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77 Cards in this Set
- Front
- Back
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Ecosystem
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the biotic community and its abiotic environment functioning as a system.
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Autotroph
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An organism that obtains food (carbon) without consuming other organisms. Autotrophs utilize carbon dioxide as a source of carbon, using energy from the sun to convert carbon dioxide (and other inorganic compounds) into organic compounds. (Primary Producers)
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Heterotroph
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An organism that obtains food (carbon) by eating other organisms or their by-products. (Secondary Producers)
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Consumer
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An organism that obtains its energy by feeding on other organisms
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Decomposer
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An organism that obtains energy from the breakdown of dead organic matter to more simple substances
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Primary producer
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autotrophs
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Secondary producer
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heterotrophs
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Food Chain
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Diagram defining the relationship between different feeding groups (groups of organisms that derive their food resources in a similar manner). Autotrophs Heterotrophs Consumers Herbivores Carnivores
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Photosynthesis
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the process by which plants use light energy to make food molecules (simple sugars - C6H12O6 ) from carbon dioxide and water. Oxygen (O2 ) is produced as a by-product.
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Respiration
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the utilization of simple sugars (carbon compounds) for the production of energy that can be stored (chemically) to do work. This process results in the consumption of oxygen and the release of carbon dioxide. The process of respiration occurs in all living cells.
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Net photosynthesis
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Photosynthesis - Respiration
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Photosynthetically active radiation (PAR)
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visible-light, visible part of the electromagnetic spectrum.
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Light energy is harnessed by ________ ______in the leaf and stored as chemical energy. This stored energy is then used in the conversion of CO2 into simple sugars
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chlorophyll molecules.
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As light energy is absorbed by the leaf, _______ in the chlorophyll molecules become excited (move to a higher orbital). As the electrons return to their original state, energy is released and stored. This process is similar to that which occurs in solar electric (photo) cells
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electrons
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Pigment that absorbs photons of light and converts it to energy
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chlorophyll
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Because ____ radiation provides the energy that drives photosynthesis, the availability of light has a direct influence on rates of photosynthesis
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solar
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Rubisco
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carbon dioxide + water → simple sugars + oxygen. The enzyme that catalyzes (speeds up) the transformation of CO2 to simple sugars in the process of photosynthesis.
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Most abundant enzyme on earth
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Rubisco
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Together with chlorophyll, ________ accounts for a significant portion (> 50%) of the total nitrogen in the leaf
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Rubisco
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Influence of light availability on the process (rate) of net photosynthesis, two terms to remember are
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Light compensation point and Light saturation point
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Increased availability of nitrogen has a direct influence on
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rates of photosynthesis by increasing the nitrogen available to the plant for the production of rubisco (and chlorophyll).
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The greater the concentration of nitrogen in the soil
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the greater the rate of nitrogen uptake by the plant roots.
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The greater the nitrogen uptake by plants
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the greater the concentration of nitrogen in the plant tissues.
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Relationship between leaf nitrogen concentration and rate of net photosynthesis
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see slide 28
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Temperature has a direct effect on the rate at which photosynthesis will occur. All enzymes have a characteristic
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temperature response.
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Tmin
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The minimum temperature below which photosynthesis does not occur (cold limit)
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Tmax
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The minimum temperature above which photosynthesis does not occur (heat limit)
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Topt
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Optimal range of temperatures for photosynthesis
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CO2 moves from the atmosphere into the leaf through pores (openings) on the surface called
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stomata.
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CO2 moves from the outside air into the leaf through the stomata. An equilibrium is not achieved because as CO2 enters the leaf it is converted into
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simple sugars in the process of photosynthesis.
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This act of CO2’s photosynthesis-assisted conversion as it enters the stomata begins to draw down the concentration of CO2 inside the leaf, therefore maintaining the
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diffusion gradient (CO2 concentration inside the leaf lower than that outside the leaf).
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The need to open the stomata to take in CO2 , and the subsequent loss of water from the plant to the atmosphere through transpiration, is one of the major tradeoffs faced by terrestrial plants. This simple constraint has a direct impact on the
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distribution and productivity of ecosystems on the Earth’s surface.
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Diffusion
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the tendency for particles of any kind to spread out spontaneously from where they are more concentrated to where they are less concentrated. The particles will diffuse down the concentration gradient until the concentrations on both sides of the membrane are equal (equilibrium is reached).
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Transpiration
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loss of water from the inside of the leaf to the atmosphere through the stomata
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Rate of transpiration (water loss) is a function of
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Number and opening of stomata (stomatal conductance)
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The rate at which CO2 moves into the leaf is a function of both the
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density and size of the stomatal opening
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Diffusion gradient driving transpiration is the difference in
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the water vapor content of the air inside the leaf and the air outside the leaf (atmosphere).
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Diffusion gradient. The air inside a leaf is close to saturation (relative humidity = 100%), so the gradient is defined by the
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relative humidity of the air.
