ALLELOCHEMISTRY

THESE RELATIONSHIPS INVOLVE COACTIONS  WHEREBY CHEMICALS SECRETED BY ONE ORGANISM AFFECT THE GROWTH, HEALTH AND BEHAVIOUR OF OTHER ORGANISMS. ALLELOPATHY IS PRODUCED IN  PLANTS  WHEN TOXINS ARE LIBERATED THAT INHIBIT SEEDLING GROWTH IN THE VICINITY. THIS MAY AFFECT SUCCESSION IN PLANT SPECIES  ESPECIALLY IMPORTANT IN THE EARLY STAGES.ANTIBIOTICS PRODUCED BY BACTERIA, FUNGI AND LICHENS  ARE WIDESPREAD IN NATURE. ALLECHEMIC EFFECTS ARE  OF GREAT VARIETY IN BOTH PLANTS AND ANIMALS: REPELLANTS, ESCAPE SUBSTANCES, SUPPRESSANTS, VENOMS, INDUCTANTS, ATTRACTANTS, SIGNALS, STIMULANTS, AUTOTOXINS, ANTOINHIBITORS, ETC. PHEROMONES, CHEMICAL MESSAGES BETWEEN  MEMBERS OF A SPECIES ARE ESPECIALLY IMPORTANT IN REPRODUCTIVE BEHAVIOUR, SOCIAL  REGULATION AND RECOGNITION, ALARM AND DEFENCE, TERRITORY AND TRAIL MARKING, FOOD  LOCATION AND SO ON.

AGGREGATIONS

THE REACTIONS MADE BY LARGE POPULATIONS ON THEIR HABITAT SHOW CONSPICUOUS EFFECTS. DUE TO THE OCCURENCE OF WATER CONDITIONING, PHYSICAL AND CHEMICAL CHANGES OCCUR AS A RESULT OF ORGANISMS LIVING IN IT. COMPARED TO UNCONDITIONED WATER, THESE CHANGES MAY EITHER PROVE TO BE HARMFUL OR BENEFICIAL ON THE ORGANISMS INTRODUCED INTO THE WATER AFTER THE ORIGINAL ORGANISMS HAVE BEEN REMOVED. THE MARINE FLATWORM WILL SURVIVE MUCH LONGER, WHEN TRANSFERRED TO FRESH WATER CONDITIONED EITHER BY THE PRESENCE OF LIVING OR DEAD  INDIVIDUALS  OF THE SAME SPECIES OR BY THE PRESENCE OF FRESH WATER SPECIES OF FLATWORMS, THAN THEY DO IN UNCONDITIONED WATER. AGGREGATIONS ENSURE  LONGER SURVIVAL  OF ORGANISMS IN TOXIC  SOLUTIONS  THROUGH FASTER GROWTH AND GREATER REPRODUCTION.

BENEFITS DERIVED FROM AGGREGATIONS IN TERRESTRIAL ANIMALS ARE ALSO WELL DEPICTED IN HONEYBEES WHEN THEY FORM CLUSTERS AND MAINTAIN  A MASS TEMPERATURE SEVERAL DEGREES ABOVE OUTSIDE TEMPERATURES. WHEN THERE IS DANGER OF OVERHEATING, THE BEES IN THE HIVE SPREAD OUT ON THE COMBS AND FAN WITH THEIR WINGS TO CREATE A CIRCULATION OF AIR.

COMPETITION

THE WORD COMPETITION DENOTES STRIVING FOR THE SAME THING. AT THE ECOLOGICAL  LEVEL IT HOLDS GREAT RELEVANCE WHEN THE THING WHICH TWO ORGANISMS ARE STRIVING FOR IS NOT EASILY AVAILABLE. EVEN IF AVAILABLE, IT IS ONLY IN SMALL NUMBERS. IF POPULATION CONSISTS OF ONLY A FEW SCATTERED INDIVIDUALS COMPETITION WILL NOT BE A FACTOR OF ECOLOGICAL IMPORTANCE.

THE RESULT OF COMPETITION IS THAT BOTH PARTIES  COMPETING WILL BE HAMPERED IN SOME MANNER OR THE OTHER. AT THE POPULATION LEVEL, OR THE DESTINY OR RATE OF POPULATION, ENERGY  FLOW WILL BE REDUCED OR HELD IN CHECK BY THE COMPETITIVE ACTION. COMPETITION ALSO OCCURS WHEN TWO ORGANISMS STRIVE FOR SOMETHING THAT IS NOT IN SHORT  SUPPLY, YET THEY INTERFERE WITH EACH OTHER, OR THEY MIGHT EVEN EAT EACH OTHER. MANY ECOLOGISTS PREFER NOT TO  INCLUDE  THIS ASPECT UNDER COMPETITION.

PLANT POPULATION AS WELL AS ANIMAL POPULATION MAY REGULATE THEMSELVES TO AVOID OVER-CROWDING. DESERT SHRUBS ARE WIDELY SPACED, ALMOST UNIFORMLY DISTRIBUTED; THIS PATTERN EXPLAINS THE COMPETITION OF SCARCITY OF WATER.HOWEVER, EVOLUTION OF SELF REGULATION OF POPULATION HAS OCCURRED IN SOME SPECIES IN THAT SEVERE COMPETITION FOR WATER IS AVOIDED BY THE PRODUCTION OF LEAF OR ROOT HORMONES THAT INHIBIT DEVELOPMENT OF OTHER INDIVIDUALS IN THE NEIGHBOURHOOD.

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.