Give an example of a food chain
Fig tree fruit —> vervet monkey —> eagle (rainforest ecosystem) What are mesocosms and what are they used for? Mesocosms are closed ecosystems, in which are present at least one autotroph, which produce carbon compounds and regenerate oxygen in cell respiration and one saprotroph, which decomposes dead organic matter and and recycles nutrients. Consumers can also be important, however, it is unethical to place a large consumer in a mesocosm with limited oxygen concentration. Mesocosms are important, as they provide a bridge between a controlled laboratory experiment and a variable uncontrolled field investigation. This is because they allow key variables to be controlled, but still provide sufficient biological complexity relative to the natural environment being changed. How does chemical energy flow through food chains? By feeding. Explain how chemical energy is obtained. Energy enters most ecosystems as sunlight energy trapped by photosynthesis. This light energy is converted into chemical energy and stored in carbon compounds. It then flows through food chains by feeding. How is energy lost in an ecosystem? Energy in an ecosystem is lost through excretion, the inability to absorb the food or cell respiration. Calculate the efficiency of the energy flow. Amount of energy available to next trophic level divided by amount of energy available at the start of the trophic level times 100. What is the common energy efficiency from one trophic level to another? 10-20% Why is the length of a food chain restricted to only 4-5 trophic levels? Because only 10-20% of the energy is available from one trophic level to the next, therefore there will be almost no energy left at the end of the food chain. How is biomass lost? Biomass is lost when carbon compounds are broken down through respiration and when carbon dioxide is excreted, as well as during the removal of waste products through excretion, such as urea. What is an ecosystem? An ecosystem is the interaction between a community and its abiotic environment. What makes an ecosystem sustainable? It is sustainable if it has sufficient sunlight, if the nutrients are recycled and if the community is not damaged. How are nutrients obtained? They are obtained from the abiotic environment. In what form is carbon dioxide present in aquatic ecosystems? Hydrogen carbonate ions. How is hydrogen carbonate formed? Carbon dioxide diffuses in water. Therefore carbon dioxide and hydrogen form hydrogen ions and hydrogen carbonate ions. CO2 + H20 —> H+ + HCO3- How is methane produced? Methane is produced in anaerobic conditions, where half-decomposed organic compounds are broken down by methanogenic archaeans and methane is released as a waste product. Why are anaerobic conditions important in this process? Because dead organic matter can only be partially decomposed, as saprotrophic bacteria and fungi cannot live in those conditions. What is limestone? It is rock that mainly consists of calcium carbonate.It contains many fossils. Why is it important for organisms such as corals and molluscs? It is important because these organisms absorb and calcium carbonate ions to secrete them as calcium carbonate to form their shells. Huge amounts of carbon dioxide are locked up in limestone. How can that carbon dioxide be released? It can be released by reacting with acid. Why is it important that oceans or rain cannot become more acidic? Because, since acid breaks down calcium carbonate, it fragilises the shells of these organisms. How is carbon dioxide produced and what sort of process is it? Explain. Carbon dioxide is produced from the combustion of carbon compounds. It is a non-biological process, as it is not carried out by living organisms. What is the greenhouse effect? The sun emits short wave radiation, to which the atmosphere is transparent. This light is reflected by the surface of the Earth, but this time in the shape of long wave radiation, which is in turn trapped (70-80%) by the greenhouse gases carbon dioxide, methane, water vapour and nitrogen oxide, re-emitting that radiation and warming the surface of the Earth. What does the impact of a gas depend on? It depends on its ability to absorb long-wave radiation and its concentration in the atmosphere. Why is there an annual dip in carbon dioxide rates in the graph? There is a dip in the colder months of the year because photosynthesis is not as occurring as in the warmer months of the year, as all the autotrophs are dead. When there is no photosynthesis, less carbon dioxide is emitted, however, the rise shows that photosynthesis is more occurring in the warmer months, and therefore there is more carbon dioxide emitted. What are the four main greenhouse gases? The four main greenhouse gases are methane, carbon dioxide, water vapour and nitrogen oxide. Outline the effects of rising temperatures. It can influence climate patterns, such as increasing the frequency of flooding or droughts. It can also increase the melting of glaciers and polar icecaps, it causes a rise in sea levels and it can melt permafrost, which releases methane into the atmosphere. Outline the effect of several human activities on the environment. Burning fossil fuels to supply energy releases more harmful greenhouse gases into the atmosphere, especially carbon dioxide. Cutting down tropical rainforests reduces the uptake of carbon dioxide due to photosynthesis and increases the release of carbon dioxide into the atmosphere from burning and rotting vegetation. Increase in cattle farming produces more methane. The increase in rice paddies also increases the anaerobic breakdown of organic compounds in the mud, which releases methane. By how much have global temperatures risen over the past 200 years and since when has most of the increase occurred? It has increased by 0.8 degrees Celsius and mostly since the 1980s. Why are coral reefs endangered? Coral reefs are endangered because the increase of carbon dioxide diffused into the seawater reacts with hydrogen and forms carbonic acid, which in turn dissipates into hydrogen ions and hydrogen carbonate ions. These hydrogen carbonate ions have formed because of the reaction between hydrogen ions and carbonate ions. Thus, carbonate ions are less present in the sea, and cannot form calcium carbonate, which is needed to form corals’ shells. Furthermore, calcium carbonate diffuses their shells. Overall, their shells become more difficult to form, which makes the organisms waste lots of energy, and it also makes them more fragile, which endangers their strength. Where are the four major carbon reservoirs found? In the ocean, in the atmosphere, in terrestrial ecosystems and in the Earth’s crust. What is the net flux? It is the difference between the input and the output from the reservoirs.
