Ecology & Ecosystems

Environmental StudiesUnit-2

Ecology and Ecosystems

Ecology is the scientific study of relations that living organisms have with respect to each other and their natural environment.

Under ecology, we study various ecosystems which are a part of the biosphere.

An ecosystem includes all the organisms and the nonliving environment that are found in a particular place.

Ecological Succession

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Ecological Succession

Ecological succession is the observed process of change in the species structure of an ecological community over time.

Ecological succession occurs when the conditions of an environment suddenly and drastically change. 2

Trophic Levels

• A tropic level is the position occupied by an organism in a food chain.Trophic levels can be analyzed on an energy pyramid.• Producers are found at the base of the pyramid and compromise the first trophic level. • Primary consumers make up the second trophic level.• Secondary consumers make up the third trophic level.• Finally tertiary consumers make up the top trophic level.

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Food Chain

A food chain shows the feeding relationship between different living things in a particular habitat.

Food chains show how energy is passed from the sun to producers, from producers to consumers, and from consumers to decomposers.

In any ecosystem, many food chains overlap. When this happens, the food chain forms a food web.

Grazing Food ChainThe "grazing" food chain includes the producers and consumers that cycle energy from living plants. The "detritus" food chain cycles energy from non-living remains of both plants and animals (also called detritus).

The "grazing" food chain has a number of steps that start with the producers, or the plants, and flows through a series of levels of consumers.

At each step only about 10% of the energy is passed up through the chain. The rest is passed back into the atmosphere as heat through breathing and decomposition.

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In the first step plants convert the sun’s energy to chemical energy through a process called photosynthesis. The chemical energy is stored both as food and as structural elements in the plant. The next step involves the primary consumers, animals that eat only plants.

At step three are the secondary consumers, also called predators; these animals eat primary consumers.

At step four are the tertiary consumers that eat secondary consumers, and sometimes primary consumers as well

Detritus food chain

The "detritus" food chain cycles energy from non-living remains of both plants and animals (also called detritus).The "detritus" food chain is a system where the energy produced by the breakdown of dead plant and animal matter is cycled into the "grazing" food chain. Detritus is organic matter formed by decaying animal or plant tissue, or fecal matter. Detritus eaters (or detritivores) such as insects, worms and other small organisms feed on dead plants, waste products from animals and dead animals. Decomposers are fungal or bacterial organisms that work within the dead material to help break it down, activating decay and decomposition. This important part of the ecosystem takes the last of the energy that was originally absorbed by the plants and returns it to the soil.

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Characteristics of Detritus Food Chain a)Primary source of energy is dead organic matter called 'detritus' which are fallen leaves, plant parts or dead animal bodies.

b) Primary consumers are 'detritivores' including protozoans, bacteria, fungi, etc which feed upon the detritus saprophytically.

c) Detritivores are in turn eaten by secondary consumers such as insect larvae, nematodes, etc.

d) Detritus food chains are generally shorter than grazing food chains

e) In nature, detritus food chains are vital as the dead organic matter of grazing food chain is acted upon by the detritivores to recycle the inorganic elements into the ecosystem.

PRODUCERS

GRASS

GRASS

PRIMARY CONSUMERS

SECONDARY CONSUMERS

CARNIVORES

DEER

HERBIVORES

LION

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Food Web

Food Webs are Food Chains that intersect each other. Food webs are what really happens in nature.

A predator from one food chain may be linked to the prey of another food chain

Several food chains linked together

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Ecological pyramids

An ecological pyramid is a graphical representation designed to show…….

the number of organisms, energy relationships, and biomass of an ecosystem. They are also called Eltonian pyramids after Charles

Elton, who developed the concept of ecological pyramids.

Charles Elton (1927) developed the concept of ecological pyramids who noted that "…the animals at the base of a food chain are relatively abundant while those at the end are relatively few in number…"

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Producer organisms (usually green plants) form the base of the pyramid,

With succeeding levels above representing the different trophic levels (respective position of the organisms within ecological food chains).

Succeeding levels in the pyramid represent the dependence of the organisms at a given level on the organisms at lower level.

There are three types of pyramids:

of numbers, of biomass, and of energy.

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Pyramid of Biomass

Biomass is (is the mass of living biological organisms in a given area or ecosystem at a given time) renewable organic (living) material.

A pyramid of biomass is a representation of the amount of energy contained in biomass, at different trophic levels for a particular time.

