Variations, Heredity & Cell division

• Voluntary actions


  Involve conscious thought (thinking time)
• Reflex actions


  Do not involve conscious thought (thinking time) and happen very quickly to avoid unnecessary damage to the body
• Synapse


  The site of communication between 2 neurons or between neuron and effector cells (muscles or glands)
• Synaptic end bulbs


  The tips of some axon terminals that swell into bulb shaped structures
• Synaptic vesicles


  Tiny membrane-enclosed sacs that store a chemical called neurotransmitter
• Presynaptic neuron


  Neuron sending the signal

  
• Postsynaptic neuron


  Neuron receiving the message

  
• Adaptation


  A feature of an organism that improves its chances of survival
• The Arctic region is characterized by a harsh climate with extreme variation in light and temperature, short summers, extensive snow and ice cover in winter and large areas of permafrost
• Deserts are the driest place on earth, They get fewer than 25cm of rainfall annually. Temperature extremes are a characteristic of most deserts. In some deserts there is a severe excess of evaporation, in desert climates are dry and hold little moisture, quickly evaporating the already little rainfall they receive
• Heredity


  How living organisms pass their particular features and traits on to their offspring
• Genetics


  The study of how living organisms pass their particular features and traits on to their offspring
• A cell containing 20 chromosomes (diploid) at the beginning of meiosis would, at its completion, produce cells containing 10 chromosomes (haploid)
• Crossing over


  Occurs in prophase I of meiosis
• Independent assortment


  Occurs in metaphase I of meiosis
• Elements are arranged in the periodic table according to their increase in atomic number
• Elements are categorized as

  • Metals
  • Non-metals