Download bio notes 13

Evidence for Internal Clocks
Rhythms continue in a constant environment.
E.g. Oxalis shows daily ‘sleep’ movements of their leaflets.
When kept in constant light, the rhythms continue.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
When a rhythm continues in constant environmental conditions, it is said
to be free-running, as it is unaffected by external cues.
Gradually these rhythms when isolated (from the zeitgeber) shift out of
synchrony with the external environment.
Relocation Experiments
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Bees normally fed at the same time every day, will continue to do so even when shifted to a new place.
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The bees will continue to feed according to the time at their place of origin.
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If their feeding was determined by an external cue they would have adapted to local time.
Rhythms vs Circa-rhythms
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Rhythms may be daily, tidal, lunar, semi-lunar or annual and only occur under natural conditions.
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Rhythms may be circadian, circatidal, circalunar, circasemilunar, or circannual
Exogenous Rhythms
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Environment dependent
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The behaviour is cyclic because neural mechanisms are responding to cyclic variations in the
environmental cues
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If kept under constant conditions the rhythm should disappear.
Studying Rhythms
Actogram
Created by recording each revolution of a running wheel b rodents or perch hops by birds. – see worksheet
from last lesson.
Free-running vs. entrained rhythms
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Free-running rhythms are not synchronized with changes in the external environment.
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If the animal is exposed to some predictable environmental cue (a “time-giver”), then its activity
becaomes entrained by that cue.
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Entrainment requires a zeitgeber (“time-giver”), usually some rhythmic cue in the environment.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Adaptive significance: How do rhythms improve survival and reproduction?
Coordination of internal physiological systems
Coordination of internal physiology with external environment
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Examples
o Saving energy during times of inactivity
o Respond to temporal variation in food and predators
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Avoid environmental stressors (Lack of food, water, severe thermal conditions, wave action, etc.)
o Tidal rhythms, circadian rhythms, hibernation, migration
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Avoid predators
Endogenous Rhythms
Internally driven responses controlled by an internal ‘clock’ usually ‘reset’ by an environmental change.
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.
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Towards light – positive phototaxis, away – negative phototaxis
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
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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.
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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.
This simple diagram illustrates the basics of an undirected
search. The animal, traveling from left to right in the diagram,
moves in a more or less straight line through unsuitable habitat.
When it begins to perceive better conditions (the blue area) two
things can change--its rate of speed and the angle of its turns.
By turning sharper angles and slowing down, it stays in the
vicinity of the improved conditions. Simple changes in
movement pattern, in response to better environmental
conditions, amount to habitat selection. Conversely, if an
animal finds itself in poor conditions, rapid, straight line
movements will increase its likelihood of finding better
conditions.
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Orthokinesis – a relationship between the speed of the reaction and the intensity of the stimulus.
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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. Photonastic - the opening and closing of flowers in response to changes in light intensity.
Homing
The ability to find and return to home site.
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Animals have to leave the home site to find food and mates
but have to return again.
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Homing is the ability of an individual to return to the home
site after being displaced.
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Home site could be a hive, nest, mound, burrow.
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Navigation is involved but generally homing relies on recognition of familiar landmarks
Migration
The annual mass movement of animals, from breeding
areas to other non-breeding areas and then returning.
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Regular, annual, or seasonal mass movements from a
breeding ground to an area where they do not breed.
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Second site has food, water and optimal weather conditions.
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Migration is a response to environmental change, a
genetic drive that is innate, or the animal has matured
and has the need to reproduce
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True migration initiated by an internal clock or
timekeeper in response to environmental cues
o e.g. change in temperature, decrease in day
length triggering zugunruhe (migratory restlessness)
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
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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
site
Return Migration
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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
Dry season or winter
Breeding site
site
winter site
Nomadic migration
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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
site
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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, eelFeeding stopover
Second generation
Dry season/ winter site
generation
winter site
First generation
ORIENTATION FOR HOMING AND MIGRATION
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Three types of orientation:
o Piloting
o Compass orientation
o True navigation
Piloting
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Movement from a familiar landmark to another until an animal
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reaches its destination.
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Used over short distances using visual cues.
