5.1b Energy in Ecosystems

01/05/2013 § Leave a comment

We’d discussed the flow of energy a little bit in the previous blog, in terms of food chains, I think. Most importantly, the arrows pointing upwards always show energy flow from the producers to the primary consumers to the secondary consumers, and so on and so forth.

Energy flow through each trophic level in a community can be shown in energy pyramids. Each rectangle in an energy pyramid shows the amount of energy per square metro of area per year. Each rectangle is always smaller or thinner than the pyramid on the level below it, or its previous level. This demonstrates the loss of energy in the transformation of energy from the first trophic level to the next trophic level. The mass is lost as well as energy so the energy content per gram of the tissues of each successive trophic level is not lower.

The law of physics is what helps to understand the loss of energy. The law states that energy transformations are never 100% efficient and in this case, that’s very true. Energy is lost in multiple ways. It’s possible for organisms to die before the next trophic level eats them. Also, parts of the organism aren’t really edible, like the bones or hair. Similarly, parts of organism are indigestible and are turned to feces. Lastly, a lot of the energy is used in respiration in the form of ATP when muscles contract or when active transport requires energy. Energy lost through cell respiration is normally lost as heat.

Essay Questions (nothing new is highlighted)

  1. Outline what is meant by the trophic level of an organism with three examples from one named habitat. (4 max)
  2. Compare the ways in which autotrophic, heterotrophic and saprotrophic organisms obtain energy. (6 max)
  3. Draw a labelled sigmoid population growth curve. 4 marks
  4. Explain the factors that cause a population to follow the sigmoid ( S-shaped) growth curve. (8 max)
  5. Apply the concept of carrying capacity to the struggle for survival resulting from overproduction of offspring. (5 max)
  6. Outline the international system used for naming species of living organisms. (4 max)
  7. Discuss the definition of the term species. (8 max)
  8. Name the levels and the specific taxa in the hierachy of classification using humans as an example. (2 max)
  9. Describe the relationship between the rise in the concentration of atmospheric carbon dioxide and the enhanced greenhouse effect. 5 marks
  10. Outline the consequences of a global temperature rise on arctic ecosystems. 6 marks
  11. Outline the precautionary principle. 5 marks
  12. Outline the structural differences which characterize bryophytes, filicinophytes, coniferophytes and angiospermophytes. 9 marks
  13. List the structural differences between bryophytes and angiospermophytes. 5 marks
  14. Briefly explain Darwin`s theory of evolution. 4 marks
  15. Outline five types of evidence which support the theory of evolution by natural selection. 6 marks
  16. Outline one modern example of observed evolution by natural selection. 2 marks
  17. Explain the evidence from homologous anatomical structures that supports the theory of evolution. 6 marks
  18. Outline how antibiotic resistance in bacteria can arise in response to environmental change. 5 marks
  19. Antibiotic resistance in bacteria is an example of evolution in response to environmental change. Using another example, explain how an environmental change can lead to evolution. 8 marks



Page 179, a marine food web

1. State the trophic level of nanophytoplankton. —> Producer.

2. Identify two primary consumers in the food web. —> nanozooplankton and microzooplankton

3. Identify in the food web:

  • a) the shortest food chain —> bacteria – nanozooplankton
  • b) the longest food chain —> nanophytoplankton – microzooplankton – macrozooplankton – small fish and squid – emperor penguins – leopard seal – toothed whales
  • c) the species with the most predators —> small fish and squid
  • d) the species with the greatest number of different types of prey —> toothed whales

4. Discuss the trophic level to which emperor penguins should be assigned. —> Emperor penguins are either tertiary consumers or quaternary consumers depending on what they eat. If they eat krill, that makes them a tertiary consumer. If they eat small fish and squid, they’re regarded then as a quaternary consumer. This gives them more options and a choice in how much energy they want to consume when eating other organisms.

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