Keystone Species


Hello Scientists!

Today we will be learning about food webs, keystone species, and the importance of trophic cascades. You will be asked to apply the new material to create your own food webs. Please complete the tasks in order and be prepared for the evaluation. We will share our findings with the class and get feedback on our food webs.

I look forward to seeing everyone's unique food webs! Be as creative as you want!


For Task 1, please watch the video below.

  • Pause at the 2:55 mark and in your notebooks write down your observations and predictions to the graph presented
  • Pause at the 3:28 mark and in your notebooks draw out the food web they present and answer the questions:
    • How would the removal of sea otters impact the flow of energy through the system?
    • Which species would be negatively impacted?
    • Would any be positively impacted?

Please come to class prepared to share your findings.

For Task 2, please create your own food web (not food chain).

  • It can be aquatic or terrestrial 
  • Include at least 4 trophic levels
  • Make sure the arrows are pointing in the correct direction for the flow of energy
  • Either draw, print, or label your organisms
  • Be creative!

For the evaluation, please answer the following questions in your notebook:

  1. What is the difference between a food chain and a food web?
  2. In your own words, explain what a keystone species is.
  3. Why are keystone species important to ecosystems?
  4. What is a trophic cascade?

Congrats students! You completed this WebQuest!

For your final item, please write on an index card what you liked about this WebQuest and what could be changed/improved for future uses. A few sentences or a bulleted list will be fine.

I will collect index cards in class.

Thank you!

Teacher Page

This WebQuest was created to teach students about the importance of keystone species and so that students would practice creating and recognizing food webs. The standards covered are:

LS2.C:  Ecosystem Dynamics, Functioning, and Resilience

  • A complex set of interactions within an ecosystem can keep its numbers and types of organisms relatively constant over long periods of time under stable conditions. If a modest biological or physical disturbance to an ecosystem occurs, it may return to its more or less original status (i.e., the ecosystem is resilient), as opposed to becoming a very different ecosystem. Extreme fluctuations in conditions or the size of any population, however, can challenge the functioning of ecosystems in terms of resources and habitat availability. (HS-LS2-2), (HS-LS2-6)
  • Moreover, anthropogenic changes (induced by human activity) in the environment—including habitat destruction, pollution, introduction of invasive species, overexploitation, and climate change—can disrupt an ecosystem and threaten the survival of some species. (HS-LS2-7)

Students are to complete this WebQuest at home and come to class the next day prepared to share their thoughts and results.