Biology

• what do fats and oils make?


  fatty acids and glycerol
• why does an incomplete heart structure affect a person's ability to transport oxygen?

  • hole in septum
  • oxygenated blood mixes with deoxygenated
  • less oxygen transported
• explain how the growth of a plant is controlled

  Auxins diffuse from the shoot tip and accumulate on the lower side which stimulates cell elongation
• how long does the shedding of the uterine occur for?


  1-8 days
• where does progesterone come from during pregnancy?


  ovary/placenta
• What does FSH do

  • matures egg
  • stimulates ovaries to release oestrogen
• Explain natural selection 


  • reference any form of mutation
  • natural selection
  • better survival advantage
  • reproduce and pass on alleles
  • occurs over many generations
• describe effects of additional carbon dioxide


  • carbon dioxide is greenhouse gas
  • global warming
  • ice caps melting
  • sea levels rise
• why do pyramids of energy have very few trophic levels?


  • energy lost
  • energy lost through processes like growth and movement
  • insufficient energy to have a lot of trophic levels
• benefits of pyramid of energy

  • shows the transfer of energy
  • more accurate
  • time taken into account
• define sustainable resource


  • a resource that can be produces as rapidly as it is used
  • it doesn't run out
• which hormone, FSH or LH, is the highest on day 14


  LH
• describe and explain how the structure of a villus allows it to adapt to its function


  • microvilli to provide large surface area
  • epithelium lining is one cell thick for better diffusion
  • good blood supply to main a steep concentration gradient
  • lacteal for fat breakdown and transport
• define stem cell


  a cell that is unspecialised and becomes specialises
• what are two features of amphibians that distinguish them from other vertebrates


  • lays eggs in water
  • moist skin
• label

  A) sclera

  B) retina

  C) fovea

  D) optic nerve

  E) ciliary muscle

  F) lens

  G) pupil

  H) cornea

  I) iris

  J) conjuctiva

  K) suspensory ligament

  
• Rods and cones are the two types of receptor cell present in the retina of the eye
• Rod cells and cone cells have different roles in detecting light stimuli: 

  • Rods can detect light at low levels, so play an important role in night vision
  • Three different types of cones can detect light at three different wavelengths, enabling colour vision
• Rods and cones are not distributed evenly across the retina:

  • Rod cells are found all over the retina, with the exception of the blind spot
  • Cone cells are concentrated in the fovea, the region of the eye onto which light is focused by the process of accommodation
  • The fovea enables the brain to form sharp, coloured images when light is effectively focused by the eye
• describe and explain the distribution of rod cells and cone cells


  • there are more rod cells than cone cells
  • cone cells peak at the fovea because they detect colour and high light
  • there are no rod cells at the fovea because they can't detect colour and low light
  • no rod cells and cone cells at blind spot because of the optic nerve
• what do rod cells detect


  low light and not colour
• what do cone cells detect


  bright light and colour
• what is the function of the fovea


  The fovea enables the brain to form sharp, coloured images when light is effectively focused by the eye
• define gene mutation


  a random change in the base sequence of DNA
• Mutations happen spontaneously and continuously but their frequency can be increased by exposure:

  • Ionising radiation (e.g. gamma rays and X - rays) - which can damage bonds and cause changes in base sequences
  • Some non-ionising radiation (e.g. ultra-violet) - can also damage bonds and cause changes in base sequences
  • Certain types of chemicals - for example chemicals such as tar in tobacco
• explain the risks to a species if the population size decreases

  • there is a reduction in genetic variation
  • can lead to inbreeding which causes increase in recessive alleles, leading to things like disease
  • risk of extinction
  • inability to find mates
• how can fish stocks be managed sustainably


  • education
  • monitoring populations
  • reduce mesh size
  • change net types
  • find alternative sources
  • licenses and laws
  • quotas
  • protected areas
  • fish farms
  • closed seasons
• balanced equation for anaerobic respiration in yeast


  C6H12O6 -> 2C2H5OH + 2CO2
• what is the mineral ion that makes protein?


  nitrate
• what organ breaks down lactic acid?


  liver
• why do red blood cells burst in water but plant cells don't?


  they don't have a cell wall
• define adaptive features


  an inherited feature that allows and organism to survive in the environment it is in
• why do hydrophytes have large air spaces?


  it reduces the density of the leaf, allowing them to float so it is more accessible to light or carbon dioxide for photosynthesis
• describe role of protein carriers


  carry molecules across the cell membrane into or out of the cell via active transport and moving agains the concentration gradient
• describe role of chlorophyll


  absorbs light so it can be converted into chemical energy for synthesis of glucose
• difference between circulatory system of a fish and mammal


  • single circulation
  • one atrium and one ventricle
  • no separation of deoxygenated and oxygenated blood
  • blood under less pressure
  • no septum in the heart
• advantages of double circulatory system 


  • prevents mixing of oxygenated and deoxygenated blood
  • blood can flow at high pressure
  • efficient supply of blood
  • efficient removal of waste
  • maintain high metabolic rate
• describe the role of the liver in excretion


  it allows for deamination by removing excess amino acids forming urea that can be released into the blood, allowing the kidney to remove it from the body
• state the organs which nutrients cross to reach the foetus

  plaenta
• advantages and disadvantages of self-pollination


  advantage

  • more chance of pollination
  • still occurs in isolated plants
  • less pollen wasted

  disadvantage

  • prone to inherited diseases
  • less genetic variation