It is measured in grams per meter2, or calories per meter2. This demonstrates the amount of matter lost between trophic levels.

Each level is dependent on its lower level for energy, hence the lower level determines how much energy will be available to the upper level. Also, energy is lost in transfer so the amount of energy is less higher up the pyramid.

There are two types of biomass pyramids: upright and inverted.

An upright pyramid is one where the combined weight of producers is larger than the combined weight of consumers. An example is a forest ecosystem.

An inverted pyramid is one where the combined weight of producers is smaller than the combined weight of consumers. An example is an aquatic ecosystem.

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Pyramid of Numbers The pyramid of numbers represents the number of organisms in each trophic level.

This pyramid consists of a plot of relationships between the number herbivores (primary consumers), first level carnivore (secondary consumers), second level carnivore (tertiary consumers) and so forth. This shape varies from ecosystem to ecosystem because the number of organisms at each level is variable

Upright, partly upright and inverted are the three types of pyramids of numbers. An aquatic ecosystem is an example of upright pyramid where the number of

organisms becomes fewer and fewer higher up in the pyramid. A forest ecosystem is an example of a partially upright pyramid, as fewer

producers support more primary consumers, but there are less secondary and tertiary consumers.

An inverted pyramid of numbers is one where the number of organisms depending on the lower levels grows closer toward the apex. A parasitic food chain is an example.

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Pyramid of EnergyThe pyramid of energy represents the total amount of energy consumed by each trophic level. An energy pyramid is always upright as the total amount of energy available for utilization in the layers above is less than the energy available in the lower levels. This happens because during energy transfer from lower to higher levels, some energy is always lost.

Ecosystem

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Functions of Natural Ecosystem

Air pollution are tapped by leaves of tree and convert into harmless compounds

Waste water gets filtrated through the natural soil and make drinkable

Types Of Ecosystems

Forest EcosystemGrassland EcosystemDesert EcosystemAquatic EcosystemEstuarine Ecosystem

Forest Ecosystem

A forest ecosystem is a terrestrial unit of living organisms.

All interacting among themselves and with the environment (soil, climate, water and light) in which they live.

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Types Of Forest Ecosystems

Tropical Rain Forest( Average rain fall: <150cm/year) Temp: 18oCWarmed , humid, high diversity of

animal, plant, insects

Tropical Deciduous Forest (Rain fall: 100-120cm/yr)Climate is not evenly distributed

Temperate Deciduous (cold climate, annual temp: 7-15oC)Summer is very hot and winter is very coldTall decidous tree

Boreal Forest/TIAGA/CONIFEROUS

Climate is very coldRainfall: 100mm to 350 mm

Temperate Rain forestVery coldWinter rain fallSummer is very hot and Dry

Functions Forest Ecosystems

Enhance the water resources in both quality and quantity

Hydrological cycle depend on the forest ecosystem

Forest gives shelter to wildlife and fishConsidered as a pathway for exchange and

regulation of atmospheric gases, water and trace elements

Coniferous forest of Alaska Tropical rain forest

Deciduous Forest15

Grassland Ecosystem

Grasslands are areas where the vegetation is dominated by grasses

Types Of Grassland Ecosystem

Tropical and Savannas grasslands

Tropical and subtropical grasslands, savannas, and shrublands are a grassland terrestrial biome located in semi-arid to semi-humid climate regions of subtropical and tropical latitudes.

Tropical grasslands include the savanna usually associated with Africa, and savanna-type grasslands found in India, Australia, Nepal and the Americas.

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Temperate grasslands Temperature: warm to hot season (often with a cold to

freezing season in winter) Soil: fertile with rich nutrients and minerals Plants: grass; trees or shrubs in savanna and shrubland Animals: large, grazing mammals; birds; reptiles Rain fall: 25-60cm/yr Although large areas have now been converted to

agriculture, in the past temperate grasslands were home to herds of large grazing animals such as bison, deer or kangaroos.

North America, the steppes of Russia and the pampas of Argentina.

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Flooded Grass land Flooded grasslands and savannas is a

terrestrial biome. Its component ecoregions are generally

located at subtropical and tropical latitudes, which are flooded seasonally or year-round.

A common term is swamp.

