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
More Definitions 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
Ecological System Concept (Concept of Ecosystem) Ecosystem is the basic structural and 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
Interactions between Organisms and Environment
Living organisms and their non-living environment are inseparable, interrelated and interact upon each other.
Specific influence of human beings on sensitive Ecosystems 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
Systems Biology A biology that sees an organism as a living system rather than a machine. Systems theory It looks at the world in terms of the interrelatedness and interdependence of all phenomena. Systems thinking is process thinking System defined A system is an object that is made up of subsystems or components, which interact in such a way that they have collectively a wholeness.
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 Systems Hierarchical System Genetic systems Cell systems Organ systems Organismic systems Population systems Ecosystems
Dynamics of ecosystems Bio-systems Energy, Gases inorganic matter water organisms Subsystems Plants animals Microbes Energy Nutrients Gases Inorganic matter Inputs Outputs
Gaseous Nutrient 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
Energy flow in an Ecosystem Solar energy Photosynthesis Solar energy is converted to chemical energy Respiration Chemical energy is used to do work Ecosystem Degraded Waste Energy
Primary Production Phototrophs (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 Production All biomass produced per unit of time by organisms called consumers.
Primary – Rate of photo synthesis by green plants.
Secondary – The energy stored at consumer level for use.
Ecological succession Progressive changes in community structure and function. Ecosystem Regulation The ecosystem tries to resist change and maintain itself in equilibrium is called Homeostasis.
Production (Stored biomass) Gross Production Producers Photosynthetic Production Secondary Production Respiration Decomposers Consumers and Decomposers Respiration Tissue growth Relationship between plant and animal production Respiration Tissue growth
3.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.
Ecosystem goods and services 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)
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. Hawks Hyperparasites (microbes) Frogs Parasites (Lice, bugs) Insects Birds Grasses Tree s
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
Functional Attributes Food 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 Herbivore Heat Produced Decomposers Simple Food – Chain Model
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
Food chains maintain energy flow and nutrient cycling.
Food chains maintain ecological balance by regulating population size.
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 Lenti c Lo t ic e.g. Ponds, Lakes e.g. Streams, Rivers Coastal ecosystems Mangrove ecosystems Seagrass ecosystems Coastal lagoon ecosystems Coral reef ecosystems Delta ecosystems Estuarine ecosystems Sandy beach ecosystems Rockyshore ecosystems Coastal upwelling ecosystems
Forest Ecosystem 1. Abiotic Component Amount of rainfall and local temperature varies according to latitude, and altitude. 2. Biotic Component Plants – trees, shrubs, climbers and ground cover. Animals – mammals, birds, reptiles amphibians, fish insects and microscopic animals.