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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.