Biology Paper 2

• Homeostasis


  An organism's ability to regulate internal conditions even when external conditions change
• Importance of homeostasis


  • Allows crucial chemical reactions involving enzymes to happen at an Optimum rate
  • Regulates blood glucose concentration, temperature, and water levels
• Nervous system regulation of homeostasis

  1. Receptor detects stimulus

  2. Electrical signal travels to spine through sensory and relay neurons

  3. Signal travels across synapse by neurotransmitter

  4. Signal goes to brain

  5. Conscious decision to act

  6. Signal goes back to effector via relay and motor neurons
• Reflex


  Signal bypasses the brain and goes straight through the spine to the effector
• Effectors


  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
• Parts of the brain

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


  Magnetic resonance imaging - way of seeing brain activity safely
• Accommodation in the eye

  1. For far objects: Ciliary muscles relax, suspensory ligaments tighten, lens becomes thin

  2. For near objects: Ciliary muscles contract, suspensory ligaments slacken, lens becomes fatter
• Pupil


  Hole in the iris that can change size depending on light intensity
• Cornea


  Transparent outer layer of the eye where light enters, has a slight lensing effect
• Retina


  At the back of the eye, consists of rods and cones that respond to light
• 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 to effectors via the blood
• 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 no longer absorb glucose properly
• Antidiuretic hormone (ADH)


  Produced in pituitary gland, causes kidneys to reabsorb more water
• Dialysis


  Process that does the job of non-functioning kidneys
• 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
  • Tubal ligation
• IVF


  In vitro fertilization - eggs harvested and 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 - cause seed germination and promote flowering/fruit growth
  • Auxins - control shoot and root growth, cause phototropism and geotropism
  • Ethylene - induces fruit ripening
• Investigating geotropism


  1. Put seeds on damp cotton wool in Petri dish

  2. Stand dish on side

  3. Leave for a few days

  4. Turn 90 degrees and observe root growth
• Meiosis


  Process that produces gametes (sex cells) 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


  The genetic code stored in DNA
• Phenotype


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


  Can reproduce on its own without a parent
• DNA


  A two-stranded polymer in a double helix shape
• 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