Study of an Ecosystem.docx

Study of an Ecosystem An ecosystem is a community of organisms and its interactions with the environment. There are hundreds of ecosystems that one can study. Examples include a rocky shore, a muddy estuary, an oakwood, or a grassland. There are five steps in studying an ecosystem. These are; 1. Map...

Study of an Ecosystem An ecosystem is a community of organisms and its interactions with the environment. There are hundreds of ecosystems that one can study. Examples include a rocky shore, a muddy estuary, an oakwood, or a grassland. There are five steps in studying an ecosystem. These are; 1. Map of the ecosystem 2. Identifying plants and animals 3. Estimating the number of plants and animals 4. Measuring the environmental (abiotic) factors 5. Presenting the Information Mapping of the ecosystem - On the first visit it is usual to make a sketch map of the ecosystem. - The area should be marked with four pegs, one at each corner. - The area should be measured by pacing it out. By taking big steps, each step can be regarded as one metre long. - All significant and obvious features should be drawn in. Diversity of Life in the ecosystem The diversity of life forms in the ecosystem is determined by making a consolidated species list. We use our eyes (direct observation) to search the ecosystem for different species. A key is a guide to identification. Two types of keys are used in the study of an ecosystem. - Pictorial key: A book with drawings of each species. One must search through the book until the species they are looking for is found. - Dichotomous key: Involves a series of questions to which there are normally two possible answers. One must pick the most appropriate answer, and this directs them to the next question in the series. One will continue doing this until the species is identified. Flora means plants while fauna means animals. Mandatory Practical – Identify five flora and fauna (1,2) Observation and Scientific Study Consolidated Species List Plants Name Main Features for Identification Daisy Yellow centre with lots of white petals, leaves flat on ground Buttercup Flower all yellow, five glossy petals. Tall plant. Dandelion Dozens of yellow petals, single flower at end of a long stalk Thistle Heart-shaped toothed flowers, stings, small green flowers Animals Name Main Features for Identification Frog Wet Skin, large, webbed back feet. Movement: hops Worm Long, thin, and reddish in colour. Wriggles, has slimy skin Snail Has a shell, slides along, has two pairs of tentacles Bee Feathers, orange or yellow beak, yellow ring around eyes A wooded grassland ecosystem contains the following habitats: - Grassland: A mown area, grazed by large herbivores. Exposed to full sunlight and thus high light intensity. Exposed to the full effects of the wind and rain, - Ash woodland: Ash is a native species and has its own specific communities living in it and on it. If other trees are present, they can be treated as a separate habitat. - Stream: A freshwater habitat, the organisms found there are determined by factors such as the rate of flow, the depth of the water, pH, the amount of dissolved oxygen and possibly pollutants. Soil near the stream is likely to be different from soil in other areas. It is likely to be much wetter, which will result in it having different flora and fauna from the surrounding areas. Mandatory Practical – Identify and use various apparatus for collection methods in an ecological study Animals Apparatus Function How to use Pooter Collect small invertebrates – insects/woodlice Suck through the tube with gauze at the end to collect animal. Container can be filled with CO2 to anaesthetise them until able to identify Pitfall Trap Catch invertebrates that walk on surface of the ground Plastic cup is buried underground, edge is flush with ground. Animals will fall in. Lid prevents container from filling with water. Prevents drowning. Beating Tray To catch insects that hide under leaves Tray held under a branch which is beaten with a stick. Insects fall onto the tray and can be collected with a pooter. Cryptozoic Trap Catch animals, like snails/woodlice, that shelter in secluded spaces during the day or in dry weather A slate is placed on top of a few supporting stones. Left overnight. Insects will use the trap and can be collected for identification. Nets Catch mobile animals, mainly insects or aquatic animals Butterfly nets are swept over an insect and twisted to close. Insect is trapped inside and can be collected with a pooter. Fishing nets are placed in a body of water with the mouth facing upstream. The current sweeps animals into the net. Tullgren Funnel Extract small animals from leaf litter Soil litter is placed into a sieve and a lamp is turned on. The lamps drive insects downwards, through the sieve and into the container. Alcohol is placed in container to preserve animals. Mammal Traps To catch small mammals Food is used as bait to attract animals. The trap will close and enclose the animal within it. Plants Apparatus Function How to use Quadrat To sample plants or sedentary animals Throw a pencil over your shoulder and lay the quadrat over where the pencil is. Belt Transect Investigate how the distribution of a species varies with a changing environmental factor Pick a line that crosses an obvious changing environmental factor. Lay out a line marked in metres and take a sample at regular intervals. Interval depends on size of study area. Line Transect Investigate how the distribution of a species varies with a changing environmental factor Lay out the line and record the species of plant that it touches or is directly below each mark on the line. Record results. Display results in bar chart. Organism Distribution There are two ways to survey organism distribution. They are - Qualitative Surveys: Record which species are present. This only gives a very limited view of the ecosystem as it provides no idea of how common or plentiful a particular species