BIOMES

A BIOME SYSTEM  IS RECOGNIZED ON THE BASIS OF COMMUNITIES, OF CHARACTERISTIC COMBINATIONS OF ANIMAL AND PLANT SPECIES, OF SUCCESSIONAL  RELATIONS BETWEEN  COMMUNITIES AND THE SUCCESSIONAL RELATIONS BETWEEN COMMUNITIES AND  THE SUCCESSION IN ALL LOCAL HABITATS WHICH EVENTUALLY CONVERT INTO A CLIMAX COMMUNITY PATTERN' AND FORMS THE MOST IMPORTANT  ECOLOGICAL CHARACTERISTIC OF A GEOGRAPHIC AREA.

THE PRINCIPAL GEOGRAPHIC UNIT IN A ECOLOGICAL SYSTEM IS THE BIOME. THE BIOME IS DIVIDED INTO PLANT ASSOCIATIONS, DISTINGUISHED  BY UNIFORMITY IN THE SPECIES COMPOSITION OF THE CLIMAX PLANT DOMINANCE AND BIOCIATIONS, IDENTIFIED BY UNIFORMITY AND DISTINCTIVENESS IN THE SPECIES COMPOSITION OF THE CLIMAX COMMUNITY, PARTICULARLY OF THE ANIMAL PREDOMINANT. SOME NINE TERRESTRIAL BIOMES AND FOUR MARINE BIOMES ARE RECOGNIZED. ON LAND, THE MOST IMPORTANT CLIMAX SPECIES ARE USUALLY PLANT DOMINANTS THAT OCCUR IN DISTINCTIVE VEGETATION AND LANDSCAPE TYPES; IN THE OCEAN, THE MOST IMPORTANT ORGANISM  THAT DEFINE BIOMES ARE USUALLY THE PREDOMINANT  ANIMALS WHICH ARE ALSO SOMETIMES ALSO DOMINANTS.

NUMBER SPECIES IN THE WORLD

WE DO NOT KNOW EXACTLY HOW MANY SPECIES INHABIT THIS EARTH. ESTIMATES RANGE FROM 4 MILLION TO 100 MILLION. THE BEST GUESS IS 10-14 MILLION. MOST OF THE SPECIES IN THE WORLD ARE INSECTS AND MICRO-ORGANISMS NOT VISIBLE TO THE NAKED EYE.

SO FAR ABOUT 1.8 MILLION SPECIES (NOT INCLUDING BACTERIA) HAVE BEEN IDENTIFIED, NAMED, AND CATALOGUED. THESE INCLUDE 270,000 PLANT SPECIES, 45,000 VERTEBRATES,  AND 950,000 INSECTS. ROUGHLY 10,000 NEW SPECIES ARE IDENTIFIED EVERY YEAR.

OVERALL, OUR KNOWLEDGE OF SPECIES AND ECOSYSTEMS IS POOR. EVEN OUT OF THE IDENTIFIED SPECIES, ONLY A ONE THIRD HAVE BEEN STUDIED TO SOME LEVEL. AMONG THESE AGAIN, WE UNDERSTAND THE EXACT ROLES AND INTERACTIONS OF JUST A SMALL NUMBER OF SPECIES.

LIMITING FACTORS

A VARIETY OF ABIOTIC FACTORS AFFECT THE NUMBER OF ORGANISMS IN A POPULATION. A GIVEN SPECIES CAN SURVIVE AND GROW ONLY IF THE FACTORS FALL WITHIN A RANGE TOLERATED BY THE SPECIES. FOR EXAMPLE, AN ORGANISM MAY ONLY TOLERATE BY THAT SPECIES. FOR EXAMPLE, AN ORGANISM MAY ONLY TOLERATE A SPECIFIC TEMPERATURE RANGE.

AGAIN, IN A GIVEN SITUATION, ONE FACTOR MAY BE MORE IMPORTANT IN REGULATING THE POPULATION GROWTH OF A SPECIES THAN OTHER FACTORS. SUCH A FACTOR IS CALLED A LIMITING FACTOR. FOR EXAMPLE, A PLANT MAY NEED JUST THE RIGHT AMOUNT OF RAINFALL----NOT TOO LITTLE AND NOT TOO MUCH.

THE LIMITING FACTOR PRINCIPLE IS AS FOLLOWS : -

TOO MUCH OR TOO LITTLE OF AN ABIOTIC FACTOR CAN LIMIT OR PREVENT THE GROWTH OF A POPULATION, EVEN IF ALL OTHER FACTORS ARE AT THE REQUIRED RANGE OF TOLERANCE.

SOME OF THE LIMITING FACTORS IN TERRESTRIAL ECOSYSTEMS ARE : -

• RAINFALL OR PRECIPITATION
• TEMPERATURE
• MICRO NUTRIENTS

IMPORTANT LIMITING FACTORS FOR AQUATIC  ECOSYSTEMS ARE : -

• WATER TEMPERATURE
• SUNLIGHT
• DISSOLVED OXYGEN CONTENT
• SALINITY

BALANCE IN NATURE

FOR LONG SCIENTISTS HAVE BELIEVED THAT THERE WAS AN INHERENT EQUILIBIRIUM  IN MOST ECOSYSTEMS OF NATURE. WHEN DISTURBED, AN ECOSYSTEM TRIES TO RETURN TO A STATE OF BALANCE. IN OTHER WORDS, PLANTS AND ANIMALS INTERACT SO AS TO PRODUCE A STABLE, CONTINUING SYSTEM OF LIFE ON EARTH. (MODERN ECOLOGY DOES NOT FULLY ACCEPT THIS IDEA.

