Food Chains and Food Webs

Food Chains & Food Webs

• Diagrams illustrating the flow of energy in ecosystems
• Show energy transfer at different trophic levels
  • Producers occupy the first trophic level
    • Organisms that create their own carbon compounds
    • Plants use carbon dioxide and water, making glucose during photosynthesis
    • Primary consumers are in the second trophic level
      • Herbivores that eat producers
    • Secondary consumers are in the third trophic level
      • Carnivores that eat primary consumers
    • Tertiary consumers occupy the fourth trophic level
      • Carnivores that eat secondary consumers

Energy Transfer

• Solar radiation acts as the primary energy source for Earth's ecosystems
  • Relying on energy stored in chemicals are in some unusual ecosystems, like deep sea
• Energy enters food chains by producers converting sunlight into stored chemical energy
  • Stored in plant biomass
  • Living matter like plant stems and leaves compose biomass
  • A small amount of light energy gets converted into biomass chemical energy
    • Most passes through leaves, or is lost as heat
  • Primary consumers digest producer tissues
    • Products build their own tissues, transferring chemical energy to their biomass
  • Biomass within secondary consumers occurs by them eating primary consumers
    • Energy moves up food chain

Decomposition

• Bacteria, fungi and other organisms breakdown energy stored in animal waste, dead organisms, and uneaten parts of animals
• Breakdown of dead and waste material is decay.
  • Microorganisms use carbon dioxide
  • Microorganisms growth is related to reproduction and repiration
  • Nitrogen turns into nitrates
• Decay is affected by environmental factors such as temperature, oxygen concentration and water availability
• The locking of carbon for extended periods of time in the dead tissues occurs during the failure to decay
  • Creates fossil fuels like coal, oil and natural gas
  • Storing chemical energy in the form of carbon

Energy Transfer in Food Chains

• Less energy transfers to each trophic level
  • Only 10% of levels of chemical energy consumed is passed one
  • Energy is lost across a food chain
• Energy is used for cell processes and may also be transferred to the environment
  • Like cell repair, maintenance, and growth
• Wasted energy releases through:
  • Heat in cellular respiration
  • Waste materials

Food Chains

• Relative short lengths due to energy loss
• Usable energy drops too low

Calculating Energy Transfer Efficiency

• Energy transfer measures can use % calculations
  • Requires dividing a part by the whole

Pyramid Diagrams

• Pyramids can vary depending on the food chain
  • Name trophic levels on each label
• Small individuals - large numbers
• Large individuals will be fewer in number
• Provide labels to indicate the number of individuals at each of the trophic levels
• Scale must be proportionate to the number of individuals
• Grid-scale creation requires drawing of accurate pyramids

Biomass Pyramids

• Shows the mass of living tissue (biomass) at each stage of given food chains
• Pyramid shaped as bars decrease in size from the base to the top
• Less biomass is in production when losses occur in the food chain
• Pyramids of biomass must have clear labels to indicate the level of the trophic and biomass

Carbon Cycle

• Carbon elements require recycling for effective ecosystems
• Built from biological molecules like Carbohydrates/fats/proteins
• Carbon in bodies are released into the atmosphere to be available again
• Plants get carbon during photosynthesis using carbon dioxide
• Plants turn Glucose into fat, carbs and proteins
• Animals transfer the carbon when consuming plants
• Organisms are returned when respiring:
  • Plants and animals undergo respiration
  • Microorganisms use dead material through Co2 release during decompisition
• Fossil fuel usage releases carbon back into the atmosphere

Nitrogen Cycle

• Nitrogen in atmosphere/biological molecules of organisms move through the nitrogen cycle
• Organisms obtain N2 through nitrogen fixation
  • Bacteria converts N2 gases into soil amonium
    • Turns into soil nitrates
  • Nitrogen-fixing bacteria live freely in legume roots.
• Lighning and fertalizers gas are able to fix nitrogen gas
• The nitrates in the soil are used to make plant proteins
• Nitrogen is gained through animals consuming plants
• Bacteria/fungi breakdown living organisms- Release ammonia
  • Then returned in soil

Ammonia

• Urea/faeces breakdown occurs- converted into ammonia through bacterial urease enzyme
• Bacteria converts ammonia into nitrates
• Nitrogen cycle steps
  • Fixation, decompsition and denitrification

Nitrogen Cycle Factors

• Microorganisms regulate it via temp/oxygen/levels and presence of heavy metals
  • Can determine the rate of decmoposition in areas like compost heaps
    • Urease breaks down urea to release ammonia

Human Impact on the Environment

Factors affecting human: Population growth Agriculture Industry Housing Resources Other Species Environmental Impact

• Environmental Impact Assessment (EIA)
• Proposed developments
• Completed environmental impact assessment
  • Determine the effects on local wildlife to protect species
  • Developers are able to avoid endangered species
  • Site conditions will grant permision Governmental agencies seek to reduce impact on environment
  • Ensure a sustainable world
  • Provide waste management

Pollution

• Indicator Species
• Oxygen Levels / pH

Water Pollution

• Raw untreated sewage is washed in the water
• Eutrophication is one cause of this.
• Excess minerals in water
  • Lack of growth in the surfaces below
  • Dependant organisms die.
  • Decomposers deplete oxygen
• Indicator diagrams are important to denote high or low levels of DO2
• Indicator species are used in the measure of water pollution
• Can vary depending on the environmental conditions

Lichen (Air Pollution)

• Lichen types are useful for indicator pollution.
• Relates to sulfur dioxide presence
• Lichen determines of air pollutants
  • High abundancy = clean
  • Bushy= very clean
  • Crustose=more polluted
• Indicator species do not provide quantitative measurement
• Data must be used with two+ lichens species to accurately mesasure pollution

Intensive Farming Methods

• More food output requires a high food output method
• Methods that aim at reducing energy and land
• Advatanges and disadvatanges to these methods
• Farm machinery helps monitor crop and reduce fossils
• Use chemical fertalizers to increase product as well as kill bugs
• Inbreed to protect a taste and yeild- however, reduced biodiversity
• Antibiotics are used to prevent diseases but can create overuse
• Battery farming = disease control
• Battery farming reduces space requirement to promote greater output
• Can have negative effects on the welfare of animals