plant's metabolism
  so that it doesn't grow during the winter. This
  leaves the plant more time for phothesis and can
  help the plant survive harsh winter months.
• Ethylene - after auxin/gibberellin initiates
  fruit growth, ethylene helps the fruit to ripen.

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Artificial selection -

•  Cut an earthworm in half and its head end will
  grow a tail. This is called regeneration.
• Only a few animals have this ability. No mammals
  have this ability.
• When an animal loses a part of its body, the
  cells around the structure change their structure
  and become less specialized. The cells then
  differentiate again to produce all the different
  types of cell needed to grow the new limb.
• Stem cell research is looking at these animals to
  try to find a way to regenerate human body parts.
  
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Selective breeding Selective breeding means
breeding from individuals that have the
characteristics you most want. This increases the
chance that more offspring will also have these
characteristics. Selective breeding can improve
resistance to disease, increase yield and make
foods more attractive to consumers.
     Selective breeding can be used in animals
and plants.      
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Cloning -

•  Cloning is using an organisms DNA to create a
  genetically identical new organism. 1. A
  sheep's egg cell is taken and the nucleus is
  removed. (Haploid-it was a gamete)2. Another
  nucleus was inserted into the egg cell, it was a
  diploid nucleus from the cell of a parent sheep.
  It had the full number of chromosomes. This is
  nucleus transfer. 3. The cell was stimulated,
  divided by mitosis and forms an embryo.
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• 4. The embryo was implanted into the uterus of a
  female sheep, which gives birth to it. The new
  sheep is genetically identical to the parent 
  sheep which the nucleus was taken from

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Gene therapy -

•  Gene Therapy Could be Used to Treat Genetic
  Disorders
•  Gene therapy is a new, experimental treatment
  for genetic disorders.
•  It can involve inserting a new, functional
  version of a faulty gene into a patients cells.
  These cells would then be able to make the
  correct protein and the symptoms would disappear.
  
•  Gene therapy would be targeted at areas that
  were badly affected by the disease.
•  In the long term, scientists hope to make these
  changes to the patients DNA permanent, but so
  far, trails testing gene therapy have only shown
  very temporary improvements.
•  Gene therapy still needs a lot of researching
  and testing. Potential dangers of gene therapy
  have already been found, e.g. the introduced
  genetic material could insert into the middle of
  another gene, causing a whole new set of medical
  problems, or suicide genes could be taken up by
  health cells.

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Cells -

• Animal cells usually have an irregular shape, and
  plant cells usually have a regular shape
• Cells are made up of different parts. It is
  easier to explain what these parts are by using
  diagrams like the ones below.
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• Cells are very small. They are the basic
• building blocks of all animals and plants.
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• Animal cells and plant cells both contain
• cell membrane, cytoplasm, nucleus
• Plant cells also contain these parts, not found
  in animal cells
• chloroplasts, vacuole, cell wall
• The table summarises the functions of these
  parts.
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Photosynthesis -

• Photosynthesis is when plants turn energy from
  the sun into food (Glucose)  by using carbon
  dioxide. A waste product (Oxygen) is formed.

                                  light Carbon 
  Water    --gt    Glucose Oxygen dioxide       
                                      chlorophyll
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Limiting factors to photosynthesis -

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• Light
• Temperature
• CO2 levels
• Water
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• If any of these increases, the rate of
  photosynthesis will increase up to a point when
  one of the others has become the limiting factor.
  
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• If the temperature exceeds 45 degrees then the
  enzymes will denature and the rate of
  photosynthesis will rapidly decrease. 

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Carbon cycle -

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Nitrogen cycle -

• Nitrogen is an important element in living
  things. It is found in proteins and DNA. Plants
  get nitrogen in the form of nitrates which they
  get from soil. The nitrogen can then pass into
  animals as they eat the plants . Nitrogen is
  naturally recycled in a similar way to the carbon
  cycle.
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• Nitrogen is mainly recycled by microorganisms in
  the soil. Decomposers break down dead organisms
  and animal waste (manure and urea) into ammonia,
  which contains nitrogen. Nitrifying bacteria then
  use a series of reactions to convert the ammonia
  into nitrates that plants can absorb.
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• Modern agriculture is extremely intensive. The
  natural nitrogen cycle cannot replace nitrates as
  quickly as they  are removed, so farmers add
  industrially made nitrate fertilizers. However
  this can cause problems in the local rivers.

