p2 biology

• 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
• 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
• 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
• Meiosis


  Process that produces gametes (sex cells) with half the normal chromosome number
• 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 an organism's characteristics
• DNA


  A two-stranded polymer in a double helix shape
• Gene


  A section of DNA that codes for a specific protein
• Genotype


  The code stored in your DNA specifically
• Phenotype


  How the genotype is expressed in your characteristics and physiology
• Allele


  Different versions of the same gene
• Dominant allele


  Results in a characteristic being expressed even if there is another recessive allele present
• Recessive allele


  Only expressed when there is no dominant allele present
• Homozygous


  Having only one type of allele
• Heterozygous


  Having two different types of alleles
• Predicting phenotype using a Punnett square

  1. Combine parental genotypes

  2. Determine possible offspring genotypes

  3. Determine possible offspring phenotypes
• Some alleles can result in disorders being inherited, like polydactyly or cystic fibrosis
• Chromosomes


  Contain human DNA, 23 pairs
• Sex chromosomes


  XX is female, XY is male
• The expression of sex genes affects every cell in the body
• Variation is a result of genes inherited from parents and environmental factors
• Darwin's theory of evolution

  Random variation in offspring results in some being better suited to their environment, more likely to survive and reproduce
• Lamarck's theory asserted that adaptation of variation is guided by DNA in response to a changing environment
• Bacterial resistance is evidence of Darwinian evolution
• Species


  Organisms that can produce fertile offspring