BIOL1007 Lecture Notes - Lecture 22: Ecological Pyramid, Food Chain, Chemosynthesis

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19 May 2018
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Professor
Review how organisms get their energy.
Autotrophs
Producers
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Make it themselves (synthesise organic from inorganic compounds)
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Green plants, phytoplankton, algae (and chemosynthetic bacteria)
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Most occur in terrestrial environments
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Without autotrophs the world would have no life
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Heterotrophs
Consumers, degraders, decomposers (make use of dead plant material)
-
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Animals
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Ride on the backs of autotrophs
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Screen clipping taken: 19/10/2017 9:11 AM
As you move from level to next level - 90% energy is lost
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Water and essential elements allow for production of energy between the trophic links in the
food chain
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Describe the concept of trophic levels.
Number of steps org is from start of chain is measure of its trophic level
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Feeding positions in food chain or web
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Trophic level 1: primary producers - make own food e.g. plants
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2: herbivores/primary consumer - consumes producers e.g. birds eat seeds
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3: predators/secondary consumer - fox eats birds
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4: carnivores/tertiary consumer - wolf eats fox
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Food chain
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Explain how energy flows within ecosystems.
Energy passed up food chain/web form lower to higher trophic levels
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Not all eneryg available to next level only about 10%
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Ecological pyramid
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Most energy used for metabolic processes or lost to env as heat
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Describe food chains and food webs (“eat or be eaten”).
L22 - Trophic ecology
Thursday, 19 October 2017
9:01 AM
mod 4 - ecology and ecosystems Page 1
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WHY?
Hypotheses
Evidence
Hyp 1: the
energy
hypothesis -
energy loss
between
trophic levels
Screen clipping taken: 19/10/2017 9:37 AM
Predicts: high productivity ecosystems should have longer chains
Screen clipping taken: 19/10/2017 9:27 AM
Observation: but food chains often short, whether energy base is
low OR high
e.g. tree hollows
-
Energy is an important factor in number of trophic links
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Number of species and trophic links highest in high
productivity group (supporting the hypothesis)
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Experimental evidence
Hyp 2: the
dynamic
stability
hypothesis
Top predators more likely to go extinct
Decrease food chain size
Fluctuations at low trophic levels magnify at high levels
Longer food chains less stable due to
-
Screen clipping taken: 19/10/2017 9:35 AM
Predicts: predictable (stable) environments should have longer
chains
Can be many links in a food chain, but USUALLY SHORT
Food chains: Describe the energy flow between organisms among trophic levels
-
Describe food chains and food webs (“eat or be eaten”).
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Document Summary

Make it themselves (synthesise organic from inorganic compounds) Without autotrophs the world would have no life. Consumers, degraders, decomposers (make use of dead plant material) As you move from level to next level - 90% energy is lost. Water and essential elements allow for production of energy between the trophic links in the food chain. Number of steps org is from start of chain is measure of its trophic level. Trophic level 1: primary producers - make own food e. g. plants. 2: herbivores/primary consumer - consumes producers e. g. birds eat seeds. Energy passed up food chain/web form lower to higher trophic levels. Not all eneryg available to next level only about 10% Most energy used for metabolic processes or lost to env as heat. Des(cid:272)ri(cid:271)e food (cid:272)hains and food we(cid:271)s (cid:894)(cid:862)eat or (cid:271)e eaten(cid:863)(cid:895). mod 4 - ecology and ecosystems page 1. Des(cid:272)ri(cid:271)e food (cid:272)hains and food we(cid:271)s (cid:894)(cid:862)eat or (cid:271)e eaten(cid:863)(cid:895).

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