Food chains

• What should you be able to do by the end of this video?

  Use food chains to represent feeding relationships
• How do the numbers of predators and prey change over time?

  They change in cycles
• What is a biotic factor that affects organisms?

  A source of food
• What do scientists use food chains to represent?

  Feeding relationships within a community
• What is the first organism in the simple food chain shown?

  Grass
• In the food chain with grass, what eats the rabbits?

  Foxes
• What is the producer in the second food chain shown?

  A tree
• What do scientists call organisms that eat producers?

  Primary consumers
• In the first food chain, who is the primary consumer?

  The rabbit
• What is a secondary consumer?

  An animal that eats a primary consumer
• In the food chain with four stages, who is the tertiary consumer?

  The bird of prey
• What are consumers that kill and eat other animals called?

  Predators
• In the first food chain, what is the prey?

  The rabbit
• In the second food chain, who is the prey?

  The caterpillar
• What do predator-prey population graphs typically show?

  • Populations rise and fall in cycles
  • Example: rabbits and foxes
• What happens to the rabbit population during a warm summer?

  It increases due to more food
• What occurs after the rabbit population increases?

  The fox population also increases
• What happens when the fox population increases?

  More rabbits are eaten, decreasing their population
• What is a stable community?

  One where biotic and abiotic factors are balanced
• What can disrupt predator-prey cycles?

  A drought or a new predator
• What are the key components of a food chain?

  • Producers
  • Primary consumers
  • Secondary consumers
  • Tertiary consumers
  • Predators and prey
• What is the role of producers in food chains?

  • Synthesize complex molecules
  • Source of biomass for consumers
  • Typically green plants or algae
• How do predator-prey relationships affect population dynamics?

  • Populations rise and fall in cycles
  • Balance between predator and prey populations
  • Influenced by environmental factors