Each ecosystem has a trophic structure of feeding relationship
This trophic structure consists of:
- Primary producers (this ultimately supports all other organisms, and consist of autotroph/photosynthetic organisms)
- Primary consumers (herbivores)
- Secondary consumers (carnivores that eat herbivores)
- Tertiary consumers (carnivores that eat other carnivors)
- Higher level of consumers
- Decomposers/detritivores (they derives energy from detritus)
Introduction
– Each ecosystem has a trophic structure of feeding relationship
– This determines the pathways of energy flow and chemical cycling
– The species in a community or ecosystem have been divided by ecologists into trophic structure based on their main sources of nutrient
– This trophic structure consists of:
Primary producers (this ultimately supports all other organisms, and consist of autotroph/photosynthetic organisms)
Primary consumers (herbivores)
Secondary consumers (carnivores that eat herbivores)
Tertiary consumers (carnivores that eat other carnivors)
Higher level of consumers
Decomposers/detritivores (they derives energy from detritus)
– All the trophic level above in an ecosystem will form a food chain (the pathways along which food is transferred from trophic level to trophic level, beginning with producer)
– The length of food chain is limited by the amount of energy that gets transferred from one level to the next
– Some ecosystems are characterized by a single, unbranched food chain
– Several types of primary consumers usually feed one the same plant species, and one species of primary consumer may eat several different plants
– Such branching food chains also occurs at the other trophic levels
– These branching food chains will then form a more complex relationship, that is called the food webs
Global energy budget
Earth is bombarded by 1022 joules of solar radiation (1 joule = 0.239 calories)
This energy is equals to 100 million atomic bombs of the one dropped on Hiroshima
The amount of the solar radiation reaching the globe limits the photosynthetic output of the ecosystem
Only a small amount of the solar energy strikes algae and plant leaves
Only some of this of wavelengths suitable for photosymthesis
Of the visible light that reaches algae and leaves, only 1 – 2% is converted into chemical energy by photosynthesis
– The efficiency of photosynthetic processes varies among plant species
– Although only a small fraction of the solar energy is converted to chemical energy, primary producers on earth collectively create 170 billion tones of organic materials per year
– This is an impressive quantity
Primary productivity
– The amount of light energy converted to chemical energy by autotrophic organisms of an ecosystem during a given time period.
– Total primary productivity is known as gross primary productivity (GPP)
– Some of this GPP is used by plants as fuel during respiration
– Or, not all of GPP is stored as organic compounds
– Therefore, net primary productivity (NPP) is GPP minus the energy used by the producers for respiration (Rs)
– The equation related to the NPP are:
NPP = GPP – Rs, or
6 CO2 + 6 H2O C6H12O6 + 6 O2
– GPP is a product of photosynthesis
– NPP is the difference between the yield of photosynthesis and the consumption of organic fuel in respiration
– Normally, 50 – 90% of the GPP is stored as NPP
– The ratio of GPP to NPP is generally smaller for large producers with elaborate non-photosynthetic structure (active stem and root system)
– The primary productivity is can be expressed as biomass (energy per unit area per unit time)
– Biomass is expressed in term of dry weight of organic matter
– Don’t be confused with the standing crop biomass, because this contain water that unusable energy
– Different ecosystem vary considerably in their productivity and their contribution to the total productivity on earth (Fig. 49.3)
Secondary productivity
The rate at which an ecosystem’s consumers convert the chemical energy of the food they eat into their own biomass.
In all cases, only a very small fraction of the energy consumed is converted into biomass as the secondary productivity
Example:
– Of 200 joule of chemical energy consumed by a caterpillar, only 33 joule is converted into biomass (growth)
– The rest is passed as feces (this is not lost from ecosystem as it can be consumed by decomposers) or used for cellular respiration (Energy used here is lost from ecosystem)
Ecological efficiency and ecological pyramids
Ecological efficiency is the percentage of energy transferred from one trophic level to the next level
Or The ratio of net productivity at one trophic level to net productivity at the level below
The value of ecological efficiency vary greatly among organisms, normally between 5 – 10%
This indicates that between 90 – 95% of the energy available at one trophic level never transfer to the next.
This multiple lost of energy from a food chain can be represented diagrammatically by a pyramid of productivity
This pyramid is typically quite-bottom heavy, because ecological efficiency is very low
Similar to pyramid of productivity, In the pyramid of biomass (standing crop biomass or total dry weight of all organisms) transfer energy through food webs also decrease (Fig. 45.6a)
In some aquatic ecosystem, such as in the waters of English channel, the biomass pyramid is inverted
In this case, the primary consumers outweigh the producers (Fig. 46.6b)
This occurs because the zooplankton consume the phytoplankton so quickly.
