1. BIOGEOGRAPHY
Theme 3:
THE STRUCTURE OF ECOYSYSTEMS
AND THE SUSTAINABILITY OF
BIOGEOGRAPHICAL ENVIRONMENTS

2. Lectures 7-9

3. ECOSYSTEM COMPONENTS
 ECOSYSTEMS CONSIST OF TWO MAIN
COMPONENTS:
 - ABIOTIC (N0N-LIVING)
 - BIOTIC (LIVING)

4. ABIOTIC COMPONENT
 PLANTS AND ANIMALS ARE DEPENDENT ON
THE PHYSICAL ENVIRONMENT FOR SURVIVAL
AND CERTAIN FACTORS SET CERTAIN LIMITS
FOR SURVIVAL:
 - WATER/MOISTURE
 - TEMPERATURE
 - LIGHT
 - SOIL CONTAINING NUTRIENTS
 - ATMOSPHERE CONTAINING NUTRIENTS
 - TOPOGRAPHY
 - FIRE
 - SALINITY OF WATER

5. WATER
 IMPORTANT FOR ALL FORMS OF LIFE
 COVERS 70% OF EARTH’S SURFACE
 97% OF THIS WATER OCCURS IN OCEANS
 2% OCCURS AS ICE
 0.2% OCCURS AS FRESHWATER WHICH
OCCURS IN RIVERS, LAKES AND DAMS
 1% OF THIS FRESHWATER CIRCULATES
THROUGH THE HYDROLOGICAL CYCLE AND IT
IS THIS WATER THAT IS USED IN ECOSYSTEMS
 0.5% OCCURS AS GROUNDWATER

6. WATER AND PLANTS
 WATER IS ONE OF THE MAIN REASONS THAT
DETERMINES WHAT PLANT TYPES ARE FOUND
IN AN AREA:
 HYDROPHYTES: PLANTS THAT LIVE IN WATER
 XEROPHYTES: PLANTS THAT OCCUR IN DRY
AREAS AND STORE WATER IN THEIR PLANT
CELLS
 MESOPHYTES: OCCUR WHERE THERE IS A
GOOD SUPPLY OF WATER OR WHERE THERE
ARE WET AND DRY SPELLS (SEASONAL
DIFFERENCES)

8. TEMPERATURE
 FOR BOTH PLANTS AND ANIMALS THE
FOLLOWING IS IMPORTANT:
 TEMPERATURE OF SOIL AND AIR
 THEY EXHIBIT A LOW TOLERANCE FOR
 TEMPERATURE VARIATIONS
 THEY USUALLY OCCUR WHERE TEMPERATURE
LIE BETWEEN 0 °C - 50 °C BUT ARE MOST
ACTIVE BETWEEN 5 °C - 35 °C

9. TEMPERATURE
 ANIMALS ARE AFFECTED MORE THAN PLANTS BY
TEMPERATURES:
 ANIMALS MAKE CERTAIN ADAPTATIONS:
 ENDOTHERMS OR HOMOIOTHERMS: ANIMALS CONTROL
THEIR BODY TEMPERATURE
 ECTOTHERMS OR POIKILOTHERMS: BODY
TEMPERATURE CAN CHANGE IN RELATION TO
ENVIRONMENTAL FACTORS
 ORGANISMS REACT IN 4 WAYS TO CHANGES IN
TEMPERATURE:
 STAY(HIBERNATE OR ESTIVATE)
 MIGRATE
 ADAPT
 BECOME EXTINCT

12. Map of the principal world vegetation types

13. LIGHT
 EXHIBITS VARIATIONS IN SPACE AND TIME
 NECESSARY FOR ALL LIFE PROCESSES
ESPECIALLY PHOTOSYNTHESIS IN PLANTS
 QUANTITY OF LIGHT AS WELL AS QUALITY OF
LIGHT ARE IMPORTANT
 NOT ALL PLANTS NEED THE SAME QUANTITY
OR QUALITY OF LIGHT TO GROW
SUCCESSFULLY

14. SOIL
 CHEMICAL COMPOSITION OF SOIL IS VERY IMPORTANT
 VERY IMPORTANT IN TERRESTRIAL ECOSYSTEMS
 SOIL IS THE GROWTH MEDIUM FOR PLANTS AND
PROVIDES PLANTS WITH NECESSARY NUTRIENTS TO
SURVIVE
 CONSIDERED TO BE A MORE PERMANENT AND LESS
CHANGEABLE PART OF THE ECOSYSTEM
 SOIL TEMPERATURE IS CRITICAL FOR PLANT GROWTH
 ACIDITY OR ALKALINITY OF SOIL IS IMPORTANT FOR
PLANT GROWTH

15. SOIL AND NUTRIENTS
 SOIL IS THE GROWTH MEDIUM FOR ALL
PLANTS:
o DISSOLVED INORGANIC MATERIAL
o MINERALS
o GASES
o WATER
o LIVING ORGANISMS
o DEAD PLANT MATERIAL (HUMUS)

16. SOIL FORMING FACTORS:
 THE FOLLOWING ARE THE MOST IMPORTANT
SOIL FORMING FACTORS:
- GEOLOGICAL SUBSTRATA
- CLIMATE
- TOPOGRAPHY
- LIVING ORGANISMS
- TIME

