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.

SYMBIOSIS

SYMBIOSIS IS AN ASSOCIATION BETWEEN TWO OR MORE ORGANISMS THAT LIVE TOGETHER IN CLOSE PHYSIOLOGICAL UNION FOR MUTUAL BENEFIT. IN THIS DEFINATION, SYMBIOSIS REFERS TO THE INTIMATE ASSOCIATION OF TWO DIFFERENT KINDS OF ORGANISMS.

THE IMPORTANCE OF NITROGEN FIXING BACTERIA, RHIZOID ASSOCIATED WITH LEGUMES IS WELL KNOWN. ROOTLETS OF LEGUMES HAVE SWELLINGS,INHABITED BY BACTERIA. HERE, THEY DERIVE CARBOHYDRATES FROM THE HOST AND IN TURN THEY FIX  THE ATMOSPHERIC NITROGEN IN THE ROOTS. THIS NITROGEN IS USED BY PLANTS.

THE WOOD BORING BEETLES HAVE AN ELABORATE APPARATUS  ON THEIR HEADS FOR CARRYING THE FUNGUS. THE FEMALES  OF THESE SPECIES HAVE AN APPARATUS CONNECTED WITH OVIPOSITOR WHICH COATS THEIR EGGS WITH FUNGAL SPORES AS THEY ARE LAID. IN ALL THESE  ASSOCIATIONS, THE FUNGUS  PROVIDES FOOD AND SHELTER, AND IT THRIVES ON THE EXCRETORY  MATERIAL OF ITS HOST.

MUTUALISM AND SYMBIOSIS ARE THE TERMS  APPLIED TO VERY SIMILAR TYPES OF ASSOCIATIONS WHERE, ONE DERIVES  NUTRITION  FROM ANOTHER AND IN TURN BENEFITS THE FOOD SUPPLIER IN SOME OTHER WAY. FOR EXAMPLE , IN LICHENS  THE  ALGAE PROVIDES PART OF FOOD FOR CONSUMPTION BY THE FUNGAL COMPONENT. IN TURN THE FUNGUS PROVIDES PROTECTION TO THE ALGAE AGAINST DESICCATION. MANY OF THESE RELATIONSHIPS AND TERMINOLOGIES OF BIOTIC COMPONENTS ARE BASED ON FOOD HABITS.

MUTUALISM

THERE ARE CERTAIN TYPES OF CLOSE BIOTIC INTERDEPENDENCE AMONG THE SPECIES LIVING IN AN ECOSYSTEM SUCH AS-MUTUALISM, WHICH IS AN ASSOCIATION BETWEEN TWO OR MORE ORGANISMS IN WHICH ALL DERIVE MUTUAL BENEFIT WITH NO HARM TO ANY OF THE PARTNERS. MUTUALISM CAN BE SEEN BETWEEN PLANTS AND ANIMALS AND BETWEEN TWO DIFFERENT ANIMALS.


MUTUALISM BETWEEN PLANTS AND ANIMALS : IT IS AN IMPORTANT ASSOCIATION WITH REGARDS TO REPRODUCTION OF MANY KINDS OF PLANT SPECIES. PLANTS ATTRACT INSECT BY THERE SWEET NECTAR OR COLOUR. THE INSECT VISIT THE PLANTS TO OBTAIN THEIR FOOD. THE PLANTS DUST THEM WITH POLLEN AND THE INSECTS CARY THE POLLEN FROM FLOWER TO FLOWER. PLANTS ALSO TAKE THE HELP OF ANIMALS IN THE DISTRIBUTION OF SEEDS. ANIMALS, AFTER CONSUMING THE FRUITS, DISTRIBUTE THE HARD COATED SEEDS WHICH PASS THROUGH THEIR ALIMENTARY CANAL, IN THEIR DROPPINGS.


MUTUALISM BETWEEN ANIMALS AND OTHER ANIMALS : MUTUALISTIC ASSOCIATES BETWEEN BIRDS AND ANIMALS SUCH AS, THE COW BIRD AND BISON, THE OXPECKER AND THE ANTELOPE,  THE CROW AND THE CATTLE, DISPLAY SUCH RELATIONSHIP. IN ALL THESE RELATIONSHIPS THE BIRDS RENDER CONSIDERABLE SERVICE TO THEIR HOST BY RIDDING THEM TO TICKS AND EXTERNAL PARASITES. THEY ALSO SERVE AS SENTINELS. IN TURN THE BIRD RECEIVES A CONSTANT SUPPLY OF FOOD.


