AMENSALISM AND ANTIBIOSIS

AMENSALISM IS A SITE-SPECIFIC RELATIONSHIP IN WHICH ONE POPULATION IS INHIBITED WHILE THE OTHER IS UNAFFECTED. A SIMPLE EXAMPLE IS THE SHADING OUT OF CERTAIN PLANTS UNDER TALL TREES. THE TREES REDUCE THE AVAILABLE SUNSHINE AT GROUND LEVEL, AND NUMEROUS PLANTS CANNOT FIND ADEQUATE LIGHT IN THE SHADE. HENCE, ONLY SHADE TOLERANT PLANTS WITH LOWER LIGHT REQUIREMENTS CAN SURVIVE AS GROUND COVER IN THE FORESTS.

ANTIBIOSIS IS A SPECIFIC TYPE OF AMENSALISM IN WHICH ONE ORGANISM PRODUCES A METABOLITE THAT IS TOXIC TO OTHER ORGANISMS. THE BEST KNOWN EXAMPLE IS MOLD, PENICILLIN, WHICH PRODUCES AN ANTIBIOTIC SUBSTANCE  CAUSING THE DEATH OF MANY BACTERIA. MANY PLANTS ALSO PRODUCE SUBSTANCES  WHICH ARE HARMFUL TO ANIMALS, FOR EXAMPLE, ALGAE BLOOMS OF SOME BLUE, GREEN AND RED ALGAE PRODUCE CHEMICALS THAT ARE TOXIC TO FISH.

PROTOCOOPERATION

IT IS A SHORT STEP AHEAD OF COMMENSALISMS AND COOPERATION. IN THIS RELATIONSHIP, BOTH ORGANISMS GAIN BY THE ASSOCIATION AND ARE MUTUALLY BENEFITTED. THE RED-BILLED OXPECKER FORM PROTOCOOPERATION WITH THE BLACK RHINOCEROS- THE BIRDS FEED ON THE PARASITES STICKING ON THE SKIN OF THE RHINOCEROS RELIEVING HIM OF THE PARASITES STICKING ON THE SKIN OF THE RHINOCEROS RELIEVING HIM OF THE PARASITES, AND IN TURN  OBTAINING THEIR FOOD.

PARASITISM

IT IS THE RELATIOSHIP BETWEEN TWO INDIVIDUALS OF DIFFERENT SPECIES IN WHICH THE PARASITE RECEIVES BENEFIT AT THE EXPENSE OF THE HOST; THEREFORE , PARASITISM IS A FORM OF THIS OPERATION. IN THIS  ASSOCIATION, THE PARASITE RECEIVES FOOD, SHELTER AND PROTECTION AT THE EXPENSE OF THE HOST.

THE ORIGIN OF A PARASITIC LIFE IN AN ANIMAL IS ASSOCIATED WITH ATTEMPTS TO SECURE FOOD FOR THEMSELVES OR THEIR OFFSPRING. THE ANCESTORS OF ECTOPARASITES  WERE CLEARLY FREE LIVING FORMS. A FREE LIVING ORGANISM COULD HAVE ACCIDENTALY SETTLED ON THE BODY OF A LARGER SPECIES WHERE CONDITIONS WERE MORE FAVOURABLE FOR SURVIVAL. THERE ARE CERTAIN MODIFICATIONS AND ADAPTATIONS WHICH MIGHT HAVE EVOLVED  IN THESE ORGANISMS.

ORGANS OF ATTACHMENTS: THE TAPEWORM HAS HOOKS FOR ATTACHMENT TO THE HOST'S GUT WALL.


BODY SHAPE: THE INTESTINAL PARASITES LIKE THE ROUND WORM HAS AN ELONGATED BODY.


CUTICLES: THE INTESTINAL PARASITES LIKE THE  TAPEWORM HAVE THICK CUTICLES WHICH OFFER THEM  RESISTANCE AGAINST THE ACTION OF THE DIGESTIVE JUICES.


LOSS OF LOCOMOTARY ORGANS: MOST ENDOPARASITES LIKE FLEAS (THEY HAVE LOST THEIR WINGS, HAVE LOST THEIR LOCOMOTIVE ORGANS AS THEY ARE NOT NEEDED. THESE ORGANS MAY DISAPPEAR OR DIFFERENTIATE  INTO ORGANS OF ATTACHMENTS.


LOSS OF SENSE ORGANS: AS THE INTERNAL ENVIRONMENT OF THE HOST  IS MORE OR LESS UNIFORM, THERE IS NO USE OF SENSE ORGANS AMONG ENDOPARASITES AS THEY ARE  PROVIDED ONLY WITH TANGO RECEPTORS.


