Advanced Higher Biology

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Advanced Higher Biology

• Unit 2
• Environmental Biology

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Section A- Circulation in Ecosystems

• 1.2.1 Energy Flow

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Reminder
100 solar radiation
36 reflected from atmosphere
64 entering atmosphere reflected or absorbed,
used then re-emitted as heat
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Extra Note

• The Laws of Thermodynamics and Matter
  Transformations
• Energy cannot be created or destroyed
• only be transformed from one kind to another
• Disorder in the universe is increasing
• During transformation the resulting energy is
  less organised and less useful.
• The final transformation is usually into heat

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Energy Flow In Ecosystems

• Energy is not recycled.
• Movement of energy is through a system.
• From an external source (the sun).
• Through a series of organisms and back to the
  environment.
• Leaves as degraded energy (heat).

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Energy Availability

• 1 of the energy reaching the earth from the Sun
  is available to life on Earth.
• Of this energy, 3 (0.03 of the total) is
  trapped by green plants or algae. (autotrophs)
• All life on Earth is comes from 0.03 of the
  energy absorbed from the Sun.

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What are Food Chains?

• Groups of animals and plants that are linked
  together by what they eat.
• Food chains exist to pass energy from one
  organism to the next!

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A Food Chain
Carnivore
Quaternary Consumer
Carnivore
Tertiary Consumer
Carnivore
Secondary Consumer
Primary Consumer
Herbivore
Plant
Producer
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Food Chains and Trophic Levels

• The stages in food chains are called trophic
  levels.
• Each trophic level depends on energy.
• Energy is passed up the trophic levels
• All life above the first trophic level gets its
  energy by consuming the one below.

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Trophic Levels
The third trophic level belongs to carnivores or
second order consumers.
The second trophic level belongs to herbivores or
first order consumers.
The first trophic level belongs to producers or
plants
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Trophic Structure

• Trophic Structure
• The organization of feeding levels in an
  ecosystem
• Species in an ecosystem are divided into trophic
  levels on the basis of their main source of
  nutrition.

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Terrestrial Food Chain
5th Trophic Level (Quaternary Consumer)
Carnivore
4th Trophic Level (Tertiary Consumer)
Carnivore
3rd Trophic Level (Secondary Consumer)
Trophic Structure
Carnivore
2nd Trophic Level (Primary Consumer)
Herbivore
1st Trophic Level (Producer)
Plant
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Marine Food Chain
Carnivore
Quaternary Consumer (5th Trophic Level)
Carnivore
Tertiary Consumer (4th Trophic Level)
Carnivore
Secondary Consumer (3rd Trophic Level)
Trophic Structure
Primary Consumer 2nd Trophic Level
Zooplankton
Producer (1st Trophic Level)
Phytoplankton
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Trophic levels

• Layers in ecosystem
• Through which energy flows
• referred to as trophic (feeding) levels
• Energy lost at each trophic level
• Much energy lost as
• Metabolic heat

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Energy and Trophic Levels

• Only about 10 of the energy from one trophic
  level can get to the next.
• The rest of the energy is lost as heat.

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Energy loss as heat in food chains
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Energy At Trophic Levels
Energy Usage
Energy flows through the system and is not
recycled
Cellular Respiration ( lost as heat)
Faeces (to decomposers)
Growth (to next trophic level)
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Trophic Levels

• Animals feeding wholly on plants occupy a single
  trophic level
• But most animals at higher trophic levels occupy
  several trophic levels simultaneously because of
  variation in their diets.

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A Simplistic Approach

• In practice food chains do not exist in
  isolation.
• Would lead to instability in populations.
• Food chains are normally interlinked to form food
  webs.

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Food Webs
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A Food Web in the Arctic Tundra
Identify the producers, 1? 2 ? 3 ? 4 ?
consumers in this food web
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Energy Loss

• Some energy
• lost as waste
• lost as uneaten material
• passes to decomposer level
• passes to next trophic level
• Only 10 of available energy passes to next level

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Energy and the Food Chain

• If 10 of the energy can be transferred from one
  trophic level to the one above it, each trophic
  level must have 10x the energy as the one above
  it.
• But this is limited by the rate that energy is
  being fed into the system

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Energy and the Food Chain

• The number of trophic levels depends upon the
  number of primary producers in the first trophic
  level
• Biomes with small numbers of primary producers
  have short food chains

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Limiting Factors In Energy Flow

• Low conversion efficiency because
• not all material at any trophic level is consumed
• not all material ingested is digested roughage
• most material digested used for catabolic
  processes
• to provide organism with its energy requirements

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The 10 Rule

• 10 rule is important because
• it places limits on potential number of trophic
  levels in a system

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A Simple Energy Flow Calculation
0.1 tonnes of level 5 consumer
1000 tonnes of primary producer

• Energy available is rarely sufficient to support
  large numbers of consumers in higher trophic
  levels
• Most food chains only have 5 trophic levels

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Could we feed a larger population of humans if we
ate only plants?
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Vocabulary List
Trophic
Related to feeding
Trophic Level
Functional classification of organisms according
to feeding relationships
Able to produce organic material from inorganic
chemicals and some source of energy
(photosynthesis)
Autotrophic
6 CO2 6 H2O ?? C6H12O6 6
O2
Require a supply of organic matter or food from
the environment.
Heterotrophic
Movement of energy and nutrients from one feeding
group of organisms to another in a series that
begins with plants and stops with carnivores and
decomposers
Food Chain
Interlocking pattern formed by a series of
interconnecting food chains
Food Web
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Summary
autotrophs
Primary Producer plant/ algae
Primary consumer herbivores
Secondary consumer primary carnivore
heterotrophs
Usually no more than 5 links in a food chain. Why?