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Deforestation global warming -

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Extreme environments -

•  Organisms need to adapt to survive.
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• They need a source of energy/food, water, a
  suitable temperature and a source of oxygen to
  survive.
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• Black smokers are hydrothermal vents and the
  environment around them is extreme. Magma heats
  up water and it is released as steam through a
  vent into the sea. This makes the sea hot and
  acidic.
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• High altitudes (3000m) are also extreme.
  Animals like snow leopards adapt to have thick
  fur and can cope with low oxygen levels and high
  levels of UV light.
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• The Antarctic is also extreme. The temperature
  can be as low as -70 Degrees Center grade, so
  animals like penguins have thick fur and fat
  layers and group together in order to share
  warmth.

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Adaptation -

• Every organism in a habitat is adapted to living
  in that habitat.
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• This means they have evolved adaptations to
  survive in particular conditions or environmental
  factors.
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• These factors include water, oxygen, light,
  temperature and the other living organisms in the
  habitat.
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• If one of these factors change it will effect
  some of the organisms. Eg if less light reaches
  the bottom of a lake, some plants will no longer
  be able to survive and die out. This causes less
  food for other organisms living in that habitat.
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• Any organism that cant adapt to the changes in
  the environment are likely to have a smaller
  population. This may cause them to die out
  altogether and become extinct.

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Predation -

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Competition -

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Air pollution -

• There are many causes of air pollution, but most
  of it is made from humans. Nitrous oxide and
  carbon dioxide are the 2 main pollutants of the
  air carbon dioxide comes burning our waste and
  such so we should recycle more. Volcanoes also
  can be a big cause of air pollution from the
  gases that are giving off, but when a volcanoes
  erupts it gives off many dangerous gases that we
  will end up breathing into our lungs that will
  damage us but they also damage the environment by
  emitting some harmful gases. A good example of a
  harmful gas was the great London smog. This was
  harming the ozone layer and making it difficult
  for people to breath outside of their homes. This
  is affecting many things such as habitats of
  animals because the gases in the air are causing
  a lot of acid rain is being produced destroying
  our environment at the same time as destroying
  our ozone. The gas that is causing this is
  sulpher dioxide which we can decrease by taking
  better care of our environment. We need to act
  now to make a change for the better soon
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• As you can see by this graph
• the rise in the pollution in the air has
• increased dramatically in in the last 
• 2000 years and it is making it more
• difficult to sort out the problem.

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Water pollution -

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• Two main types of water pollution ACID RAIN and
  FERTILISERS
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• ACID RAIN
• The main causes of acid rain are the burning of
  fuels and vehicle exhausts. These produce the air
  pollutants of sulphur dioxide (SO2) and Nitrogen
  oxide (NO2).
• These pollutants dissolve in water to form acids
  (ACID RAIN)
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• FERTILISERS
• 1. The fertiliser runs of into a river or pond.
• 2. The fertiliser makes the algae grow fast. The
  increased algae growth cuts out sunlight and uses
  up oxygen.
• 3.The plants do not get enough sunlight and they
  die. Dead plants and algae build up on the river/
  pond bed.
• 4. The dead plants and algae rot, using up oxygen
  in the water. There are fewer animals in the
  water.

