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Concepts of Ecology
Definition
Ecology is the scientific study of interaction between living systems and their environment
Objective Ecology discovers and understands
the relationship between living things and their environment
Hilaire, 1835 -Milieu ambient (French)
Haeckel, 1866 – Science associated with life
Elton, 1927 – Scientific natural history
Shelford, 1929 – Science of communities
Andrewartha, 1961 – Study of the distribution and abundance of organisms
Odum, 1963 – Study of structure and functions of
nature
More Definitions
Ecologis
t A person who studies ecology
e.g., Plant ecologist, Animal ecologist, Terrestrial / Aquatic
ecologist, Palaeo-ecologist,
Mathematical ecologist, Systems ecologist,
Chemical ecologist, Social ecologist, Anthropo-
ecologist, Autecologist, Synecologist.
TEN RULES IN ECOLOGY1. Ecology is a Science.
2. Ecology is only understandable in the light of evolution.
3. Nothing happens ‘for the good of the species’.
4. Genes and environment are both important.
5. Understanding complexity requires models.
6. ‘Story telling’ is dangerous.
7. There are hierarchies of explanations.
8. There are multiple constraints on organisms.
9. Chance is important.
10. The boundaries of physical environment are in the mind of the Ecologist.
Branches of EcologyHabitat ecology Desert ecology
Grassland ecologyFreshwater ecologyForest ecologyCropland ecologyMarine ecology
Population ecologyCommunity ecologyEcosystem ecologyProduction ecologyConservation ecologyRadiation ecologyPalaeoecologyGene ecologySystems ecologyMicrobial ecology
Concept of Concept of EnvironmentEnvironment
Definition
The total surrounding of an organism. Environment is an interacting system of physical, chemical, biological social and cultural elements.
Attributes 1. Environmental systems usually do not have well defined
boundaries.2. Environmental characteristics change over a gradient.3. Environmental system is open because it receives inputs
from and gives outputs to other systems.4. Environment ultimately determines the quality and survival
of life.
Lithosphere
- Solid earth
Divisions Environment
Physical environment
Biotic environment
Hydrosphere Atmosphere
- Water - Gaseous envelope
Biosphere
Flora Fauna
- Plants, microbes Animals
Ecological System Concept(Concept of Ecosystem)
Ecosystem is the basic structural andEcosystem is the basic structural and functional unit of ecology.functional unit of ecology.
“Ecosystems are the basic units of nature on the face of the earth”.
An ecosystem is an ecological unit, or a subdivision of the landscape, or a geographic area that is relatively homogeneous and reasonably distinct from adjacent areas.
J.W. Marr, 1961
Tansley, 1935
Definition
Ecosystem – another view
• Ecosystem is a spatial functional structure• The space may be geographically large or
small
• Largest ecosystem. e.g., Planet earth• Smallest ecosystem (microcosm):• e.g. a handful of soil and moss in a sealed
jar.
Components of an EcosystemAbiotic components-
(geographical, climatic, (geographical, climatic, physicochemical physicochemical
characteristics)characteristics) Biotic components-
(Plants, animals, microbes) (Plants, animals, microbes)
Ecological Cycle
Ecosystem Structure
Living organisms and their non-living environment are inseparable, interrelated and interact upon each other.
Interactions between Organismsand Environment
Mountain ecosystem – Removal of forest cover
Evergreen forests – Over exploitation of forest resources
Coral reefs – Human interference, Dynamite fishing
River ecosystem – Pollution
Land ecosystem – Dumping solid wastes
Specific influence of human beings on sensitive
Ecosystems
Properties of Ecological Systems
1. Networks –Interdependence, diversity, complexity
2. Boundaries- Scale and limits3. Cycles – Recycling of resources and
partnership4. Flow –through – Energy and resources5. Development – Succession and co-evolution6. Dynamic balance- Self – organization,
flexibility, stability, sustainability
Systems Systems BiologyBiology
A biology that sees an organism as a living system rather than a machine.
Systems theoryIt looks at the world in terms of the interrelatedness and interdependence of all phenomena.
