CONCEPT OF AN ECO SYSTEM

Dr.R.Priscilla, HoD of Physics, ADM. College for Women, Nagapattinam.

Eco System The various communities of living interact among themselves As well as with their physical environment like , air and water. This functional unit or ‘system’ made up of living and non-living components is called an ‘’. This term ‘ecosystem’ was coined by Tansley in 1935. The interaction is through and cycling of materials. *This makes the ecosystem to sustain life continuously. *An eco system may be of any size. i.e, the whole world may be considered as an ecosystem called biosphere. *They are natural but some man made and none of the eco system is independent but all of them are interdependent.

Structure and function of an ecosystem

Two major components

1. The which includes the physical environment.

2. The comprising of all the living organisms. ABIOTIC COMPONENTS BIOTIC COMPONENTS

Sunlight Primary producers

Temperature

Precipitation

Water or moisture

Soil or water chemistry (e.g., P, NH4+)

etc. etc. Abiotic component consists of

1. the solid mineral matter of the earth(lithosphere) 2. the water in the oceans, lakes, rivers and ice caps etc.(hydrosphere). 3.the gaseous mixture in the air(atmosphere) and 4. the radiant solar energy. The environment created and maintained by the interactions of the common environmental factors, function as a whole unit. Any of these factors cannot be removed or altered without affecting the other factors. Therefore, the environment is called HOLISTIC. Producers, consumers and

Biotic Component – the organisms of are divided into two classes.

1. The producers: (green plants & certain bacteria) – produce their own food. Since these organisms produce food for all the other organisms they are also known as producers.

2. consumers: Heterotrops – depends on the producers for the food. Depends directly or indirectly upon the autotrophs for their food.

Consumers Decomposers.

Consumers are of three kinds.

They are

1. Primary consumers 2. Secondary consumers 3. tertiary consumers. Primary consumers - a is a primary . - it derives its nutrition directly from plants Secondary consumers - a is a secondary consumer. - it derives its energy from the producers (plants) Tertiary consumers - they are Carnivores that feed on other carnivores. Omnivores are consumers that derive their energy from both producers and herbivores.

Decomposers

- consists of bacteria and fungi. - produce enzyme within their bodies. - act on dead plant & animal material and some of the degraded and digested products and then absorbed. - perform an invaluable service to the ecosystem by the mineralization of organic matter and made available for reuse.

The process of eating and being eaten forms a chain. Producer  herbivore  carnivore  carnivore – back to producers.

The position of the in the is indicated by tropic levels.

Tropic level may be defined as the no. of links by which it is separated from the producer.  Grass -» Grasshopper -» Lizard -» Snakes -» Hawks.  Grass -» Mice -» Snakes -» Hawks  Grass -» Rabbits -» Dogs -» Tigers/Lions.  Trees -» Deer/Goats -» Foxes -» Tigers/Lions.  Trees -» Birds -» Snakes -» Hawks.  Phytoplankton -» Larvae -» Fishes -» Whales. First Tropic Level – producers 2nd Tropic Level – herbivores 3rd Tropic Level – carnivores  The same organism may operate in the ecosystem at more than one tropic level,i.e, deriving food from more than one source.  An organism may be eaten by several organisms of a higher tropic level or an organism at a lower tropic level may feed upon several different organisms.  Thus we obtain several food chains linked together and intersecting each other to form a network known as Energy flow in a Eco system

Energy flow : In any eco system, for their structural development and functioning obtain energy from a group of organisms that are already present in a particular system.

1.Energy travels only through single way 2.There is reduction of energy in each tropic level

* Energy level is const. for every ecosystem * One cannot increase or decrease the energy level * Can be converted into one state to another state * A portion of energy remains unused during the conversion of energy * After conversion its reaction capacity gets reduced. * Because of this, there is flow of energy from higher tropic level to the lower tropic level. * A part of the radiant energy of the sunlight is converted into chemical energy by the producers and is stored in the organic compounds * The rest of the radiant energy is converted into heat energy. Food Chains, Food Webs and Ecological Pyramids. Food Chains : The transfer of food energy from producers (plants) through a series of organisms, i.e, Herbivores Carnivores  Top carnivores  Decomposers with repeated eating and being eaten is known as a food chain. It is also called as .

Example : In grassland ecosystem, the food chain starts from grasses and goes through the grasshopper, calotes, snake and the eagle or hawk in an orderly sequence.

