Transcript Slide 1 - hagley13bio

Biological Orientation Responses
Tropisms (plants only) – growth towards or away from a stimulus
coming from one direction.
towards = positive, away = negative
towards light  positive phototropism, away  negative
phototropism
Taxes (animals and a few mobile plants) – movement of the whole
organism towards or away from a stimulus coming from one direction.
May be positive or negative.
towards light – positive phototaxis, away – negative phototaxis
Kinesis (animals only) – non-directional response to a stimulus or a
change in activity rate in response to a change in the intensity of the
stimulus.
•Tropotaxis – 2 or more receptors which can simultaneously
judge the intensity of the stimulus, the animal can find a
balance between them. This allows the animal to move directly
towards or away from the stimulus
•Klinotaxis – animal has only one receptor and needs to keep
turning its head from side to side. In response to an increase
in the stimulus intensity the animal increases its rate of head
turning. Although he animal has no directional receptors, it
can perform a directional response.
•Orthokinesis – a relationship between the speed of the
reaction and the intensity of the stimulus.
•Klinokinesis – the rate of the turning and change of direction
alter in relation to the intensity of the stimulus.
Nastic movements (plants) – this is a response to a stimulus
which is independent of the direction of the stimulus, e.g. the
opening and closing of flowers in response to changes in light
intensity.
Homing (animals) – ability to find and return to home site.
Migration (animals) - annual mass movement of animals, from
breeding areas to other non-breeding areas and then
returning.
Homing
•Animals have to leave the home site to find food
and mates but have to return again.
•Homing is the ability of an individual to return to
the home site after being displaced.
•Home site could be a hive, nest, mound, burrow.
•Navigation is involved but generally homing relies
on recognition of familiar landmarks
Migration
•Regular, annual, or seasonal mass movements from a
breeding ground to an area where they do not breed.
•Second site has food, water and optimal weather
conditions.
•Migration is a response to environmental change, a
genetic drive that is innate, or the animal has matured
and has the need to reproduce
•True migration initiated by an internal clock or
timekeeper in response to environmental cues
e.g. change in temperature,
decrease in day length triggering zugunruhe
(migratory restlessness)
Migration
Advantages – remain in favourable conditions, grow
larger, leave more young, constant food supply, reduces
predation/parasitism/disease, greater genetic mixing,
better breeding conditions, may lead to colonisation of
new areas
Disadvantages – may get eaten by predators, caught in
storms, starve, use up too much energy during the
migration, huge energy investment
•Migration would not occur unless it had some
reproductive or survival advantage.
•Migratory behaviour is inherited and maintained by
natural selection.
Types of Migration
Dispersal – one way migration
One way movement. Animal does not return to its
original home range. Used to escape deteriorating
habitats and to colonise new ones.
e.g. muskrat, locusts,
Breeding site
Breeding site
Breeding site
Breeding site
Original home range
Breeding site
Return Migration
•Animals move to a winter feeding ground
•The same animals return to their home range in the spring which is
where they have their breeding sites.
• Return journey may not be the same path taken to the
overwintering site.
•E.g. caribou, cuckoo, shearwater, turtles, whales
Breeding site
Dry season or winter site
Nomadic migration
•One way movement away from the original home site.
•Similar to dispersal but individuals may breed at several locations
during their lifetimes.
•No set pattern to the movement (directionless)
•Each stopover is a potential breeding site
•May also include temporary non-breeding stopovers for a dry or
winter season
e.g. humans : Bedouin, Inuit
Breeding site
Non –breeding site
Breeding site
Remigration circuits
•The return leg of a migration may have stopovers and may be
completed by one or more subsequent generations.
•Winter and dry season areas as well as stops at feeding areas by
juveniles and adults
•May include closed circuits where animals die after breeding
•E.g. salmon, monarch butterfly, eel
Feeding stopover
Second generation
Dry season/winter site
First generation
ORIENTATION FOR HOMING AND MIGRATION
Three types of orientation:
• piloting
• compass orientation
• true navigation
Piloting
• Movement from a familiar landmark to another until an animal
• reaches its destination.