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Still busy with the topic of ecology, we are now tackling climate change, and more specifically how the greenhouse effect works. There is evidence for a correlation between atmospheric carbon dioxide and average global temperatures, the temperature rising as the carbon dioxide rate does. This correlation is supported by ice core data over the last 400,000 years. Temperature shows greater variation than the CO2 however most, but not all rises and falls have correlated with CO2 rises and falls. To observe this, our class has organised an experiment that involves creating the same atmosphere as the earth's, but in miniature. As you can see, two beakers have been filled with water, both with a thermometer measuring their temperature, and cling film obstructing any air that would leave or enter the beaker. Both are also placed under the light of a lamp, substituting for the sun. However, one of the beakers is subject to an increase of carbon dioxide. At the end of the experiment, we looked at the temperature that was indicated by the thermometer. Since we had not taken long enough to wait for the extra CO2 to make a difference in the beaker on the left, the temperature between the two beakers did not change. However, this experiment should have shown that the temperature in the beaker with the extra carbon dioxide was higher than the control experiment, due to the additional CO2.
The BBC has made available to us a few videos about the life of rock pools, which hide an entire kingdom with "a lot of drama", as the presenter states. Here are the links:
Adaptations for rock pool survival: http://www.bbc.co.uk/programmes/p019n5g7 Evolution of seaweed: http://www.bbc.co.uk/programmes/p019n5zf Fighting off predators: http://www.bbc.co.uk/programmes/p017mg1v Housing issues: http://www.bbc.co.uk/programmes/p017mfjb The cuttlefish - the most deadly predator on the rocky shore: http://www.bbc.co.uk/programmes/p017mdp1 Battling for space: http://www.bbc.co.uk/programmes/p017mdyy While studying the food chain, our class dissected a few barn owl pellets, to discover what the owl had eaten in the previous 24 hours. My owl pellet contained the bones of a vole, more specifically its lower jaw, and a few leg bones. The pellet also contained fur and, to the class' dismay, a horrible smell.
A few brief but important points about respiration:
A few long questions that might be asked in the test:
--> Make as many points as the number of marks that the question is at Species are groups of organisms that can potentially interbreed to produce fertile offspring. Species have either an autotrophic or heterotrophic method of nutrition. Some species can do both. Heterotrophs, such as ladybirds or mushrooms, are consumers that feed on living organisms by ingestion.
Autotrophs, or also called producers, make their own food through photosynthesis. They convert carbon dioxide into organic compounds. They synthesise sugars, like glucose, which are then converted into other organic compounds such as complex carbohydrates (starch, cellulose), lipids and amino acids. the inorganic nutrient compounds, such as water, carbon dioxyde, phosphorous, nitrates and oxygen are obtained from the abiotic environment, such as the soil, air or water.
making it an autotroph, as well as traps and digests insects and spiders to compensate for the nutrient poor soil of the wet land on which it lives, making it a heterotroph.
Here are three equations that are vital to understand and know in respiration: Aerobic respirationAnaerobic respirationPhotosynthesisElodea is this plant: Because of time constraints, we only managed to let the plant soak there for seven minutes, and we did not manage to see many bubbles coming out of the plant, only a very few, small ones. However, this can support the idea that light, and in this case heat as well, helps the rate of photosynthesis. In our last class, we experimented on the pigments in a leaf through the use of chromatography. The colours that you can see on the sheet and that have climbed up the paper are the different pigments of the leaf, which contain heavier atoms if they are at the bottom, and lighter ones if they are at the top.
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PaulineIB Biology student |