AN INTERESTING EXAMPLE IS BETWEEN THE CROCODILE AND THE BIRD, PLUVIANUS AEGYPTIUS. THE BIRD REMOVES LEECHES AND FRAGMENTS OF FOOD IN DECAYING CONDITION FROM THE CROCODILE. THE CROCODILE OPENS ITS JAWS AND PERMITS THE SEARCH AND THEN FINALLY THE BIRD RECEIVES THE FOOD FROM THE CROCODILE. THE COMMON STARLING BIRD ALSO PERFORMS THE SAME FUNCTION WITH THE SHEEP.


SPONGES GROWING ON THE SHELL OF THE HERMIT CRAB PROTECT IT BY PRODUCING BAD ODOUR. HERE THE ADVANTAGE TO THE SPONGE IS THAT, IT IS CARRIED TO NEW WATERS FOR ITS OWN FOOD. THUS, THE MUTUALISTIC RELATIONSHIPS BETWEEN PLANTS AND ANIMALS AND ANIMALS SHOW THEIR INTERDEPENDENCE FOR MUTUAL BENEFITS.


MUTUALISM MAY BE OBLIGATORY OR FACULTATIVE. AN EXAMPLE OF OBLIGATORY  MUTUALISM OCCURS BETWEEN A HORSE AND CERTAIN MICRO-ORGANISMS. MILLIONS OF CILITATE PROTOZOA AND BACTERIA LIVE IN THE STOMACH AND CAESUM OF A HORSE WHICH DIGEST CELLULOSE FOR THE HORSE  AND PROVIDES 20 PERCENT OF ITS NITROGEN REQUIREMENT PER DAY.THESE INTESTINAL MICRO-ORGANISMS ARE ESSENTIAL FOR THE NORMAL GROWTH AND HEALTH OF THE HORSE.


MANY MUTUALISTIC RELATIONSHIPS ARE FACULTATIVE, I.E., BOTH ARE FAVOURED WHEN LIVING TOGETHER. THOUGH BABOONS AND IMPALAS CAN SURVIVE WELL WITHOUT EACH OTHER, BUT EACH PROVIDES A PROTECTIVE WARNING SYSTEM  FOR THE OTHER WHEN THEY LIVE IN ASSOCIATION. SQUIRRELS FACILITATE THE EXTENSION OF THE HISKORY TREE  BY BURYING THE NUTS, THOUGH THE HISKORY TREE CAN PROPAGATE WITHOUT SQUIRRELS. IN THE SAME MANNER, SQUIRRELS  CAN SURVIVE WITHOUT HISKORY NUTS, IF AN ADEQUATE SUPPLY OF OTHER NUTS IS AVAILABLE.


MAN HAS CAPITALIZED ON MUTUALISM AS BIOLOGICAL  PRINCIPLE IN THE DEVELOPMENT OF AGRICULTURE. DEVELOPMENT OF AGRICULTURE RESULTED IN THE RELATIONSHIP OF FACULTATIVE COMMENSALISMS OR MUTUALISM OF PLANTS AND ANIMALS WITH MAN. AT THE DRAWN OF AGRICULTURE 10,000 YEARS AGO, MAN COULD LIVE WITHOUT DOMESTICATION OF PLANTS AND ANIMALS, BUT AS HE DEVELOPED THESE RELATIONSHIPS HE GOT INVOLVED IN OBLIGATORY MUTUALISM. MODERN MAN OBVIOUSLY CANNOT LIVE WITHOUT THE DOMESTICATED PLANTS AND ANIMALS OF AGRICULTURE, AND MANY OF THESE DOMESTICATED FORMS CANNOT LIVE WITHOUT THE SPECIAL HUSBANDRY PROVIDED BY MAN.

SPECIES INTERACTIONS

ALL POPULATION OF LIVING ORGANISMS EXISTS IN A NETWORK OF INTERACTIONS WITH OTHER POPULATION. MANY OF THESE INTERACTIONS ARE SUBTLE AND COMPLEX WHILE OTHERS ARE DIRECT. THE DEGREE OF INTIMACY IN THE RELATIONSHIPS OF THE ORGANISM INHABITING A PARTICULAR HABITAT VARIES GREATLY. THESE ASSOCIATES MAY BE EITHER BENEFICIAL OR HARMFUL TO BOTH THE PARTNERS OR BENEFICIAL TO ONE PARTNER AND HARMFUL TO THE OTHER. IF THE RELATIONSHIP IS BENEFICIAL TO ONE OR BOTH PARTNERS, IT IS CALLED POSITIVE INTERACTION OR COOPERATION. THE INTERRELATIONS OF INDIVIDUALS THAT ARE HARMFUL TO ONE OR MORE OF THE PARTICIPANTS ARE CALLED NEGATIVE INTERACTION.

