biology 2

• Carbon Cycle

  • Carbon dioxide is in the atmosphere, from respiration
  • Carbon dioxide is absorbed by producers, such as plants, for photosynthesis
  • Animals feed on the plants, exhaling out the CO2 as respiration
  • Decomposers feed on the dead organisms, returning carbon in the organisms bodies back to the atmosphere, and respiring as they do so.
• FSH


  Stimulates oestrogen production and causes egg to mature
• LH


  Triggers release of an egg from the overy
• Oestrogen


  Thickens uterus lining
• Homeostasis


  The ability of a body to maintain a constant internal environment
• Receptors


  Detect stimulus
• Sensory neurones 


  Carry electrical impulses from receptors to CNS
• CNS

  Consists of brain and spinal cord, processes electrical impulses from receptor cells, brings about a response, sends an impulse along a motor neurone
• motor neurone


  Carry electrical impulses from CNS to effectors
• effectors


  receive electrical impulses from CNS and respond to the stimuli
• synapse


  Two neurones joining together and use chemicals to transfer electrical impulses between them
• how do impulses travel across a synapse?

  1. An electrical impulse travels through the first neurone
  2. Neurotransmitters released and travel between the neurones
  3. Neurotransmitters diffuse between the gap and binds to receptors on the second neurone
  4. Sets off new electrical impulse that travels along second neurone
• reflex arc

  1. danger detected by receptors
  2. impulse sent down a sensory neurone to CNS
  3. impulse sent along a relay neurone in the CNS and down a motor neurone into an effector
  4. The effector produces a quick response
• pituitary gland


  master gland, releases hormones
• thyroid


  produces thyroxine, which helps regulate metabolism
• pancreas


  produces insulin which controls blood glucose
• adrenal gland


  produces adrenaline which is involved in fight or flight responses
• ovaries


  produces oestrogen in females which is vital in the menstrual cycle
• testes


  produce testosterone in males which controls puberty and sperm production
• glucagon


  when blood glucose levels are too low, the body releases glucagon, which turns glycogen in the liver back to glucose and is released into blood
• negative feedback cycle

  • pancreas detects blood glucose levels
  • glucagon is released, or insulin is released
  • insulin helps glucose move into liver and muscle cells and converts it to glycogen
• type 1 diabetes


  Pancreas produces little insulin, causing high blood sugar levels.
• type 2 diabetes


  Pancreas produces insulin, but body cells are resistant, causing high blood sugar levels
• menstrual cycle

  • DAY 1 - uterus lining breaks down
  • DAY 4 - lining of uterus builds back up to prepare for a fertilized egg
  • DAY 14 - ovulation, an egg is released from the ovary and travels down the oviduct into the uterus
  • DAY 28 - wall is maintained in 14 days, if there is no fertilized egg the menstrual cycle begins again
• progesterone 


  produced in the ovaries, maintains uterus lining
• meiosis


  creates gametes with half the genetic information, so when they fuse together, they have a full set of chromosomes
• meiosis


  produces 4 gametes, involves 2 cell divisions, creates haploid cells, cells are genetically different to each other, used to create gametes in sexual reproduction
• alleles


  different versions of the same gene
• cystic fibrosis


  caused by recessive alleles, caused by damaged cell membranes which create thick mucus build up
• polydactyly 


  extra fingers/toes, caused by a dominant allele
• advantages of embryonic screening

  • saves money as disease treatments can be expensive
  • avoids suffering
• disadvantages of embryonic screening

  • expensive
  • can create designer babies
  • implies people with disorders are undesirable
• variation

  • caused by mutation
  • caused by environmental factors
• fossil formation

  1. Parts of organisms that wont decay easily, such as bones, get replaced by minerals, forming rocks with the same original shape
• why is the fossil record incomplete?

  because early forms of life were soft bodied so have been destroyed by geological activity
• how to prevent antibiotic resistant bacteria

  • only prescribe bacteria for serious bacterial infections
  • complete full course of antibiotics
  • use less antibiotics in farming
• advantages of genetic engineering

  • produce bigger fruit
  • food with higher nutritional value
  • disease resistant
  • herbicide resistant
  • frost resistant
• what is genetic engineering

  Process of changing an organisms DNA so it has a desired trait, by cutting out a desired gene and inserting it into a vector
• how can genetic engineering be used to help diabetes?

  bacterial cells can be modified to produce human insulin which can be extracted and can help people with diabetes.
• how does genetic engineering work

  1. gene that has desired trait extracted from DNA using enzymes
  2. gene is inserted into a vector
  3. vector is used to insert the gene into the required cells