CharacteristicsFlooded grasslands are characterized by: very wet to saturated soil moisture

content in nutrient rich soils. in temperate—warm to tropical—hot

climates. They are found as grasslands, savannas,

and wetlands.18

Tundra Biome

Tundra is the coldest of all the biomes. Tundra comes from the Spanish word tunturia, meaning treeless plain. It is noted for its frost-molded landscapes, extremely low temperatures, little precipitation, poor nutrients, and short growing seasons. The two major nutrients are nitrogen and phosphorus. Nitrogen is created by biological fixation, and phosphorus is created by precipitation. Tundra is separated into two types: arctic tundra and alpine tundra. characteristics Extremely cold climate Low biotic diversity Simple vegetation structure Short season of growth and reproductionEnergy and nutrients in the form of dead organic material

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Arctic

Arctic tundra is located in the northern hemisphere, encircling the north pole and extending south to the coniferous forests of the taiga.

The arctic is known for its cold, desert-like conditions.

The growing season ranges from 50 to 60 days.

The average winter temperature is -34° C (-30° F), but the average summer temperature is 3-12° C (37-54° F) which enables this biome to sustain life.

Rainfall may vary in different regions of the arctic. Yearly precipitation, including melting snow, is 15 to 25 cm (6 to 10 inches). Soil is formed slowly.

Alpine Alpine tundra is located on mountains throughout the world at high altitude where trees cannot grow. The growing season is approximately 180 days Mammals: pikas, marmots, mountain goats, sheep, elk Birds: grouselike birds Insects: springtails, beetles, grasshoppers, butterflies

Montane

High-altitude grasslands located on high mountain ranges around the world, like the Páramo of the Andes Mountains. They are part of the montane grasslands and shrublands biome and also constitute tundra.

Desert and xericAlso called desert grasslands, this is composed of sparse grassland ecoregions located in the deserts and xeric shrublands biome

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Desert Ecosystem

A desert ecosystem exists where there is little rainfall and the climate is extreme in harshness.

It occupies about 17% of the earth’s surface.

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Types Of Desert Ecosystem

Temperate Deserts: Sahara in Africa, Thar in RajasthanTropical Deserts: Mojave in south CaliforniaCold Deserts: Gobi desert in China

Components of desert Ecosystem

A biotic components: Nutrition's present in the soil and aerial environment

Biotic Components:

Producers: There are shrubs, Grasses and few trees. Some time few cacti

Consumers: Reptiles, Insects, Birds mammals and camels

Decomposers: There are very few, as due to poor vegetation the amount of dead organic matter is less.

There are few fungi and most of them are thermophlic

Thar DesertSahara Desert

Mojave in south CaliforniaGobi desert in China

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Aquatic Ecosystem

It is an ecosystem located in a water bodies.

The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems. 23

Types Of Aquatic Ecosystem

Freshwater Ecosystem

1. Pond ecosystem2. Lake ecosystem3. Stream

4. Riverine Ecosystem 5. Fresh water marshes ecosystem

On the basis of water flow, fresh water ecosystem classified into two

- Lentic ecosystem (Standing water

bodies)

- Lotic ecosystem (Running or flowing

water bodies)

LOTIC ECOSYSTEMS Lotic ecosystem may be perennial or seasonal Perennials occasionally subjected to floods which

cause damage to the surrounding areas Lotic series distinguished by continued flow of water in

one direction Lotic systems are richer in oxygen and nutrients than

lentic systems

Egs:Spring,Stream or river ecosystems

LENTIC ECOSYSTEM

It may be perennial or seasonal Oxygen content in the surface water to a depth of 3-

5 meters is enough to support life In deeper levels oxygen is less and biological

activities decreases In bottom levels anaerobic conditions prevail and

organisms that can thrive under such conditions are found at this depth

Egs: Lake,Pond,Swamp,Reservoirs etc

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POND ECOSYSTEM

It is a simplest fresh water aquatic ecosystem

It is a small body of standing shallow water

It may receive enough water during rainy season

It is a self sufficient & self regulatory ecosystem

Life span of small seasonal ponds ranges from a few weeks or months Life span of larger ponds are several hundred yearsPond water contain a mixture of living organisms, both plants & animals, and inorganic and organic components.

LAKE ECOSYSTEMBig and natural fresh water bodies with standing water

Functions like a giant permanent pond

Lakes are formed when precipitation run-off or ground water seepage fills up depressions in the land formed by geological changes.

ZONATION

A large lake has four zones(depending on the depth).They are: - LITTORAL: upper zone ,shallow water near the shore of lake. -LIMNETIC: open water away from the shore of lake. -PROFOUNDAL:deep water,too dark,not found plants or algae. -BENTHIC: bottom of the lake.

