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Interspecific
Relationships
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AS Explanatory note
• interspecific relationships (predation,
parasitism, mutualism, commensalism,
competition for resources)
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Mutualism (+,+)
= a close, co-operative association between
individuals of two species from which both
benefit, often characterised by
communication between the participants; a
form of symbiosis.
e.g. pollination
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• Co-evolution is the evolution of two species
to become totally dependent on each other.
Each of the species involved exerts selective
pressure on the other, so they evolve together.
Co-evolution is an extreme example of
mutualism
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• Some examples of
co-evolution :
Acacia ants and acacia trees
Acacias are small, Central
American trees in the
Leguminosae. They have large,
hollow thorns. The acacia ants
live in the thorns. On the tips of
its leaflets, the plant makes a
substance used by the ants as
food. The ants defend the tree
from herbivores by
attacking/stinging any animal that
even accidentally brushes up
against the plant. The ants also
prune off seedlings of any other
plants that sprout under “their”
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tree
Lichens
Lichens are composed of a
mixture of fungi and algae.
In each “species” of lichen,
the alga and fungus are so
closely intertwined that
whole lichens are classified
as species, rather than the
component fungus/alga.
The type of fungus and alga
are species-specific. The
alga does photosynthesis
and produces sugars as fuel
for both. The fungus
attaches the whole lichen to
its substrate (tree, rock) and
holds in water needed by
the alga.
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3 Main Types of exploitation
• Predation
• Parasitism
• Grazing
Exploitation is when one organism gains benefit at
the expense of another which is harmed.
(+,-)
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• http://www.youtube.com/watch?v=c81bcjyfn
6U&feature=PlayList&p=A0AD6A14E53D2
CCE&playnext=1&playnext_from=PL&inde
x=90
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Predation
• Predation = predator kills prey
(+/-)
• Short term effect = p+p affect each others
numbers
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Two species of mites demonstrate the coupled
oscillations of predator and prey densities
Interpretation: It is apparent from the graph that both populations
showed cyclical behaviour, and that the predator population
generally tracked (lagged) the peaks in the prey population.
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Predator – prey numbers
• Predators can only reproduce if they eat
enough prey.
predator numbers are influenced by prey
numbers
Mostly found in simple ecosystems – tropical
ecosystems have complex food webs
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• Kiore numbers increase when more grass
seed available
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• Canadian Lynx mainly prey on Snowshoe
Hare. An increase in hare numbers is soon
followed by an increase in lynx numbers
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Ladybeetle larvae eating an aphid
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• Long term effect = p+p shape each others
evolution
The idea of an arms race between a prey
animal evolving better ways to defend itself
against a predator that is improving its own
offensive abilities
In this snowy environment, the
polar bear is white to avoid being
noticed as it approaches the seal,
and the seal pup is white to avoid
being noticed by the bear.
Predator prey evolution explanation
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Predator Strategies
• Belonging to a group - can increase food
intake via:
-locating food
-catching food
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• Snares eg spider webs;
glow worms lure and
trap prey.
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• Mimicry = Resemblance of an organism
(the mimic) in color, pattern, form,
behavior, or a combination of these to
another organism or object (the model).
• The taking on by an animal of the look of
another sort of animal or thing for the
purpose of:
• keeping itself safe (traditional sense)
• enhancing predation
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Female fireflies of the genus Photuris
• Photuris females mimic the signal of other
firefly species.
• Responding male firefly is captured and
eaten.
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• http://www.youtube.com/watch?v=EqJzuc9p
E00
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•(Cleaner Fish + host = mutualism). A Cleaner Fish look-alike is
able to get close to bite chunks off fin and gill.
While the cleaner Labroides dimidiatus (top) is a symbiont to
other marine fish, removing their ectoparasites, the mimic
Aspidontus taeniatus (below) bites off parts of other fishes'
skin and fins
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• Speed e.g. cheetah
http://www.planetarkive.org/topics/attack2.html
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• Camouflage
•
http://www.planetarkive.org/topics/attack2.html
•
http://www.ryanphotographic.com/crypsis.htm
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• http://www.youtube.com/watch?v=fSdICt60Z
DA&feature=related
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• Poison
http://www.planetarkive.org/topics/attack2.html
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• Sensitive senses Great white sharks use their
amazing sense of smell to track down their prey
underwater. They can detect a speck of blood,
no bigger than a pinprick, that is floating
around in over 100 litres of water from more
than 4km away!
http://www.planetarkive.org/topics/attack2.html
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• Stalking
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Prey Defences
• Living in Groups
• - greater vigilance (may be further
enhanced by combining sensory capabilities
of another species).
