energy flow
SKILLS
- Quantitative representations of energy flow using pyramids of energy
NATURE OF SCIENCE
- Use theories to explain natural phenomena: the concept of energy flow explains the limited length of food chains
INTERNATIONAL MINDEDNESS:
The energetics of food chains is a factor in the efficiency of food production for the alleviation of world hunger.
GUIDANCE:
Pyramids of number and biomass are not required.
Sources: Chapter 4 Ecology notes, PDF Energy flow and succession, Pearson Book.
- Quantitative representations of energy flow using pyramids of energy
NATURE OF SCIENCE
- Use theories to explain natural phenomena: the concept of energy flow explains the limited length of food chains
INTERNATIONAL MINDEDNESS:
The energetics of food chains is a factor in the efficiency of food production for the alleviation of world hunger.
GUIDANCE:
Pyramids of number and biomass are not required.
Sources: Chapter 4 Ecology notes, PDF Energy flow and succession, Pearson Book.
sunlight and ecosystems
4.2.1 Most ecosystems rely on a supply of energy from sunlight
For most biological communities, the initial source of energy is sunlight. Living organisms can harvest this energy by photosynthesis. Three groups of autotrophs carry out photosynthesis:
- Plants
-Eukaryotic algae
-Cyanobacteria
Heterotrophs do not use the light energy directly, but they indirectly are dependent on it. There are several groups of heterotrophs on an ecosystem:
- Consumers
-Saprotrophs
-Detritivores
All of this 3 use carbon compounds in their food as a source of energy.
The amount of energy supplied to ecosystems in sunlight varies around the world. The percentage of this energy that is harvested by producers and therefore available to some organisms and some not.
For most biological communities, the initial source of energy is sunlight. Living organisms can harvest this energy by photosynthesis. Three groups of autotrophs carry out photosynthesis:
- Plants
-Eukaryotic algae
-Cyanobacteria
Heterotrophs do not use the light energy directly, but they indirectly are dependent on it. There are several groups of heterotrophs on an ecosystem:
- Consumers
-Saprotrophs
-Detritivores
All of this 3 use carbon compounds in their food as a source of energy.
The amount of energy supplied to ecosystems in sunlight varies around the world. The percentage of this energy that is harvested by producers and therefore available to some organisms and some not.
energy conversion
4.2.2 Light energy is converted to chemical energy in carbon compounds by photosynthesis
Producers absorb sunlight by using chlorophyll and other photosynthetic pigments. This converts the light energy into chemical energy. This energy is used to make carbohydrates, lipids and other carbon compounds.
Producers release energy from their carbon compounds by cell respiration and then use it for all cell activities. Energy released in this way is lost to the environment as waste heat. The largest part of this carbon compounds remains in the cells tissues of producers.This energy is also available for heterotrophs.
Producers absorb sunlight by using chlorophyll and other photosynthetic pigments. This converts the light energy into chemical energy. This energy is used to make carbohydrates, lipids and other carbon compounds.
Producers release energy from their carbon compounds by cell respiration and then use it for all cell activities. Energy released in this way is lost to the environment as waste heat. The largest part of this carbon compounds remains in the cells tissues of producers.This energy is also available for heterotrophs.
Energy transformation
•Aquatic and terrestrial communities rely on sunlight as source of energy
• Light energy is converted to chemical energy in carbon compounds by photosynthesis
• Chemical energy in carbon compounds flow through food chains by feeding.
• The transfer of energy from one trophic level to the next is inefficient
– Producers convert only about 1% of solar energy available to them to organic matter
– 10-20 % of the energy on one trophic level will be assimilated at the next higher trophic level
– Energy is used to run cell activities (to make ATP via cellular respiration)
– Energy mostly lost via heat
•Aquatic and terrestrial communities rely on sunlight as source of energy
• Light energy is converted to chemical energy in carbon compounds by photosynthesis
• Chemical energy in carbon compounds flow through food chains by feeding.
• The transfer of energy from one trophic level to the next is inefficient
– Producers convert only about 1% of solar energy available to them to organic matter
– 10-20 % of the energy on one trophic level will be assimilated at the next higher trophic level
– Energy is used to run cell activities (to make ATP via cellular respiration)
– Energy mostly lost via heat
Energy flow in a food chain
•Energy is also lost:
– Not consumed
– Not absorbed/assimilated
• I=input, A=assimilation, R=respiration, NU=not utilized, P=production, B=biomass
•Energy is also lost:
– Not consumed
– Not absorbed/assimilated
• I=input, A=assimilation, R=respiration, NU=not utilized, P=production, B=biomass
energy in food chains
4.2.3 Chemical energy in carbon compounds flows through food chains by means of feeding.
Food chain: Is a sequence of organisms each of which feeds on the previous one. There are usually between 2 to 5 organisms in a food chain. As they do not obtain food from other organisms, producers are always the first organisms in the food chain. The subsequent organisms are consumers given that primary consumers feed on producers, secondary consumers feed on primary consumers and tertiary consumers feed on secondary consumers, and so on. Consumers obtain energy from carbon compounds in the organism on which they feed. The arrows in a food chain therefore indicates the direction of energy flow.