19. ATMOSPHERE
 CONSISTS OF A MIXTURE OF GASES
IMPORTANT FOR USE BY PLANTS:
 OXYGEN FOR RESPIRATION
 CARBON DIOXIDE FOR PHOTOSYNTHESIS
 NITROGEN FOR THE MANUFACTURE OF
PROTEINS
 WATER VAPOUR FOR CERTAIN CHEMICAL
REACTIONS
 WIND ALSO PLAYS AN IMPORTANT ROLE IN
POLLINATION

20. TOPOGRAPHY
 ORIENTATION OF SLOPES MAY INFLUENCE THE
AMOUNT OF SUNSHINE PRESENT AND ALSO
THE TEMPERATURE
 THIS IN TURN INFLUENCES THE TYPE OF
PLANTS PRESENT IN AN AREA
 SOUTHERN HEMISPHERE:
o WARM NORTH FACING SLOPES
o COLDER SOUTH FACING SLOPES

21. FIRE
 FIRE IS A VERY IMPORTANT ECOLOGICAL
FACTOR AND OCCURS IN TERRESTRAIL
ECOSYSTEMS
 Natural fires (Usually caused by lightning)
o not always detrimental to vegetation
o vegetation can adapt - pyrophytes
o seasonal fires in savanna grasslands
 Unnatural fires (caused mainly by man):
o usually cause great damage
o can be controlled by man in burning programmes

22. SALINITY OF WATER
 USUALLY AFFECTS MARINE AND AQUATIC
ECOSYSTEMS
 OCCURS MAINLY AT RIVER MOUTHS,
ESTUARIES AND INLAND AREAS
 TO SURVIVE IN SALINE CONDITIONS
ORGANISMS MUST MAKE ADAPTATIONS
 VERY FEW ORGANISMS CAN LIVE IN BOTH SALT
AND FRESHWATER SYSTEMS FOR LONG
PERIODS OF TIME

23. BIOTIC COMPONENT
 THE FOLLOWING BIOTIC ELEMENTS ARE
IMPORTANT
 PLANTS
 ANIMALS
 MAN
 THE BIOTIC ELEMENT FORMS A SORT OF CYCLE
 THESE ELEMENTS CAN BE CLASSIFIED ACCORDING TO :
o THE FLOW OF MATTER THROUGH THE ECOSYSTEM IN
THE FORM OF BIOCHEMICAL CYCLING, OR
o THE FLOW OF ENERGY THROUGH THE ECOSYSTEM

24. BIOTIC ELEMENTS
 THE FOLLOWING BIOTIC ELEMENTS ARE
IMPORTANT:
 AUTOTROPHS OR PRODUCERS: THESE ARE THE GREEN
PLANTS THAT PRODUCE THEIR OWN FOOD
 HETEROTROPHS OR COMSUMERS: THESE ARE ORGANISMS
THAT EAT THE PLANTS OR OTHER ANIMALS. HERE WE CAN
DISTINGUISH BETWEEN:
o PRIMARY CONSUMERS = HERBIVORES
o SECONDARY CONSUMERS = CARNIVORES OR OMNIVORES
o DECOMPOSERS OR DETRIVORES FOR EXAMPLE BACTERIA,
FUNGI ETC.

26. BIOTIC CYCLE
 IN THE BIOTIC CYCLE NO ORGANISM CAN LIVE
IN ISOLATION
 THE BIOTIC ENVIRONMENT IS THEREFORE:
o FIRSTLY A PRODUCT OF THE INTERACTIONS BETWEEN
ORGANISMS AND THEIR ABIOTIC HABITAT, AND
o SECONDLY A PRODUCT OF THE INTERACTIONS BETWEEN
ORGANISMS OF EITHER THE SAME SPECIES OR ORGANISMS OF
DIFFERENT SPECIES
 THERE ARE THEREFORE DIFFERENT TYPES OF
BIOTIC INTERACTIONS

27. HIERARCHICAL NATURE OF THE
BIOTIC ELEMENT
 SPECIES:
A GROUP OF PLANTS OR ANIMALS WHICH MATE
SUCCESSFULLY WITH OTHER MEMBERS OF THEIR GROUP
 POPULATION:
A NUMBER OF INDIVIDUALS OF THE SAME SPECIES
WHICH OCCUR IN A CERTAIN AREA E.G. A HERD OF BUCK
 COMMUNITY:
A GROUP OF PLANT OR ANIMALS POPULATIONS WHICH
LIVE IN HARMONY TOGERTHER IN A CERTAIN AREA

29. MAN AS AN ECOLOGICAL FACTOR:
THE ECOLOGICAL DOMINANT
 MAN IS CONSIDERED TO BE THE MOST IMPORTANT
FACTOR IN THE ENVIRONMENT BECAUSE:
o HIS INFLUENCE IS NOT CONSTANT
o HIS BEHAVIOUR CANNOT BE PREDICTED
o HIS INFLUENCE IS OFTEN NEGATIVE
o HE OFTEN DESTROYS
o HE CAN CREATE NEW HABITATS OR DESTROY OTHERS
 IN OTHER WORDS HE DOMINATES THE
ENVIRONMENT AND BY ASSOCIATION THE
ECOSYSTEMS WITHIN WHICH HE LIVES