food chains

• What is the main focus of today's video?

  Energy passing through an ecosystem
• 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 a food chain?

  A producer, like a green plant
• What does "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 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
• If there are 1,000 joules of energy in grass, how much energy might be passed to mice?

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

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

  The flow of energy up the chain
• 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 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?

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

  The mouse population declines
• Why does the owl population decline after it peaks?

  There are fewer mice to eat
• What allows the mouse population to rise again?

  The decline of the owl population
• Why do predator-prey cycles not reach a steady equilibrium?

  Populations take time to increase or decrease
• How long does it take for owl populations to increase?

  Multiple generations of breeding
• What are the main components of a food chain?

  • Producers (e.g., grass)
  • Primary consumers (e.g., mice)
  • Secondary consumers (e.g., owls)
  • Tertiary consumers (if present)
• What are the stages of the predator-prey cycle?

  1. Low owl population, increasing mouse population
  2. High mouse population, increasing owl population
  3. High owl population, declining mouse population
  4. Declining owl population, rising mouse population
  5. Cycle repeats