World Geography 3202 Chapter 6

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World Geography 3202Chapter 6

• Life Systems

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Life Systems - Introduction

• Earth is the only planet in our solar system
  capable of supporting complex life forms.
• Energy is most important ingredient for this life
  which living organisms usually get from food
  sources.
• Energy in food is obtained from heat and light
  from sun (ie solar energy is converted into food
  energy).
• See Figure 6.1, 6.2 Pages 92-93.

• Figure 6.1 - Components Needed to Produce Food
  Energy

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The Web of Life

• Ecosystem the network of relationships among
  plants, animals and the non-living organisms in
  an environment.
• See Figure 6.3 Page 94

• Figure 6.3 Typical Ecosystem

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Organisms in an Ecosystem

• There are many living things (plants animals)
  and non-living things (soil, water sun,
  temperature etc.) that affect each other.
• It is the system of relationships between the
  organisms and between the organisms and the
  non-living environment that makes up the
  ecosystem
• Producers a plant which can convert the sun's
  energy into carbohydrates (food energy) for all
  other organisms in the ecosystem. (ie. They
  actually produce the food for the ecosystem)

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Organisms in an Ecosystem

• Consumers All those organisms in trophic levels
  other than producers. Consumers eat their food.
• For example in figure 6.3 on page 94 all the
  animals, Raccoon, bass, duck etc. are consumers.
• 1st-order or primary consumers eat producers.
• 2nd-order or secondary consumers eat primary
  consumers.
• 3rd-order or tertiary consumers eat secondary
  consumers

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Organisms in an Ecosystem

• Decomposers Simple organisms that obtain their
  food from dead organisms and wastes.
• For example in Figure 6.3 on page 94 of your text
  the colony of bacteria, protozoa, and flatworms
  are all decomposers.
• So named because they are actually responsible
  for decomposing dead organisms.
• Similaritiesall three are terms referring to
  the way organisms obtain food energy
• Differencesthe way they obtain food. Producers
  make it, consumers eat it, decomposers feed on
  wastes dead material.

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Food Chains

• Food chain linear sequence representing the flow
  of energy nutrients from the simplest plant to
  the top carnivore.
• Tree insect insect-eating bird hawk
• Producer Tree
• 1st-order consumer insect
• 2nd-order consumer insect eating bird
• 3rd-order consumer hawk

• Food chain from fig. 6.4. P. 95

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Food Webs

• Food web a series of interconnecting food chains
  in an ecosystem
• Similarityboth food chains and food webs show
  the flow of nutrients and energy in an ecosystem.
• DifferencesFood webs are more complex
  composed of several food chains a more realistic
  picture of an ecosystem.

• Food web in a temperate deciduous forest
• Figure 6.4 on page 95

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Energy Flow in an Ecosystem

• the Sun is the source of all ecosystem energy
• producers make food via photosynthesis
• consumers eat plants and other consumers to get
  energy
• each time energy moves from one organism to
  another, energy leaves the system in the form of
  heat
• decomposers return nutrients to the soil but
  energy is not recycled

• Figure 6.5 on page 95 main energy flows in an
  ecosystem

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Food Pyramid

• is a diagram showing each trophic level as a
  horizontal bar
• producers are located on bottom higher trophic
  levels are placed on top of each other
• each bar is drawn in proportion to the mass of
  organisms, giving the triangle shape
• (See Figure 6.6, Page 96)

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Food Pyramids

• Pyramid of Numbers
• There are fewer organisms at each increasing
  trophic level
• less energy available at each increasing level
• fewer organisms can obtain energy to live
• therefore fewer organisms at increasing levels

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Food Pyramids

• Pyramid of Energy
• There is a high degree of energy loss at each
  trophic level
• The producers only store 1 of the sun's energy
  as food energy.
• Each consumer level looses energy for several
  reasons
• much of the energy is lost as heat
• most of the energy is used to carry out life
  functionsie. we burn many calories of energy
  each day. so do all organisms if an organism
  dies without being eaten the energy goes to the
  decomposers and not up the trophic levels
• consequently only about 10-15 of the energy is
  stored as usable food energy at each level..

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Food Pyramids

• in terms of units of energy and we start with
  1000 units of energy at the producer level then
• the primary consumers would only have 100-150
  units of food energy stored for the next level
• the secondary consumers would only have 10-15
  units of food energy stored for the next trophic
  level
• the tertiary consumers would only have 1-1.5
  units of food energy stored as food energyit is
  easy to see why we do not often see a quaternary
  trophic level

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Implications

• people can gain much more energy from consuming
  plants for food than eating animals higher up
  food chain
• Much more food energy can be supplied to humans
  by using land to grow edible plants/crops than by
  using land for pasture to feed animals

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Unfortunate Consequence

• Biological Amplification
• Toxic chemicals introduced at low trophic levels
  build up through the food chain and reach
  amplified proportions by the time higher order
  consumers join the chain
• Consumers eat organisms that contain toxic
  chemicals, they receive a higher concentration of
  the toxins than did the lower-level organisms
  because
• Toxic chemicals are fat soluble (collect and
  remain in tissue of organisms and do not get
  flushed away in waste)
• Higher up an animal is in food chain, more
  organisms has to consume at lower levels in order
  to get all food energy it requires thus consuming
  more of the toxic chemicals