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• Sensitive senses e.g.
impala - keen sense
of smell
+ baboon excellent colour
vision)
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• -increased
armament – more
teeth to deter
predators e.g. a
group of baboons
can kill a leopard
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• -dilution effect - more for predator to
choose from = less impact if one is lost
• -confusion effect – difficult for
predator to focus on one individual
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• Deception
• camouflage + appropriate behaviour, e.g.
ground-nesting chicks ‘freeze’.
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• counter-shading e.g. pelagic (open water)
fish (e.g. Kahawai) silvery underside, dark
top
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Batesian Mimicry - a palatable animal
mimics an unpalatable one e.g. viceroy
resembles toxic monarch butterfly
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Don’t eat the monarch – it’s
chunderous!
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One of the snakes in the picture below is poisonous and the other
one is a mimic. Coral snakes are very easy to see because of their
bright red, yellow, and black stripes. They are colored this way so
that other animals know they are poisonous and will leave them
alone. The Scarlet Kingsnake looks almost EXACTLY like the
Coral snake, but it is perfectly harmless!
The scarlet king snake on the left is the mimic, and the coral snake
on the right is the poisonous one. The scarlet king snake is hoping
that its enemies will think it is poisonous and not eat it! If you
couldn't tell the difference, don't worry about it! The Kingsnake, or
the mimic, would be really happy that you couldn't! If you ever see
one of these snakes, here is a rhyme to help you remember the
difference between the two.
"Red on yellow, kill a fellow. Red on black, won't hurt Jack." 36
• Mullerian Mimicry - several unpalatable
species resemble one another – yellow and
black stripes warn of danger – used by
wasps, snakes, bees, frogs
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Müllerian mimicry in Dendrobates frogs near Tarapoto, Peru
(a - c) The three frogs are all putative members of a single species,
Dendrobates imitator. Each of these different morphs is sympatric with a
different species in a different geographical region. The species with
which each morph is sympatric is shown directly below that morph.
From left to right, the species in (d - f ) are: Dendrobates variabilis
(Tarapoto), Dendrobates fantasticus (Huallaga Canyon) and38
`Dendrobates ventrimaculatus’ (Yurimaguas).
• diversion of attack
- eg ‘eyespots’ on
butterfly and moth
wings. Predator
diverted away from
body, or scared
away.
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• autotomy - shedding
of a body part when
attacked eg NZ lizards
and Tuatara can lose
their tails.
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• Synchronised
Breeding
-shortens breeding
season therefore less
offspring lost to
predators e.g.
Gannets
-saturates feeding
capacity e.g. coral.
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Parasitism
A parasite is any organism that feeds at a host’s
expense. The host is harmed but not killed.
Parasites are always smaller than their host.
One host may support many parasites of the
same species.
• Host specific = when a parasite depends for
its food on one organism.
• Parasites may weaken the host so that it
becomes more vulnerable to other hazards.
• There are more parasitic than free-living sp.
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• Ectoparasites live on the outside of the
host e.g. mosquitoes, lice.
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• Endoparasites live
inside the host e.g.
liver flukes,
tapeworm.
Beef tapeworm = 7½ m –
world’s biggest ‘microbe’
Ascarids or roundworm infections are
primarily a problem of young horses. They
seldom cause significant damage in animals
that are 11 years or more old. They are
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primarily found in the small intestine.
– They have reduced structures (inc sensory,
muscular, & nervous systems)
– ‘Holding-on’ structures eg hooks
• Reproduction based on transmission of offspring to
a new host. Adults cannot survive outside the host.
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• http://www.youtube.com/watch?v=vMGLWyNcAs
• http://www.youtube.com/watch?v=dy4cQON
7-JU
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– produce many eggs though getting them
to a new host is often difficult.
– complex lifecycle with several different
young stages, each in a different host.
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• Social Parasites
e.g. cuckoo - a brood parasite.
e.g. ants ‘slave-making’ of other ants
nests.