IN GENERAL, THE INTERACTIONS AND PROCESSES IN THE ECOSYSTEM ATTEMPT TO MAINTAIN A BALANCE. SOME EXAMPLES ARE

• FOOD CHAINS AND FOOD WEBS ENSURE THAT POPULATIONS ARE UNDER CONTROL.
• WASTE PRODUCTS PRODUCED BY ONE SPECIES ARE USED BY ANOTHER.
• RESOURCES USED BY SOME ARE REPLENISHED BY OTHERS.
• PLANTS PRODUCE THE OXYGEN NEEDED BY ANIMALS, WHILE THE WASTE PRODUCT OF ANIMAL RESPIRATION, CARBON DIOXIDE, IS USED BY PLANTS IN PHOTOSYNTHESIS.
• THE  WATER CYCLE KEEPS THE WORLD'S WATER CIRCULATING PROVIDING WATER WHERE AND WHEN IT IS NEEDED.

THE ACTIVITIES OF HUMAN BEINGS CAN, AND FREQUENTLY DO, DISRUPT THE BALANCE OF NATURE AND AFFECT BIODIVERSITY.

DISTRIBUTION OF BIODIVERSITY IN THE WORLD

THE VAST MAJORITY OF ALL SPECIES IN THE DEVELOPING COUNTRIES. NEARLY 50 TO 75 PERCENT OF ALL SPECIES ARE TO BE FOUND IN THE TROPICAL MOIST FORESTS THAT ACCOUNT FOR JUST 6 PERCENT OF THE LAND AREA. A HANDFUL OF SOIL IN A TROPICAL FOREST CONTAINS HUNDREDS OF SPECIES AND MORE THAN A MILLION INDIVIDUAL ORGANISMS.

IN THE TROPICS AND THE SUBTROPICS, WHERE WE FIND MOST OF THE DEVELOPING COUNTRIES, THERE WAS ALWAYS AN EVOLUTIONARY ACTIVITY GIVING RISE TO A RICH BIODIVERSITY.BIODIVERSITY IS LESS IN THE COLDER NORTHERN REGIONS BECAUSE THE RECURRENT ICE AGES THERE SLOWED DOWN THE PROLIFERATION OF LIFE FORMS.

THE MEGA DIVERSITY COUNTRIES OF THE WORLD ARE : -

AUSTRALIA

ETHIOPIA

PERU

BRAZIL

INDIA

PHILIPPINES

CAMEROON

INDONESIA

SOUTH AFRICA

CHINA

MADAGASCAR

VENENZUELA

COLOMBIA

MALAYSIA

ZAIRE

COSTA RICA

MEXICO

ECUADOR

MYANMAR

THE ABOVE LIST SHOWS THAT THE MAJORITY OF THE WORLD'S BIODIVERSITY IS FOUND IN THE DEVELOPING COUNTRIES. THE GENETIC DIVERSITY NEEDED TO MAINTAIN THE WORLD AGRICULTURAL SYSTEM IS MAINLY FOUND IN THESE COUNTRIES MOST OF THE MEDICINAL PLANTS TOO ARE FOUND ONLY IN THE DEVELOPING COUNTRIES. HOWEVER, MOST OF THE BIODIVERSITY DATA HAS BEEN COLLECTED AND ANALYSED IN INSTITUTIONS THAT ARE BASED IN RICHER COUNTRIES.

MICRONUTRIENTS

MICRO NUTRIENTS ARE ESSENTIAL ELEMENTS,  WHICH LIVING ORGANISMS (INCLUDING HUMAN BODIES AND PLANTS) NEED IN VERY LOW CONCENTRATIONS FOR NORMAL GROWTH. MICRO NUTRIENTS INCLUDE VITAMINS, IRON, CHLORINE, COPPER, MANGANESE, ZINC, MOLYBDENUM, AND BORON.

MILLIONS OF PEOPLE IN POOR COUNTRIES SUFFER FROM MICRO NUTRIENT DEFICIENCY AND THE CONSEQUENT PHYSICAL AND MENTAL AILMENTS, SUCH AILMENTS INCLUDE BLINDNESS, ANAEMIA, AND MENTAL RETARDATION.

 MICRO NUTRIENTS FOR PLANTS

IRON-----------------------ESSENTIAL FOR CHLOROPHYLL SYNTHESIS

COBALT--------------------CATALYST IN FIXING NITROGEN

BORON---------------------INVOLVED IN CARBOHYDRATE TRANSPORT

CHLORINE-----------------ASSISTS PHOTOSYNTHESIS

COPPER--------------------DEFICIENCY CAUSES BROWNING OF LEAF TIPS

MOLYBDENUM------------USED FOR NITROGEN FIXATION