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Ecology Ecology – Greek = oikos meaning home and logos meaning study Define – You MUST use the definitions in the syllabus and give examples of; Ecology ecosystems populations community species habitat Food chain trophic level food web autotroph heterotroph carnivore Detritivore (detritus) saprophyte (saprotroph) herbivore omnivore producer decomposer chemoautotroph consumer decomposer **Check syllabus • be able to draw three food chains, each with four organisms in them – specific names→ grass, tree and bird won’t work • construct a food web with 10 organisms (bacteria can act as an Autotroph, heterotroph and detritivore food web is better as it shows more links more realistic, the more links, the more stable – WHY trophic level - position in food chain determined by number of energy transfers - as not all animals stay in one category like a bear is a herbivore but will eat meat if.. Organisms can be both primary and secondary consumers V W X Y Z Make sure you know which way the arrows are going and the flow detritivore (decomposers) and detritus not shown on chains Detritivore – organisms that feed on the detritus (wastes) and decomposing organic material of living organisms. Eg. dung beetle Saprotrophs or decomposers – organisms that feed on dead organisms and products of living organism. They secrete enzymes…. Extracellular digestion so they do not ingest whole food but absorb. Eg. bacteria and fungi. * Extremely vital for the recycling of nutrients Discuss the pyramids of biomass, pyramid of numbers and energy. Energy is lost as you go up the food chain or pyramid. Energy transformations are not 100% efficient. (Discuss the transducers and what energy changes and laws of thermodynamics) 1020% energy transfers per transfer. Rest is used for; catching animal – cellular respiration, not eating all parts, heat energy etc. More efficient to eat grass but culture dictates ?. This is why food chains are rarely more than four links long and why the pyramid of energy is the shape it is. Note units for pyramid are J/m2/yr or J m-2 yr-1 or kJ m-2 yr-1 Discuss Biological Amplification – higher tropic levels are a good indication of problems in the ecosystem •Light is the main, initial source for almost all communities. Remind about photosynthesis. Chemosynthesis is rare How energy enters and leaves a community = sunlight → light energy → chemical energy → consumers energy lost to decomposers and as heat may stay in the community but not eaten. Energy is NOT recycled. Remember your second law of thermodynamics – energy cannot be created or destroyed – but is changed into an unusable form. – heat (which is more disorganised) Principle of allocation – each organism has a limited amount of energy that can be allotted to obtaining food, escaping from predators growing, repair, reproducing etc. Energy expended on homeostasis can not be used on other activities. (winter animals live on the edge) Greenhouse Effect Energy drives all biotic and abiotic cycles. Energy does NOT recycles. It is changed into a form that is not useable to life and radiated off. Albedo – describes the ability to reflect, snow albedo is high, cloud cover and dust from volcanoes have a high albedo as can reflect light back to earth. A cloudy evening is warmer than a clear night, which is why desert is cold at night. Organisms withdraw elements form the environment in order to build and maintain cells. Six elements are responsible for over 95% of the mass of all living things –carbon, hydrogen, oxygen, nitrogen, phosphorous and sulphur. The movement of these material through the biosphere is termed their biogeochemical cycles. We will look at carbon in the form of carbon dioxide. Carbon cycle – be able to draw, photosynthesis, respiration, fossilization, carbons are coming from carbohydrates like glucose CO2 in air respiration photosynthesis C in animals fossilization feeding combustion C in plants fossilization Fossil fuels CO2 taken in by plants is same as given off in respiration – direct correlation. Fossil fuels are reservoir of energy-bearing organism, occurred when decay is slow and allowed to accumulate, Saprophytes release CO2 into air. We can measure over time (CO2 trapped in glaciers) Increase in CO2 due to burning of fossil fuels and deforestation (30% increase in [CO2] since 1850 due to burning (before 1850 was 274/1000000 (ppm) and 1981 was 357 ppm) The greenhouse effect – is a natural, normal phenomenon. We need it or else all the heat that is “lost’ or radiated off would leave and the Earth would be too cold. Mechanism – Check text – incoming waves are shorter waves of radiation. Reflect off the Earth and loss some energy and re-radiated as a longer wave. A lot of this longer- lower energy wave can’t leave the atmosphere due to greenhouse gases. And what are greenhouse gases you ask??? Methane, CO2, oxides of nitrogen (NO2) Problem – too much man made CO2. Note [CO2] will fluctuate normally with the seasons due to different rates of photosynthesis Pros – will increase photosynthesis and increase producers and first order consumers etc. Also will increase temperature, which will increase reaction rates and increase metabolism. “Under existing laws, most chemicals are considered innocent until proven guilty and estimating their toxicity to establish guilt is difficult, uncertain and expensive” APES textbook. Precautionary Principle – when there is reasonable but incomplete scientific evidence of significant harm to humans or the environment from a proposed or existing chemical or technology, we should take action to prevent or reduce the risk instead of waiting for more conclusive evidence. “some human induced changes can have catastrophic consequences so those responsible for the change must prove it will cause no harm before proceeding – this is the reverse of historical practices SEE SYLLABUS Eg. Fishing industry – science of how the ecosystem works and what affects it and how much fishing is sustainable is still unclear. Precautionary principle – sharply reduce fish harvest and close some over fished areas until they recover and we have more information about what levels of fishing are sustainable. Invasive species – Australia and New Zealand no longer assume that a potential invasive species is innocent until proven guilty. Species not on an approved list are denied entry into the country. NOTE – 5.2.5 Discuss And 5.2.6 TEXT has very good questions – DO. Increased rates of decomposition of detritus trapped in permafrost Populations Review definition of population Change in population size is by the process of adding new members or subtracting natality, morality, immigration, emigration Natality > mortality and immigration > emigration then – go through possibilities Exponential growth rate – bacteria do fission every 20 minutes if factors are favorable. If this continued for 11/2 days, there would b enough bacteria to form a layer one foot deep over the entire Earth. But other organisms have slower potential like elephants that produce a maximum of 6 kids/lifetime and a lifetime is 100 years. Even still, a single mating pair could produce 19 million offspring in 750 years. What are the limits to this? We know there is a struggle to survive. Carrying capacity – maximum number of members of a species that an environment can hold. If a population exceed it by overproduction struggle for survival and factors will decrease the size. These factors can be divided into two groups – density- dependent and density independent. (like food, space, competition, emigration, disease) Populations tend to overshoot or overproduce which leads to natural selection. Really, everything related to natural selection – go though the requirements for it and relate. Plot growth on graph giving sigmoid curve with an exponential growth phase, plateau phase and transitional phase. Be able to explain all; During exponential phase - pop is increasing, natality rate is higher than mortality. The resources needed by the population such as food and space are abundant and diseases and predators are rare. Most offspring survive and live to reproduce. Transitional phase- birth rate begins to decrease, natality is still larger than mortality but the difference between them is slowing decreasing as resources start to decrease, wastes leading to diseases and predation start to take hold. Plateau phase -is reached as pop levels off, natality = mortality, resources become so low that no further reproduction can take place Carrying capacity reached –caused by limiting factors Transitional phase is when the limiting factors start effecting growth List some limiting factors – available resources, disease, space, predators What is the Earth’s carrying capacity for us? Earth can support more herbivores than carnivores (why) Man’s exponential growth is the major reason for the degradation of the populations and biomes. Due to lack of habitat, pollution, hunting, unstable food webs, monocultures, loss of species diversity …. Some great questions, data analysis in tiger book on whole ecology, greenhouse and populations. They MUST be done.