Food webs

Though many food chains can be traced in an ecosystem they never operate as isolated sequences. But they are interconnected with each other forming some interlocking pattern. This is known as food web. Ecological Pyramids The interrelation between numbers, and energy contents of consumersof the first order, second order and upto the top carnivores in any ecosystem is represented in diagrammtic ways. They are called as ecological pyramids. They are of three Ecologicaltypes, viz., Pyramids

Pyramid of Pyramid of Pyramid of numbers biomass energy

1. Pyramid of numbers :

The relationship between the number of producers and the primary, secondary and tertiary consumers constitutes the pyramid of numbers.  

Tiger or lion(Top carnivores)

   Fox (Sec.carnivores)  

Rabbit(Pri.consumer)

       

                                  Grasses(Pri. Producer)                         

Grassland ecosystem shows upright pyramid In the grassland ecosystem the wide base of the pyramid represents the large number of primary producers.

 The primary consumers like the rabbit and the grasshopper form the second large number.

 The top carnivores like the tiger is present in the least number and occupy the peak of the pyramid.

 So in this way the numbers are represented in a diagramatic way and an upright pyramid is formed. Pyramid of Biomass

 Biomass is the amount of living organisms and living matter present in a particular ecosystem Tiger

 In grassland ecosysytem, the Biomass of the producers is the Fox highest of all the trophic levels. Grasses Pyramid of Biomass in Grassland Ecosystem  Here, not only the number decreases but the biomass also continue to decrease from primary producers to the top carnivores.

 The relationship between the biomass of producers and the consumers of the ecosystem can again be represented in the form of upright pyramids. Pyramid of energy

______Carnivores(Tertiary consumers)

______Carnivores(Sec.consumers)

______Herbivores (Pri.consumers)

______Producers In an ecosystem the primary producers trap the sunlight energy and convert into chemical energy through .

 The energy traped in the food materials flow in the food chain from the producers to the herbivores and then to carnivores and finally to top carnivores.

 Here the energy flow is always unidirectional and at successive trophic levels it decreases.

 Therefore the pyramid of energy is always vertical. The components of a forest ecosystem are

 Abiotic components – organic and inorganic matter present in the land and atmosphere.

 Biotic components – living flora and fauna are the living cpts. of a forest. They are recognized as Producers consumers Decomposers Producers:

* trees are the primary producers.

* Vines and epiphytes are the two characteristics of evergreen forest.

* In India tropical evergreen forest are found along the West Ghats and the NEFA Consumers: *The macro consumers (animals) in different forests are well adapted for the conditions prevailing there.

*Foliage arthropods such as ants, flies, beetles, leaf hoppers, bugs and spiders are found.

*Moles, squirrels, fruit bats, mongooses are also present. Decomposers:

The soil organisms found in the forest are protozoan, flat worms, nematodes, annelids, snails, millipedes, centipedes, spiders, spring tails, termites, trips and ants.

Some of the soil organisms and soil bacteria play the role of decomposers. :

*Different types of forest vary in gross productivity

*The plants and other autotrophic organisms store some dry matter by their photosynthetic activity. The rate at which this dry matter is stored in the ecosystem is called the primary productivity.

*The productivity is the highest due to the stable environment, large availability of water and high constant temperature.

Pond Ecosystem :

Ponds are small bodies of shallow standing water. They are characterized by relatively quite waters and abundant vegetation. A pond serves as a good example for a fresh water ecosystem. It consists of both abiotic and biotic components. The chief components of abiotic components are heat, light, pH value, organic and inorganic compounds namely carbon di oxide, oxygen, calcium, nitrogen, phosphates, amino acids, humic acids, etc. The amount of these components are estimated for biomass determination. The various organisms of the biotic components are producers, consumers and decomposers.

Producers – larger hydrophytes and phytoplanktons which are minute floating plants. Consumers – primary consumers (insect larvae, fish, mollies, zooplanktons), secondary consumers ( insects and fish ) and tertiary consumers (large fish).

Decomposers – microbes such as bacteria, actinomycetes and fungi. They bring about the of complex dead organic matter to simple forms.

 The term was first coined by the entomologist E.O. Wilson in 1986.  A neologism from and diversity, it refers to the variety of life on the planet.  There is no single standard definition for biodiversity.

 1. Biodiversity may be defined as the totality of different organisms, the genes they contain, and the ecosystems they form.  2. The Convention on Biological Diversity defines biodiversity as the variability among living organisms from all sources including, among other things, terrestrial, marine, and other aquatic ecosystems and the ecological complexes of which they are a part; this includes diversity within species, between species and of ecosystems.