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Water that is lost by the plant to the atmosphere through transpiration must be replaced by water from the soil that is taken up by the root system and transported to the leaves. This process assumes that there is
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sufficient water in the soil to replace that water lost by the plant through transpiration.
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The drier the air
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the lower the somatal conductance.
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Stomatal conductance (components)
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how many stoma, how wide open are they?
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Whole plant carbon balance, carbon uptake – carbon loss =
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net carbon uptake)
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The carbon gain of the plant will be a function of the
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- Rate of photosynthesis per unit of leaf - The total amount of leaves
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The carbon loss of the plant will be a function of the
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Total plant mass (leaves + stem + roots)
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The process in which plants allocate the net carbon gain to the production of new tissues is called
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carbon allocation.
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Environmental conditions that reduce the rate of photosynthesis (e.g., low availability of ____, _____ or light and/or extreme temperatures) will decrease the total carbon gain of the plant and therefore the rate of plant growth. In turn, the lower plant growth rates will reduce overall net primary productivity
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water, nutrients, reduce
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In submerged aquatic plants, the CO2 diffuses directly across
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the leaf surface into the leaf interior.
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Net primary productivity (NPP)
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Net Primary Productivity = Photosynthesis - Respiration, for all Autotrophs in the Ecosystem
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NPP increases with
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an increase in both precipitation and temperature
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There is greater variation in NPP as temperature and precipitation increase. This is due to the fact that
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the combination of both temperature and precipitation come into play as either temp or precipitation increases.
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Values of AET(Actual Evapotranspiration) can be low because
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rainfall is low, temperatures are low or both.
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For AET to be high temperatures must be high (providing thermal energy for evaporation) as well as
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sufficient rainfall to meet the potential for evaporation.
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As the amount of water available to the plant is reduced, the rate of photosynthesis will decline. This reduction is a result of
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the stomata closing because of the inability of the plant to replace water that is lost to the atmosphere (transpiration).
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Dependence of secondary productivity on primary productivity.
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see slide 70
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The amount of herbivores that you have is a function of
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the amount of autotrophs, the amount of carnivores, a function of the amount of herbivores.
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On average (globally), only about 10% of net primary productivity is consumed by herbivores. The remaining 90% goes directly to
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dead organic matter where it is consumed by decomposers.
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Decomposition is
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The breakdown of complex organic compounds into simpler ones.
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Dead leaves (litter) are a major source of
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dead organic matter for decomposers in forest ecosystems.
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The process of decomposition is studied by following the
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decay (mass loss) of dead organic matter (such as dead leaves) through time.
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Permafrost is
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subsurface layer of soil that remains frozen throughout the year (occurs in the high latitudes of Arctic and Antarctic regions)
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The dead organic matter on which decomposers feed provides both a source of energy and nutrients. The carbon is utilized as an energy source and is eventually lost to the atmosphere (as CO2 ) in the process of
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respiration.
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Nutrients, such as nitrogen, are converted from an organic to an inorganic (mineral) form in the process of mineralization and are
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released to the soil or water where they are then made available to autotrophs.
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How does nutrient cycling differ in terrestrial and open-water (lakes and ocean) ecosystems?
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The major factor influencing NPP is nutrient availability in open-water ecosystems . Nutrients are secondary to climate and temperature in terrestrial ecosystems
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There are Changes in available light, gross productivity, respiration and net primary productivity (gross productivity – respiration) with water depth. Respiration rate is relatively constant with depth, while gross productivity (photosynthesis) declines with depth as a function of
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declining available light.
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The depth at which gross productivity is equal to respiration (net photosynthesis equal to zero) is called the
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compensation depth.
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How does the thermocline influence the seasonal patterns of nutrient availability in the surface waters?
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As surface waters cool, the thermocline breaks down and vertical mixing occurs. This mixing brings nutrients from the deep waters to the surface.
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How does the thermocline influence the seasonal patterns of net primary productivity?
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See slide 104, Decline in nutrients in surface waters during Summer and Spring is a result of nutrient uptake in NPP
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Influence of thermocline dynamics on patterns of aquatic productivity in tropical, temperate and polar regions?
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In the tropics not as much nutrient cycling as in the temperate or polar regions. Because of the permanent persistence of the thermocline.
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What is the Influence of equatorial upwelling on ocean productivity?
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Thermocline dynamics are different in the tropics, along the equator for equatorial, where upwelling brings cooler waters to the surface.
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Geosphere
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the solid Earth, consisting of the entire planet from the center of the core to the outer crust.
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Hydrosphere
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all of Earth’s water, which circulates among oceans, continents, and the atmosphere.
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Atmosphere
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the mixture of gases surrounding the Earth and retained by gravity.
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Biosphere
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the zone inhabited by life.
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Ecology
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the study of the interaction of organisms with their environment
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Population
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a group of individuals of the same species living in a given area at a given time.
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Community
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a group of interacting plants and animals inhabiting a given area
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Ecosystem
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the biotic community and its abiotic environment functioning as a system.
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