Science in Focus: Shedding Light: Workshop 6

Energy and Ecosystems

In this program participants are shown that light energy that has been absorbed by plants during photosynthesis and transformed into chemical energy can now be transferred to other organisms. Energy is contained within food molecules such as sugar and starch made by plants, therefore when animals eat plants, or eat other animals, the energy is passed to them.

However, the transfer of energy between plants and animals is inefficient and there are energy losses. Consequently, energy must constantly be put into natural systems. The source of energy for ecosystems is generally visible light energy.

Energy transfer between organisms can be described by constructing food chains and food webs for each ecosystem. In this program, we shall visit classrooms where children are learning about chains and webs. We shall also look at the interconnectedness of organisms in pond and ocean ecosystems.

Finally, the program will show that matter from the bodies of dead organisms is decomposed by bacteria, fungi and worms. The process of decomposition returns nutrients, such as minerals and carbon dioxide, to the environment for future plant growth.

This program illustrates some important aspects of our understanding of energy:

Energy can be transferred and transformed, but it cannot be created or destroyed.
Some energy will be lost to the system as it is undergoing a transformation and is generally given off as heat.

While matter in ecosystems can be recycled, energy cannot. Energy flows through ecosystems and must constantly be provided to plants for photosynthesis by the Sun.

Learning Objectives

Participants will gain:

An understanding that plants and animals are interconnected in ecosystems by their feeding relationships because food contains energy.
Recognition that energy is transferred and transformed as it flows through an ecosystem from the Sun as the source to producers which make food and on to consumers which eat food.
Recognition that because the transfer of energy between organisms is inefficient, ecosystems must receive a continuous input of light energy to sustain them.

Standards

National Science Education Standards

K-4 Standards: http://bob.nap.edu/html/nses/html/6c.html#csck4

All animals depend on plants. Some animals eat plants for food. Other animals eat animals that eat plants.

Content Standards: K-4: Life Science: Organisms and Their Environments

5-8 Standards: http://bob.nap.edu/html/nses/html/6d.html#csc58

Populations of organisms can be categorized by the function they serve in an ecosystem. Plants and some micro-organisms are producers Ð 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.
For ecosystems, the major source of energy is sunlight. Energy entering ecosystems as sunlight is transferred by producers into chemical energy through photosynthesis. That energy then passes from organism to organism in food webs.

Content Standards: 5-8: Life Science: Population and Ecosystems