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Recycling -

•  -Recycling has many benefits. If all the glass,
  metals, plastic and paper in our dustbins were
  recycled that would be nearly half the contents
  of the average bin.
• -  This could reduce the problem of waste
  disposal and landfill sites that are getting
  full.
• -  Recycling uses less energy and produces less
  damaging carbon dioxide than manufacturing new
  materials.
• -  For Example, recycled steel uses 75 less
  energy and produces only 15 of the carbon
  dioxide produced when steel is made from iron
  ore.
• -  Not everything can be recycled and some
  materials are more difficult to recycle than
  others.
• -  Plastics have to be sorted by hand and many
  types are not suitable for re-use
• -  Paper can only be recycled about five times
  before the fibres become too short and weak.
• -  Refrigerators are a particular problem because
  of the harmful gases they contain.
• -  Although recycling uses less energy and
  resources it is still an industrial process.
• -  Some materials need a lot of cleaning and
  reprocessing. Where materials are difficult to
  recycle it can be easier and cheaper to make new
  products.

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Environment, the human effect -

•  Human activity can have negative effects on the
  environment. Manufactured gases called CFCs have
  damaged the ozone layer in the upper atmosphere.
  Ozone filters out much of the ultraviolet light
  from the Sun, which can damage the skin possibly
  leading to skin cancer. Cases of skin cancer have
  almost doubled in UK in the last 20 years
  therefore the ozone layer is not protecting us as
  well as it used to.

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  Lichens are good indicators of our impact on
the environment as they are very sensitive to air
pollution, especially sulphur dioxide.   Mayfly
larvae are found only in very clean water with
lots of oxygen. They are used as living
indicators to monitor water quality in streams.
Lots of mayfly larvae means that a stream has
high quality water.
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Species in peril -

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• Species in peril means animals that are rare
  because they are in danger or cannot adapt to
  climate change. Every time a species becomes
  extinct biodiversity is reduced.
• Careful management of the environment is called
  conservation.
• The causes of this are deforestation, hunting,
  co2 levels rising, building and economy
  development, landfill sites.
• All of these species are forced out of habitats
  because of these causes and if we cut down on co2
  levels and recycle more we could improve the
  lives of us and animals.
• More and more plants and animals are become
  extinct or rare because of the changing climate
  due to our actions.
• Two of every five species on the planet that have
  been assessed by scientist face extinction.
• THE MAIN CORSE OF EXTINCTION IS PEOPLE!

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Conservation managment -

•  Conservation measures protect species by
  maintaining their habitats and protecting them
  from poachers and overhunting/havesting
• There are several reasons why its important to
  conserve species and natural habitats
• Protecting endangered species Many species are
  becoming endangered, often due to hunting and the
  destruction of their habitats. They need to be
  protected to stop them becoming extinct.
• Protecting the human food supply Overfishing
  has greatly reduced fish stocks in the sea.
  Conservation measures (e.g. quotas on how many
  fish can be caught) encourage the survival and
  growth of fish stocks. This protects the food
  supply for future generations.
• Maintaining biodiversity Biodiversity is the
  variety of different species in a habitat the
  more species there are, the greater the
  biodiversity. If one species in a habitat is
  destroyed it affects the other species living
  there the food web will be affected. Its
  important to protect biodiversity.
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• You can
• Coppicing this involves cutting down trees down
  to just above ground level. The stumps sprout
  straight, new stems which can be regularly
  harvested.
• Reforestation you can replant to recreate the
  habitat that has been lost.
• Replacement planting This is when new trees are
  planted at the same rate that others are cutting
  down. So the total of trees remains the same.

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Effects of exercise -

•  When you exercise, your muscles get energy from
  respiration. Glucose and oxygen must be supplied
  while carbon dioxide is removed.
•       glucose oxygen       carbon dioxide
  water ( energy)
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• If you exercise more vigorously, your muscle
  cells need more energy to do the extra work. They
  need to respire faster, this means
• More oxygen must be absorbed by your lungs.
• More carbon dioxide must be removed by your
  lungs.
• More oxygen and glucose must be delivered to your
  muscles by your blood.
• More carbon dioxide must be removed from your
  muscles by your blood.
• Your breathing system and heart have to work
  harder. You breathe faster and more deeply. This
  increases the rate of gas exchange in your lungs
  more oxygen is absorbed into your blood and more
  carbon dioxide is removed. Your heart rate also
  increases, pumping more blood to your muscles.

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Improving measurements -

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