Compass orientation
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Animal can detect a compass direction and travel in a straight line
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path until it reaches its destination.
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Accomplished using magnetic field lines, chemical cues, sound
True navigation
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Determining one’s position relative to other locations.
Requires a map sense and a sense of timing
o The ability to orient towards a target area without the use of landmarks and regardless of its
direction
o Map sense – ability to be aware of the latitude and longitude of an area.
o Sense of timing – an internal clock that can compensate for the movement of the sun or stars.
o 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
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Requires a precise internal clock
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Use of the sun to navigate home/migrate. Sun always moves East to west.
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Some animals can detect polarised (due to differential absorption, some of the light becomes
polarized plane of polarization tells position of sun)
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Enables them to detect where the sun is even with the smallest patch of blue sky.
o 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.
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Round dance – points directly to a food source within 50m
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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.
o The number of waggles indicates the distance.
o 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 
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Star compass orientation similar to sun
compass.
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Groups and geometric patterns of stars are
important.
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Generally based on the brightest (northern stars)
stars as they move the least during the night.
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Rotational axis of star field (around North and South celestial poles) is important
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Requires precise internal clock
Magnetic Fields
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Animal has a magnetic compass
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Able to follow the magnetic field lines of the
earth
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Direction and position derived from direction
and inclination of field components
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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
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Used by pigeons, whales, dolphins, turtles, salamanders, some bacteria, some bees
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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?
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When birds have clocks shifted by 6 hours (using artificial lighting), direction is off by 90 deg.
When sky is overcast (sun not visible), clock- shifted birds head off in correct direction. Appear to be
using another mechanism independent of sun and time of day.
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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.
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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.
Animal Behaviour
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Animals Response to the biotic Environment
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Responses of animals to other animals can be intraspecific or interspecific
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They can be further classed as aggressive or co-operative behaviours
Intraspecific
Aggressive Behaviour and Responses
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Agonistic behaviour is aggressive behaviour towards another member of the same species involving
threats, submissions, chases and physical combat.
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Agonistic behaviour is a contest to determine who gains access to a resource.
o (Does not include predatory aggression for obtaining food)
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Conflicts between members of the same species are usually resolved with ritualistic behaviour. This
prevents serious injury to the combatants.
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Fighting to the death is non-adaptive to most animals. Only occurs when eliminating a stranger from
another group.
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The more scarce the resource the more intense the fighting.
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Belligerent behaviour by an animal that threatens to harm or kill another animal with which it is
competing.
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Combat is more likely to be physical if it is essential to the survival and reproductive success of the
competitors.
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Natural selection favours a quick end to combat to prevent the winner from becoming too injured, to be
able to take advantage of the resources won.
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Fighting between males for mates is common. Winner mates with female and passes on genes for
successful fighting. Selection may cause males to become larger than females (sexual dimorphism).
Territories
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A territory is an area defended against other members of the same species.
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It provides food, water supplies, nesting areas, and refuges from danger.
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Ownership of a territory is signalled by vocalisations, scent marking, visual displays.
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Boundary marking warns against accidental intrusion by others of its species.
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Another animal is only likely to attempt to dislodge the owner of the territory if it has a chance of being
successful.
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Territorial behaviour is reinforced by natural selection where the benefits to the species outweigh the
risks and the energy costs of defending the territory.
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Territories help to regulate the population to a size that can be supported by the available resources.
Lair or Nest
Territory
Home range
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Territorial behaviour varies widely. Most animals have a definite home. The area the animal covers
regularly in search of food and mates is the home range. This area is not defended.
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The part of the home range defended against others of the same species is the territory.
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Aggressive behaviour is used to hold on territories.
Adaptive Features of Territoriality
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Ensures enough space for each animal – if in short supply and needed for breeding, keeps population
down.
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By spreading out reduces the spread of disease and parasites. Also harder for predators to find them.
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Most successful males hold best territories and so ensure best genes are passed on to offspring.
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Once territories are established the resources have been divided. The losers will spread out and look for
food elsewhere rather than go on fighting.
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In some species males without territories do not attract mates and do not breed.
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Territories ensure enough food for the animals and their families.
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Territories ensure a safe, protected nest or home for the young or at least a place to breed in the case of
communal breeding grounds.