Systems thinking is process thinking
System definedA system is an object that is made up
of subsystems or components, which interact in such a way that they have collectively a wholeness.
Salient features of system concept
1. There is a collection of elements (subsystems) in a system.
2. The components (subsystems) and their processes are organized.
3. The interactions between the subsystems are repeated in time and space.
4. There is unidirectional flow of energy and matter.
• A healthy system is self-regulating based A healthy system is self-regulating based upon upon the feed-back control from subsystems.the feed-back control from subsystems.
Examples : Animal social systems – An Ant hill, a bee hive,
a termite mound.Human social systems – a family.
SystemSystem
InputsInputs OutputsOutputs
Simple System Simple System ModelModel
System
Feedback A cybernetic system is a collection of parts or events that acts as a single thing and regulates its activities about an ideal state or set point
Cybernetic systems use feedback to maintain this ideal state.
The feedback that causes the adjustment to the set point is called negative feedback.
Cybernetic systems can also display positive feedback.
Positive feedback is a continually increasing tendency away from the system’s set point.
Systems Concept
A system consists of a set of interdependent subsystems enclosed in a defined boundary.
A system receives inputs and outputs.
An input is any resource from outside to which the system responds.
An output is any attribute transmitted to the environment.
A system has feed back mechanism, which provides a degree of control (or homeostasis)
Positive feedback
Set point
Negative feedback
Deficiency
Excess
Negative feedback
Death
Positive feedback
Death
Homeostatic Plateau
A Cybernetic system of Ecosystem Regulation
Systems Concept
NutrientsGasesH2O
Radiant Energy
NutrientsGases
H2O
Bio-systems
Producers consumers
Decomposers(Cycling of energy and
matter)
Outputs
Inputs
Biotic compone
nt 1
Biotic compone
nt2
Biotic component
3
Input
Output
Ecosystem
Output
Input
Output
Input
Output
Nutrient Flow model
System X Y Z
SubsystemX
Subsystem Y
Subsystem Z
Inputs Outputs
Open system with components
Plant Cow ManInput
Sunlight
Output - Input
Chemical energy in
leaves
Output - input
Chemical energy in meat of cow
Output
Heat given
off during
Series open system components
Features of an open Features of an open systemsystem Open systems process inputs and produce outputs
The amount of output produced is directly related to the amount of input received.
Features of Complex systems
• Complex systems are composed of many interconnected and interacting subunits.
• They are capable of adaptation and self-organization.
Open systems
All living systems are open systems.
A cell is an open system because it constantly acquires food from outside itself and eliminates wastes.
It gives off heat as it carries on chemical processes (respiration).
Biological Biological SystemsSystems Hierarchical SystemHierarchical System
Genetic systems
Cell systems
Organ systems
Organismic systems
Population systems
Ecosystems
Dynamics of ecosystems Bio-systems
Energy, Gases
inorganic matterwater
organisms
Subsystems
Plants animals
Microbes
Energy Nutrients
GasesInorganic
matter
Inputs Outputs
GaseousNutrient cycles
Sedimentary nutrient cycles
Biogeochemical cycles and population
– Evolution spiral
Outputs
Heat radiated
into space
Inputs
Sunlight (energy
)
The earth as a single system
Earth Ecosystem
Functional aspects
Inputs Energy,
Nutrients, Gases,
Inorganic matter
Photosynthesis
HerbivoryCarnivory
Decomposition
EnergyNutrients Gases, Inorganic matter
Outputs
Biosystems
Solar energy
PhotosynthesisSolar energy is converted to chemical energy
RespirationChemical energy is used to do
work
Ecosystem
Degraded Waste Energy
Energy flow in an Ecosystem
Primary Primary ProductionProductionPhototrophs (Plants) – The rate of photosynthesis
per unit of time.Gross Production – Quantity of organic matter produced per unit of time.Net Production – Gross P – metabolic losses (respiration,
excretion)
Secondary ProductionSecondary ProductionAll biomass produced per unit of time by organisms called consumers.
Primary and Secondary Production Primary – Rate of photo synthesis by green plants. Secondary – The energy stored at consumer level for use.
Ecological successionProgressive changes in community structure
and function.
