Biology Paper 2

• Homeostasis


  An organism's ability to regulate internal conditions even when external conditions change
• Nervous system


  • Consists of the CNS (central nervous system - brain and spinal cord) and the PNS (peripheral nervous system - nerves that go through the rest of the body)
  • Receptors detect changes due to stimuli
  • Electrical signals travel through sensory and relay neurons
  • Signals travel across synapses by neurotransmitters
  • Signals can go to the brain for conscious decision or directly to effectors for a reflex arc
• Reflex arc


  1. Stimulus detected by receptor

  2. Electrical signal travels to spine

  3. Signal bypasses brain and goes straight to effector
• Effectors


  Muscles or glands that produce specific chemicals the body needs
• Investigating reaction time


  1. Hold ruler between finger and thumb

  2. Drop ruler without warning

  3. Measure distance fallen before caught

  4. Repeat multiple times and take mean average
• Brain regions


  • Cerebral cortex - higher level functions like memory, speech, problem solving
  • Cerebellum - motor skills, movement, balance, coordination
  • Medulla oblongata - controls unconscious actions like heart rate and breathing
• MRI scans


  Magnetic resonance imaging - way of seeing brain activity safely
• Eye


  • Accommodation - ability to change lens shape to focus light from different distances
  • Pupil - hole in iris that changes size depending on light intensity
  • Cornea - transparent outer layer that refracts light
  • Retina - contains rod and cone cells that detect light and colour
• Myopia


  Shortsightedness - can't focus on far objects
• Hyperopia


  Longsightedness - can't focus on near objects
• Thermoregulation


  1. Brain senses blood temperature

  2. Sends nervous and hormonal signals to effectors

  3. Effectors cause body to lose or retain heat
• Endocrine system


  System of glands that produce hormones that travel in the blood to target organs
• Pituitary gland


  Main or 'master' gland that produces hormones in response to stimuli
• Pancreas


  Produces insulin to regulate blood glucose levels
• Type 1 diabetes


  Pancreas can't produce enough insulin
• Type 2 diabetes


  Cells don't absorb glucose properly
• Water and nitrogen balance

  1. Kidneys filter blood and reabsorb useful substances

  2. ADH from pituitary gland controls water reabsorption

  3. Urea produced from excess proteins is excreted in urine
• Dialysis


  Blood is filtered by a machine when kidneys don't work properly
• Menstrual cycle


  1. FSH causes egg maturation and estrogen production

  2. LH causes egg release

  3. Progesterone maintains uterus lining
• Contraception methods


  • Pills that inhibit FSH
  • Progesterone injections
  • Implants
  • Condoms
  • Diaphragms
  • IUDs
  • Sterilization
• IVF


  In vitro fertilization - eggs and sperm fertilized in lab then implanted
• Adrenaline


  Hormone that increases heart and breathing rate in stressful situations
• Thyroxin


  Hormone secreted by thyroid that controls metabolic rate
• Plant hormones


  Gibberellins - promote seed germination and flowering

  Ethylene - induces fruit ripening

  Auxins - control shoot and root growth, cause phototropism and geotropism
• Meiosis


  Process of cell division that produces gametes with half the normal number of chromosomes
• Mitosis


  Process of cell division that produces genetically identical daughter cells
• Genome


  All the genetic material in an organism
• Gene


  Section of DNA that codes for a specific protein
• Genotype


  Genetic code stored in DNA
• Phenotype


  How the genetic code is expressed in an organism's characteristics
• Nucleotides


  Monomers that make up DNA, consisting of a sugar, phosphate, and nitrogenous base
• Asexual reproduction


  Only one parent is needed, e.g. a plant on its own can still reproduce to survive
• Some parasites and fungi can reproduce both sexually and asexually
• Genome


  The term given to all the genetic material in an organism
• DNA


  A two-stranded polymer in a double helix shape that stores the genetic code
• Gene


  A section of DNA that codes for a specific protein
• The Human Genome Project completed its initial goal in 2003 when scientists mapped out what every gene is responsible for coding
• Genotype


  The code stored in your DNA specifically
• Phenotype


  How the genotype is expressed in your characteristics and physiology
• Nucleotides


  The monomers between the two strands of DNA, made from a sugar and phosphate group