Food Chains & Predator Prey Cycles #85

• 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 "photosynthetic" mean?

  Organism produces 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?

  Third level consumer in a food chain
• What happens to energy as it moves up the food chain?

  Most energy gets lost at each level
• If there are 1,000 joules in grass, how much energy reaches mice?

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

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

  Flow of energy up the chain
• What is a predator-prey cycle?

  Population variations of predators and prey
• How do predator and prey populations interact over time?

  They cycle up and down together
• What does it mean when 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?

  Mouse population increases
• What occurs when there are many mice available?

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

  Mouse population starts to decline
• Why do populations cycle rather than reach equilibrium?

  It takes time for populations to change
• What is necessary 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, increasing mouse population
  5. Cycle repeats
• What is the significance of energy loss in food chains?

  • Energy diminishes at each trophic level
  • Only a fraction of energy is passed on
  • Impacts population sizes and ecosystem dynamics