Biology

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• Terrestrial (land) food chain

  • Water lily
  • Water beetle
  • Small fish
  • Large fish
• Aquatic (water) food chain


  • Phytoplankton
  • Zooplankton
  • Tilapia
  • Shark
• Food web


  Interconnected food chains in an ecosystem (a community and its physical environment)
• Feeding relationships in ecosystems are never straight chains
• Many types of organisms can occupy one level and one type of organism may feed at different levels
• Omnivores


  Organisms that feed on organisms at all trophic levels; plants, animals and fungi
• Pyramid diagrams


  • Pyramid of numbers
  • Pyramid of energy
  • Pyramid of biomass
• Pyramid of numbers


  Based on counting the number of organisms at each trophic level
• Pyramid of energy


  Shows the relative amount of available energy at each trophic level
• Pyramid of biomass


  Biomass refers to the total mass of the organism and is estimated for each trophic level
• Biomass decreases with successively higher feeding levels
• Symbiosis


  Close relationship which exists between two or more organisms of different species living together
• Types of symbiotic relationships

  • Mutualism
  • Parasitism
  • Commensalism
• Mutualism


  Close relationship between living organisms of different species which is beneficial to both organisms
• Ruminants


  Contain cellulose digesting bacteria that convert cellulose into simple compounds
• Leguminous plants


  Contain nitrogen-fixing bacteria living in root nodules
• Parasitism


  Close relationship between two living organisms of different species which benefits one (the parasite) and harms the other (the host)
• Types of parasites


  • Ectoparasites
  • Endoparasites
• Parasites possess numerous adaptations that allow them to survive inside or outside the host
• Commensalism


  Close relationship between two living organisms of different species which benefits one (the commensal) and does not affect the other (the host)
• Examples of commensalism


  • Remora and sharks/stingrays
  • Hermit crab and abandoned shells
  • Spanish moss and oak trees
• Epiphytes


  Plants that grow upon other plants but do not suck them
• In all ecosystems, materials are cycled between the environment and the organism
• Human activity generally affects the movement of material through the cycles and in turn upset the balance of cycles
• Carbon cycle


  The main source of carbon for living organisms is the 0.03% of carbon dioxide in the atmosphere and the gas is also dissolved in surface waters
• Carbon cycle


  1. Carbon dioxide is incorporated into organic compounds during photosynthesis by green plants

  2. Carbon compounds move through the food chains

  3. Carbon dioxide is returned to the atmosphere when living organisms respire

  4. Decay activities of decomposers release carbon dioxide
• Carbon may be trapped in limestone and fossil fuels only to be released by weathering and combustion
• Nitrogen cycle


  Nitrogen in the atmosphere is very unreactive and cannot be utilized by plants in the gaseous form
• Nitrogen cycle


  1. Nitrogen-fixing bacteria form nitrogenous compounds from gaseous nitrogen

  2. Nitrogen compounds are converted into nitrites and nitrates by nitrifying bacteria

  3. Green plants absorb the nitrates dissolved in soil water

  4. Denitrifying bacteria convert nitrogenous compounds into gaseous nitrogen