Branch: Civil EngineeringSemester: 3rd

Subject: Enviromental Studies

Chapter- Ecosystem

Name of Faculty: Er.Raghabendra Mohapatra

(Lect.In Civil Engineering Department)

AY:2021-2022

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Civil Engineering Department

Contents

• What is an ecosystem
• Three major principles of ecosystem
• Components of an ecosystem
• Abiotic components
• Biotic components
• Movement of energy and nutrients
• Food chain
• Food webs
• Trophic levels, biomass and biome
• Linkages and interactions in an ecosystem
• Carbon cycle and oxygen cycle
• Model of nutrient cycle
• Environmental Limitation in ecosystem development.

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What is an ecosystem

• An ecosystem is a grouping of organisms that interact with each other and their environment in such a way as to preserve the grouping.
• There is a great variety of ecosystems in existence, all of them are characterized by general structural and functional attributes.

Three major principles of ecosystem

• Nutrient cycling:
• Movement of chemical elements from the environment into living organisms and from them back into the environment through organisms live, grow, die and decompose.
• Energy flow:
• Energy is required to transform inorganic nutrients into organic tissues of an organism.
• Energy is the driving force to the work of ecosystem.
• Structure
• It refers to the particular pattern of inter-relationships that exists between organisms in an ecosystem.

Nutrient cycling

Energy flow

Structure

Ecosystem: �Nutrient cycling, energy flow and structure

Components of an ecosystem

Abiotic components

• They form the environment and determine the type / structure of ecosystem.
• Sunlight (temperature)
• Nutrients
• Rainfall, minerals, carbon, nitrogen,…..
• Type of ecosystems:
• Tropical rainforest, Desert, Tundra, Grassland,…..

Distribution of vegetation / ecosystem

Biotic components

• Producers (Autotrophs):
• All green plants. They use solar energy, chlorophyll, inorganic nutrients and water to produce their own food. (Photosynthesis)
• Consumers:
• They consume the organic compounds in plant and animal tissues by eating.
• Herbivores (plant feeders) Primary consumers
• Carnivores (meat eaters) Secondary consumers
• Omnivores (general feeders)

Biotic components

• Decomposers
• They are tiny organisms includes bacteria and fungi, which turn organic compounds in dead plants and animals into inorganic materials.
• They cause the continual recirculation of chemicals within ecosystem (nutrient cycle)

Biotic components and food chain

Movement of energy and nutrients

• Food chain
• Food webs
• Trophic level, biomass and biome

Food Chain

• The particular pathway of nutrient and energy movement depends on which organism feeds on anther.

Decomposers

Food Webs

Trophic Levels

• A trophic level means a feeding level.
• First level – all producers
• Second level – all herbivores
• Third level – first level carnivores
• Fourth level – second level carnivores
• So on……..

Trophic levels

• Energy and Nutrients passed through the ecosystem by food chains and webs from lower trophic level to the higher trophic level.
• However, only 5% to 20% energy and nutrients are transferred into higher trophic level successfully.
• For this reason, first trophic level has the largest number of organisms, and second trophic level is less than first one; the third level is less than second level, and so on.

Trophic levels

Biomass

• Biomass means the total combined weight of any specified group of organisms.
• The biomass of the first trophic level is the total weight of all the producers in a given area.
• Biomass decreases at higher trophic levels.

Biomass

Biomass and productivity

Trophic Level (Food Pyramid)

Biome

• This is a total different concept apart from Biomass.
• Biome are defined as
• “the world’s major communities, classified according to the predominant vegetation and characterized by adaptations of organism to that particular environment.

Linkages and Interactions in an ecosystem

• Carbon and Oxygen cycle
• Nitrogen cycle
• A model of nutrient cycle

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Carbon Cycle and Oxygen Cycle

Nitrogen Cycle

Nitrogen cycle

• Nitrogen cycle can be affected by man in five major ways:
• Fertilizer production (mainly nitrates and ammonium salts) to grow more food by increasing yields, and replenishing lost nitrogen from the soil.
• Burning of fossil fuels in cars, power plants, and heating which puts nitrogen dioxide into the atmosphere.
• Increasing animals wastes (nitrates) from more people and from livestock and poultry grown in ranches.
• Increased sewage flows from industry and urbanization.
• Increased erosion of and runoff nearby streams, lakes and rivers from cultivation, irrigation, agricultural wastes, mining, urbanization and poor land use.

