Ecosystem Unit 1

What is Ecosystem?Definition:- Ecosystem is defined as a structural and functional unit of biosphere consisting of community of living beings and the physical environment both interacting and exchanging materials between them.The term 'ecosystem' was coined by A.G. TansleyEcosystem is the basic functional unit in ecology.Ecology is the study of the relationship of plants and animals to their physical and biological environment. The physical environment includes light and heat or solar radiation, moisture, wind, oxygen, carbon dioxide, nutrients in soil, water, and atmosphere. The biological environment includes organisms of the same kind as well as other plants and animals.

Type of ecosystemTemporary Permanent NaturalMan madeSmallLarge

Homeostatis:-Ecosystem maintain a functional balance or relatively stable state of equilibrium among its various componentMaintained through different number of controls - Carrying capacity - self regulation- Capacity to recycle - feed back Growth of prey populationGrowth of predator population +ve -ve

Structure of Ecosystem:

Each ecosystem has two main components:

1. Abiotic componentsThe nonliving factors or the physical environment prevailing in an ecosystem form the abiotic components. They are mainly of two types:

(a) Climatic factors: Rain, temperature, light, wind, humidity.etc

(b) Edaphic factors: Soil, pH, Minerals, Topography.

2. Biotic components:

The living organisms including plants, animals, and micro-organisms (Bacteria and fungi) that are present in an ecosystem.On the basis of their role in ecosystem they are classified into two main groups:

AUTOTROPS HETEROTROPS1) producer- Any organism that can photosynthesize2) Consumer - An organism that cannot make its own energy but must acquire it by eating green plants or other consumers. 3) Decomposer - An organism that helps to breakdown and decay dead organisms and animal waste products, thereby returning nutrients into the soil.

Producers The producers are plants and some bacteria capable of producing their own food photo-synthetically or by chemical synthesis.

Autotrophs : (autotrophic = self-nourishing)

Green plants fix radiant energy in the presence of the green pigment, chlorophyll, and with the help of minerals (C, H, O, N, P, Ca, Mg, Zn, Fe etc.) taken from their soil and aerial environment ,they build up complex organic matter (carbohydrates, fats, amino acids, proteins, nucleic acids etc).

So green plants are also called as converters (or) transducers

Therefore, autotrophs are called producers.

HeterotrophsThe consumers are animals that obtain their energy and protein directly by grazing , feeding on other animals, or both.

Heterotrophs: (heterotrophic = other - nourishing)

The radiant energy is transferred to various other trophic levels like consumers.

Heterotrophic organisms, chiefly animals, which ingest other organisms (or) particulate organic matter are included in this category,

Function of ecosystem

Macroconsumers: They are of three types :1- primary consumers eg: herbivores, 2- secondary consumers eg: carnivores 3- tertiary consumers eg: Carnivores and Omnivores (Phagotrophs).

Microconsumers It includes parasites, detritivores and decomposers.

Microconsumers:- 1. Parasites: They obtain food directly from other organism of all trophic levels. Parasites cause disease and depend on the host for food.

2. Detrivores and Scavengers: Detrivores (e.g., termites, earth worms, wood lice, millipede etc) feed on organic fragments whereas, scavengers (e.g., vulture, carrion beetle) feed on dead bodies.

Scavengers and detrivores seem to be essential for quick breakdown of dead bodies of organisms.

3. Decomposers: They are mostly parasitic and saprophytic bacteria, actinomycetes and fungi

Macroconsumers:Herbivores :Some animals do not eat other animals. They survive on plants (producers) are known as herbivores.Carnivores:-Some animals eat only other animals. These animals are called carnivores. Omnivores:- Some animals eat both plants and animals. These animals are called omnivores

Trophic Levels i8n An EcosystemProducers herbivores carnivores 2nd carnivoresDecomposers T1T2 T3T4 T6

Function of Ecosystem:i) Flow of Energy: The rate of biological energy flow community varies. (ii) Nutrient Cycling: Rate of materials (or) nutrient cycles (iii) Biological (or) Ecological regulation which includes regulation of organisms by environment (eg: Photoperiodism) and regulation of environment by organisms (nitrogen fixation by organisms).

