Ecosystem System

Ecosystem

a system formed by the interactions between a community of organisms and the physical environment

Ecosystem ecology

•studies the flow of energy and the production of biomass (the total mass of living matter in each area)

oForest ecosystem — trees, shrubs, insects, birds, mammals, fungi, soil, rainfall, sunlight

oDesert ecosystem — cacti, reptiles, insects, camels, extreme temperatures, sand, scarce water

oTundra ecosystem — mosses, lichens, caribou, arctic foxes, permafrost, cold climate

oFreshwater ecosystem — lakes, rivers, ponds with fish, algae, amphibians, aquatic plants

oMarine ecosystem — oceans, coral reefs, whales, fish, plankton, saltwater currents

What is a food chain

•Food chain – linear depiction of energy flow

•Each feeding level in a chain is a trophic level

Food chain levels

Autotroph, primary consumer (herbivore), secondary consumer (carnivore), tertiary consumer (secondary carnivore)

Primary consumers eat

Heterophs

•eat primary producers

oHerbivores

Secondary consumers eat

•eat primary consumers

oCarnivores

Detritivores or decomposers eat detritus eat

•unconsumed plants, animal remains, and waste products

oGet energy from all trophic levels

oDecomposers absorb food of molecular size, not big pieces

oExtremely common, eating large percentage of total matter

An omnivore is an animal that

eats producers and consumers of different levels.

Food web energy transfer

Chain lengths are short in most food webs

•Energy that is eaten is often used for an animal’s survival, thus not available for the next trophic level

•On average, only 10% of available energy is transferred from one trophic level to another

As energy is transferred some is lost as heat

Detritivores eat most

primary production is eaten by detritivores than herbivores, typically.

Viewing ecosystems as communities through which energy flows:

•Photosynthetic organisms are by far the most important, then detritivores

•Consumers, especially higher-level consumers are much less important

The natural carbon cycle

•Carbon is present in the atmosphere in low concentrations

•Autotrophs incorporate it into organic matter via photosynthesis – about 1/7 of the CO₂ in the atmosphere

•Cellular respiration and decomposition of plants recycle a similar amount back into the atmosphere as CO₂ (gas)

•Cellular respiration from animals is an small contributor of CO₂ emissions (not included in the diagram).

•Carbon (as calcium carbonate) is incorporated into shells of marine organisms, eventually forming limestone deposits 

•Volcanoes and fires also release carbon dioxide to the atmosphere

Human activity is increasing carbon emissions and unbalancing

Carbon Dioxide Release From Fossil Fuels

•Fossil fuels are deposits of oil, natural gas, and coal that were plants in the deep past (its is “sequestered” carbon)

•Burning fossil fuels is adding CO₂ to the atmosphere, as does deforestation (cutting or burning trees). Other industrial processes such as concrete production, also contribute to carbon emissions

what causes phosphorus

All living organisms require phosphorus

o Relevant for ATP, nucleic acids, and phospholipids

oAn essential mineral

•No gaseous or atmospheric phase

•Earth’s crust is the main storehouse

•Natural: Weathering and erosion of rocks release phosphorus into the soil

Man-caused: Runoff from fertilizers

Uptake of Phosphorus

•Herbivores obtain their phosphorus only from eating plants

•Carnivores obtain it by eating herbivores

•When plants and animals excrete wastes or die, the phosphorus becomes available to decomposers, which release it back to the soil

•Leaching and runoff wash phosphate into aquatic systems, where plants and algae use it

what bad about excess phosphorus

•Phosphorus is usually a limiting nutrient in freshwater ecosystems, meaning algae cannot grow much without it. When excess phosphorus is added, this limitation is removed

•When the algae die, they are decomposed by bacteria that consume all the dissolved oxygen. That leads to “ Dead Zones”, where fish and aquatic invertebrates may suffocate (Eutrophication)

Eutrophication –

•elevated nutrient levels lead to an overgrowth of algae and subsequent depletion of water oxygen levels

•Fish can drown from a lack of oxygen in the water

•Lake Erie became eutrophic in the 1960s due to fertilizer runoff

oReduction of discharge by 80% has led to recovery

•Major “dead zones” persist today in many locations

•Other causes of eutrophication are pollution, such as sewage, industrial waste, and animal waste from livestock operations.

Nitrogen cycle importance

•Limiting nutrient because it is an essential component of proteins, nucleic acids, and chlorophyll

•78% of Earth’s atmosphere is N_2, which is chemically inaccessible to most organisms. 

•Nitrogen needs to be “fixed” into accessible chemical forms for use by organisms. This can occur naturally through the Nitrogen Cycle or industrially to make fertilizers.

Five parts of the Nitrogen Cycle

. Nitrogen fixation

•Only certain bacteria are able convert to N₂ and release ammonia (NH₃) or ammonium

Nitrification soil bacteria convert it to nitrate used by plants

assilmilation- plants and animals use nitro as ammounium

ammonfication- conversion of organic nitrogen by bacteria and fungi

drntrification- reduction to gas nitrogen and turns it back to atmosphere

•Human alterations of the nitrogen cycle have approximately doubled the rate of nitrogen input to the cycle

•Fertilizer runoff can cause eutrophication 

•Excess nitrates in drinking water are a health hazard for infants

•Burning fossil fuels also releases nitrogen oxides which cause smog and contribute to acid rain (as nitric acid)