Standard LS.7
VDOE - Revised 2003 Standards

Standard LS.7
The student will investigate and understand that organisms within an ecosystem are dependent on one another and on nonliving components of the environment. Key concepts include
a) the carbon, water, and nitrogen cycles;
b) interactions resulting in a flow of energy and matter throughout the system;
c) complex relationships within terrestrial, freshwater, and marine ecosystems; and
d) energy flow in food webs and energy pyramids.

Overview / Key Concepts

• In order to understand how an ecosystem functions, one must understand the concept of a system and be able to envision models of systems.

• To analyze the interactions resulting in a flow of energy and matter throughout the ecosystem, one must identify the elements of the system and interpret how energy and matter are used by each organism.

• Many important elements and compounds cycle through the living and nonliving components of the environment as a chain of events that continuously repeats.

• Energy enters an ecosystem through the process of photosynthesis and is passed through the system as one organism eats and is, in turn, eaten.
This energy flow can be modeled through relationships expressed in food webs.

• Materials are recycled and made available through the action of decomposers.

• The amount of energy available to each successive trophic level (producer, first-order consumer, second-order consumer, third-order consumer) decreases. This can be modeled through an energy pyramid, in which the producers provide the broad base that supports the other interactions in the system.


Knowledge & Skills

• classify organisms found in local ecosystems as producers or first-, second-, or third-order consumers. Design and construct models of food webs with these organisms.

• observe local ecosystems and identify, measure, and classify the living and nonliving components.

• identify examples of interdependence in terrestrial, freshwater, and marine ecosystems.
• differentiate among key processes in the water, carbon, and nitrogen cycles and analyze how organisms, from bacteria and fungi to third-order consumers, function in these cycles.

• determine the relationship between a population’s position in a food web and its size.

• apply the concepts of food chains, food webs, and energy pyramids to analyze how energy and matter flow through an ecosystem.