Trophic levels

• What does a food chain illustrate?

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

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

  A producer, like a green plant
• What does the term "photosynthetic" mean?

  Organisms produce glucose using sunlight
• What is biomass in the context of plants?

  Incorporated biological molecules in plants
• 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 type of animal is typically a secondary consumer?

  A predator, like an owl
• What does the term "tertiary consumer" refer to?

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

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

  About 100 joules
• How much energy might an owl receive from the food chain?

  About 20 joules
• How do the populations of field mice and owls vary over time?

  They cycle up and down together
• What do the arrows in a food chain represent?

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

  Population variations of predators and prey
• What does it mean when we say 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 significantly
• 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 begins to decline
• Why does the cycle of predator and prey populations repeat?

  Due to time taken for population changes
• What is the main reason for the predator-prey cycle?

  Time taken for populations to change
• 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)
• What are the key features of predator-prey cycles?

  • Populations cycle up and down
  • Predator population lags behind prey
  • Changes occur due to food availability