Therefore, the phytoplankton never develop a large population size (standing crop)
In this case, The phytoplankton has a very short turnover time (low standing crop biomass compared to productivity)
Turnover time = Standing crop biomass (mg/mL)
Productivity (mg/m2/day)
One thing that must be remembered here is, the productivity pyramid of the above waters ecosystem is always upright
This because of the productivity of the phytoplankton is always higher than zooplankton
This indicates that the efficiency of energy transfer from the lowest trophic level to the highest level is always very low
This partly explain why food webs usually include only 3 – 5 trophic levels
This trophic structure consists of:
- Primary producers (this ultimately supports all other organisms, and consist of autotroph/photosynthetic organisms)
- Primary consumers (herbivores)
- Secondary consumers (carnivores that eat herbivores)
- Tertiary consumers (carnivores that eat other carnivors)
- Higher level of consumers
- Decomposers/detritivores (they derives energy from detritus)
Introduction
– Each ecosystem has a trophic structure of feeding relationship
– This determines the pathways of energy flow and chemical cycling
– The species in a community or ecosystem have been divided by ecologists into trophic structure based on their main sources of nutrient
– This trophic structure consists of:
Primary producers (this ultimately supports all other organisms, and consist of autotroph/photosynthetic organisms)
Primary consumers (herbivores)
Secondary consumers (carnivores that eat herbivores)
Tertiary consumers (carnivores that eat other carnivors)
Higher level of consumers
Decomposers/detritivores (they derives energy from detritus)
– All the trophic level above in an ecosystem will form a food chain (the pathways along which food is transferred from trophic level to trophic level, beginning with producer)
– The length of food chain is limited by the amount of energy that gets transferred from one level to the next
– Some ecosystems are characterized by a single, unbranched food chain
– Several types of primary consumers usually feed one the same plant species, and one species of primary consumer may eat several different plants
– Such branching food chains also occurs at the other trophic levels
– These branching food chains will then form a more complex relationship, that is called the food webs
Global energy budget
Earth is bombarded by 1022 joules of solar radiation (1 joule = 0.239 calories)
This energy is equals to 100 million atomic bombs of the one dropped on Hiroshima
The amount of the solar radiation reaching the globe limits the photosynthetic output of the ecosystem
Only a small amount of the solar energy strikes algae and plant leaves
Only some of this of wavelengths suitable for photosymthesis
Of the visible light that reaches algae and leaves, only 1 – 2% is converted into chemical energy by photosynthesis
– The efficiency of photosynthetic processes varies among plant species
– Although only a small fraction of the solar energy is converted to chemical energy, primary producers on earth collectively create 170 billion tones of organic materials per year
– This is an impressive quantity
Primary productivity
– The amount of light energy converted to chemical energy by autotrophic organisms of an ecosystem during a given time period.
– Total primary productivity is known as gross primary productivity (GPP)
– Some of this GPP is used by plants as fuel during respiration
– Or, not all of GPP is stored as organic compounds
– Therefore, net primary productivity (NPP) is GPP minus the energy used by the producers for respiration (Rs)
– The equation related to the NPP are:
NPP = GPP – Rs, or
6 CO2 + 6 H2O C6H12O6 + 6 O2
– GPP is a product of photosynthesis
– NPP is the difference between the yield of photosynthesis and the consumption of organic fuel in respiration
– Normally, 50 – 90% of the GPP is stored as NPP
– The ratio of GPP to NPP is generally smaller for large producers with elaborate non-photosynthetic structure (active stem and root system)
– The primary productivity is can be expressed as biomass (energy per unit area per unit time)
– Biomass is expressed in term of dry weight of organic matter
– Don’t be confused with the standing crop biomass, because this contain water that unusable energy
– Different ecosystem vary considerably in their productivity and their contribution to the total productivity on earth (Fig. 49.3)
Secondary productivity
The rate at which an ecosystem’s consumers convert the chemical energy of the food they eat into their own biomass.
In all cases, only a very small fraction of the energy consumed is converted into biomass as the secondary productivity
Example:
– Of 200 joule of chemical energy consumed by a caterpillar, only 33 joule is converted into biomass (growth)
– The rest is passed as feces (this is not lost from ecosystem as it can be consumed by decomposers) or used for cellular respiration (Energy used here is lost from ecosystem)
Ecological efficiency and ecological pyramids
Ecological efficiency is the percentage of energy transferred from one trophic level to the next level
Or The ratio of net productivity at one trophic level to net productivity at the level below
The value of ecological efficiency vary greatly among organisms, normally between 5 – 10%
This indicates that between 90 – 95% of the energy available at one trophic level never transfer to the next.
This multiple lost of energy from a food chain can be represented diagrammatically by a pyramid of productivity
This pyramid is typically quite-bottom heavy, because ecological efficiency is very low
Similar to pyramid of productivity, In the pyramid of biomass (standing crop biomass or total dry weight of all organisms) transfer energy through food webs also decrease (Fig. 45.6a)
In some aquatic ecosystem, such as in the waters of English channel, the biomass pyramid is inverted
In this case, the primary consumers outweigh the producers (Fig. 46.6b)
This occurs because the zooplankton consume the phytoplankton so quickly.
Therefore, the phytoplankton never develop a large population size (standing crop)
In this case, The phytoplankton has a very short turnover time (low standing crop biomass compared to productivity)
Turnover time = Standing crop biomass (mg/mL)
Productivity (mg/m2/day)
One thing that must be remembered here is, the productivity pyramid of the above waters ecosystem is always upright
This because of the productivity of the phytoplankton is always higher than zooplankton
This indicates that the efficiency of energy transfer from the lowest trophic level to the highest level is always very low
This partly explain why food webs usually include only 3 – 5 trophic levels
Tidak ada komentar:
Posting Komentar