Where Have All the Salmon Gone? Teacher Notes
The brief, formative assessment resources included with these units are called "assessment probes." They are called "probes" because they are designed to probe and uncover student thinking. Teacher and researcher Page Keeley has written extensively about the probes as part of the Curriculum Topic Study approach to analyzing science and mathematics topics. See the Curriculum Topic Study website for more information. These probes are designed to be used diagnostically and formatively. They are intended to help you to tap into students' thinking about particular science topics -- topics that are identified by the National Science Education Standards as significant and developmentally appropriate for the target age level of the unit. While they are intended to sample students' thinking (and to probe for common misconceptions), they are NOT intended to measure what students have learned as a result of the unit content. We encourage you to use these tools--and to develop your own--to better understand each student's development as a learner, and to modify your teaching accordingly.
Ongoing assessment throughout the investigations is important for several reasons. It can reveal when students are confused or have misunderstandings, need more time to investigate, or need more explanation. You can tailor the investigations to meet the needs of your students, and change direction whenever necessary. Frequent assessment does not have to be time consuming or tedious. A quick assessment can give you a lot of information about student comprehension and understanding.
The purpose of this probe is to elicit students’ ideas about the ways organisms interact with and depend on one another in various ways.
The best answer is B: Bears, eagles and sea lions all depend on the salmon for food. If the salmon were not there, some of the animals may not be able to live there anymore. All the animals listed depend on salmon for food, and although salmon isn't the only thing they eat, salmon is an important part of their diet. If there were no salmon, some of the animals would more than likely leave the area.
Choice A is not the best choice because even though all the animals listed depend on salmon for food, that is not the only thing they eat and they will not all die.
Choice C is not the best choice because even though all the animals listed depend on salmon for food, and although salmon isn't the only thing they eat, salmon is an important part of their diet. If there were no salmon, some of the animals would leave the area.
"Every species is linked, directly or indirectly, with a multitude of others in an ecosystem. Ecosystems are shaped by both the nonliving environment and by its inhabitants, including humans." "Students may not regard food as a scarce resource for animals and, hence, may not consider competition among species for food resources." (Atlas of Science Literacy, Vol. 2, p. 32)
Lower elementary-school students can understand simple food links involving two organisms. Yet they often think of organisms as independent of each other but dependent on people to supply them with food and shelter. Upper elementary-school students may not believe food is a scarce resource in ecosystems, thinking that organisms can change their food at will according to the availability of particular sources (Leach et al., 1992)
Administering the Probe
Allow students to read the scenario individually. Students should choose the idea that they think best describes what might happen if there were no more salmon in the area. Make sure that students understand they need to explain their reasoning.
Grade Level Curricular and Instructional Considerations
Children build understanding of biological concepts through direct experiences with living things and their habitats, including observation and interactions with the natural world. The idea that organisms depend on their environment and on other organisms is not well developed in young children. In grades K-4, the focus should be on making sense of the way organisms live in their environments and on establishing the primary association of organisms with their environments. This should be followed in upper elementary by the secondary ideas of dependence on various aspects of the environment and of behaviors that help various animals survive. (National Science Education Standards, p. 128).
Children often understand a link between two organisms, but more often think in terms of the organisms acting independent of each other and as often dependent upon people. Students also tend to use common language rather than scientific terminology to explain their understanding and terms like “community” or “interdependence” can be confusing. For example, students can select pictures to produce a balanced community of consumers and producers, but few use the idea of interdependence to explain their selection. (Making Sense of Secondary Science, p. 60-61).
Introduction to simple food chains as a prelude to food webs may contribute to children failing to use ideas about interdependency to explain relationships in complex ecosystems. Many students think that a population high on a food chain is a predator of all the organisms below it. In addition, some students believed the change in prey population would have no effect on its predator population, while others believe an organism can change its food source if it needs to. Some students saw energy adding up through an ecosystem, such that a top predator would have all the energy from the producers and other consumers in the chain. (Making Sense of Secondary Science, p. 60-61).
Related National Science Education Standards
K-4 The Characteristics of Organisms
- Organisms have basic needs. For example, animals need air, water, and food; plants require air, water, nutrients and light. Organisms can survive only in environments in which their needs can be met.
K-4 Organisms and Their Environments
- All animals depend upon plants. Some animals eat plants for food. Other animals eat animals that eat plants.
- An organism's patterns of behavior are related to the nature of that organism's environment, including the kinds and numbers of other organisms present, the availability of food and resources, and the physical characteristics of the environment. When the environment changes, some plants and animals survive and reproduce, and others die or move to new locations.
5-8 Populations and Ecosystems
- A population consists of all individuals of a species that occur together at a given place and time. All populations living together and the physical factors with which they interact compose an ecosystem.
- Populations of organisms can be categorized by the function they serve in an ecosystem. Plants and some microbes are producers – they make their own food. All animals, including humans, are consumers, which obtain food by eating other organisms. Decomposers, primarily bacteria and fungi, are consumers that use waste materials and dead organisms for food. Food webs identify the relationships among producers, consumers and decomposers in an ecosystem.
Related Benchmarks for Science Literacy
3-5 Interdependence of Life
- For any particular environment, some kinds of plants and animals survive well, some survive less well, and some cannot survive at all.
Related Probes in Uncovering Student Ideas in Science by Page Keeley.
Habitat Change V2, p. 143