Food Chains & Predator Prey Cycle

• 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 chain
• 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 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 is passed to the 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 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 predator and prey populations are out of phase?

  The predator population lags behind the prey
• 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 starts to decline
• 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 population growth?

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

  • Producers (e.g., green plants)
  • Primary consumers (e.g., mice)
  • Secondary consumers (e.g., owls)
  • Tertiary consumers (if present)
  • Energy flow represented by arrows
• What are the stages of the predator-prey cycle?

  1. Low predator population, increasing prey population
  2. High prey population, increasing predator population
  3. High predator population, declining prey population
  4. Declining predator population, increasing prey population
  5. Cycle repeats