Ecosystem RegulationThe ecosystem tries to resist
change and maintain itself in equilibrium is called Homeostasis.
Production (Stored biomass)
Gross Production
Producers Photosynthetic Production
Secondary Production
RespirationDecomposers
Consumers and
Decomposers
Respiration Tissue growth
Respiration Tissue growth
Relationship between plant and Relationship between plant and animal productionanimal production
Properties of Bio-systemsProperties of Bio-systems 1. It is intrinsically dynamic, flexible, open systems.
2. There is cyclical patterns of information flow.
3. The structure and function are established by the system itself (self-organising system).
4. It exhibits a certain degree of autonomy.
5. There is self-transformation and self-transcendence.
6. It has a high degree of stability (Homeostasis).
7. There is a state of continual fluctuations within limits.
8. It has the ability to adapt to changing environment.
9. It exhibits self-maintenance which includes the processes of self-renewal, healing, homeostasis and adaptation.
1.Energy cycles – Ecological pyramids2.Food chains, food webs and trophic
structure3.Diversity of organisms – Variety and
variability.4.Nutrient cycles – biogeochemical cycle
e.g. Water cycle, Carbon cycle, Oxygen cycle, Nitrogen cycle.
5. Ecosystem development and regulation.
Functional aspects of Bio-systems
Direct values
Consumptive use value – Non-market value of fruits, fodder, firewood, small timber etc.(People collect them from their surrounds and use them)
Productive use value – Commercial value of timber, fish, medicinal plants etc.
(People collect for sale)
Ecosystem goods and services
Indirect values
• Non-consumptive use value – Scientific research, watching wildlife, ecotourism, jungle safaris etc.
• Option value – Maintaining options for the future – Preserving and reaping the economic benefits in the future.
• Existence value – Ethical and emotional aspects of the existence of wildlife and nature.
Ecological Pyramids
Pyramid of numbers: No of individuals at each trophic level
Graphic representation of tropic structure and function of an ecosystem.
HawksHyperparasites (microbes)
FrogsParasites (Lice, bugs)
InsectsBirds
GrassesTrees
Pyramid of biomass: Total biomass (dry matter) at each tropic level
Fox
Rabbit
Herbs
Pyramid of energy:Amount of energy present at each trophic level.
Top Carnivores
Carnivores
Herbivores
Producers
Energy Energy relationshiprelationship
Energy cycleEnergy cycle
Nutrient cycling
Cycling of DDT
At every trophic level there is 90% loss of energy (respiration, activity).
Only 10% energy is transferred from one trophic level to the other.
There is one-way flow of energy.
Nutrient Cycling
Nutrients like C, N, S, O, H, P etc.
Move in circular paths.
Hydrological cycle
Nitrogen cycle
Carbon cycle
Phosphorous cycle
Energy flow in an ecosystem
Hydrologic cycling
Biogeochemical Cycling
Functional AttributesFood chains
The sequence of feeding relationships in an ecosystem is called food chain.
Trophic structure
Each organism in the ecosystem is assigned a feed level or trophic level.
Simple food web model
Producer : Pond grass
Herbivore : Water insects
Carnivore : Large fish
Herbivore : Small fish
Carnivore : Duck
Top Carnivore : Man
Sunlight
Producer
Carnivore
HerbivoreHeat
ProducedDecompose
rs
Simple Food – Chain Model
Kinds of food chain 1. Grazing food chain – Starts with green plants and ends with carnivores.
Grass Rabbit Fox
2. Detritus food chain – Starts with dead organic matter and ends with predators.
Mangrove ecosystem
Leaf litter Saprotrophs / detritivores (crabs) Small carnivorous fish Large Carnivorous fish
- a complex inter connected network of food chains at different trophic
levels.
Food web
Significance of food chain
1.Food chains maintain energy flow and nutrient cycling.
2.Food chains maintain ecological balance by regulating population size.
3.Food chains biologically magnify toxicity of some chemicals.
