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 for conscious decision

  5. Signal goes back to effector (muscle) 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, drop without warning

  2. Measure distance fallen before caught

  3. Repeat multiple times, take mean average
• Parts of the brain

  • Cerebral cortex - higher level functions
  • Cerebellum - motor skills, movement, balance, coordination
  • Medulla oblongata - controls unconscious actions
• MRI scans


  Safely see activity in the brain
• 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 where light enters the eye, has a slight lensing effect
• Retina


  Contains rods (detect light intensity) and cones (detect color)
• Thermoregulation


  1. Brain senses blood temperature

  2. Sends nervous and hormonal signals to effectors (sweat glands, blood vessels)

  3. To increase or decrease heat loss
• 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
• Insulin


  Hormone produced by the pancreas that causes glucose to move from blood into cells
• Glucagon


  Hormone produced by the pancreas that causes the liver and muscles to turn glycogen back into glucose
• Type 1 diabetes


  Pancreas can't produce enough insulin
• Type 2 diabetes


  Cells no longer absorb glucose properly
• Water and nitrogen balance

  1. Body loses water through exhaling, sweating, urinating

  2. Kidneys remove excess water from blood and mix with urea

  3. Antidiuretic hormone (ADH) regulates water reabsorption in kidneys
• 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
• IVF


  In vitro fertilization - eggs harvested and fertilized, embryos inserted into uterus
• Adrenaline


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


  Hormone secreted by the thyroid that controls metabolic rate
• Plant hormones


  • Gibberellins - seed germination, flowering, fruit size
  • Ethene - fruit ripening
  • Auxins - control shoot and root growth
• Investigating plant tropisms


  Put seeds on damp cotton wool, stand dish on side, turn 90 degrees - 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


  Genetic code stored in DNA
• Phenotype


  How the genetic code is expressed in characteristics
• Nucleotides are the monomers between the two DNA strands, made of a sugar, phosphate, and one of four nitrogenous bases
• 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
• Phenotype


  How the genotype is expressed in your characteristics and physiology