COMMUNITIES AND
ECOSYSTEMS
COMMUNITIES AND ECOSYSTEMS
• COMMUNITY-LEVEL ECOLOGY
– COMMUNITY
• DEF ??
• DEFINING CHARACTERISTICS OF A COMMUNITY
–
–
–
–
DIVERSITY (BIO-DIVERSITY)
PREVALENT FORMS OF VEGETATION
RESPONSE TO DISTURBANCES
TROPHIC STRUCTURE
COMMUNITIES AND ECOSYSTEMS
• BIODIVERSITY
– THE VARIETY OF DIFFERENT OF DIFFERENT KINDS
OF ORGANISMS THAT MAKE UP A COMMUNITY
– 2 COMPONENTS
• SPECIES RICHNESS
• RELATIVE ABUNDANCE
COMMUNITIES AND ECOSYSTEMS
• TROPHIC STRUCTURE
– THE FEEDING
RELATIONSHIPS AMONG
THE VARIOUS SPECIES
MAKING UP THE
COMMUNITY
COMMUNITIES AND ECOSYSTEMS
• COMPETITION MAY OCCUR WHEN A SHARED
RESOURCE IS LIMITED
– INTERSPECIFIC COMPETITION
• TWO DIFFERENT SPECIES COMPETING FOR THE SAME
RESOURCE
– COMPETITIVE EXCLUSION PRINCIPLE
• TWO SPECIES, SO SIMILAR, THAT THEY COMPETE FOR
THE SAME LIMITING RESOURCES CANNOT CO-EXIST IN
THE SAME PLACE
COMMUNITIES AND ECOSYSTEMS
• COMPETITIVE EXCLUSION PRINCIPLE
COMMUNITIES AND ECOSYSTEMS
• COMPETITIVE EXCLUSION PRINCIPLE LEADS TO
THE FORMATION OF NICHES
– NICHE
• A SPECIES’ ROLE IN ITS COMMUNITY; OR THE SUM
TOTAL OF ITS USE OF THE BIOTIC AND ABIOTIC
RESOURCES OF ITS HABITAT
• 1 SPECIES PER NICHE RULE!!!!!!!
COMMUNITIES AND ECOSYSTEMS
• 1 SPECIES PER NICHE RULE LEADS TO
RESOURCE PARTITIONING
– THE
DIFFERENTIATION
OF NICHES THAT
ENABLES
SIMILAR
SPECIES TO
COEXIST IN A
COMMUNITY
COMMUNITIES AND ECOSYSTEMS
• PREDATION LEADS TO DIVERSE ADAPTATIONS IN BOTH
PREDATOR AND PREY
– PREDATION
• DEF 
– PREDATOR
• DEF 
– PREY
• DEF 
– PARASITISM
• A PARASITE LIVES ON, OR IN, ITS HOST AND OBTAINS ITS NUTRITION
FROM THE HOST; MAY BE CONSIDERED A FORM OF PREDATION
– CO-EVOLUTION
• A SERIES OF RECIPROCAL ADAPTATIONS IN TWO SPECIES
COMMUNITIES AND ECOSYSTEMS
• PREDATION CAN LEAD TO UNUSUAL
RELATIONSHIPS
– MIMICRY
• ONE SPECIES COMES TO LOOK LIKE ANOTHER,
UNRELATED, SPECIES
• TWO MAJOR FORMS
– BATESIAN MIMICRY VS MULLERIAN MIMICRY
COMMUNITIES AND ECOSYSTEMS
BATESIAN MIMICRY
MULLERIAN MIMICRY
COMMUNITIES AND ECOSYSTEMS
• PREDATION HELPS MAINTAIN DIVERSITY IN
COMMUNITIES
– KEYSTONE SPECIES
• A SPECIES THAT EXERTS A STRONG CONTROL ON
COMMUNITY STRUCTURE BECAUSE OF ITS ECOLOGICAL
ROLE, OR NICHE
COMMUNITIES
AND ECOSYSTEMS
PREDATION HELPS
MAINTAIN DIVERSITY IN
COMMUNITIES
KEYSTONE SPECIES
A SPECIES THAT
EXERTS A
STRONG
CONTROL ON
COMMUNITY
STRUCTURE
BECAUSE OF ITS
ECOLOGICAL
ROLE, OR NICHE
COMMUNITIES AND ECOSYSTEMS
• SYMBIOTIC RELATIONSHIPS HELP STRUCTURE
COMMUNITIES
• SYMBIOTIC RELATIONSHIPS
– AN INTERACTION
BETWEEN TWO
OR MORE SPECIES
THAT LIVE
TOGETHER IN
DIRECT CONTACT
COMMUNITIES AND ECOSYSTEMS
• SYMBIOTIC RELATIONSHIPS
– 3 MAJOR TYPES
• PARASITISM
• COMMENSALISM
• MUTUALISM
COMMUNITIES AND ECOSYSTEMS
COMMUNITIES AND ECOSYSTEMS
• DISTURBANCE IS A PROMINENT FEATURE OF MOST
COMMUNITIES
– DISTURBANCE
• EVENTS SUCH AS
STORMS, FIRE,
FLOODS,
DROUGHTS,
OVERGRAZING, OR
HUMAN ACTIVITIES
THAT DAMAGE
BIOLOGICAL
COMMUNITIES,
REMOVE
ORGANISMS FROM
THEM, AND ALTER
THE AVAILABILITY OF
RESOURCES
COMMUNITIES AND ECOSYSTEMS
