A2 Energy Flow Through the Biosphere PDF

A2 - Energy Flow Through the Biosphere I can… Link the roles of producers and consumers to energy flow in the biosphere Discuss and provide examples of energy flow through trophic levels Quantitatively interpret the flow of energy using models, such as pyramids of energy, numbers...

A2 - Energy Flow Through the Biosphere I can… Link the roles of producers and consumers to energy flow in the biosphere Discuss and provide examples of energy flow through trophic levels Quantitatively interpret the flow of energy using models, such as pyramids of energy, numbers, and biomass Food Chains vs. Food Webs Food chain: A model that shows the linear pathway through which energy moves in ecosystems Food web: Shows connections between different food chains Food Webs Food webs are used to represent energy transfer within an ecosystem as opposed to linear food chains Are a more accurate reflection of an ecosystem, as they allow us to show how some organisms feed at multiple trophic levels Arrows always point in the direction of energy flow Energy Transfer Between Trophic Levels Most food chains have very few trophic levels ○ Length is limited by thermodynamics - only some energy is transferred from one level to another Amount of energy transferred from one level to the next ranges (~5-20%) ○ Remaining energy isn’t passed on because it isn’t stored in tissues ○ 80-95% isn’t available from one level to the next, it is lost as heat Recall Rule of 10: Only about 10% of energy is passed on from one trophic level to the next Ecological Pyramids Ecological pyramids: Used to model feeding relationships throughout the trophic levels Represent distribution of energy, biomass, or number of organisms in an ecosystem Three types: ○ Pyramid of Numbers ○ Pyramid of Biomass ○ Pyramid of Energy Pyramid of Numbers Each bar of the pyramid represents a different trophic level The width represents relative numbers of organisms at that level Because more energy is available to lower trophic levels, the number of producers usually outnumbers the consumers an ecosystem Grassland ecosystem Forest ecosystem Pyramid of Biomass Biomass: Dry mass of living organisms per unit of area (g/m2) Pyramid of biomass indicates biomass present at each trophic level in an ecosystem Is a better demonstration of how energy is transferred from one trophic level to another ○ Because it takes into account the size of the organisms rather than just the number In what type of ecosystem might you see an inverted pyramid of biomass? Inverted Pyramids Pyramids of numbers and biomass can sometime be inverted (upside down) due to certain situations within ecosystems ○ Inverted pyramids then lose their ability to accurately represent passage of energy from one trophic level to the next Inverted numbers pyramids occurs when we have a large number of primary consumers feeding on single producers Pyramid of Energy Represents the amount of energy that is transferred through each trophic level (measured in J or kJ) Pyramids of energy will always be upright - there can never be less energy in a lower level Good at depicting why food chains are restricted in size Humans Use of Energy in Ecosystems Like all other organisms, humans are dependent on energy flow through ecosystems ○ A person eating vegetables: primary consumer ○ A person eating steak: secondary consumer ○ A person eating salmon: may be a tertiary consumer Human use of energy in an ecosystem often changes the ecosystem itself ○ Most ecosystems can adapt to small changes ○ Large-scale changes permanently change the types and sizes of populations found in the ecosystem (ex. hunting, fishing, extensive crop growth) Energy Transfer and Stability of Ecosystems As climate changes, so will distribution of organisms in an ecosystem If organisms at bottom of ecological pyramids are affected, those changes will be passed on through the food chain If ecosystem has fewer and less varied producers, then food webs in this ecosystem will change - results in more fragile ecosystem Monocultures Monoculture: Cultivation of a single species Historically, humans have used ~700 different species of plants, however today we rely on ~20 species: wheat, rice, cotton, barley, & corn Many wild plants are helpful to humans ○ Ex. Rosy periwinkle (Madagascar) helps to treats Hodgkin’s disease (leukemia), but many plant species are destroyed to grow food crops, especially in tropical rainforests Monocultures Nutrient-poor soil of tropical rain forests are not well-suited for cereal grains like wheat and barley - require renewal of decomposed matter for nitrogen and phosphorus. These cycles should not be disrupted in the rain forests Soil not renewable and will not support crops after a few seasons Greatest biodiversity exists in tropical rainforests