Model of Nutrient Cycle

• Nutrients (chemicals, minerals or elements) are circulated around the ecosystem and recycled continually.
• Gersmehl identified three storage compartments.
• Litter: the surface layer of vegetation which may eventually become humus.
• Biomass: the total mass of living organisms, per unit area.
• Soil: the nutrients store in soil (weathered material) and semi-weathered material.

Model of Nutrient Cycle

3 Difference Nutrient Cycles

Environmental Limitation in ecosystem development

• Principles of limiting factors
• Law of the maximum
• Law of the minimum
• Principle of holocoenotic environment
• Limiting factors of an environment
• Light
• Temperature
• Water
• Wind
• Topography
• Soil
• Biotic factors

Law of Maximum and Minimum

Principle of holocoenotic environment

• A German ecologist Karl Friederich (1927) suggested that 'community-environmental relationship are holocoenotic'. This means that there are no 'walls' or barriers between the factors of an environment and the organism or biotic community.
• If one factor is changed, almost all will change eventually.
• Example:

Temperature 🡩

Air can hold more water

Evaporation rates 🡩

Transpiration 🡩

Plants absorb soil water 🡩

Free water in soil 🡫

Dryness of soil 🡩

Relative Humidity 🡫

Limiting factors of an environment

• Light
• Temperature
• Water
• Wind
• Topography
• Soil
• Biotic Factors

Light

• Light is an very important environment factor:
• Source of energy for ecosystem
• Control factor for reproduction and migration.

Light

• Quality of light:
• Red and blue light: green plants (photosynthesis)
• Green light: plants in woods or deep water
• Ultraviolet light: retards plant growth
• Duration of light
• Affect the behaviour of plants and animals (flowering, migration, mating….)
• Intensity of light:
• Controlling factor for rate of photosynthesis
• Net productivity is the function of photosynthesis and respiration.

Temperature

• Very important factor affecting
• Directly effects on organisms
• Indirectly effects in modifying other environmental factors such as relative humidity and water availability.
• Each species has its own minimum, maximum and optimum temperatures for life. (vary with age and water balances in the body)
• Aquatic life has narrower tolerance ranges for temperature than those which live on land.
• Tropical plants: > 15^oC,
• Temperate cereals: >-2^oC,
• Coniferous forests: withstand many degrees below freezing.

Water

• Water restrict ecosystem development because ,most organisms need large amounts of water to survive.
• Water requirement for plants will vary both with environmental conditions and among different species.
• Actual rate of transpiration is the function of
• relative humidity
• Air movement
• Size of leaves
• Size of stomata

Water

• Plants classification by water requirement.
• Xerophytes: plants can survive in extremely arid areas.
• Halophytes: plants can survive in saline conditions
• Hydrophytes: plants live in water or in moist soil.

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Wind

• Wind can act as an environmental factor
• Directly by causing mechanical damage to plants
• Indirectly affecting relative humidity and evaporation rates.
• High wind speed increases the rate of transpiration.
• Mountain summits, coasts and open plains vegetation may be dwarfed as a result of wind action.

Topography

• Topography can influence ecosystem development in three major ways.
• Direct effects of altitude on temperature
• normal lapse rate (-6.5^oC/km)
• The combination of changes in temperature and relative humidity
• an altitudinal zonation of ecosystems.
• Slope orientation and angle
• South-facing slopes (in the northern hemisphere) are warmer and drier than north-facing slopes.
• Angle of slope will be a critical factor in soil formation and drainage.

Topography

Topography

Soil

• Attributes of soils, such as texture, pH, soil climate and organic content operate in a closely inter-related fashion to exert control on
• rates of decomposition
• nutrient cycling,
• plant distribution
• productivity.

Biotic Factors

• Biotic factors are the interactions that occur between living things.
• Some species are beneficial or even essential for the existence of others, whereas some may be harmful.
• The dominant plants will grow tallest and modify the light conditions for the rest of the community.
• Plants struggle for light will influence root development and the competition for water and nutrients in the soil.
• Many plants rely on animals for pollination and seed dispersal.
• Many animals are directly dependent on plants for food.

Biotic Factors

• Man is by far the most important biotic factor.
• Man modifies of ecosystems by fire, hunting and agriculture,…...
• Industrialization and the intensification of agriculture, man has obliterated large areas of natural systems and caused pollution of both terrestrial and aquatic habitats.

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