Aquatic Ecosystems

Approach

Do it:

Students engage in hands-on activities, such as setting up a model pond. Students also design and conduct their own investigation to answer a question about dragonfly nymphs.

Talk it:

Students are provided with many opportunities for small group discussions to help them make sense of science ideas. For example, students discuss how the organisms in their model pond interact, and debate whether or not they should release their mosquitofish.

Read it:

Students read nine science books, including Eat and Be Eaten, about how a real ecologist uses food chains and food webs. Students use comprehension strategies such as making connections, and learn how to navigate informational text.

Write it:

Students write scientific descriptions including descriptions of each organism in their model pond. Throughout the unit, students write to record observations and reflect on their learning.

Student Books

Learning Goals

Science Content

The Aquatic Ecosystems unit teaches important life science concepts about ecosystems, using mostly aquatic ecosystems as examples.

Ecosystems: An ecosystem is a community of organisms together with the non-living things where they live. Students learn about behaviors of organisms, interactions among organisms, and interactions between organisms and the non-living parts of the ecosystem. Students learn that factors in the non-living parts of an ecosystem, such as temperature or water clarity, affect which kinds of organisms live in the ecosystem, and where in the ecosystem certain organisms live. Students learn about a variety of ecosystems around the world.

Flow of energy and matter in ecosystems: Students learn that all organisms need energy in order to live. Organisms use energy to move, grow, reproduce, and more. Organisms also need materials to build and repair their bodies. In almost all ecosystems, the energy in the ecosystem comes from sunlight. Producers, such as plants and algae, get their energy directly from sunlight, and get the materials they need from air and water. Consumers get their energy and materials by eating other organisms. Ecologists classify consumers based on what kinds of organisms they eat: herbivores eat producers; carnivores eat other animals; omnivores eat both producers and animals; decomposers get their energy and materials from droppings and dead organisms. When a consumer eats another organism, it never gets all of the energy that organism has taken in. Some of the energy has already been used by the organism being eaten and some is left in body parts that can’t be eaten. For this reason, there is less and less energy available as you move up in an ecosystem from producers, to herbivores, to omnivores and carnivores. Because of this, in almost any ecosystem there are fewer herbivores than producers, and fewer carnivores than herbivores. Ecologists make diagrams such as food chains and food webs to help make clear what eats what in an ecosystem.

Human impact on ecosystems: Students learn that humans affect most ecosystems on Earth. Humans can harm an ecosystem with pollution, by removing organisms, or by adding kinds of organisms not originally found in the ecosystem. A change to one part of an ecosystem can affect many other parts of the ecosystem. Humans can also help ecosystems, for example by reintroducing kinds of organisms that have been removed, or preventing pollution. Knowing as much as possible about an ecosystem can help people protect the ecosystem.