B7 Biology across the ecosystem

A summary of each of the topics included in B7

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  • Life depends on solar energy absorbed during photosynthesis and stored in chemicals like starch
  • Autotrophs make food from minerals, carbon dioxide, and water but heterotrophs (like humans) need ready-made food
  • Some glucose is used in respiration and to make cellulose, protein, starch, and chlorophyll
  • Nitrates are absorbed and added to glucose to make proteins
  • Starch has little effect on the osmotic balance of the cell, so it is used for energy storage
  • Compensation points occur when respiration makes as much carbon dioxide as photosynthesis uses
  • Pyramids of biomass show the food available to the herbivores and carnivores in an ecosystem
  • Only 10% of the energy in biomass is passed on at each part of the food chain, the rest is lost to decomposers or as waste heat
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Further up the food chain

  • Mutualistic relationships benefit partner species; commensalism benefits one without harming the other; parasitism harms the host.
  • Parasites cause human disease and reduce farmers' yields
  • Parasites evolved with their hosts, so they can evade the host's immune system. For example, malaria parasites hide in red blood cells. They produce large numbers of offspring to ensure transfer to a new host.
  • Sickle-cell anaemia is caused by a faulty recessive allele. It makes red cells jam in small capillaries, causing pain, organ damage, and early death
  • Natural selection has increased the allele's frequency where malaria exists because having one copy of the sicle-cell allele protects you. 
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New technologies

  • Bacteria have a cell wall (like a plant), cell membrane, circular DNA chromosome, and plasmids
  • Bacteria and fungi are grown in fermenters to produce antibiotics, single-cell protein, and enzymes like rennin.
  • Genetic modification involves isolating and copying genes and putting them in new cells
  • This is done by adding a plasmid or virus to a vector.
  • GM bacteria make drugs, and hormones such as insulin. GM plants have added characteristics like disease resistance which lead to higher yields
  • Economic, social, and ethical implications have to be considered before genetically modified organisms are released.
  • Genetic tests are carried out by isolating DNA, adding gene probes, and using UV or autoradiography to locate them.
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  • A gene with three alleles, decides your blood type.
  • Of the three alleles, IA, IB, IO, two (IA and IB) are codominant
  • The chance of inheriting each blood group can be predicted using genetic diagrams
  • The recipitent of blood transfusion must not have antibodies to the donor's red cells.
  • The heart has an atrium on each side, to collect blood from the veins, and a ventricle on each side to pump it into the arteries
  • We have a double circulatory system. The right ventricle sends blood to the lungs for gas exchange, and the left ventricle sends it around the body.
  • Valves in the heart and veins keep blood flowing in the right direction
  • Tissue fluid bathes cells and aids diffusion of oxygen, carbon dioxide, glucose, and urea between capillaries and tissues 
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  • Aerobic respiration releases large amounts of energy.
  • This energy is used to synthesize ATP, the cell's energy currency.
  • During exercise, respiration increases to provide more energy (ATP) for muscle contraction.
  • Heart and breathing rates increase to supply oxygen and glucose faster, and remove carbon dioxide faster, during exercise.
  • 'Normal' measurements for heart rate and blood pressure vary for each person compared to one another and themselves.
  • Anaerobic respiration releases less energy. It is used in short bursts of energy when aerobic respiration cannot meet the demand.
  • The oxygen debt is the amount of oxygen used to break down lactic acid after anaerobic respiration.
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Skeletal system

  • Vertebrate skeletons support the body and allow movement
  • Bones are held together by slightly elastic ligaments. Non-elastic tendons attach bone to muscle
  • Cartilage and synovial fluid reduce friction at the joints.
  • Muscles work in antagonistic pairs as they can only contract
  • Health information is needed before medical treatment so regular contact with health or fitness practitioners is essential alongside accurate records.
  • The benefits of treatment have to be weighed against their side-effects
  • Assessments of progress have to take the accuracy of equipment and reliability of data into account
  • Sprains are treated through use of the RICE method
  • Physiotherapists use exercise to build muscles and stop joint problems
  • Excessive exercise can dislocate a bone from its socket, tear a ligament or tendon, or sprain a ligament
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George Rhatigan


Best notes ever!!!!!!!!!!



great brief notes! 

Temi Danso


Thanks for these!

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