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Types of LakeArtificial lake: Due to construction Obligotrophic lake: Low nutrition concentrationMasotrphic: Moderate NutritionEutrophic: More amount of Nutrition : Dal LakeDystrophic lake: Brown water with low pH and humic acidDesert salt lake: High concentration of Salts: Sambhar lake RajasthanVolcanic lake: It occures by volcano: JapanMeromictic lake : Rich in salt

RIVER AND STREAM ECOSYSTEM

They are flowing fresh water bodies.

Flowing water follows distinct “channels”.

Small channels – STREAMS

Large channels – RIVERS

Plants and animals live in streams and rivers depend upon the movement and speed of the water.

FRESHWATER MARSHES ECOSYSTEM

It tend to be naturally fertile ecosystem.

It is valuable in maintaining water tables in adjacent ecosystems.

Periodic fluctuations in water levels resulting from seasonal and annual rainfall variation often accomplishes tidal like actions in terms of maintaining long range stability and fertility.

Marine Ecosystem

70% world cover by the water and 97% of this water is available in oceans and Seas.

They play key role in survival of 2,50,000 species

Oceans are major sinks of CO2 and play important role in Carbon cycle, Hydrological cycle

Major ocean: Pacific, Atlantic, Indian, Arctic

Pacific: Largest and cover 1/3 part of Earth

Coastal Zone: Relatively warmer, Nutrition rich shallow water with sunlight and high production

Open Sea: Deeper part of ocean and away from submerged part of Continent is called continental shelf.

Euphotic zone: Received Enough light Bathyal Zone: Dim light Abyssal Zone: 1.5 to 5 km deep dark zone. No solar energy

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Components of marine ecosystem

Abiotic Components: Salt concentration in open sea is usually 3.5 % while dominant ions are sodium, chloride, sulpher magnasium and calciumBiotic components:

Producers: phytoplanktons : macro and micro algae, cynobacteriaConsumers: Herbivorous and Carnivores and top carnivorous Decomposers: Bacteria and fungi

Biogeochemical CyclesBiogeochemical Cycles

Biogeochemical Cyclesdescribe the flow of essential elementsessential elements from the environment through living

organisms and back into the environment.

The biogeochemical cycle is the continuous flow of elements and compounds between organisms and the earth

Types of cycles

Hydrological cycle: deal with the interchange of water with organisms and environment

Gaseous cycle: Deal with inter change with gases

Sedimentary cycle: Deals with SO4 and PO4 cycle and concern with the interchange of nutrition and minerals

Elemental CyclesH, O, and C make up > 99 % of the Earth’s biomassN, Ca, K, Mg, S, and P are significant nutrientsCycling of C, O, N, P, and S are discussed in this chapter

Concepts in Biogeo. Cycles Reservoir - where material or mass is stored Flux: rate of flow of material Steady state: inflow = outflow Dynamic state: fluxes are reservoirs are changing

with time Residence time: length of time a chemical stays in a

reservoir Feedback: positive and negative

Hydrological cycle

1. Reservoir – oceans, air (as water vapor), groundwater, lakes and glaciers; evaporation, wind and precipitation (rain) move water from oceans to land.

2. Assimilation – plants absorb water from the ground, animals drink water or eat other organisms which are composed mostly of water.

3. Release – plants transpire, animals breathe and expel liquid wastes.

Steps

Evaporation and transpiration

Condensation and formation of cloud: Rising air current all the vapour up into the atmosphere cool formation of cloud cloud is made

up of droplet of water

Precipitation: Snow or rain fall

Run off and collection of under ground water

Infiltration and percolation

Hydrological Cycle

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Human Impact

Pollution of waterReduces the vegetation cover increases the surface ran off decreases the percolationGlobal warmingHeavy deforestation reduces the transpiration loss of water through plants and trees

Carbon cycle

Earth atmosphere contains 0.03% of CO2

CO2 is the basic source of carbon and constitutes of all organic material

It found in caves ands mines and also evolves from volcanoes

Reservoirs of Carbon

Carbon is found in all four spheresBiosphere - organic matterAtmosphere - CO2, CH4

Hydrosphere - H2CO3 ,HCO3 - , CO3 =

Lithosphere - CaCO3 , coal, oil, and gasProcesses: photosynthesis, formation of sediments, weathering, combustion, plate tectonicsDecay of organic material

Carbon CycleCarbon Cycle(carbon is required for building organic compounds)

1. 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.