• Used over short distances using visual cues.
Compass orientation
• Animal can detect a compass direction and travel in a straight line
• path until it reaches its destination.
• Accomplished using magnetic field lines, chemical cues, sound
True navigation
• Determining one’s position relative to other locations.
• Requires a map sense and a sense of timing
True Navigation
•The ability to orient towards a target area without
the use of landmarks and regardless of its direction
•Map sense – ability to be aware of the latitude and
longitude of an area.
•Sense of timing – an internal clock that can
compensate for the movement of the sun or stars.
•Both are required for solar and stellar navigation.
Methods used for Navigation
Visual cues – animal learns its surroundings. Memorise
the shape of coastlines, other topography of the area
e.g. trees, streams, hills
e.g. digger wasps
Solar Navigation
•Requires a precise internal clock
•Use of the sun to navigate home/migrate. Sun always
moves East to west.
•Some animals can detect polarised (due to differential
absorption, some of the light becomes polarized plane of
polarization tells position of sun)
•Enables them to detect where the sun is even with the
smallest patch of blue sky.
e.g. honeybees – keep the sun on one ommatidium of their
compound eye during the outward journey and on a corresponding
opposite ommatidium on the return journey.
Bee indicates where a food source is to the hive, by doing one of
two dances.
Round dance – points directly to a food source within 50m
Waggle dance – bee traces a figure 8. The axis of the
waggle (in regards to the vertical nature of the comb in
the hive) indicates the direction of the food in relation
to the direction of the sun.
The number of waggles indicates the distance.
Fewer, slower waggles the further away the food is.
Birds – fly mainly during the day
•Compensate for the changing direction of the sun
related to time of day.
e.g. northern hemisphere bird flying south in
autumn
9am flies 45º left of the sun
3pm flies 45º right of the sun
•Retard internal clock with artificial light-dark cycles
and the bird will fly in direction based on perceived
time. Reset internal clock.
e.g. retard by 6 hours; bird released at 3pm
sees sun at 9am and will fly west.
 Star Compass 
•Star compass orientation similar to sun compass.
•Groups and geometric patterns of stars are
important.
•Generally based on the brightest (northern stars)
stars as they move the least during the night.
•Rotational axis of star field (around North and South
celestial poles) is important
•Requires precise internal clock
Magnetic Fields
•Animal has a magnetic compass
•Able to follow the magnetic field lines of the earth
•Direction and position derived from direction and
inclination of field components
•Some animals have small amounts of magnetite in their
brains these respond to magnetic fields and information
is transferred to nerve endings and processed by brain
•Used by pigeons, whales, dolphins, turtles, salamanders,
some bacteria, some bees
•Magnetic storms, over magnetic anomalies and
orientation in room with manipulated magnetic field
animals navigation disrupted
Homing Pigeon’s Orientation
•Pigeons can navigate hundreds of km to a goal, even
with no visual cues to the path home.
•Appears that they have multiple cues
How do we know that?
When birds have clocks shifted by 6 hours (using
artificial lighting), direction is off by 90 deg.
When sky is overcast (sun not visible), clockshifted birds head off in correct direction. Appear
to be using another mechanism independent of sun
and time of day.
When birds are wearing magnets, they are
confused on overcast days, but not on sunny days.
Chemical Navigation
Animals recognise and memorise chemical trails/markers to aid
navigation
e.g. dogs, ants, salmon, eels
Ambient Pressure
Sensitivity to atmospheric changes – altimeter
e.g. pigeons
Sound
Infrasound-frequency less than 10Hz. Travels long
distances
Humans can not hear this low.
Elephants communicate up to 8km using infrasound.
Pigeons may use sound of surf on beaches to aid
navigation
Humpback whales – use sonar, ultrasound,
infrasound
Bats – use sonar, ultrasound
Many animals use more than one
method of navigation.
Many of the mechanisms used for
homing and migration are not yet
fully understood.