• DISTURBANCES CAN LEAD TO ECOLOGICAL
SUCCESSION
– ECOLOGICAL
SUCCESSION
• TRANSITION IN
A SPECIES
COMPOSITION
IN A
COMMUNITY
COMMUNITIES AND ECOSYSTEMS
• ECOLOGICAL SUCCESSION
– TWO LEVELS
• PRIMARY SUCCESSION
– A COMMUNITY
ARISES IN A
VIRTUALLY LIFELESS
ARE WITH NO SOIL
COMMUNITIES AND ECOSYSTEMS
• ECOLOGICAL SUCCESSION
– TWO LEVELS
• SECONDARY SUCCESSION
– WHEN A DISTURBANCE HAS DESTROYED EXISITING
COMMUNITY BUT LEFT THE SOIL INTACT
COMMUNITIES AND ECOSYSTEMS
• ECOLOGICAL SUCCESSION
– EVENTUALLY RESULTS IN A CLIMAX COMMUNITY
• A PERMANENT FINAL STAGE IN SUCCESSION; MATURE,
STABLE COMMUNITIES THAT WILL PERSIST
INDEFINITELY
COMMUNITIES AND ECOSYSTEMS
• STANDARD ECOLOGICAL SUCCESSION
EXAMPLES INCLUDE
COMMUNITIES AND ECOSYSTEMS
• NOT ALL DISTURBANCES ARE NECESSARILY A
BAD THING
COMMUNITIES AND ECOSYSTEMS
• ECOSYSTEM-LEVEL ECOLOGY
– ECOSYSTEM
• A BIOTIC
COMMUNITY AND
THE ABIOTIC
ENVIRONMENT
WITH WHICH IT
INTERACTS
COMMUNITIES AND ECOSYSTEMS
• ENERGY FLOW AND CHEMICAL CYCLING ARE THE TWO
FUNDAMENTAL PROCESSES IN ECOSYSTEMS
– ENERGY FLOW
• THE PASSAGE OF ENERGY
THROUGH THE
COMPONENTS OF THE
ECOSYSTEM
– CHEMICAL CYCLING
• THE CIRCULAR MOVEMENT
OF MATERIALS WITHIN
THE ECOSYSTEM
– **ENERGY FLOWS IN AND OUT, WHEREAS CHEMICALS
ARE RECYCLED
COMMUNITIES AND ECOSYSTEMS
• TROPHIC STRUCTURE IS A KEY FACTOR IN
ECOSYSTEM DYNAMICS
– TROPHIC STRUCTURE
• A PATTERN OF FEEDING
RELATIONSHIPS
– FOOD CHAIN
• THE SEQUENCE OF FOOD
TRANSFER FROM TROPHIC
LEVEL TO TROPHIC LEVEL
COMMUNITIES AND ECOSYSTEMS
• TROPHIC STRUCTURE
– PRODUCERS 
– PRIMARY CONSUMERS 
– SECONDARY CONSUMERS 
– TERTIARY/QUATERNARY CONSUMERS 
– DETRITIVORES 
– SCAVENGERS VS DECOMPOSERS 
COMMUNITIES AND ECOSYSTEMS
• FOOD CHAINS
INTERCONNENT,
FORMING FOOD WEBS
– A NETWORK OF
INTERCONNECTING
FOOD CHAINS
COMMUNITIES AND ECOSYSTEMS
• ENERGY SUPPLY LIMITS THE LENGTH OF FOOD
CHAINS
– BIOMASS
• THE AMOUNT,
OR MASS, OF
LIVING
ORGANIC
MATERIAL IN AN
ECOSYSTEM
– WHY ARE THERE
SO FEWER
TERTIARY
CONSUMERS??
COMMUNITIES AND ECOSYSTEMS
• ENERGY SUPPLY LIMITS THE LENGTH OF FOOD
CHAINS
– PRIMARY PRODUCTIVITY
• THE AMOUNT OF SOLAR ENERGY CONVERTED TO
CHEMICAL ENERGY (ORGANIC COMPOUNDS) BY AN
ECOSYSTEMS AUTOTROPHS DURING A GIVEN TIME
PERIOD
COMMUNITIES AND ECOSYSTEMS
• ENERGY SUPPLY LIMITS THE LENGTH OF FOOD
CHAINS
– RULE OF 10
• ONLY 10% OF ENERGY IS PASSED TO NEXT TROPHIC
LEVEL
– PRODUCTION
PYRAMID
• MEAT
IS
A
LUXURY!
COMMUNITIES AND ECOSYSTEMS
• CHEMICALS ARE RECYCLED BETWEEN
ORGANIC MATTER AND ABIOTIC RESERVOIRS
– THE PART OF THE ECOSYSTEM WHERE A
CHEMICAL ACCUMULATES OR IS STOCKPILED
OUTSIDE OF LIVING ORGANISMS
COMMUNITIES AND ECOSYSTEMS
COMMUNITIES AND ECOSYSTEMS
COMMUNITIES AND ECOSYSTEMS
COMMUNITIES AND ECOSYSTEMS
COMMUNITIES AND ECOSYSTEMS
• EUTROPHICATION
– ADDING NUTRIENTS IN PONDS AND LAKES
CAUSES PHOTOSYNTHETIC ORGANISMS TO
RAPIDLY MULTIPLY
COMMUNITIES AND ECOSYSTEMS
• HUMANS CAUSE A LOT OF PROBLEMS!! WHAT
CAN WE DO TO ALLEVIATE THESE PROBLEMS?
WELL, WE
NEED TO SKIP
A CHAPTER TO
FIND OUT…
BUT DON’T
WORRY, WE’LL
COME BACK
TO IT 