Kinds of Ecosystems
Ecosystem
Terrestrial Aquatic Man-engineered
e.g. Forest, Desert Grassland, Steppe, Savanna
e.g. Agricultural land use, Urban / industrial land use
Freshwater Marine
Lentic Lotic e.g. Ponds, Lakes
e.g. Streams, Rivers
Coastal ecosystemsMangrove ecosystemsSeagrass ecosystemsCoastal lagoon ecosystemsCoral reef ecosystemsDelta ecosystemsEstuarine ecosystemsSandy beach ecosystemsRockyshore ecosystemsCoastal upwelling ecosystems
Ecosystems
Forest EcosystemForest Ecosystem 1. 1. Abiotic Abiotic ComponentComponentAmount of rainfall and local
temperature varies according to latitude, and altitude.
2. 2. Biotic ComponentBiotic Component
Plants – trees, shrubs, climbers and ground cover.
Animals – mammals, birds, reptiles amphibians, fish insects and microscopic animals.
Kinds of Forests• Coniferous
e.g. Himalayan region -needle –like leave forests.• Tropical rain forests
e.g. Western Ghats –broad–leaved forest.• Deciduous forests – e.g. Teak trees• Thorn forests – e.g. Semi – arid.• Mangrove forests – e.g. River deltas.
Forest servicesForest services Natural forests control local climate and water regimes. Forest vegetation helps recycle nutrients. Forest prevent erosion of soil. Forests control flow of water in streams and rivers. Forests absorb carbon dioxide and release oxygen that we breathe.
Forest services - cont’d
Forests maintain gene banks of wild relatives.
Forest supply food, fodder, medicine, timber, poles and fuel wood as well as raw materials for industry.
Forests and wilderness areas are valued as sites of natural and cultural heritage as well as education and recreation.
Ecotourism is a vital source of income for some countries.
The Grassland ecosystemThe Grassland ecosystem1.Abiotic Components – C, H, O, N,
P, S. are supplied by Carbon dioxide, Nitrate, Phosphates and Sulphates.
2. Biotic ComponentsProducers – grasses, few herbs and shrubs.Primary consumers – grassing animals- cows,
deers, rabbit.Secondary consumers – snake, lizard, birds, Jackels.Tertiary consumers – hawks.Decomposers – bacteria.
Desert ecosystemDesert ecosystem
1.Abiotic components – High temperature, low rainfall dry climate.
2. Biotic componentsProducers – Shrubs, bushes, grasses, few trees.
Consumers – Insects, reptiles, birds, camels.
Decomposers – Fungi, bacteria.
Aquatic ecosystem1.Abiotic components – Temperature, light, pH, organic and inorganic matter.
2.Biotic components Producers – Macrophytes, Phytoplankton.
Consumers – Zooplankton (insects, fish), Herbivores.Decomposers – Bacteria, Fungi.
e.g. Industrial areas, Cities and Towns.
Urban EcosystemEcosystems in which man lives and works.
Control of man over land ecosystem
Approx 11 percent of earth’s land surface is intensely managed.
30 percent moderately managed.
59 percent only slightly utilized.
General Features
Urban Ecosystem
1. Most intensively managed ecosystem by man.
2. Approx. 20 percent of world population lives in urban regions.
3. The city is an open ecosystem.4. Inputs include air, water, energy
(food, fuel), natural resources, and people.
5. Outputs include products, waste, garbage heat, people, ideas, education, technology,
6. Numerous feedback loops or cycles.Keep various city subsystems in balance.
Outputs City
Ecosystems
Inputs
Typical urban ecosystem model
Ecosystem distress Syndrome(Indicators of Ecosystem)
1. Altered primary production.2. Altered rates of decomposition.3. Altered rates of nutrient cycling.4. Reduced efficiency of energy
cycling.5. Increased frequency of disease.6. Changed amplitude of fluctuations.7. Reduced species diversity.8. Retrogression to opportunist /
weedy / pest species.9. Size, enlargement in natural abiotic
zones.
Threats from Agricultural Ecosystems Ecological simplicity – large monocultures. Ecosystem instability. High degree of biological uniformity (minimum genetic variability). Widespread disease outbreaks or pest infestations. Depletion of fertilizers (nutrients) and energy (fossil
fuels). Elimination of other crop species and other ecosystems.