leaves of a pine tree an adaptation to dry conditions
The chemical equations for oxygenic photosynthesis and aerobic respiration are exactly the reverse of each other.
What Does Adaptation Mean? - MBGnet
In most dicotyledonous plants - the number of stomata isgreater on the lower surface than on the upper. This arrangementensures that carbon dioxide can enter the leaf while at the sametime cutting down on transpiration rate (the lower surface beingcooler than the upper). In addition, the stomatal mechanism ofclosing at night also reduces water loss by evaporation. Plantsliving in water deficient habitats have evolved furtheradaptations in order that water loss does not become critical. Itis not just hot desert conditions and rapidly draining soils thatcan exert such pressures. In the tundra, soil water is frozen forlong periods and so is unavailable to plants. Plants living athigh altitudes and in exposed sites will be subjected to thedrying effects of strong winds.
The oxygenation of RuBP produces 2-phosphoglycolate, a 2-carbon toxic compound which undergoes a series of reactions in the peroxisome and mitochondria, releasing CO2 and resulting in loss of organic carbon and energy production. This process is called – an awfully misleading name for students, because it has nothing to do with respiration and yields no ATP. All Biol 1510 students need to remember about photorespiration is that it reduces photosynthetic efficiency, and that it occurs when Rubisco oxygenates RuBP instead of carboxylating RuBP.
Annual plants escape unfavorable conditions by not existing
Carbon dioxide (CO2) is an essential building block of the process of photosynthesis. Simply put, plants use sunlight and water to convert CO2 into energy. Higher CO2 concentrations enhance photosynthesis and growth (up to a point), and reduce the water used by the plant. This means that water remains longer in the soil or recharges rivers and aquifers. These effects are mostly beneficial; however, high CO2 also has negative effects, in addition to causing global warming. High CO2 levels cause the nitrogen content of forest vegetation to decline and can increase their chemical defences, reducing their quality as a source of food for plant-eating animals. Furthermore, rising CO2 causes ocean waters to become acidic (see FAQ 6.3), and can stimulate more intense algal blooms in lakes and reservoirs.
There is general consensus among scientists that climate change significantly affects marine ecosystems and may have profound impacts on future ocean biodiversity. Recent changes in the distribution of species as well as species richness within some marine communities and the structure of those communities have been attributed to ocean warming. Projected changes in physical and biogeochemical drivers such as temperature, CO2 content and acidification, oxygen levels, the availability of nutrients, and the amount of ocean covered by ice, will affect marine life. Overall, climate change will lead to large-scale shifts in the patterns of marine productivity, biodiversity, community composition and ecosystem structure. Regional extinction of species that are sensitive to climate change will lead to a decrease in species richness. In particular, the impacts of climate change on vulnerable organisms such as warm water corals are expected to affect associated ecosystems, such as coral reef communities. Ocean primary production of the phytoplankton at the base of the marine food chain is expected to change but the global patterns of these changes are difficult to project. Existing projections suggest an increase in primary production at high latitudes such as the Arctic and the Southern Ocean (because the amount of sunlight available for photosynthesis of phytoplankton goes up as the amount of water covered by ice decreases). Decreases are projected for ocean primary production in the tropics and at mid-latitudes because of reduced nutrient supply. Alteration of the biology, distribution, and seasonal activity of marine organisms will disturb food web interactions such as the grazing of copepods (tiny crustaceans) on planktonic algae, another important foundational level of the marine food chain. Increasing temperature, nutrient fluctuations, and human-induced eutrophication may support the development of harmful algal blooms in coastal areas. Similar effects are expected in upwelling areas where wind and currents bring colder and nutrient rich water to the surface. Climate change may also cause shifts in the distribution and abundance of pathogens such as those that cause cholera. Most climate change scenarios foresee a shift or expansion of the ranges of many species of plankton, fish and invertebrates towards higher latitudes, by tens of kilometres per decade, contributing to changes in species richness and altered community composition. Organisms less likely to shift to higher latitudes because they are more tolerant of the direct effects of climate change or less mobile may also be affected because climate change will alter the existing food webs on which they depend. In polar areas, populations of species of invertebrates and fish adapted to colder waters may decline as they have no place to go. Some of those species may face local extinction. Some species in semi-enclosed seas such as the Wadden Sea and the Mediterranean Sea, also face higher risk of local extinction because land boundaries around those bodies of water will make it difficult for those species to move laterally to escape waters that may be too warm.
