Chapter 55: Ecosystems and Restoration Ecology

Chapter 55 Ecosystems and Restoration Ecology 55.1 Physical laws govern energy flow and chemical cycling in an ecosystem Ecosystem: The sum of all organisms living in each area and the abiotic factors with which they interact. There are not always discrete boundaries. Energy flows through an ecosystem starting from sunlight, going up through the trophic levels and dissipating as heat Chemicals cycle through an ecosystem between biotic and abiotic components Both are transferred around, but energy needs constant input of energy from the sun The first and second laws of thermodynamics are always at play in energy flow and most ecosystems would vanish without the sun’s constant inputs of energy *Reminder for the 2 laws of thermodynamics:   First law: The law of conservation of energy: energy is neither created nor destroyed only transformed Second law: The entropy of the universe is always increasing or its implication that in every energy transformation some is always lost as heat The law of conservation of mass explains why chemicals cycle through an ecosystem The flow of energy through an ecosystem Sunlight or Chemicals  Primary Producers (autotrophs)  Primary Consumers (herbivores)  Secondary Consumers (Carnivores that eat herbivores)  Tertiary Consumers (Carnivores that eat other carnivores) Decomposers: Organisms that eat dead organic matter, aka detritus, and play key roles in the ecosystem by cycling chemicals 55.2 Energy and other limiting factors control primary production in Ecosystems Primary production: The amount of light energy converted to chemical energy by autotrophs during a given period. The amount of solar energy that reaches the planet’s surface limits the photosynthetic output of ecosystems as well as only certain wavelengths of light can be used for photosynthesis. Gross primary production: the amount of light or chemicals converted to chemical energy in organic molecules per unit of time. Net primary production: The gross primary production minus energy used by the primary producer for their cellular respiration. NPP = GPP - Ra *Think of this like a paycheck where GPP is your gross pay, R a is taxes, and NPP is the take-home pay* Net ecosystem production: This is a measurement of all the biomass accumulated by both producers and consumers. NEP=GPP-Rr *Remember the Rr is the cellular respiration of all organisms not only producers in an environment The NEP is useful in finding out if environments are carbon sinks, where carbon is stored in biomass more than breathed out, or if they are carbon producers, where carbon is not stored as much as it is breathed out. In aquatic ecosystems, light and nutrients are required. Light cannot go down super far even in clear water, and you don’t a gradient like would expect The main factor that limits primary production is nutrients. Limiting nutrients is the element needed to be added to an environment for production to increase. 2 common limiting elements are phosphorus and nitrogen. Eutrophication: The way nutrients become highly concentrated in water and can cause growth in organisms such as algae and cyanobacteria This can cause a dramatic reduction in oxygen in the water because of the decomposition of algae and cyanobacteria. Iron can be another element that can limit growth as well as a micronutrient. Upwelling in bodies of water can contribute to high primary production by increasing the nutrient concentrations in the upper bodies of water. In terrestrial biomes, moisture, and temperature limit primary production. As it gets wetter, the PP increases and the hotter it gets, PP also increases. Evolution has helped create adaptations that help increase scare element uptake in the soil such as symbiotic relationships and enzymes. Recently climate change has led to increased sunlight and droughts that have reduced primary production by significant margins. Other factors such as fires or barking beetles or insects lead to problems. 55.3 Energy transfer between trophic levels is typically only 10% efficiency. Secondary production: The amount of chemical energy in consumer’s food that is converted into their own new biomass during a given period Most biomass that is consumed doesn’t get used to make more biomass and leaves as either feces or used for cellular respiration Efficiency of energy transformation Production efficiency= Net secondary production ∗100 % Assmimlation of primary producion *Net Secondary Production= energy consumed and used for growth and reproduction, Assimilation of primary production= total energy used for growth, reproduction, and respiration Production efficiency: The % of energy stored in assimilated food that is used for growth and reproduction not respiration. Many are efficient and many are not Trophic efficiency: the % of production transferred from on trophic level to the next. It only averages about 10% to take an account for respiration and feces as well as not everything is converted to the next level. Multiply this each time a level goes up and this is why the food chains are limited by this to only about 4 or 5 links This is shown by energy pyramids om which net production is shown at different tropic levels and organized into tiers Biomass pyramids show the total dry mass of all organisms on tropic level and is generally reduced dramatically as it goes up the levels of the pyramid because of inefficient energy transfer. In some aquatic biomes, there can be some primary consumers with higher biomass than the producers. 55.4 Biological and Geochemical processes cycle nutrients and water in an ecosystem Decomposers have the same limits to growth as all other organisms and usually grow faster in warmer environments than in colder environments Fast decomposition time can lead to low concentrations of stuff show a fast cycle time. Water is hard on decomposers. Biogeochemical cycle: Any of the various chemical cycles which involve both biotic and abiotic components of an ecosystem Reservoir: The place consisting of either organic or inorganic material that are available for direct use or unavailable as a nutrient Different Biogeochemical cycles Water cycle:    Importance: Water is essential to all organisms and regulates many things such as primary production and decomposition. Liquid water is what is mostly used by organisms of which 97% of it is found in the oceans and the rest is in ice caps and lakes. Parts of the cycle include evaporation, condensation, precipitation, and heat drives each process in the cycle. Ther is also transpiration which adds water to the atmosphere and run-off that helps water flow to the ocean. Carbon Cycle:   Importance: It is the formation of all organic molecules needed for life. Photosynthesis turns carbon dioxide in a form that consumers can use as organic molecules. Sedimentary rock is the largest reservoir of carbon on the planet as well as the atmosphere.  Key processes: Photosynthesis takes carbon out of the atmosphere which roughly equals the carbon dioxide released by cellular respiration. Carbon dioxide is added through burning wood, burning fossil fuels, or volcanos Nitrogen Cycle:      Nitrogen is needed for amino acids, nucleic acids, and proteins Forms available: Plants can use NH4+ , Nitrate, and organic forms. Bacteria can use nitrite as well as the rest of the forms. Animals can only use organic forms. The atmosphere and the soil are the biggest reservoirs Nitrogen fixation is the main way atmospheric nitrogen gets turned into a form that can be used. Human activity has added tons of it to the soils and it can cause bacteria to convert nitrogen to nitrogen dioxide and many other forms Phosphorus cycle:     Needed for organic molecules such as ATP, Phospholipids, and nucleic acids Most phosphorus is found in the form of phosphate and taken up and used by plants . Found in sedimentary rock, soil, organisms, and the oceans Stays localized and heating rocks and uptake by plants are the main ways that phosphate cycles and decomposition return it to the soil 55.5 Restoration ecologists return degraded ecosystems to a more natural state Ecosystems can recover from many disturbances but if it gets too damaged biologists come in and attempt to restore the environment and speed up its recovery Restoration ecology works under 2 assumptions: 1. Some changes are reversible 2. Not all ecosystems are infinity resilient Ecologist can restore ecosystems by doing many things such as:     Bioremediation: using organisms to detoxify a polluted environment Biological augmentation: using organisms to add essential nutrients to a degraded ecosystem o Identification of the missing/ essential nutrient is key to recovery Adding certain animals or plants to new restored ecosystems Repairing physical environmental changes such as building up hills or filling in mines Ecologists try their best to identify what will be both the most economically viable and best for the environment solutions