Carbon Cycle

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Human Interference

Human-induced processesExtraction and combustion of fossil fuels (speeds up the medium-term cycling)

Cement manufacturing

Deforestation (biomass burning)

All of these processes release CO2 into the atmosphere and affect the natural cycling of carbon

Nitrogen cycle

Nitrogen is an essential constituent of animals and plants.Green plant combined with Nitrogen and carbohydrates to make proteins and Nucleic acid78 %Not directly used most form of lifeTaken by Process called nitrogen fixation

Nitrogen CycleNitrogen Cycle(Nitrogen is required for the manufacture of

amino acids and nucleic acids)

1. Reservoir – atmosphere (as N2); soil (as NH4+ or

ammonium, NH3 or ammonia, N02- or

nitrite, N03- or nitrate

Nitrogen CycleNitrogen Cycle2. Assimilation – plants absorb nitrogen as either

NH4+ or as N03

-, animals obtain nitrogen by eating plants and other animals. The stages in the assimilation of nitrogen are as follows:

Steps

Nitrogen fixation

Ammonification

Nitrification and Denitrification

Nitrogen fixation

Nitrogen Fixation: N2 to NH4+

by nitrogen-fixing bacteria (prokaryotes in the soil and root nodules), N2 to N03

- by lightning and UV radiation.

1. Biological : Nitrogen fixing bacteria2. Industrial fixation: fertilizer3. Electrification( N2 + O2-- Nitrogen Oxide

Amonification: Amino acid and urea- Ammonia

Nitrification: 1. Nitrogen fixation

Combination of Nitrogen with other element

2. AmmonificationOrganic Nitrogen- NH3

3. Nitrification and denitrificationAmmonia(NH3)- ----- Nitrite forming bacteria(Nitromonas)----- Nitrite(NO2)

Nitrite(NO2)--------Nitrobacter--------------- Nitrate

Nitrate(NO3)--------Denitrification(Pseudomonas)--- Nitrogen

Nitrogen CycleNitrogen Cycle3. Release – Denitrifying bacteria convert N03

- back

to N2 (denitrification); detrivorous bacteria convert organic compounds back to NH4

+ (ammonification); animals

excrete NH4+

(or NH3) urea, or uric acid.

Nitrogen Cycle

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Human ImpactHarvesting of timber Automobile and industrial exhaustAcid rain is caused by emissions of sulfur dioxide and nitrogen oxide, which react with the water molecules in the atmosphere to produce acids.

NO2 + OH· → HNO3

Eutrophication

Oxygen Cycle

Essential for aerobic lifeClosely linked to carbon cycleVery large reservoir (21% of gas in atm.), not susceptible to human interferenceAlso, not a greenhouse gasReservoirs: atmosphere, surface organic material (biosphere), and buried organic matter (lithosphere)

Oxygen Cycle

Processes Photosynthesis/ respiration: short-term cycle; balanced on land; excess O2 in ocean -phytoplanktons

Mineral oxidation, weathering, burial - removes O2 from atmosphere

Combustion or weathering of organic matter - removes O2 from atmosphere

Atmosphere => marine biota => sediments => rocks => atmosphere (fig )

Oxygen Cycle

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Phosphorus Cycle

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Phosphorus CyclePhosphorus Cycle(Phosphorus is required for the manufacture

of ATP and all nucleic acids)

1. 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 processes

2. Assimilation – plants absorb inorganic PO43-

(phosphate) from soils; animals obtain organic phosphorus when they plants and other animals

3. Release – plants and animals release phosphorus when they decompose; animals excrete phosphorus in their waste products

Phosphorus CyclePhosphorus Cycle

1. 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 processes

2. Assimilation – plants absorb inorganic PO4

3- (phosphate) from

soils; animals obtain organic phosphorus when they plants and other animals

3. Release – plants and animals release phosphorus when they decompose; animals excrete phosphorus in their waste products

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Biogeochemical cycles of other minerals, such as calcium and magnesium, are similar to the phosphorus cycle.

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33. https://lh4.ggpht.com/OuvgkVuf6hIxtMC8KZ1aiJmiSscQ3MfjqPR0BHrhNkjLNzt9wE_RNXsLPraJtHPm32kDS1U=s97

Book/Web Resources

• Environment & Ecology by Dr Gourkrishna Dasmohapatra