SC15.BIO.8 | ALEX

Science (2015) Grade(s): 09-12 - Biology

Developing and Using Models

Systems and System Models; Energy and Matter

Students know:

A food chain is a simple model representing the transfer of energy from organism to organism (e.g., sun → plant → grasshopper → mouse → snake).
Each step of a food chain represents a trophic level always starting with an autotroph in the first level and heterotrophs in the remaining levels.
The overlapping relationships between multiple food chains are shown in a food web.
An ecological pyramid is a model that can show the relative amounts of energy, biomass, or numbers of organisms at each trophic level in an ecosystem.
In an energy pyramid, only 10% of energy is passed from one trophic level to the next due to loss of energy in the form of heat caused by cellular respiration (10% rule).
In a biomass pyramid, the total mass of living matter at each trophic level tends to decrease.
In a numbers pyramid, it shows the number of organisms at each trophic level tends to decrease because there is less energy available to support organisms.
The exchange of matter through the biosphere is called the biogeochemical cycle and involves living organisms (bio), geological processes (geo), and chemical processes (chemical).

Students are able to:

Use a self-created food web diagram to predict the impact of removing one organism on other organisms within the food web.
Use data to create ecological pyramids to show flow of energy, biomass and number of organisms.
Model the cycling of matter (e.g., Carbon, water, nitrogen) through the biosphere.
Combine a food web diagram with a matter cycling diagram to provide a holistic view of the many aspects that make up an ecosystem.

Students understand that:

Everything in an ecosystem is connected to everything else (both abiotic and biotic), either directly or indirectly.
Nutrients, in the form of elements and compounds, flow through organisms in an ecosystem (e.g., grass captures substances from the air, soil and water and converts them into usable nutrients → cow eats the grass → human eats the cow → decomposers return the nutrients to the cycle at every level).