Food chain: Is a sequence of organisms each of which feeds on the previous one. There are usually between 2 to 5 organisms in a food chain. As they do not obtain food from other organisms, producers are always the first organisms in the food chain. The subsequent organisms are consumers given that primary consumers feed on producers, secondary consumers feed on primary consumers and tertiary consumers feed on secondary consumers, and so on. Consumers obtain energy from carbon compounds in the organism on which they feed. The arrows in a food chain therefore indicates the direction of energy flow.
respiration and energy releases
4.2.4 Energy released from carbon compounds by respiration is used in living organisms and converted to heat.
Living organisms need energy for cell activities such as these:
All cells can produce ATP by cell respiration. Cell respiration transfer chemical energy from glucose and other carbon compounds to ATP. Chemical energy in carbon compounds are no immediately available for the cell, but the chemical energy in ATP can be used directly.
-The second law of thermodynamics states that energy transformations are never 100% efficient.
The reminder energy from oxidation of carbon compounds is converted to heat. Some heat is also produced when ATP is used in cell activities. ex: when muscles warm up.
*Energy from ATP may reside for a time in large molecules when they have been synthesized such as DNA or protein, but when these molecules are eventually digested the energy is released as heat.
Living organisms need energy for cell activities such as these:
- Synthesizing large molecules like DNA, RNA and proteins
- Pumping molecules or ions across membranes by active transport
- Moving things around inside the cell. ex: vesicles, chromosomes
All cells can produce ATP by cell respiration. Cell respiration transfer chemical energy from glucose and other carbon compounds to ATP. Chemical energy in carbon compounds are no immediately available for the cell, but the chemical energy in ATP can be used directly.
-The second law of thermodynamics states that energy transformations are never 100% efficient.
The reminder energy from oxidation of carbon compounds is converted to heat. Some heat is also produced when ATP is used in cell activities. ex: when muscles warm up.
*Energy from ATP may reside for a time in large molecules when they have been synthesized such as DNA or protein, but when these molecules are eventually digested the energy is released as heat.
heat energy in ecosystem
4.2.5 Living organisms cannot convert heat to others forms of energy
Living organisms can perform various energy conversions:
Living organisms can perform various energy conversions:
- Light energy to chemical energy to photosynthesis
- Chemical energy to kinetic energy in muscle contraction
- Chemical energy to electrical energy in nerve cells
- Chemical energy to heat energy in heat-generating adipose tissue
heat losses from ecosystems
4.2.6 Heat is lost from ecosystems
Heat resulting from cell respiration makes living organisms warmer. According to the laws of thermodynamics in physics heat passed from hotter to cooler bodies, so heat produced in living organisms is all eventually lost in the abiotic environment. The heat may retain in the ecosystem for a while but ultimately is lost. Ex: when heat is radiated into the atmosphere, ecologist assume that all energy released by respiration for use in cell activities will ultimately be lost from the ecosystem.
Heat resulting from cell respiration makes living organisms warmer. According to the laws of thermodynamics in physics heat passed from hotter to cooler bodies, so heat produced in living organisms is all eventually lost in the abiotic environment. The heat may retain in the ecosystem for a while but ultimately is lost. Ex: when heat is radiated into the atmosphere, ecologist assume that all energy released by respiration for use in cell activities will ultimately be lost from the ecosystem.
energy losses and ecosystems
4.2.7 Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels
Biomass: Total mass of a group of organisms. Because carbon compounds have chemical energy then biomass has energy. By measuring the energy of the biomasses the same trend is found: the energy added to biomass by each successive trophic level is less. In secondary consumers for example: the amount of energy is always less per year per square metre of ecosystem than in primary consumers.
The reason for this trend is loss of energy between trophic levels
The biomass of higher trophic levels is usually smaller than the lower levels.
Biomass: Total mass of a group of organisms. Because carbon compounds have chemical energy then biomass has energy. By measuring the energy of the biomasses the same trend is found: the energy added to biomass by each successive trophic level is less. In secondary consumers for example: the amount of energy is always less per year per square metre of ecosystem than in primary consumers.
The reason for this trend is loss of energy between trophic levels
- Most of the energy in food that is digested and absorbed by organisms in a trophic level is released by them in respiration for use in cell activities. The only energy available to organisms in the next trophic level is the chemical energy.
- The organisms in a trophic level are not usually entirely consumed by organisms in the next trophic level. Predators may not eat material from the bodies of their prey such as bones or hair. Energy in uneaten materials passes to saprotrophs and detritivores
- Not all parts of food ingested by the organisms in a trophic level are digested or absorbed. Some material in indigestible and is egested in feces.
The biomass of higher trophic levels is usually smaller than the lower levels.
pyramids of energy
The amount of energy converted to new biomass by each trophic level in an ecological community can be represented with a pyramid of energy.
This is a type of bar chart with a horizontal bar for each trophic level. The amounts of energy should be per unit area per year. The bars should be labeled producer, first consumer, second consumer and so on. If a suitable scale is chosen the length of each bar can be proportional to the amount of energy that it shows.
This is a type of bar chart with a horizontal bar for each trophic level. The amounts of energy should be per unit area per year. The bars should be labeled producer, first consumer, second consumer and so on. If a suitable scale is chosen the length of each bar can be proportional to the amount of energy that it shows.
gross production vs net production
Energy is not entirely lost; organisms do trap some of the energy in the form of biomass
• Gross production (GP) = total amount of energy trapped in organic matter produced by plants in an ecosystem
• Net production (NP) = GP
– energy lost through respiration
– Amount of biomass that is available to the next trophic level
• Gross production (GP) = total amount of energy trapped in organic matter produced by plants in an ecosystem
• Net production (NP) = GP
– energy lost through respiration
– Amount of biomass that is available to the next trophic level