Download Ecosystems and Energy Transfers2

Ecosystems and Energy
Transfers
WONG HONG CHING
Index
• 1. Definition of key words
• 2. Energy transfers in ecosystems
• 3. Ecological pyramids
1. Definition of key words
• Ecosystem
• Population
• Community
• Habitat
• Niche
• Environment
Ecosystem
• Ecosystem stands for Ecological system.
• It is an ecological unit which includes all living organisms and the
abiotic factors that surround the organisms, results from the dynamic
interactions abiotic and biotic factors.
• The abiotic factors:
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Temperature
pH
Light intensity
Oxygen level
Humidity
Rainfall
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The biotic factors:
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Animals
Plants
Micro-organisms
Population & Community
• Population refers to all the organisms of the same
species in a area.
• Community refers to all living organisms of different
species living in a given area.
• Living organisms interact with each other and are
interconnected by food chains or food webs.
Habitat
• Habitat refers to the place where the
communities live.
• Examples of habitats:
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Forest
Sea
Rock shore
Soil
Niche
• It is a word which is used to describe the relational
position of a species in an area.
• It refers to the roles of an organism in an area.
• Different species have different roles, niches.
• Roles:
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What it eats
Where it lives
When it is active
When it eats
Environment
• Environment is the conditions surrounding the
organisms.
• The conditions include both abiotic factors and
biotic factors.
• The abiotic factors:
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Temperature
Rainfall
pH
Light intensity
Oxygen level
Humidity
• The biotic factors:
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Predation by other organisms
Competition of nutrients, food
Energy transfers Cycle
• First step:
• Solar energy  Plants (Act as producers)
• Second step:
• Producers’ energy  Primary consumer (herbivores)
• Third step:
• Primary consumers’ energy  Secondary consumers (carnivores)
• Forth step:
• Secondary consumers’ energy  Tertiary consumers
• Final step:
• When tertiary consumers die, the energy and nutrients are returned
to the soil by saprotrophic organisms which feed on dead
organisms.
• Decomposers: Start the cycle again
Energy Transfers in Ecosystem
• Is the energy totally transferred between different trophic levels?
• The answer is no.
• Only 10% energy is transferred between different trophic level.
WHY??
• 30% of energy is used in respiration.
• 60% of energy is lost in excretion of waste products, like faeces,
urine, gas.
• Amount of energy stored and transferred to another trophic level:
• 100% - 30% - 60% = 10%
• No food chain can exceed more than 5 links.
• Otherwise, the consumers at the end of food chain cannot get
enough food and energy.
Ecological Pyramids
• What is ecological pyramids?
• They are the graphs which are used to show the
relationship between energy and trophic levels
of an area.
• Three types of pyramids:
• Pyramid of number
• Pyramid of biomass
• Pyramid of energy
Feature: Primary producers are at the bottom.
Pyramid of number
• Feature:
• It is a ecological pyramid which shows the
number of organisms in different trophic levels.
• Advantage:
• Just counting the number of organisms, is easy to
produce.
• Disadvantages:
• The pyramid shape is messed up by small amount of big
producers (like trees) and large amount of tertiary
producers (like fleas).
Abnormal cases of pyramids of number
• Small amount of large
producers.
• Large amount of small
tertiary consumers.
Pyramid of biomass
• It is a ecological pyramid which measures the dry mass
of organisms in different trophic levels.
• The unit of dry mass is kg/m2
• Advantage:
• Pretty accurate, often have a normal pyramid shape.
• Disadvantages:
• Difficult to get the data. (Need to kill the organism and evaporate all
of it’s water inside the body)
• If the producers have small sizes, short life and reproduces quickly,
then the pyramid shape is distorted.
Pyramid of energy
• It is a ecological pyramid which measures the
amount of energy in the organisms in different
trophic levels.
• The unit is kJ/m-2/yr-1
• It is the most accurate among other pyramids.
• However, it is very difficult to measure the
amount of energy in the organism.
Bibliography
• http://ecokids.ca/pub/eco_info/topics/frogs/chain
_reaction/index.cfm
• http://www.arcytech.org/java/population/facts_foo
dchain.html