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Animal now has an area with which it can become familiar, can learn where food, water and protection
from predators is located.
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Territorial behaviour is set. Defenders and intruders know their roles.
Marking and Defending Territories
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Vocalisations
o e.g. birds singing on boundaries of their areas at dawn and dusk
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Scent
o e.g. marking with urine (dogs and cats) or faeces
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Scent glands – special glands produce chemo markers.
o e.g.: on rump, between horns (deer), wrists (lemur), behind ears (cats)
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Physical gesturing
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crabs wave claws at edge of territory
Hierarchies
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Many animals that live in social groups have a
dominance or social hierarchy
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It is established and maintained by agonistic
behaviour.
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Once established it is maintained by ritualised
displays unless a new animal enters the group or a low ranking individual challenges a higher ranking
animal. Cuts down competition and tension in the group.
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Body postures are common dominance signals
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Males and females may have separate dominance systems, in monogamous systems female usually
acquires mates status because he defends her from threats and attack.
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An established hierarchy reduces the number of competitive conflicts in which individuals may get
injured or killed as each animal knows its position.
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Selective advantage is that higher-ranking individuals leave more offspring than lower ranked
individuals , lower members have a higher chance of mating than if they were outcast.
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Gender, age and size or fighting ability are factors affecting dominance in a hierarchy.
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Position in a hierarchy is normally established early in life e.g. puppies play fighting to assert
dominance.
o Wolves – female dominated hierarchy. Alpha female dominates the behaviour of those below her.
Including which females are allowed to mate. Helps control the number to be fed when food is
scarce and ensures survival of her own pups.
o Pukeko – both males and females have hierarchies in their communal groups.
o Barn-yard hens – linear order of dominance based on pecking order. Top bird pecks all, bird below
pecks the bird below them, etc, etc. Lowest bird pecks no one.
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Strongest animal is Alpha all subordinate to them. Get best food and choice of mates.
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Dominance maintained by posture - make look bigger, standing on hind legs, fluffing up fur, holding tail
erect : threat displays- slaps, bites : vocalisations – snarls
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Subordinate responds with appeasement gestures which prevent the dominant animal from attacking.
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Subordinate displays are the opposite to dominance behaviours. Include lowering head and eyes, make
look smaller, cringing, tail between legs, exposing vulnerable parts
Win-Loss Tables
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Used to show hierarchies
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Each interaction recorded with the winner and loser shown.
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Wins shown in columns and losses in rows.
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Diagonal is theoretical, monkey paired against itself.
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e.g.:
Total
Intersection of column E with row I shows
that E won 8 times over I.
H
0
Intersection of column I with row E shows
that never won against E.
E 5
5
H E I
I
4
8
R 2
5
Total
R
2
8
14
15
When column I is paired with R, I wins 8 times.
Whilst R wins 2 times. This is rare, as once
dominance is established there are few
challenges by the lower animal.
It is most likely R is a younger animal that is on the
Intraspecific Co-operative Responses
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Includes group formation, pair bond formation and parental care.
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Requires a form of communication:
o can be visual, vocal, chemical or tactile
Group Formation – Advantages of group behaviour
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Hunting - work as a team to kill prey. E.g. wolves, lions,
wild, dogs.
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Defence – form defensive circles or post guards to watch
for danger whilst rest of group feeds. E.g. Himalayan yaks
(circles), baboons (guards).
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Protection – Dolphins protect mothers during birth process and help carry baby to surface until it
has learned to breathe.
o Baboons, mother and young in safest position in
the pack (centre).
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Insect societies (animal colonies) – organisms specialised
to carry out aspects of maintenance of nest or hive.
Centred around a queen who co-ordinates group with
pheromones.
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Clumping – confuses predators, difficult to pick out individuals. E.g. shoals of fish, flocks of birds
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Breeding – Many groups form for breeding purposes. Safest breeding sites are in the centre of the
group.
o E.g. penguins, gannets, gulls
Disadvantages of group behaviour –
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Competition for resources- abiotic and
biotic
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Spread of disease – closer contact of
individuals
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Parasites – closer contact, less likely if were spread out
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Increased conflict – due to competition for resources