The picture shows a queen of a social
parasite, Acromyrmex insinuator,
being harassed by a worker of its host
species, Acromyrmex echinatior.
Socially parasitic ants use the nests
and workforce of other ant species to
raise their own offspring. The queens
of social parasites need to get inside
the nests of other ants, where they will
lay eggs which are reared by the
workers of their host.
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• Plant parasites. Connect with vascular
tissue of host.
Total Parasites rely fully on their host
e.g. wood rose has no roots, no
chlorophyll.
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• Partial parasites (hemiparasite) have
chlorophyll and only get water and
minerals from host e.g. mistletoe.
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Grazing
A grazer consumes part of many
organisms which are not killed.
Like predators, grazers feed off
populations.
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• Chemical Defences of plants
• toxic and distasteful. Cyanogenic glycosides
release hydrogen cyanide when plant damaged
e.g. clover leaves and karaka seeds
Cardiac glycosides e.g. Tutu, Swan plant
Tannins are bitter e.g. Tea leaves.
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Allelopathy
Odours may discourage browsing
by big and little animals. Another
reason, however, is to suppress the
growth of a nearby plant. These
toxins, called allelochemicals,
permeate the soil around a plant and
act as germination inhibitors.
Because these allelochemicals are
present, seeds from a nearby plant,
although spread over a large area,
can remain dormant for decades.
Since the toxins are hydrocarbons,
they are burned when a fire roars
through the area.
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• interruptive. ferns and conifers produce
chemicals similar to insect hormones which
disrupt insect growth e.g. inhibit
metamorphosis. Toxicity: Known to be poisonous to livestock throughout
Also allelopathic
the US, Canada, and Europe. Simple stomach animals like
horses, pigs, and rats develop a thiamine deficiency within
a month. Acute bracken poisoning affects the bone
marrow of both cattle and sheep, causing anemia and
hemorrhaging which is often fatal. Blindness and tumors
of the jaws, rumen, intestine, and liver are found in sheep
feeding on bracken fern.
Toxicity: All parts of brackenfern, including rootstocks,
fresh or dry leaves, fiddleheads and spores, contain toxic
compounds, and are poisonous to livestock and humans.
Consumption of brackenfern causes vitamin B1
deficiency in horses, and toxins can pass into the milk of
cattle. Young leaves of brackenfern have been used as a
human food source, especially in Japan, and may be
linked to increased incidence of stomach cancer. Humans
working outdoors near abundant stands of the plant
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be at risk from cancer-causing compounds in the spores
•
All parts of deadly nightshade plant, especially
deadly
e.g.
alkaloids
of Hemlock,
Deadly
berries,
are venomous
and responsible
of
toxicologic symptoms, typical indeed for all
Nightshade
(extremely
toxic
to
mammals
but
members of Solanaceous family, the so-called
not “anticholinergic
to birds – disperse
and strychnine
syndrome”, seed)
whose symptoms
are
synthesized in an old english rhyme:
plant
of Asia.
“hot as a hare” (increase in body temperature)
“blind as a bat” (pupillary dilatation and
accomodation paralysis)
“dry as a bone” (block on perspiration and
salivation)
“red as a beetroot” (face and neck congestion)
“crazy as a hen” ( psychomotor excitement,
hallucinations).
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Mechanical Defences
• Spines – e.g. sea
urchins, cacti,
hedgehogs, roses
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• Shells – e.g. barnacles, shellfish, hermit
crabs, nuts
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Animal counter-measures
• Sheep can detoxify
clover
• Monarch butterfly
caterpillars accumulate
poisons from food (e.g.
nettles) to be used for
their own defence;
poison retained in adults
as protection against
birds
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Pests
Introduced animals often
become pests because there
are few or no predators e.g.
rabbits, goats, wasps, gorse,
possums in NZ
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Biocontrol
• An introduced predator can
control an introduced pest
E.g. parasitoid wasps have
brought cabbage white
butterfly under control
adult of
Apanteles sp.
(parasitoid of
Pieris sp.)
Larvae of Apanteles sp.
(parasitoid) emerging from Pieris
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sp. larva
Argentinian moth
controls prickly
pear cactus in
Australia
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Abiotic pop’n control
• Barnacles compete for
space
• Muskrats without
territory starve or get
eaten
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