Microbiology Lesson Intro » Unit One
Unit One: Food Webs in the Marine Environment

"Go Fish...or crab, or shrimp, or shark..."


Objective
Students will use the marine environment to demonstrate an understanding of the fundamental connections between organisms based on their need for energy

Background | Materials | Procedure | Discussion


Background
All living organisms have at least one thing in common – they need energy in order to live, grow and reproduce.

Check your pulse. Is your heart beating? Of course it is, and probably faster than normal because you’re excited to start learning about food webs …

Okay, let’s just say that it’s beating, but the point is that you are a living organism, which means that you need energy to stay alive.

Try to recall all your sources of energy over the last 24 hours. Where did these sources of energy originally come from (think “beyond the supermarket”)? Where do you think your sources of energy got their energy?

A wide variety of organisms are found in the marshes, bays, and ocean environments along the coastlines of the world. Many of these animals are connected to one another in different ways through their need for energy. Although all organisms need energy, they don’t all necessarily get their energy in the same way, or from the same sources.

Some organisms, known as autotrophs or producers, can create their own food from inorganic (non-living) sources of energy such as light and chemical reactions. Most plants are autotrophs because they use light energy from the sun to power chemical reactions (known as photosynthesis) to produce the food they need.

Other organisms, known as heterotrophs or consumers, get their energy from organic (either living or once-living) sources. Most animals are heterotrophs because they get their energy by consuming other living or dead animals or plants.

Hopefully you’ve already determined whether you’re an autotroph or a heterotroph, but if not, just lay out in the sun for a few days without eating and see if you get hungry…

Believe it or not, some scientists spend their lives studying how energy and matter move between organisms, and how organisms are dependent on one another and their environment for the energy they need to survive. In addition to being interesting (yes, it can be…), this information is also important for understanding:

  • How to carefully manage species that are important sources of food for people
  • How to protect species that are endangered, or at-risk of being endangered
  • How to minimize the impacts of humans on the delicate balance of life on our planet

Most of the life on our planet resides in the ocean, and just like life on land, the plants and animals in and near the ocean are constantly trying to eat and survive without being eaten themselves. Let’s take a look at some marine organisms typically found along the Atlantic Coast of the U.S. for a better understanding of how they are connected to one another by their need for energy.

View the Marine Organisms Cards

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Materials

  • Copies of the student worksheet (PDF) for each student
  • Computers with Internet access for groups of 3-4 students
  • Copies of the Marine Organism Cards and connecting arrows for each group (printable version)

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Procedure

  1. Divide students into groups of 3-4 based on the available number of computers, or preferred group size
  2. Review with students that all organisms need energy to live and grow. Ask them to consider that they are organisms, and therefore need energy. Have each student reflect on all their sources of energy over the last 24 hours. Where did these sources of energy originally come from (think “beyond the supermarket”)? Where do they think their sources of energy got their energy? Students can record their responses on the student worksheet.
  3. In groups, have the students review the Marine Organisms Cards. Once all the cards have been reviewed, tell the students that all of these organisms are related through their need for energy. Ask the groups to spread out the cards and arrange them in whatever fashion they choose to depict the relationships between the organisms. The groups should use the accompanying arrows to indicate connections between the organisms (note: arrow length varies simply to allow for differences in spacing between the cards).
  4. Ask students to record any questions that arise in their groups as part of the process on their worksheets
  5. Once the groups have arranged their organism cards, allow them a few minutes to rotate to see the results of other groups and note any differences in how the cards are arranged between groups.
  6. Initiate a brief discussion to address any questions that arose within groups as they arranged their cards, and any differences the groups noted as they reviewed how other groups arranged their cards.
  7. Assign each group to a computer station and have them link to the Marine Food Web Challenge. Each group should proceed through the guided tutorial and record responses on their worksheets, ultimately arriving at the interactive feature where they can attempt to create a sample marine food web. In addition to the abbreviated clues provided in the interactive feature, groups can also refer to their organisms cards for more details when trying to create their marine food web.

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Questions for Discussion

  1. Can you assume that all sharks would fit into the same trophic level in a marine food web? Why, or why not?
  2. What do you think happens to organisms that die but aren’t directly consumed by a predator?
  3. Do you think all organisms stay at only one trophic level in the food web throughout their lives? If not, why?

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