Ecosystem - csbs.edu.hk

Ecosystem - csbs.edu.hk

Ecosystem HO Puising 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. 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 interrelationships 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 worlds 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 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. Temperature Air can hold more water Example:

Evaporation rates Relative Humidity Dryness of soil Transpiration Free water in soil

Plants absorb soil water 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: > 15oC, Temperate cereals: >-2oC, 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. 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 d evelopment in three major ways. Direct effects of altitude on temperature normal lapse rate (-6.5oC/km)

The combination of changes in temperatur e and relative humidity an altitudinal zonation of ecosystems. Slope orientation and angle South-facing slopes (in the northern hemispher e) are warmer and drier than north-facing slope

s. Angle of slope will be a critical factor in soil for mation and drainage. Topography Topography

Soil Attributes of soils, such as texture, pH, soil climate and organic content operate in a closely interrelated 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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