Transcript Lesson 7 Homing and migration

Animal and plant responses
Homing and Migration
(CB pg 216 – 222)
HOMING
Ability of an organism to return to the home
site after it has been away sometimes over
considerable distances.
e.g. social insects
bees  hive
ants  nest
termites  mound
rabbits  burrow
Cataglyphis ants live in the desert and go out to look for food during the hottest
part of the day (It gets up to 50oC). They search (Route A) for food and when
they find it they will track their way directly back to the nest (Route B).
• D
Food
Route B
The dots on route A and
B indicate where the
ant stops and spins
around slowly.
The dots on
route A and B
indicate
where the ant
stops and
spins around
slowly.
Route A
Nest
Contrast the method used by Cataglyphis for finding its food to that of
returning to it’s nest. Give the benefits of both behaviours.
HAVE A GO AT ANSWERING THIS ON YOUR OWN
Achievement: Describes the random searching movement
in route A and the direct route of return route B
Merit: Achieved plus explains the movements.
A – to cover terrain in search of food is random to cover
more ground and discover sources of food
B – is direct home after food is found to save time and
energy in the direct heat/sun and get food back to nest.
Excellence: Merit and discusses orientation movement.
Ants use the sun as positioning/orientation on route A to
find food and this allows more direct route to home with
fewer turns to orientate on return route B vs on outward trip
A
MIGRATION
• Regular, annual or seasonal mass
movements made by animals from their
breeding area to another area
TASK: Complete a t-chart that shows the
advantages and disadvantages of migration
Advantages
•Animals remain in favourable
temperature (reduces energy
expenditure of having to stay
warm)
•Grow larger (salmon that don’t
migrate grow to 20cm, those that
do grow to 100cm)
•Leave more offspring (in salmon
up to 125 x more)
•Have constant food supply
•May lead to colonisation of new
area
•Reduces predation/parasitism/
disease
•Greater genetic mixing
•Better breeding conditions
Disadvantages
•May get lost or caught in storm
•May get eaten by a predator
•May use up too much energy in
the migration, leading to
exhaustion
•They may starve
•Huge investment in energy
Triggers to migration
• Maturation as sex organs mature
• Environmental cues e.g. drop in
temperature, shortening of day length 
Triggers zugunruhe (migratory
restlessness in birds)
• Genetic drive (built in/innate)
• Endogenous circannual rhythm
METHODS OF HOMING AND
MIGRATION
• Piloting – moving from one familiar landmark to
another (visual clues). Short distances only
• Compass orientation – travelling in a straight line
using magnetic field lines, chemical clues and
sound
• True Navigation – requires a map sense
(latitude and longitude) and a sense of timing
(internal clock)
Both of these are needed for solar (sun) and
stellar (star) navigation.
METHODS USED FOR
MIGRATION OR HOMING
1.
2.
3.
4.
5.
6.
Visual clues
Solar navigation
Magnetic fields
Star (stellar) navigatipn
Chemical navigation
Sound used as sonar
Visual clues
• Birds – learn shape of coastline
• Other animals – learn where streams and
food trees lie
Digger wasp
Explain how the wasp finds its way when returning to its
burrow from a hunting expedition
The following figure shows the results of an experiment carried out to
study homing behaviour in a hunting wasp. The wasp digs a burrow
and then flies off to capture a caterpillar, which it will leave in the
burrow as food for its young (2006).
1. Pine cones placed round burrow while wasp inside: wasp leaves
and returns to nest
2. Pine cones moved while wasp away on hunting trip
Gray whales
Solar navigation
• Sun moves from east to west during the
day so can be used to tell direction if you
have a clock
• Birds and honeybees use the sun as a
compass which suggests they have an
inbuilt clock
Large migratory birds
• Birds that fly during the
daytime are thought to
use the sun as a
compass
• They compensate for
changing direction of
the sun.
• In autumn in NH bird
flies S at an angle of 45
to the left of the sun at
9am and 45 to the right
of the sun at 3pm
Honey bees
Round dance – used when nectar is within
50m of the hive.
Waggle dance – indicates distance and
direction
• Slow and few waggles on the straight – flowers
far away
• Fast and rapid waggles – closer
• Direction is then determined from the direction of
the straight to the sun
Honey bees
Stars as a compass
• Birds use star patterns for migration
• Important factor is the South Celestial Pole
in the Southern Hemisphere – it doesn’t
move
South
Magnetic field as a compass
• Many animals can detect the earth’s magnetic
field (birds, bees, mice, some fish)
• Often used to supplement other compasses
• Can be used to determine latitude as the
magnetic field is horizontal at the equator and
vertical at the poles
• Different areas have different field strengths,
animals may build up a map of strengths in
areas
Magnetic fields
• Thought to be used by homing pigeons
• Involves following of magnetic field lines of the
earth i.e. have magnetic compass
• If a magnet deflecting the normal magnetic field
is attached to the head of a homing pigeon, the
bird can be made to fly off course. On clear
days, however, the birds use the sun and visual
landmarks and still manage to get home
• Whales, dolphins and bacteria are all known to
have magnetic compasses