Measuring the rate of photosynthesis - Science and …
Although is responsible for the vast bulk of organic carbon on the surface of the Earth, its oxygenase activity can severely reduce photosynthetic efficiency. Some plants have evolved a way to minimize the oxygenase activity of Rubisco.
Many desert plants have solved the problem to a degree. A number of them use that quickly capture carbon dioxide, allowing the stomata to be closed more often than in plants not adapted for this. These so-called C4 plants (as opposed to C3 plants without the adaptation) also do much better in strong light and hot temperatures. C3 plants under such conditions tend to burn more carbohydrates than they manufacture. Many warm-climate grasses and such things as four-wing saltbush are C4 plants. Cacti and many succulents (such as the century plants, or agaves) utilize a different physiological strategy call photosynthesis. The stomata generally are opened at night, when temperatures tend to be cooler and relative humidity higher, and the carbon dioxide stored in the form of an acid; during the day, the stomata are closed and photosynthesis uses the stored carbon dioxide. CAM plants also can go into a slowed mode for extended periods of time during particularly hot, dry periods by closing the stomata and utilizing carbon dioxide from cellular respiration to manufacture food and burning food to supply energy for respiration. This makes some sense if you know that plants, like animals, produce carbon dioxide as a waste product when breaking down food stuffs to produce usable energy. Of course, energy is lost at each such cycle and eventually the process runs down.
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Photosynthesis is the biological pathway whereby green plantsmake energy available to all living things. Plants exhibit a widerange of leaf form, however, typically a leaf comprises a thinlamella and large surface area. This enables effectivephotosynthesis by minimizing the distance between thephotosynthesis factory (palisade cells) and the supply of rawmaterials (carbon dioxide and water). At the same time the largesurface area maximizes light capture. To ensure that sufficientcarbon dioxide can enter the plant when light energy isavailable, the stomata must be open, but this in turn allowswater to evaporate from the large leaf surface duringtranspiration. In order to prevent the rate of transpirationexceeding water uptake but without compromising the needs foreffective photosynthesis, plants have evolved a variety ofadaptations to keep water loss by evaporation to a minimum.
WG1 – The Physical Science Basis
Transpiration is the loss of water from a plant in the form of water vapor. Water is absorbed by roots from the soil and transported as a liquid to the leaves via xylem. In the leaves, small pores allow water to escape as a vapor and CO2 to enter the leaf for photosynthesis. Of all the water absorbed by plants, less than 5% remains in the plant for growth and storage following growth. This lesson will explain why plants lose so much water, the path water takes through plants, how plants might control for too much water loss to avoid stress conditions, and how the environment plays a role in water loss from plants.
At the completion of this lesson, students will be able to:
How do we know the world has warmed
So why would cacti evolve these two unusual features of green stems and non-photosynthetic stabby leaves? Well, these combination of traits are adaptations to dry and resource-poor environments. Big and flat leaves have lots of surface area which is typically a good thing from a plant’s perspective as it captures lots of sunlight for photosynthesis. But many plants have more sunlight than they can handle and more photosynthetic area means more water loss. All photosynthesis requires gas exchange, carbon dioxide in and oxygen and water vapor out. So for plants in water-limited and very sunny environments, like deserts, adaptations that limit photosynthetic area (and thus limit water-losing gas exchange) are likely to be advantageous and selected for.
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