Ch. 6 - Orientation responses in animals

Overview:

Orientation responses divided into either simple responses or complex responses. Both types are innate responses

^^Simple responses:^^ Taxes (sing. taxis) and kineses (sing. kinesis)

  • Occur to abiotic factors ie. light, humidity, chemicals, heat.
  • Helps remove the animal from unfavourable conditions into favourable conditions

^^Complex responses:^^ Homing and migration

  • May occur over long distances + time frame to a predetermined location
  • Navigation influenced by external abiotic factors
  • Homing and migration arise from internal factors
  • Not in direct response to either favourable or unfavourable conditions

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Prefixes

photo- light

thermo- temperature

geo/gravi- gravity

chemo- chemical

thigmo- touch

hydro- water

rheo- current

tropho - food

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Taxes

  • Definition: Innate movement response ^^towards or away^^ from a ^^directional^^ stimulus   * ^^Towards^^ stimulus: ^^positive^^ taxis   * ^^Away^^ from stimulus: ^^negative^^ taxis
  • Examples of describing taxis responses:   * Movement towards light: positive phototaxis   * Movement away from light: negative phototaxis
  • Adaptive advantage of taxis responses:

  Allows the animal to take a direct route ^^away from unfavourable conditions^^, and ^^towards more favourable conditions^^

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Kineses

  • Definition: Innate movement response to an external ^^non-directional stimulus^^   * Direction of movement is random + no relation to direction of stimulus
  • Orthokinesis   * Definition:

    The ^^speed^^ of an animal in response to a stimulus is ^^proportional to the intensity of the stimulus^^ causing the movement - unfavourable conditions = faster, favourable conditions = slower

  • Klinokinesis   * Definition:

    The ^^rate of turning^^ of an animal in response to a stimulus is proportional to the intensity of the stimulus.

    Unfavourable conditions = faster rate of turning

  • Adaptive advantage of orthokinesis and klinokinesis:

  Fast speed + rapid turning = cover more ground at higher rate => higher chance of finding favourable environments

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Homing

  • Definition: An animal’s ability to ^^return home over unfamiliar territory^^
  • Activity rhythm: Can be daily, annually, or biennially
  • Examples:   * Honeybees ^^return to their hive after foraging^^

    Daily/circadian rhythm

    Foraging may take them as far as 10km from the hive   * Salmon will return to the river that they were born to breed

    They grow up + spend their adult lives at sea, and ^^only return during breeding season^^   * Adult Southern royal albatross or toroa (Diomedea epomophora) will return to the established breeding and nesting colony at the tip of the Otago Peninsula ^^bienially^^ (taking place every two years), to lay an egg, incubate it, to then have it hatch (September-November-February). They will also fly to find food ^^daily^^, and ^^regularly return^^ to check on their chicks.

  All three examples above exhibit the ability to return home after finding food (often daily), or to breed (often annually or biennially)

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Migration

  • Definition: ^^Mass movement^^ of individuals from ^^one geographical location to another^^ over a ^^long period of time^^
  • Cyclical/Return migration:   * Definition: Animals will exhibit an ^^annual cycle of migration^^ from breeding grounds to feeding grounds (overwintering grounds).   * For some, cyclical migration will occur at different stages in their life instead of annually
  • One way migration:   * Definition: Migration that involves ^^leaving the home range^^ for a new location and ^^never returning^^ to the original home range   * Eg. Migrants die at the end of migration
  • Migration preparation: Controlled by their biological clock   * ^^Building up^^ their ^^fat reserves^^ to ensure an energy supply for the journey   * Moulting feathers + replacing them with new ones => ensure maximum flight efficiency

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  • Animals need to use navigation methods to find their way home (homing) or to travel to overwintering or breeding grounds (migration) over unfamiliar territory
  • ^^Navigation is^^ ^^innate,^^ but skill can be ^^improved through experience^^
  • Often animals will need to use a ^^combination of navigation methods^^ to ^^increase the success of migration^^   * Eg. An animal that usually uses solar navigation may need to use magnetic or topographical navigation on cloudy days.
  • Topographical memory   * Navigation system using visual cues like landmarks.   * More common in homing responses with familiar landmarks   * Migrating animals may use coasts, islands, mountain ranges or rivers etc
  • Solar navigation - Sun compass   * Navigation system using the sun as a compass as it moves across the sky from east to west during the day   * By maintaining a set angle with the sun, the animal is able to move in a straight line   * The animal’s biological clock compensates for the sun’s movement and allows it to change its position relative to the sun accordingly   * Bees and migratory animals use a Sun compass
  • Stellar navigation - Star compass   * Where animals can navigate by orientating to star patterns ie. constellations.   * Animals in the northern hemisphere can locate the north by using the Pole Star   * Animals in the southern hemisphere can locate the south by using the South Celestial pole (NOTE: This is not an actual star)   * All migratory birds use a star compass
  • Magnetic fields - Magnetic compass   * Animals use the Earth’s magnetic field lines to navigate   * Some birds such as pigeons have a spot of magnetite in their beaks to detect changes in the magnetic field
  • Chemical navigation - Scent trails   * Animals can use scent trails to find their way to a specific location
  • Sound navigation - Sonar   * Animals such as bats and dolphins can use echolocation to home   * How: Sound waves are emitted that echo (bounce back) from objects and then they use the speed of the bounce back to position themselves in relation to the object

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