ECOSYSTEMS All of the organisms living in a community and the abiotic factors with which they interact. “global ecosystem” Energy flows Nutrients cycle Trophic levels = species grouped into feeding relationships, used to follow energy transformations through the whole ecosystem

Trophic levels Primary producers ; autotrophs, plants Heterotrophs ; indirectly need photosynthetic output Primary consumers ; herbivores – directly eat the plants or algae Secondary consumers ; carnivores that eat herbivores Tertiary consumers ; carnivores that eat other carnivores Detritivores/ decomposers ; obtain energy from detritus ( nonliving organic material)

Decomposition Vital role in linking nutrient cycle Fungi, bacteria, invertebrates and some vertebrates Lots of organic matter in things like fallen leaves that are consumed by crayfish or worms Make chemical elements available Digestive enzymes of fungi make ‘wood’ available to other organisms.

Interdisciplinary …. Can’t create or destroy matter Nutrients cycle Can’t create or destroy energy Energy flows (overall) Entropy increases ENERGY TRANSFORMATIONS Global energy budget is joules of solar energy per day

Production Gross primary production = amount of solar energy that is converted to chemical energy by photosynthesis per unit time Net primary production = gross – energy used by primary producers for respiration. NPP = GPP – R Remember that producers (plants and algae) are doing photosynthesis AND RESPIRATION in order to grow and develop.

Lab 12 : Dissolved Oxygen Oxygen is generated by photosynthesis The amount of dissolved oxygen can be measured quantitatively If one system has more production, their should be more oxygen If algae samples are kept in dark, respiration rates should overcome photosynthesis rates and oxygen should go down. The oxygen should show the same trend as the light…. Other limiting factors ? N and P also have roles As does the heat (temperature) associated with the light source

Herbaceous plants have a higher ratio of green stem to leaves and support less tissue through respiration Trees/ woody plants have mores stem, trunk and roots tissue to support through respiration BIOMASS = energy per area per time, this is the weight of plant matter added to the environment per area per time (dry mass) g/m 2 /year ( energy = J/m 2 /year)

Aquatic Ecosystems Limiting factors increase or decrease Limits to primary productivity Light More light = more photosynthesis “photic zone” Only 10% reaches in about 20 m in clear water Not nec. more productive nearer equator Nutrients Limiting nutrients must be added to cause an increase, these are actually minimal in surface waters at equator and increase with depth N nitrogen P phosphorus Increase without creating a bloom Fe Iron also of interest in cyanobacteria

Fresh water ecosystems Solar radiation Nutrients TEMPERATURE Eutrophication = shift from phytoplantkon to cyanobacteria, gradual filling in of lakes at edges and bottom. Negative if man made/accelerated because of pollution

Terrestrial Ecosystems Water availability/ moisture Solar energy Seasonal Nutrients Dissolved in soil TEMPERATURE Tropical rain forests are warm and wet Deserts are dry and vary in temperature

Secondary Production Amount of chemical energy in the CONSUMERS food that is converted to new biomass in a given time period Grass  cow + manure + CO2 + methane + growth ….. How much grain mass became cow mass ? Usually between 10 - and 20 % (limits number of trophic levels)

Energy pyramids

Nutrient cycling Biogeochemical cycles Cycling of gases (C, N, O and S) in atmosphere Less mobile elements (P, K, Ca, etc.) usually on a more localized scale Absorbed by roots from soil Returned to area by decomposers in fallen leaves

Generalized model of cycling Organic Available Living and detritus Organic Unavailable Coal, oil, peat Inorganic Available Atmosphere, soil and water Inorganic Unavailable minerals

Carbon cycle

Nitrogen cycle

Water cycle

Phosphorus cycle