Energy Flow in an EcosystemEnergy flow is the movement of energy through an ecosystem from the external environment through a series of organism and back to the external environment.

Ecosystem is maintained by the flow of energy.

With the exception of chemosynthetic bacteria all other autotrophs obtain energy from the sun. They trap the light energy and convert it into chemical energy of organic compounds during the process of photosynthesis.

The amount of energy trapped varies from ecosystem to ecosystem.

Flow of Energy Flow of Energy

>The energy is used for their growth and maintenance. There is always loss of energy at each step of its transfer.

>Some energy is degraded into heat and dissipated (wasted)

>The flow of energy in the ecosystem is always unidirectional.

>The flow of energy follows the two laws of Thermodynamics:

>1st law of Thermodynamics states that energy can neither be created nor be destroyed but it can be transformed from one form to another.

FOOD CHAINIt is sequence of populations or organisms of an ecosystem through which the food and its contained energy passes with each member becoming the food of a later member of the sequence.All organisms, living or dead, are potential food for some other organism and thus, there is essentially no waste in the functioning of a natural ecosystem.

Some common examples of simple food chains are:

Examples :-Grass > grasshopper > Frog > Snake > Hawk (Grassland ecosystem)

Phytoplanktons > water fleas > small fish > Tuna (Pond ecosystem)

Each organism in the ecosystem is assigned a feeding level or trophic level depending on its nutritional status.

Types of food chains1. Grazing food chain: It starts with green plants (primary producers) and culminates in carnivores. Example : Grass > Rabbit > Fox Phytoplankton > Zooplantkton > Fish > Man Grass > Grasshopper >frog > snake > HawkEcosystems of such type of food chains are directly dependent on an influx of solar energy.

2. Detritus food chain: It starts with dead organic matter which the detritivores and decomposers consume. Partially decomposed dead organic matter and even the decomposers are consumed by detrivores and their predators.

Example - Mangrove and estuarine areas.Dead organic matter > Detrivores >predators.Fallen leaves and dead plants >soil mites > Insects > Fish.

Food web Food web is a network of food chains where different types of organisms are connected at different trophic levels, so that there are a number of options of eating and being eaten at each trophic level.

In ecosystems, some consumers feed on a single species, but most consumers have multiple food sources.

In this way, linear individual food chains interconnect to form a food web.

ECOLOGICAL PYRAMIDSGraphic representation of trophic structure and function of an ecosystem, starting with producers at the base and successive trophic levels forming the apex is knows as an ecological pyramid.

Types of ecological pyramids Ecological pyramids are of three types:

Pyramid of Numbers:Pyramid of Biomass: Pyramid of Energy:

Pyramid of Numbers:It represents the number of individual organisms at each trophic level. It may be upright or inverted pyramid of numbers, depending upon the type of ecosystem and food chain A grassland ecosystem and a pond ecosystem show an upright pyramid of numbers

Pyramid of biomassIt is based upon the total biomass (dry matter) at each trophic level in a food chain. The pyramid of biomass can also be upright or inverted. The pyramid of biomass in a forest is upright. The pond ecosystem shows an inverted pyramid of biomass. a) Grassland ecosystem b) pond ecosystem

Ecological pyramids at a glance

Pyramid of EnergyThe amount of energy present at each trophic level is considered for this type of pyramid. Pyramid of energy is always upright.

At every successive trophic level, there is a huge loss of energy (about 90%) in the form of heat, respiration etc.

Thus, at each next higher level only 10% of the energy passes on. Hence, there is a sharp decline in energy level of each successive trophic level as we move from Producers to top carnivores

Biogeochemical cycles Biological and geologic processes move nutrients between organic and inorganic compartments

Biogeochemical cycles are the circulation pathways of elements (e.g., carbon, oxygen, hydrogen, nitrogen or mineral elements) through the biotic and abiotic components of an ecosystem.

Biogeochemical cycle A reservoir is that portion of the earth that acts as a storehouse for the element.

An exchange pool is the portion of the environment from which producers take chemicals, such as the atmosphere or soil.