INTERACTIONS BETWEEN PLANTS AND ANIMALS

IN A NATURAL ECOSYSTEM THE SUN'S ENERGY WILL BE CAPTURED BY THE TREES, GRASS OR OTHER HERBS AND CONVERTED INTO PROTEINS, CARBOHYDRATES AND OTHER FOOD COMPONENTS. THESE WILL BE CONSUMED BY PLANT EATING MAMMALS, BIRDS, INSECTS AND A GREAT VARIETY OF OTHER ANIMALS WHICH IN TURN WILL PROVIDE FOOD FOR THE MEAT-EATING ANIMAL. ALL LIVING ORGANISMS ULTIMATELY PROVIDE FOOD FOR THE ORGANISMS OF DECAY WHICH BREAKS DOWN THE PLANT AND ANIMAL MATERIALS AND RESTORE THE CHEMICAL COMPONENTS OF THE SOIL.

HERBIVORES FEED ON DIFFERENT PARTS OF A PLANT AND ALSO ON DIFFERENT PLANTS. GRAZING ANIMALS EAT UNHARVESTED HERBS AND GRASSES WHILE BROWSING ANIMALS EAT FOLIAGE OF SHRUBS AND TREES. SHEEP PREFER BROWSING ON HIGH HERBS, GOATS AND DEER ON BROAD LEAVED SHRUBS, CAMELS ON TENDER SHOOTS OF TALL TREES, WHILE HORSES AND CATTLE PREFER GRASSES.GRAZING AND BROWSING IN LIMITED NUMBERS IS BENEFICIAL BECAUSE LIGNEOUS VEGETATION BECOMES DRY AND INFLAMMABLE DURING HOT SEASONS WHEN TEMPERATURES SHOOT UP. LIGHT TRAMPLING BY ANIMALS MIXES HUMUS AND LITTER . HERBIVORES ALSO KEEP A CHECK ON PLANT GROWTH. A NUMBER OF PLANTS GIVE SHELTER TO ANIMALS, BIRDS, INSECTS, REPTILES AND MICROBES APART FROM  PROVIDING THEM PALATABLE FOOD.

PLANTS MODIFY THE PHYSICAL ENVIRONMENT AND MAKE IT MORE CONGENIAL FOR HUMAN AND LIVING . THEY ACT AS WIND BREAKERS TO STORMS AND GALES THERE BY REDUCING THEIR VELOCITY, AND THUS REDUCING ENVIRONMENTAL DAMAGE, ESPECIALLY SOIL EROSION. PLANTS ALSO HELP IN MODERATING TEMPERATURE CONDITIONS, AND THROUGH TRANSPIRATION HELP IN BRINGING LOCAL RAIN. PLANTS ABSORB LARGE QUANTITIES OF WATER WHICH IN TURN PREVENTS WATER LOGGING OR FLOODING, IN CATCHMENT AREAS THEY RETAIN LARGE AMOUNTS OF WATER WHICH BECOMES AVAILABLE TO SPRINGS AND RIVERS. THE ROLE OF PLANTS IN NATURE AND ITS INHABITANTS IS INDISPENSABLE AS THEY ARE CLOSELY RELATED TO BOTH, THE BIOTIC AND ABIOTIC COMPONENTS OF THE ENVIRONMENT.

A NUMBER OF ANIMALS, ESPECIALLY INSECTS ARE INVOLVED IN POLLINATION OF FLOWERS. THEIR BODIES HAVE BEEN FRAMED TO SUCK NECTAR, EAT/COLLECT POLLEN GRAINS AND PERFORM POLLINATION. SOME FLOWERS ARE ALSO POLLINATOR SPECIFIC. FLOWERS OF SNAP DRAGON (DOG FLOWER) HAVE CLOSED LIP-LIKE PETALS WHICH OPEN ONLY WHEN AN INSECT LANDS OVER ITS LOWER LIP. THESE ARE THE MAJOR POLLINATORS OF CROP PLANTS. FRUITS AND SEEDS OF MANY PLANTS ARE DISPERSED BY ANIMALS ESPECIALLY BIRDS AND ANIMALS. IN MANY CASES PLANTS PROVIDE FOOD TO ANIMALS FOR THIS JOB. THE GALL WASP LAYS EGGS INSIDE THE LEAVES AND YOUNG STEMS TO ENSURE THEIR PROTECTION, HATCHING AND FEEDING.