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 a conscious decision
• 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

  4. Introduce independent variable like stimulant or depressant
• 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, releases adrenaline
• MRI scans


  Safely see brain activity
• Accommodation


  1. Ciliary muscles relax and suspensory ligaments tighten to focus on distant objects

  2. Ciliary muscles contract and suspensory ligaments slacken to focus on near objects
• Pupil


  • Changes size depending on light intensity
• Cornea


  • Transparent outer layer where light enters, has slight lensing effect
• Retina


  • Contains rods and cones that respond to light
• Thermoregulation


  1. Brain senses blood temperature, sends signals to effectors to lose or retain heat

  2. Sweat glands cause evaporation to cool body

  3. Blood vessels dilate or constrict to increase or decrease heat loss

  4. Shivering causes muscles to produce heat
• Endocrine system


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


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


  Produces insulin to regulate blood glucose levels
• Glucagon


  Hormone produced by pancreas that causes liver and muscles to convert glycogen to glucose
• Type 1 diabetes


  Pancreas can't produce enough insulin
• Type 2 diabetes


  Cells don't 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 to form urine

  3. Antidiuretic hormone regulates water reabsorption in kidneys
• Dialysis


  Process that artificially filters blood 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 that prevent fertilization or implantation
• IVF


  In vitro fertilization, eggs and sperm fertilized outside body 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, ethylene, auxins control growth and development
• Meiosis


  Process that produces gametes with half the normal number of chromosomes
• Asexual reproduction


  Produces genetically identical offspring
• Genome


  All the genetic material in an organism
• Gene


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


  Mapped out what every gene is responsible for coding
• Genotype


  Genetic code stored in DNA
• Phenotype


  How the genetic code is expressed in characteristics
• Nucleotides


  Monomers that make up DNA
• Asexual reproduction


  Only one parent is needed, e.g. a plant on its own can still reproduce to ensure species survival
• Parasite that causes malaria

  Can do both sexual and asexual reproduction
• Genome


  The term given to all the genetic material in an organism