Life in the ocean is characterized by great diversity. The smallest and the largest forms of life on Earth are found in the ocean. The range of sizes goes from the tiny bacteria which are less than 1 micron (about one hundred thousandths of an inch) in size to the blue whale which is 30 meters (100 feet) long. As on land, the number of individuals is greater for smaller organisms than for larger ones. Ocean life adapts to water motion and the patterns of physical and chemical properties. Favorable physical and chemical substrates -- the base on which organisms live and grow -- facilitate the explosion of diverse communities. Other non-living factors that influence the patterns of ocean life include large-scale circulation, local tides, and storm events.
Knowing this, scientists try to create order out of all the observations about plants and animals that they have made. Biologists identity plants and animals in the field by carefully describing all distinguishing characteristics (shape, color, size, etc.). They can then look them up in field identification guides. Correct identification of members in a habitat is important because it allows scientists to describe and monitor changes within and between species. Moreover, changes in a species' population might indicate a change in the physical environment.
In this activity, students will explore one process by which biologists identify and classify organisms: they will observe and record distinguishing characteristics of classroom "organisms" (pencils, pens, and crayons). They will record as many details as possible and use their notes as a field guide to help identify their species.
  • Species are groups of the same kinds of organisms that can be described as having a unique set of distinguishing characteristics
  • Observing and recording distinguishing characteristics enables scientists to identify organisms
  • Correctly identifying organisms helps scientists define a system of species called a community, and to monitor changes within a community
1 pencil, 1 ball-point pen, 1 crayon in a paper bag for each group of students (Optional: Use plastic fish of different sizes, shapes and colors that are slightly different from one another.), 1 data sheet for each group, Watch or timer
Sort one pencil, one pen, and one crayon and place in a bag. All of the pencils, crayons, and pens used should be slightly different from one another. For example, pencils can have slightly different lengths, crayons can be the same color but have variations in the paper wrapper, and pens can have different colored caps. In the general analogy being used, a red crayon would be an example of an individual organism, and all crayons would represent a species. Groups of pencils, pens, and crayons would represent communities. When the students have finished recording their observations of their different organisms, collect all of the pencils, pens, and crayons. Mix them up and set them out at several different locations around the room. The students will have to move from station to station and try to identify their organisms using their notes. Make sure that the students do not know about the identification part of the activity. This will prevent students from marking their objects during the first part of the activity beforehand. Divide class into small groups.
Many biologists identify organisms within ecosystems using field guides. As a researcher, you need to correctly describe the community of organisms in your bag. In this activity, you will make and then use a field guide to help you to identify the subtle variations in different organisms in your "classroom community."
  1. Each group should collect a bag and a data sheet from the teacher. Within each bag is a community of classroom "organisms."
  2. Students should take one object ("organism") out of the bag at a time. They should spend one minute observing and describing the object on the data sheet. It is a good idea for them to make a quick sketch of each organism to capture its details.
  3. Continue this process with the second and third organisms. Have all students return the organisms to the teacher.
  4. The classroom communities will be set out at different stations around the room. Students will move from station to station and find their objects (specific organisms) observed in steps 2 and 3. They may use only their observation sheets as a reference.
  5. The ability to clearly communicate information is an important aspect of science. Test the student's ability to communicate by having them exchange their data sheets with another group. See if anyone can identify their organisms using their notes.
  6. What sets of objects from the various communities might be classified as the same species? In other words, what organisms might be put into one category because of shared characteristics, even though individual organisms vary slightly, for example, in shape or size?
  7. When do biologists use field guides? Are there any instances when a field guide might not help to identify an organism? What other techniques or instruments might help biologists identify species?
  8. Discuss the role of microscopic observation in accurately describing phytoplankton. What types of attributes do phytoplankton have that can be identified using microcopes? What about those that cannot be identified by microscope? What other techniques might be used?
  • Have students create field guides for animals and/or plants that they find on the school grounds, or around their houses, or in a park.
  • Conduct this activity in conjunction with samples collected in Build a Plankton Net. Using the principles learned in this activity, can students easily group plankton by shape? Size? Color?
  • Read the material in "Classifying Isn't Easy". Discuss the challenges associated with classifying organisms that are unlike any others ever studied before. Brainstorm about how future breakthroughs in cell imaging techniques might change our present-day classification schemes.
Adapted from Long, Jennifer, Science Television Curriculum, Orange County Marine Institute, Dana Point, CA. 1993 AND "Visit to an Ocean Planet" CD-ROM, Copyright 1998, California Institute of Technology and its licenses.