Unit 2

• What are the main components discussed in Unit 2 of the study material?

  Food chains, food webs, and food pyramids
• What does a food chain illustrate?

  A food chain shows how each living thing gets its food and how energy passes from one trophic level to the next
• What is the starting point of a food chain?

  A food chain always starts with a producer
• Why can a food chain not have too many links?

  Because the animals at the end would not get enough food and energy to stay alive
• What is the primary source of energy for food chains?


  The primary source of energy for food chains is the Sun
• How does energy flow in a food chain?

  Energy flows from the Sun to producers and then to other trophic levels
• What do the arrows in a food chain represent?

  The arrows indicate the direction in which energy flows and mean "eaten by"
• What happens to energy when plants and animals die?

  The energy is used by decomposers
• What is the difference between a food chain and a food web?

  • A food chain shows a linear sequence of energy flow.
  • A food web shows interconnected food chains and is more accurate in representing energy flow in ecosystems.
• Why are food webs considered more accurate than food chains?


  Food webs account for the fact that most organisms eat more than one kind of food and are part of multiple food chains
• What is the efficiency of energy transfer between trophic levels?

  Energy transfers between trophic levels are not 100% efficient
• What percentage of energy is typically stored in a herbivore after it eats plants?

  About 10% of the energy from the plant food becomes stored in the herbivore
• What happens to the energy that is not stored in the herbivore?

  The rest of the energy is lost as heat or waste, or used for life processes
• How does energy loss affect the number of organisms at each trophic level?

  As energy is lost between trophic levels, there are fewer organisms at each successive level
• What are the three types of ecological pyramids?

  1. Pyramid of energy
  2. Pyramid of numbers
  3. Pyramid of biomass
• What does a pyramid of energy show?

  A pyramid of energy shows the relative amount of energy available at each trophic level
• Why is the base of a pyramid of energy wider than the top?

  Because there is a large amount of energy trapped in the producers at the bottom
• What does a pyramid of numbers illustrate?

  A pyramid of numbers illustrates the number of organisms at each trophic level
• What does a pyramid of biomass show?

  A pyramid of biomass shows the total mass of living tissue at each level
• How does the mass of organisms change as you move up a pyramid of biomass?

  A larger mass of organisms is needed at lower levels to support a smaller mass at higher levels
• Why do animals at the top of the pyramid need to eat large quantities of organisms at lower levels?

  Because a lot of energy is lost between trophic levels