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 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
• 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, and release of adrenaline
• MRI scans


  Magnetic resonance imaging to see brain activity safely
• 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


  • Can change size depending on light intensity
• Cornea


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


  • Consists of rods and cones that respond to light
• Thermoregulation


  1. Brain senses blood temperature

  2. Sends nervous and hormonal signals to effectors

  3. Effectors cause body to lose or retain heat
• Vasodilation


  Blood vessels dilate to increase blood flow to skin and heat loss
• Vasoconstriction


  Blood vessels constrict to decrease blood flow to skin and 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 convert glycogen back into glucose
• Type 1 diabetes


  Pancreas can't produce enough insulin, requires insulin injections
• Type 2 diabetes


  Cells no longer absorb glucose properly, requires dietary control and weight management
• Water and nitrogen balance

  1. Body loses water through exhaling, sweating, and urinating

  2. Kidneys remove excess water and mix it with urea to form urine

  3. Antidiuretic hormone regulates water reabsorption by 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 where eggs are fertilized in a lab and embryos inserted into the uterus
• Adrenaline


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


  Hormone secreted by the thyroid that controls metabolic rate
• Gibberellins


  Plant hormones that cause seed germination, promote flowering, and increase fruit size
• Ethylene


  Plant hormone that induces fruit ripening
• Auxins


  Plant hormones that control shoot and root growth, causing 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


  The genetic code stored in DNA
• Phenotype


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


  Monomers that make up the DNA polymer
• 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 reproduce both sexually and asexually