DIGESTIVE SYSTEM: THE TAPEWORM HAS LOST ITS DIGESTIVE SYSTEM, ITS MOUTH PARTS  HAVE DEVELOPED PIERCING AND SUCKING APPARATUS TO CONSUME THE ALREADY DIGESTED FOOD.


COMPLICATED REPRODUCTION : THE ROUNDWORM IN HUMANS LAYS EGGS AT THE RATE OF 1500 A DAY, THE TERMATODES LAY EGGS CONTINUOUSLY, AND THE TAPEWORM LAYS EGGS ANNUALLY, ESTIMATED AT 80 MILLION PER YEAR.

THE EFFECT OF PARASITISM ON THE HOST IS USUALLY HARMFUL. THE EFFECT OF PARASITISM ON THE HOST IS USUALLY HARMFUL. THE EFFECTS OF ENDOPARASITES ARE MORE MARKED THAN THOSE ECTOPARASITES.

PREDATION

IN THIS RELATIONSHIP THE PREY IS KILLED BY ONE ANIMAL AND EATEN BY ANOTHER, THE PREDATOR. A PREDATOR IS A FREE LIVING ANIMAL USUALLY LARGER THAN ITS PREY. PREDATORS ARE MOSTLY CARNIVORES. HERBIVORES ANIMALS THAT EAT PLANTS OR SEEDS OF PLANTS ARE ALSO IN A WAY PREDATORS BECAUSE THEY REMOVE INDIVIDUALS  FROM THE POPULATION. SOME PLANTS PREDATORS ARE CALLED CARNIVORES OR INSECTIVOROUS, FOR EXAMPLE UTRICULARIA, DIONAEA, ETC. SOME PREDATORS FUNCTION AS PREYS FOR OTHERS, EXAMPLE FROG THAT FEEDS ON INSECTS IS A PREY FOR AN EAGLE OR A PEACOCK. IN NATURE THE POPULATION OF PREDATORS IS QUITE SMALL AND THAT OF PREY IS MUCH LARGER SO THAT THE LATTER IS NEVER ELIMINATED COMPLETELY.

COMMENSALISM

THIS TYPE OF RELATIONSHIP IS ESTABLISHED WHEN TWO OR MORE ORGANISMS LIVE TOGETHER WITHOUT HAVING ANY PHYSIOLOGICAL UNION. THE RELATION IS UNEQUAL IN THAT ONLY ONE INDIVIDUAL GETS THE BENEFIT FROM THE ASSOCIATION WHILE THE OTHER REMAINS UNAFFECTED.

THE CHIEF BENEFITS OF THIS ASSOCIATION ARE SHELTER, ANCHORAGE , TRANSPORTATION AND FOOD SUPPLY. A COMMENSAL THAT ATTACHES  OR LIVES  UPON THE HOST'S BODY IS CALLED ECTOCOMMENSAL. A COMMENSAL THAT LIVES INSIDE THE BODY OF THE HOST IS REFFERED TO AS AN ENDOCOMMENSAL. SUCKER FISH IS AN ECTOCOMMENSAL THAT ATTACHES ITSELF TO THE BODY OF A SHARK. ALL THE ECTOCOMMENSALS ARE SMALL IN SIZE AND NOT BURDENSOME TO THE HOST. THE HARMLESS PROTOZOAN IN THE INTESTINAL TRACT OF MAMMALS AND MICRO-ORGANISMS IN THE CANAL SYSTEM OF SPONGES ARE EXAMPLES OF ENDOCOMMENSALS.

MANY LARGE TROPICAL TREES PROVIDE HABITATS FOR NUMEROUS COMMENSAL PLANTS AND ANIMALS. TRUNKS AND BRANCHES PROVIDE ATTACHMENT SITES FOR PLANTS SUCH AS ORCHIDS. ATTACHMENT HARBOURAGE  IS PROVIDE BY THE TREES FOR BATS, TREE FROGS, LIZARDS, INSECTS AND MANY OTHER ANIMALS. WHALES PROVIDE ATTACHMENT SITES FOR BARNACLES, ALGAE, ETC. THESE PLANTS AND ANIMALS ARE NOT PARASITIC.

ANOTHER COMMON TYPE OF COMMENSALISMS OCCURS WHEN VARIOUS SPECIES OF PLANTS AND ANIMALS USE BURROWS OR NESTS CONSTRUCTED BY OTHER SPECIES . TERMITE NESTS PROVIDE ECOLOGIC NICHES  FOR MORE THAN A HUNDRED SPECIES OF OTHER ANIMALS SUCH AS ANTS, BEETLES AND MILLIPEDS.