The biotic community is the pathway (i.e., food chains) through which chemicals move.

Some cycles are primarily gaseous cycles (carbon and nitrogen); others are sedimentary cycles, (phosphorus).

There are two ecological processes energy flow mineral cycling involving interaction between the physico -chemical environment and the biotic communities This is considered as the 'heart' of ecosystem.

Energy flow is always in non-cyclic manner (unidirectional) from sun to the decomposers via producers and macro consumers.

But minerals keep on moving in a cyclic manner

Hydrological Cycle(water cycle)1. Reservoir oceans, air (as water vapor), groundwater, lakes and glaciers; evaporation, wind and precipitation (rain) move water from oceans to land2. Assimilation plants absorb water from the ground, animals drink water or eat other organisms which are composed mostly of water3. Release plants transpire, animals breathe and expel liquid wastes

The carbon cycle

The carbon cycle involves the movement of carbon from the air, into plants, animals, people, the earth, and back into the air. It also includes the mining and release of carbon that was trapped in the bodies of ancient plants and animals.

Carbon Cycle(carbon is required for building organic compounds1. Reservoir atmosphere (as CO2), fossil fuels (oil, coal), durable organic materials (for example: cellulose).2. Assimilation plants use CO2 in photosynthesis; animals consume plants.3. Release plants and animals release CO2 through respiration and decomposition; CO2 is released as wood and fossil fuels are burned

The carbon cycle fits the generalized scheme of biogeochemical cycles better than water.

OXYGEN CYCLE

Nitrogen cycle The majority of Earth's atmosphere (78%) is nitrogen, making it the largest pool of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems. Nitrogen is necessary for all known forms of life on Earth. It is a component in all amino acids, as incorporated into proteins, and is present in the bases that make up nucleic acids such as RNA and DNA. In plants, much of the nitrogen is used in chlorophyll molecules, which are essential for photosynthesis and further growth. Nitrogen is present in the environment in a wide variety of chemical forms including organic nitrogen, ammonium (NH4+), nitrite (NO2-), nitrate (NO3-), nitrous oxide (N2O), nitric oxide (NO) or inorganic nitrogen gas (N2)

Nitrogen cycle 1. Reservoir atmosphere (as N2); soil (as NH4+ or ammonium, NH3 or ammonia, N02- or nitrite, N03- or nitrate2. Assimilation plants absorb nitrogen as either NH4+ or as N03-, animals obtain nitrogen by eating plants and other animals. 3. Release Denitrifying bacteria convert N03- back to N2; detrivorous bacteria convert organic compounds back to NH4+ ; animals excrete NH4+, urea, or uric acid.

Apatite, the chief source of phosphate for living systems via the phosphorous cycle.

Humans mine phosphate ores for use in fertilizer, as an animal feed supplement, and for detergents. Organisms use phosphate in phospholipids, ATP teeth bones and shells

PHOSPHORUS CYCLE1. Reservoir erosion transfers phosphorus to water and soil; sediments and rocks that accumulate on ocean floors return to the surface as a result of uplifting by geological processes2. Assimilation plants absorb inorganic PO43- (phosphate) from soils; animals obtain organic phosphorus when they eat plants and other animals3. Release plants and animals release phosphorus when they decompose; animals excrete phosphorus in their waste products

Ecological niche Ecological niche has been defined as "the range of ecological variables (e.g., temperature, moisture, etc.) in which a species can exist and reproduce." Niche can also be thought of as all the biotic and abiotic factors to which members of a population are adapted.Identifying the different niches in an ecosystem helps us to understand the interactions between populations.

Understand ecological niche The Fundamental Niche is the total niche volume determined solely by Abiotic factors

The Realized Niche is a subset of the F. Niche that an organism actually occupies the difference being the influence of Biotic factors: e.g., predators, competitors, food

Fundamental NicheIdeal niche that would exist in the absence of competition from other species is called a species' fundamental niche determined solely by Abiotic factors

Realized NicheThe actual niche that a species fills in the face of interspecific competition is called its realized niche. It is under influence of Biotic factors:

The eastern wolf now resides primarily in Canada, though its territory once extended into the northeastern United States.

