Ecosystems & Energy Chapter 55

YOU MUST KNOW How energy flows through the ecosystem by understanding the terms that relate to food chains & food webs The difference between gross primary productivity and net primary productivity The carbon and nitrogen biogeochemical cycles How biogeochemical cycles impact individual organisms and/or populations and ecosystems

Ecosystem ecology A. Involves energy flow and chemical cycling B. Governed by physical laws 1. 1st Law of Thermodynamics – energy cannot be created or destroyed but only transferred and transformed 2. 2nd Law – When energy is transformed/transferred, entropy (disorder) increases

1. Primary producers – autotrophs, support all other organisms Nutrient cycling 1. Primary producers – autotrophs, support all other organisms Diet of berries, fish, and insects

2. Heterotrophs – eat other organisms Nutrient cycling 2. Heterotrophs – eat other organisms a. Herbivores – eat primary producers, primary consumers b. Carnivores – those that eat herbivores are secondary consumers, and those that eat other carnivores are tertiary consumers Diet of berries, fish, and insects *** Often feed at more than one trophic level***

3. Detritovores/decomposers – feed on nonliving organic material, 3. Detritovores/decomposers – feed on nonliving organic material, convert organic material to inorganic for use by autotrophs Diet of berries, fish, and insects

Primary production – the amount of light energy converted to chemical energy by autotrophs in an ecosystem A. Gross primary production (GPP) – total primary production B. Net primary production (NPP) – GPP minus the energy used by the primary producers for “autotrophic respiration” (Ra) NPP = GPP – Ra

Limiting factors affecting primary production 1. Availability of light & nutrients (primarily nitrogen & phosphorus) 2. Evapotranspiration – combination of water lost by transpiration in plants and evaporation

Energy transfer between trophic levels A. Only about 10% efficient Ecological pyramids – can display energy, biomass, of population sizes Pyramid can never be inverted

Biogeochemical cycles – nutrient cycles that contain both biotic and abiotic components A. Carbon cycle https://www.youtube.com/watch?v=aLuSi_6Ol8M

B. Nitrogen Cycle https://www.youtube.com/watch?v=leHy-Y_8nRs Nitrification – ammonium (NH4+) is oxidized to nitrite (NO2-) and then nitrate (NO3-) by bacteria Most of Earth’s nitrogen is in the form of N2, unusable by plants (can use nitrates and ammonium) Denitrification – bacteria releases nitrogen to the atmosphere Nitrogen fixation – conversion of N2 to forms plants can use by bacteris

Restoration Ecology A. Return degraded ecosystems to their natural state B. Bioremediation – use of organisms (usually prokaryotes, fungi, or plants) to detoxify polluted ecosystems (from mining, oil drilling, radioactivity, etc.) C. Bioaugmentation – introduction of desirable species such as nitrogen fixers to add essential nutrients