Energy Flow in Ecosystems and Biogeochemical Cycles

Hierarchy of ecology  Organism - individual living thing  Population- a group of the same species  Community – a group of different species  Ecosystem  Ecosystem – all organisms as well as nonliving things in an area  Biome - a major regional or global community of organism - can be as small as the microorganisms living on your skin or as large as the entire biosphere

What’s an Ecosystem?  An ecosystem consists of all the organisms (biotic) in a community and the environment (abiotic) with which they interact.  Biotic - living things plants animals, fungi, bacteria  Abiotic - non-living things Moisture, temperature, wind, sunlight, & soil

Biodiversity The assortment, or variety, of living things in an ecosystem KEYSTONE Species = a species that has an unusually large effect on its ecosystem

Producer Herbivore (primary consumer) Detritivores (decomposers) Carnivore (secondary consumer) Energy flow Energy flows THROUGH ecosystems – open system Chemical cycling Nutrients cycle WITHIN ecosystems – closed system

Get their energy from non-living sources and make their own food Get their energy by eating living, or once living, resources, such as plants and animals Break down organic materials into simpler cpmpounds

Energy Flow in Ecosystems  Almost all energy used in ecosystems comes from the sun  From there it flows through a food chain or web and exits the ecosystem in the form of heat, light, kinetic or chemical energy

 A food chain is a sequence that links species by their feeding relation  A food web is a model that shows the complex network of feeding relationships and flow of energy within an ecosystem

Types of Consumers  Herbivores – eat only plants  Carnivores – eat only animals  Omnivores – eat both plants and animals  Detritivores – eat detritis or dead and dying organic matter  Decomposers - - detritivores that break down organic matter into simpler compounds (example : fungi)  Decomposers

 Energy pyramids show the efficiency of energy transfer between trophic levels  Generally 10% of energy is transferred  Food chains never get beyond 4-5 trophic levels

Carnivores that eat secondary consumers Carnivores that eat herbivores Herbivores because they are the first consumer above the producer The first, or bottom, trophic level

Consumers Producers Nutrients available to producers Detritivores Biogeochemical Cycle Abiotic reservoir

Biogeochemical Cycling of Nutrients  The movement of a particular chemical through the biological and geological, or living and non-living parts of an ecosystem.  Most ecosystems require a constant inflow of energy from the sun. In terms of matter, such as oxygen and carbon, the Earth is a closed system and it recycles its resources.  Water cycle  Oxygen cycle  Carbon cycle  Nitrogen cycle  Phosphorous cycle

Water Cycle  Solar energy drives the global water cycle – Precipitation – Evaporation – Transpiration  Water cycles between the land, oceans, and atmosphere  Forest destruction and irrigation affect the water cycle

Solar energy Net movement of water vapor by wind Evaporation from ocean Precipitation over ocean Evaporation and transpiration from land Transport over land Precipitation over land Percolation through soil Runoff and groundwater

Carbon Cycle Abiotic reservoirs = atmosphere, sedimentary rocks, dissolved carbon in oceans, and fossil fuels – Taken from the atmosphere by photosynthesis – Used to make organic molecules – Decomposed by detritivores – Returned to the atmosphere by cellular respiration

Photosynthesis Burning of fossil fuels and wood Primary consumers Higher-level consumers Cellular respiration Detritus CO 2 in atmosphere Carbon compounds in water Decomposition

Global warming: CO 2 lets sunlight through but retains the heat radiated from Earth. CO 2 in the atmosphere CO 2 Human activities and natural processes add CO 2 to the atmosphere, increasing the effect. Photosynthesis removes CO 2 from the atmosphere, decreasing the effect.

Nitrogen Cycle The nitrogen cycle relies heavily on bacteria Atmospheric N 2 is not available to plants – Soil bacteria convert gaseous N 2 to usable ammonium (NH 4 + ) and nitrate (NO 3 - ) – Some NH 4 + and NO 3 - are made by chemical reactions in the atmosphere

Nitrogen in atmosphere (N 2 ) Nitrogen fixation Detritivores Decomposition Assimilation by plants Denitrifying bacteria Nitrates (NO 3 – ) Nitrifying bacteria Nitrogen-fixing bacteria in root nodules of legumes Nitrogen-fixing soil bacteria Ammonium (NH 4  ) 80%

Phosphorus Cycle Depends on the weathering of rock Phosphorus and other soil minerals are recycled locally Weathering of rock adds PO 4 3- to soil – Slow process makes amount of phosphorus available to plants low

Runoff Sedimentation