In this video about IB ESS Topic 2.2 Communities and ecosystems, I cover the concepts of communities and ecosystems, how they are structured, and how energy and matter flow through them. The video explains the following concepts:
Food chains and trophic levels: A food chain shows the linear transfer of energy and matter from one organism to another. Trophic levels are the positions of organisms in a food chain. The video gives examples of food chains and how to identify the trophic levels of producers, consumers, and decomposers.
Food webs: A food web shows the complex network of feeding relationships in an ecosystem. The video compares food chains and food webs, and explains the roles of keystone species, omnivores, and detritivores in a food web.
Ecological pyramids: Ecological pyramids are graphical representations of the relative amounts of energy, biomass, or numbers of organisms at each trophic level in an ecosystem. The video describes the three types of ecological pyramids: pyramid of energy, pyramid of biomass, and pyramid of numbers. It also explains why energy pyramids are always upright, while biomass and numbers pyramids can be inverted.
Bioaccumulation and biomagnification: Bioaccumulation is the increase in concentration of a substance in an organism over time. Biomagnification is the increase in concentration of a substance along a food chain. The video illustrates how these processes affect organisms in an ecosystem, especially those at higher trophic levels.
The key words and concepts that students must know for topic 2.2 are:
Community
Ecosystem
Trophic level
Producer
Consumer
Decomposer
Food web
Omnivore
Detritivore
Ecological pyramid
Pyramid of energy
Pyramid of biomass
Pyramid of numbers
Bioaccumulation
Biomagnification
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