Food Chains

• What do food chains illustrate in an ecosystem?

  What gets eaten by what
• How does a food chain differ from a food web?

  A food chain shows one interaction chain
• What is the starting point of all food chains?

  A producer
• What is a producer in a food chain?

  A photosynthetic organism like grass
• What does the term 'photosynthetic' mean?

  Can produce glucose using sunlight
• What do we call the biological molecules produced by plants?

  Biomass
• Who are the primary consumers in a food chain?

  Organisms that eat producers
• What is the role of secondary consumers?

  They feed on primary consumers
• What does 'tertiary' refer to in a food chain?

  The third level of consumers
• What happens to energy as it moves up the food chain?

  Most of it gets lost
• If there are 1,000 joules of energy in grass, how much energy is passed to mice?

  About 100 joules
• How much energy might be passed to the owl from the mice?

  About 20 joules
• What do the arrows in a food chain represent?

  The flow of energy
• What is a predator-prey cycle?

  Population variations of predators and prey
• How do the populations of field mice and owls vary over time?

  They cycle up and down together
• What does it mean when we say predator and prey populations are out of phase?

  Predator population lags behind prey population
• What happens to the mouse population when the owl population is low?

  The mouse population increases
• What occurs when there are many mice available for owls?

  The owl population starts to increase
• What happens when the owl population becomes too high?

  The mouse population declines
• Why do populations cycle rather than reach equilibrium?

  It takes time for populations to change
• What is the main reason for the lag in predator-prey cycles?

  Time for populations to breed
• What are the steps in a food chain?

  1. Producer (e.g., grass)
  2. Primary consumer (e.g., mice)
  3. Secondary consumer (e.g., owls)
  4. Tertiary consumer (if present)
  5. Energy flow represented by arrows
• What are the key features of predator-prey cycles?

  • Populations cycle up and down
  • Predator population lags behind prey
  • Changes in one affect the other
  • Cycle repeats over time