Food Webs and Ecosystem Ecology CHAPTER 20 CONTINUED

Trophic Structure Feeding relationships among organisms Determines passages of energy and nutrients from producers (autotrophs) to consumers (heterotrophs) Sequence of this food transfer is called the food chain

What is missing from this food chain? Omnivores, Scavengers, Detritivores, Decomposers

Scavengers Secondary Secondary Decomposers Primary Primary Detritivore Producer Primary

Food Webs

Biomagnification The increasing concentration of a substance, such as a toxic chemical, in the tissues of organisms at successively higher levels in a food chain.

Birds of Prey and DDT

What happened? DDT Long-lived: half life of 15 years Mobile: transported in water, soil, organisms Soluble in fats: builds up in fatty tissues

Eggshell thinning Birds were crushing their own eggs Populations dropped

Why do we care? Still happening today Know your area! Can’t regulate what you don’t know New chemicals being manufactured Know your area! cfpub.epa.gov

Ecosystem Ecology Ecosystems: community + abiotic components Energy flow – the passage of energy through the components of the ecosystem Chemical cycling – the use and reuse of chemical elements within an ecosystem

Transfer of materials through all abiotic and biotic components Constant input of E from sun

Ecological Pyramid Shows cumulative loss of E with each transfer in the food chain 80–95% of the energy at one trophic level never reaches the next This explains why top-level consumers such as lions and hawks require so much geographic territory. It takes a lot of vegetation to support trophic levels. Most food chains are limited to three to five levels.

Biogeochemical Cycling Components Biotic (living) Abiotic (non living) from an abiotic reservoir, where chemicals are stored outside of living organisms

Three types of abiotic reservoirs

The Carbon Cycle Photosynthesis removes CO2 from atmosphere, incorporating it into organic molecules Organic molecules are passed along food chain via consumers Cellular respiration returns CO2 to atmosphere 4. Decomposers break down carbon in detritus eventually releasing it into the atmosphere Burning wood and fuels releases carbon back into the atmosphere

The Phosphorus Cycle - P as PO4-3 Breakdown of rock adds inorganic phosphate to the soil Plants absorb dissolved phosphate from soil, build phosphorus atoms into organic compounds Consumers obtain organic phosphorus by eating plants 4. Phosphates returned to soil via decomposition Phosphates drain into water where they settle Geologic processes lift rock and expose it to weathering

The Nitrogen Cycle Nitrogen fixation – conversion of gaseous N2 to ammonia (NH3) and then to ammonium (NH4+), which can be used by plants This process is essential because atmospheric nitrogen is not readily usable

The Nitrogen Cycle Some bacteria live on roots, a mutualistic relationship that supplies its host with direct source of usable nitrogen Free living bacteria fix nitrogen, resulting in NH4+ Some fixed N is absorbed by plants Nitrifying bacteria convert NH4+ to nitrate (NO3- )

The Nitrogen Cycle Nitrate is also readily absorbed by plants Animals form N containing waste products Decomposition of organic compounds releases ammonium into the soil (refilling reservoir) Denitrifying bacteria strip nitrates of their oxygen atom, releasing N2 back into the atmosphere

Helpful review videos Carbon and Nitrogen cycles https://www.youtube.com/watch?v=NHqEthRCqQ4&t Phosphorus cycle https://www.youtube.com/watch?v=_IBx0zpNoEM