The coyote now inhabits places formerly inhabited by the eastern wolf. competitive exclusion principle: Two species cannot coexist in the same habitat if they have the same niche.

The niche concept was investigated in some classic experiments in the 1930s by Gause..

He used flasks of different species of the protozoan Paramecium, which eats bacteria

Conclusion:Experiment 1)

>These two species of Paramecium share the same niche, so they compete. >P. aurelia is faster-growing, so it out-competes P. caudatum.

Experiment 2)

>These two species (P. caudatum & P. bursaria) of Paramecium have slightly different niches, so they don't compete and can coexist.

Types of ecological niche Specialists - Species with narrow niches are called specialists.Example - warblers in a coniferous forest

Generalists - Species with broad niches are called generalists.Example migrating birds

Ecological Succession

Ecosystems are not fixed, but constantly change with time. This change is called succession.A stable community is called the climax communityThe climax community is usually a forest, though this varies depending on the climate and the underlying rock.

kinds of succession:

Primary succession starts with bare rock or sand, such as behind a retreating glacier, after a volcanic eruption, following the silting of a lake or seashore, on a new sand dune, or on rock from erosion and weathering of a mountain.Eg- a lithosere, a hydrosere, Secondary succession starts with soil, but no (or only a few) species, such as in a forest clearing, following a forest fire, or when soil is deposited by a meandering river.

Classification Of Ecosystem

FORESTS

40% earth surfaceHas abiotic and biotic factors

There are three major types of forests: TropicalTemperateArtic.

Each of these major forest types have other groups of forests that are named because of the weather and seasons they have.

Tropical forests cluster near the equator. It includes evergreen rain forest and deciduous forest.

Temperate forests include coniferous, Mediterranean and rain forests.

Forest EcosystemA forest ecosystem is a natural woodland unit consisting of all plants, animals and micro-organisms (Biotic components) in that area functioning together with all of the non-living physical (abiotic) factors of the environment

Components of Forest EcosystemProducers : The trees are of different kinds depending upon the kind of the forest formation developing in that climate.

They have several climbers, shrubs and a ground vegetation.

In tropical moist deciduous forest the producers, are Tectona grandis, Butea frondosa, Shorea robusta and Anogeissus latifolia and Adina cordifolia.

temperate deciduous forests the dominant trees are Quercus, Acer, Betula

temperate coniferous forests have Abies, Picea, Pinus, Cedrus, Juniperus and wide range of flowering plants.

Consumers(a) Primary consumers: ants, flies, beetles, leafhoppers, bugs and spiders, elephants, nilgai, deer, moles, squirrels, shrews, flying foxes, fruit bats, mangooses etc.,(b) Secondary consumers. These are the top carnivores like snakes, birds, lizards, fox etc..(c) Tertiary consumers. These are the top carnivores like lion, tiger, etc.,

Decomposersfungi (Aspergillus, Coprinus, Polyporus, Ganoderma, Fusarium, Alternariq, Trichoderma etc.)

bacteria (Bacillus, Clostridium, Pseudomonas, Angiococcus etc.,)

actinomycetes

Grassland Ecosystem19% earth surfaceType of terrestrial ecosystemHas abiotic and biotic factors Abiotic factors:Nutrient in soil and aerial environmentC, H, N, O, P, S Chief elementsBiotic factors:Producers:Grass species (Dichanthium, Cynodon, Digitaria, Setaria, Sporobolus)Some shrubs and forbs

Consumers:(a) Primary consumers: Animals (cow, buffalo, deer, sheep, rabbit, mouse) and Insects (leptocorisa, dysdercus, cicincella, grashooper )(b) Secondary consumers: snakes, birds, frogs, lizards, fox etc..(c) Tertiary consumers: hawk, jackal

Decomposers:fungi (Aspergillus, Penicillium, Cladosporium, Rhizopus)bacteriaactinomycetes

Desert Ecosystem17% earth surfaceTerrestrial ecosystemRainfall less than 25 cm/ yearExtremely high temperature and water scarcityProducers:Shrubs, bushes, grasses and treesLichens and mossRoots penetrate deeply into soilConsumers:Reptiles and insectsNocturnal rodents and birdscamelDecomposers:Thermophilic bacteria and fungi

Aquatic EcosystemAquatic ecosystems dealing with water bodies and the biotic communities present in them.

