Food chains

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

  Energy passing through an ecosystem
• 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 type of organism is a producer?

  Photosynthetic organism
• What does the term 'photosynthetic' mean?

  Produces glucose using sunlight
• What example of a producer is used in the video?

  Grass
• What is biomass?

  Incorporated biological molecules in plants
• Who are the primary consumers in a food chain?

  Organisms that eat producers
• What is an example of a primary consumer mentioned?

  Mice
• What is the role of secondary consumers?

  They feed on primary consumers
• What type of animal is given as an example of a secondary consumer?

  Owl
• What does the term 'tertiary consumer' refer to?

  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 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
• 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?

  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
• What allows the mouse population to rise again?

  Decline in the owl population
• Why do predator-prey cycles not reach a steady equilibrium?

  Populations take time to change
• What is necessary for owl populations to increase?

  Multiple generations of breeding
• 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 in one affect the other
• What factors influence the dynamics of predator-prey relationships?

  • Availability of food
  • Population growth rates
  • Time for breeding and reproduction