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 via relay and motor neurons
• Reflex arc


  Signal bypasses the brain and goes straight through the spine to the effector, faster than conscious decision
• Glands can also be effectors which 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
• Brain regions


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


  Safely see brain activity
• 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 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

  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, requires insulin injections
• Type 2 diabetes


  Cells don't absorb glucose properly, requires diet and weight control
• Kidneys regulate water and nitrogen balance
• Kidney regulation of water balance

  1. Kidneys remove excess water from blood

  2. Antidiuretic hormone (ADH) causes kidneys to reabsorb more water

  3. Negative feedback to return water level to normal
• Dialysis is required if kidneys aren't working properly
• Menstrual cycle


  1. FSH causes egg maturation and estrogen production

  2. LH causes egg release

  3. Progesterone maintains uterus lining
• Contraception methods


  • Pills inhibiting FSH
  • Progesterone injections
  • Implants
  • Condoms
  • Diaphragms
  • IUDs
  • Tubal ligation
• IVF


  In vitro fertilization, eggs fertilized in lab then implanted
• Adrenaline


  Hormone that increases heart and breathing rate in stress
• Thyroxin


  Hormone secreted by thyroid that controls metabolic rate
• Plant hormones


  • Gibberellins - seed germination, flowering, fruit size
  • Ethylene - fruit ripening
  • Auxins - shoot and root growth
• Meiosis


  Chromosomes copied and paired, genes swapped, cell divides twice to form haploid gametes
• Asexual reproduction


  Daughter cells genetically identical to parent
• Genome


  All the genetic material in an organism
• Gene


  Section of DNA that codes for a specific protein
• Human Genome Project


  Mapped what each gene codes for
• Genotype


  Genetic code stored in DNA
• Phenotype


  How the genetic code is expressed in characteristics
• Nucleotides are the monomers between the DNA strands
• Asexual reproduction


  Only one parent is needed
• Parasite that causes malaria

  Can do both sexual and asexual reproduction
• 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