Freshwater ecosystems are further another type Lentic: slow moving water, includingpools,ponds, andlakes.Lotic: faster moving water, for examplestreamsandrivers.Wetlands: areas where the soil is saturated or inundated for at least part of the time

Freshwater ecosystems are varied because they are influenced not only by local climate, soil, but also by the surrounding terrestrial ecosystems.

Pond EcosystemBiotic component:1. Producers :(a) Macrophytes : large rooted plants partly or completely submerged or floating The common plant species are Trapa, Typha, Sagittaria, Nymphara, Potamogeton, Chara, Hydrilla, Vallisheria, Utricularia, Marselia, Eicchornia, Spirodella, Lemna etc also occur in the pond.(b) Phytoplankton:filamentous algae such as Ulothrix, Spirogyra, Cladophora and Oedogonium

a. Primary consumers:Benthic populations include fish, insect larvae, beetles, mites, molluscs, crustaceans etc.mammals as cows, buffaloes, birdsZooplankton: Brachionus, Asplancha Lecane Protozoan: Euglena, Coleps, Dileptus b. Secondary consumers:insects and fishes which feed on zooplankton.c. Tertiary consumers:large fishes, ducks, spoon billsConsumers:

Decomposers:

Aspergillus, Cephalosporium, Pythium, Rhizopus, PenicilliumHelp in nutrient recycling

River EcosystemIt is a type of fresh water ecosystemIt is lotic ecosystemBiotic components:Producers:Green algae (cladophora), diatoms and mossConsumers:Fresh water sponges, caddis fly larvae, snails, flatworms, fishes, stonefly.Decomposers:bacteria and fungi

Marine EcosystemBiotic components:Producers:Brown and red algae Phytoplanktons (diatoms, micro algae and moss)Sea weedsConsumers:a. Primary consumers: molluscs and fishesb. Secondary consumers: herring, shad, mackerelc. Tertiary consumers: cod, haddockDecomposers:bacteria and fungi

Estuaries EcosystemAn estuary is a part at the mouth of a river where fresh water and sea water meet.Organisms present in estuaries show a wide range of tolerance to temperature and salinity. Biotic components:Producers:Micro algae, Phytoplankton Marsh grass, mangrooves and sea grassConsumers:a. Primary consumers: molluscs, zooplanktons, oysters, clams, mussels and fishesb. Secondary consumers: worms, amphipods and fishesc. Tertiary consumers: eel, salmon, heron, sea horse, sea trout, striped bass and sea gulls Decomposers:bacteria and fungi

Wetland EcosystemA wetland is a land area that is saturated with water, either permanently or seasonally, such that it takes on the characteristics of a distinct ecosystem water found in wetlands can be freshwater, brackish, or saltwaterThe main wetland types include swamps, marshes, bogs, and fens

Ecosystem value and services Products

FoodFuel wood Non-timber forest products Fisheries products Marine productsWetlands productsMedicinal and biomedical products Forage and agricultural productsWater ReedsBuilding material

Functions/Services

Hydrological servicesPurification of waterCapture, storage and release of surface and groundwaterMitigation of floods and droughts

BiodiversityMaintenance of biodiversity (plants and animals)

ClimatePartial stabilization of climate through carbon sequestrationModeration of temperature extremes and the force of winds and waves

Why value?Understand how much an ecosystem contributes to economic activity or society. For example, on average forests benefits in the Med region amount to about 1% of GDP. Indirect use value such as watershed protection contributes about 35% of total estimated value.

Understand what are the benefits and costs of an intervention that alters the ecosystem (conservation investment, development project, regulation or incentive) and make ecosystem goods and services comparable with other investments

Carrying capacity of an ecosystemCarrying capacity is the maximum number of organisms that can be supported in a given habitat.The carrying capacity of a biological species in an environment is the maximum population size of the species that the environment can sustain indefinitely, given the food, habitat, water and other necessities available in the environment.

Ecosystem value