Transcript Interspecific aggressive responses

Interspecific aggressive
responses
Year 13
•
Competition between animals is usually
for:
1) Food
2) Water
3) Space
4) Breeding sites
If the competition is intense, one population
may become extinct.
Predator-prey relationships
• Most predators tend to catch weak, sick or old
animals. This way the gene pool of the prey
population is kept strong.
• In a predator-prey relationship, the two
species are dependent on each others wellbeing. A predator that eats too many prey will
cut off its own food source. The predators
also regulate the size of the prey population.
• http://www.youtube.com/watch?v=c81bcjyf
n6U&feature=PlayList&p=A0AD6A14E53
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index=90
• Honey badger
In any predator-prey graph, the prey always has a higher
population and precedes the predator.
Adaptations for getting food
There are 3 ways of getting food:
1) Stay in one spot and let the food
come to you
2) Move and find food
3) Parasitise another organism.
1. Letting the prey come to the
predator
A. Sifting the environment
Baleen whales swim
through the sea,
trapping their food on
baleen sieves.
Barnacles open their trapdoors
and wave hairy feet about in
the water to trap plankton.
B. Dangle bait
Angler fish has a glowing
appendage on the top of
its head that it dangles to
attract prey.
• http://www.youtube.com/watch?v=EqJzuc9
pE00
The snapping
turtle has a wormlike structure on
it’s tongue. It
waits with it’s
mouth open,
wriggling the
“worm”. Fish go
to eat the “worm”,
the turtle snaps its
mouth shut,
catching the fish.
C. Webs and traps
Trapdoor spiders dig holes in the
soil, and cover them with a
trapdoor. If an animal comes near,
spider shoots out and pulls prey
into hole.
Webs: Web spiders
spin strong sticky
threads to trap flying
insects.
D. Lying in ambush
• Many animals lie in ambush to get their
prey, using camouflage and stealth rather
than speed.
Example – praying
mantis. Sits
motionless until prey
comes by. It then
lunges and grabs prey
between two front
legs.
2. Move and find food
A. Speed: Cheetah outrun prey
and match evasive maneuvers
over short distances.
B. Having the right appendages
•
Many animals have special appendages in
order to eat their food.
1) Snakes can disengage their lower jaw in
order to swallow an egg.
2) Teeth are often specialised depending on
the food source. Eg meat eaters have
incisors.
3. Different birds have different beaks which
are adaptations related to their food source.
Other birds have small
beaks for picking up
fine seeds.
Woodpeckers can chisel a
hole to get at beetle grubs.
C. Hunting in swarms
Army ants hunt in a
group (750 000) and
overcome opposition
with their bites and
sheer numbers.
Army ants swarm on a scorpion.
D. Hunting in teams
Lions, hyenas and wolves hunt in packs
with coordinated team work.
Barracuda drive fish into shallow water where they
are easier to catch.
E. Using tools
E. Tool use: Chimpanzees use
twigs or grass stalks to extract
termites from their holes.
3. Parasite/ host relationships
• Parasites live in or on a host organism. The host is
always harmed by the presence of the parasite, but it
is not usually killed.
Tick ectoparasite on a
bird wing
Head louse -ectoparasite
Tape worm from puppy endoparasite
• 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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• http://www.newscientist.com/gallery/mg20
327161300-enemy-within-human-parasites
Defence strategies against
predators
Just as predators have strategies for locating
and capturing prey, prey have counter
strategies to avoid being detected, subdued,
and eaten.
1. Camouflage
Camouflage is used to avoid detection.
Adaptations in form, colour, patterning, and
behaviour enable prey species to blend into their
surroundings.
• http://www.youtube.com/watch?v=fSdICt6
0ZDA&feature=related
2. Startle the predator
• An owl can screech and flap its wings,
startling a predator.
• Many moths have eye patterns on their
wings which they flash. This startles the
predator, allowing the moth to escape.
3. Avoid the Predators
Meerkats have lookouts to
warn the group against
predators.
Some animals like fawns
hide.
Group vigilance and alarms in meerkats
Hiding is a common strategy of fawns
4. Mimicry
• Mimicry is when an organism looks like
another organism to which it is unrelated.
Batesian Mimicry
In Batesian mimicry, a harmless,
palatable species resembles a toxic or
dangerous species. Mimics benefit
because predators avoid all
individuals
with a similar appearance.
The dangerous common wasp
For Batesian mimicry to be effective, the
mimic must not significantly
outnumber the model. Predators must
have a greater chance of encountering
the unpalatable species.
…and its harmless Batesian
mimic, the wasp beetle
Müllerian Mimicry
In Müllerian mimicry,
unpalatable species tend to
resemble each other. The
mimics present a common
image for predators to
avoid.
Monarch butterfly: Danaus plexipus
Orange and black, or
yellow and black are
common warning colours
in insects. For example,
yellow and black stripes
are a warning used by
bees, snakes and wasps.
Queen butterfly: Danaus gillipus
5. Warning Colours
Many prey species taste bad, are toxic, or inflict pain
on attackers.
Truly toxic or noxious species, such as arrow poison
frogs and skunks, make little or no attempt to conceal
themselves from predators. Instead, they often have
warning (aposematic) colouration.
The conspicuous patterns and colours advertise their
unpalatability to predators.
Warning Colours
Arrow poison frog
Lionfish
Monarch butterfly
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) and37
`Dendrobates ventrimaculatus’ (Yurimaguas).
Stag beetle
6. Body Armour
Tough outer coverings, such
as shells, are common in
several taxa.
Almost all mollusks have
protective shells. The head
and muscular foot can be
withdrawn into the shell.
Pill millipede
Turtles and tortoises are
characterized by their hard,
protective shell, virtually
their only defense.
Tortoise
7. Curling up
• Some animals like the porcupine, armadillo and
hedgehogs curl into a ball when attacked. Spines
and scales protect the animal from attack.
8. Chemical Defense
Many insects, including
the Bombadier beetle
and pentatomid bugs
(stink bugs), exude or
spray a noxious fluid
when attacked.
North American skunks
can squirt a strongly
smelling, nauseous fluid
from their anal glands,
at would-be attackers.
Pentatomid (stink) bug
North American skunk
9. Group Defense
Individuals within large groups
are each less vulnerable to
attack than they would be if
alone.
Large flocks of birds and
schools of fish tend to move
together as one mass in a way
that confuses predators and
makes the isolation of
individuals difficult.
Large groups also provide
greater surveillance;
a predator is much less likely to
approach a large group
Flamingoes congregate in large flocks
Large schools confuse predators
The Evolutionary Arms Race
Morphology and behaviour are shaped by
natural selection.
Predation provides strong selective
pressure on prey populations to evolve
effective defense mechanisms, e.g.…
greater speed and agility
Slower, more vulnerable individuals are
often those that fall prey to predators
better surveillance
In turn, natural selection favors counter-
adaptations in predator populations,
e.g.…
group cooperation
greater stealth
Natural selection favors the more
capable hunters