 Biodiversity may be considered at three levels: genetic diversity, , and

Genetic diversity

 refers to the differences in genetic make-up between distinct species, as well as the genetic variations within a single species. This is the least visible and, arguably, least studied level of biological diversity.  Genetic diversity is the variety present at the level of genes. Genes, made of DNA, are the building blocks that determine how an organism will develop and what its traits and abilities will be.  This level of diversity can differ by alleles (different variants of the same gene, such as blue or brown eyes), by entire genes (which determine traits,  such as the ability to metabolize a particular substance), or by units larger than genes such as chromosomal structure.  More genetic diversity in a species or population means a greater ability for some of the individuals in it to adapt to changes in the environment.  Less diversity leads to uniformity, which is a problem in the long term, as it is unlikely that any individual in the population would be able to adapt to changing conditions.  As an example, modern agricultural practices use monocultures, which are large cultures of genetically identical plants.  This is an advantage when is comes to growing and harvesting crops , but can be a problem when a disease or parasite attacks the field, as every plant in the field will be susceptible.  Monocultures are also unable to deal well with changing conditions.

 Within species, genetic diversity often increases with environmental variability, which can be expected.  If the environment often changes, different genes will have an advantage at different times or places.  In this situation genetic diversity remains high because many genes are in the population at any given time.  If the environment didn't change, then the small number of genes that had an advantage in that unchanging environment would spread at the cost of the others, causing a drop in genetic diversity.  Since the gene is the fundamental unit of natural selection, and thus of , some scientists argue that the real unit of biodiversity is genetic diversity.

Species diversity

- the number of species within a particular sample area. in combination with)  Species evenness - this refers to the evenness in number of individuals of each species in the area  E.g. for two sample areas X and Y, there are two species, a, and b. In X, there are 92 individuals of species a, and only 8 of species b, while in Y, there are 50 individuals of each species.  If species richness only was used to account for species diversity in X, the diversity might seem lower than Y (although both have the same number of species), because almost all the individuals encountered would be from only one species.  Species evenness in conjunction with species richness is thus a more useful indicator of species diversity, because it takes into account rarer species.  The number of species currently described on earth is between 1.4 and 1.7 million but the Global Diversity Assessment suggests a conservative estimate of 1.75 million.  On land there are more species known than in the sea.  This is largely due to the extraordinary diversity of beetles (Coleoptera);400,000 species are described.  An important aspect of species diversity is , that is, the species occurring in a restricted locality).  The Antarctic has a higher degree of endemism than the Arctic.  When biodiversity is measured quantitatively, usually as the number of species or the value of a diversity index for a given or area of , it is known as ecosystem diversity.  Ecosystem is defined as a dynamic complex of plant, animal and micro-organism communities and their non-living environment interacting as a functional unit.  Habitat diversity is a more useful term than the of ecosystem diversity since are easy to envisage(e.g forest, a coral reef, an estuary).  All species are presumed to interact with each other and to be competing for similar limiting resources.  Ecologists have called this within habitat (or alpha) diversity.  At slightly larger scales habitat and / or community boundaries are crossed and sampling covers more than one habitat and community.  This scale has been called between habitat (or beta) diversity.  At an even larger scale (regional scale) where evolutionary rather than ecological processes operate the pattern has been called gamma diversity or more recently landscape diversity.  Landscape diversity can be defined as the mosaic of habitat over larger scales often hundreds of km.  Biodiversity assessment need to be made at the community habits and landscape levels if we are to predict changes over time.  It is primarily the loss of habitats that leads to both genetic and species diversity.  Therefore, species diversity can be assessed in terms of the number of species or the range of different types of species an area contains.  Current estimates for the total number of species in existence vary from 5 million to nearly 100 million.  About 1.7 million of these species have been identified to date. A complete and current inventory of species is impossible because many invertebrates, and lower plants (the three most diverse life-forms) have not yet been identified and named.  There has been a definite bias towards describing large organisms, those that are considered attractive or appealing (such as flowering plants and butterflies), those most closely resembling humans (vertebrates, especially mammals), and those that have a direct impact on human activities  Organisms that can be studied without complex procedures or expensive equipment have also taken precedence, as have those which are relatively easy to locate.  This, however, underestimates the importance of microorganisms including algae, bacteria, fungi, protozoa and viruses, which are vital to life on Earth.  So far, less than 3-5 percent of microorganisms have been described.

Values of biodiversity  Consumptive use  Productive use  Social value  Ethical value  Aesthetic value  Option value India – A Mega Diversity Zone

 Genetic diversity  Ecological diversity  Forest of India  Plant diversity  Animal diversity Thank You