is . - Quantitative Surveys: They determine not only which species are present, but also provide you with a measure of how many individuals of each species are present in the ecosystem. Mandatory Practical – Conduct a quantitative study of plants in an ecosystem - Percentage cover of plants or stationary animals (use % area covered in each quadrat or use a graduated quadrat : number of touches x 100 = 10 x 100 = 40%) number of squares 1 25 1 - Frequency - the chances of finding a named species with any one throw of the quadrat. (Slugs found in 4 out of 16 gives a frequency of 4/16 x 100 = 25 %) This method is fast and easy. Disadvantages: dependent on organism and quadrat size and presumes that organisms are evenly distributed throughout habitat. Transects: Line transects (rope marked at intervals – record what touches the line and measure environmental conditions at each). Belt transect – take quadrats in a line Capture – recapture method (use paint, tags, legs ringed) Number of animals – C1st x C2nd M 2nd Assumptions: - Marking must not harm the animals e.g., make it more visible to predator - Animals mix evenly in habitat (not bunched e.g., colonies of ants) - Animals are restricted to local area - Marked animals must be given time to mix with the unmarked population Mandatory Practical – Investigate any three abiotic factors Sample Factor Measured by Influence Soil pH pH meter/Indicator paper Favours some plants and therefore some animals Light Intensity Light meter Plants are adapted to different light intensities Temperature Thermometer/Probe Flora and fauna different than normal at discharge points of cooling water from electricity Analysis & Presentation of results - Tables, lists, charts, graphs, diagrams, histograms. - Include food chains, food webs, pyramid of numbers (identify the role of the organism in energy transfer) - Identify local ecological issues related to the woods. - Portfolio/Report Sources of error in an ecosystem study - Human error - from mistakes in measuring (judgement) or recording. - Changing conditions, both natural e.g., seasonal: autumn – summer or artificial e.g. pollution. - Accidental discoveries maybe made – e.g. rare animal (bird of prey) may be present on a rare occasion or at night (owl) or shy animal discovered by quiet walker and not a class. - Sample size - habitats studied may not accurately reflect the overall ecosystem if habitat is too small to include all animals and plants or of only a few habitats are studied. Organism Adaptations **Need to know one** Organism Adaptation Benefit Primrose Early growth and flowering Less competition for light before leaves grow on trees Ladybirds Brightly coloured Indicates their presence (full of formic acid) Organisms found in Woodland **Need to know 5 plants & 5 animals** Vegetation Invertebrates Higher Predators Trees & shrubs layer Ash, hawthorn, blackthorn, elder, holly, willow Greenfly, caterpillars, ladybirds, spiders Chaffinch, blue-tit, robin, sparrowhawk Herb layer Primrose, stitchwort, cow parsley, celandine Butterflies, snails, slugs, flies, wasps, midges, bees Blackbird, thrush, fieldmouse Ground layer Ivy, ferns, fungi, mosses Woodlice, centipedes, beetles, millipedes Pygmy shrew, hedgehog, badger, fox Soil layer Fungi, bacteria Earthworms, flatworms Exam Questions 2013- HL – Section B – Question 7 7. (a) Distinguish between the terms habitat and ecosystem by writing a sentence about each. (i) Habitat. The place where an organism lives ii) Ecosystem. A community of organisms that interact with their environment. (b) Answer the following questions in relation to a named ecosystem which you have investigated. Ecosystem - Woodland (i) How did you investigate a named abiotic factor, other than temperature or pH? Abiotic factor – Wind Speed How investigated - Measured at a number of different locations in the habitat using an anemometer (ii) How were you able to identify the animals that you found in the ecosystem? Animal identification Key (iii) When conducting a quantitative survey of plants, how did you ensure that your sample was random? By throwing a pencil over the shoulder and then placing the quadrat down at the location the pencil landed. This was repeated a number of times (iv) In the case of a named animal and a named plant give an example of an adaptation to its habitat that you observed. Animal – Snail. Adaptation- Shell for protection Plant – Nettle. Adaptation – Stinging hairs to protect from herbivores (v) As part of your study of your selected ecosystem you constructed a pyramid of numbers. Name the species that occupied the top of your pyramid. Fox (vi) What is the main prey of the species referred to in part (v)? Rabbit 2013 – HL – Section C – Question 11 Name the ecosystem which you investigated during your study of ecology. Woodland (i) Explain the terms 1. Flora – Photosynthetic organisms such as plants 2. Fauna – Animals, such as insects (ii) Name one animal from your named ecosystem and describe how you carried out a quantitative study of that animal. Squirrel Captue re-capture method Count the number of squirrels in a particular habitat. - Mark each squirrel with a dot or an X using a black permanent marker or, in the case of mammals caught using a mammal trap, tag them or mark their fur in a way that does not harm the mammal or make it more visible to predators. - Black will not make it visible to predators but will still be visible to the experimenter. - Release organisms back into their habitat - A period of time later, revisit the habitat. - Count the number of organisms present and, of those counted, record the number that had the mark - Calculate the approximate population of the organism in the habitat using the formula: No. caught 1st visit X No. caught 2nd visit Number of Organisms = No. marked 2nd visit (iii) Suggest one way in which marking an animal might endanger it. It may make it more visible to predators (iv) Ecosystems are subject to changes, both natural and artificial. Mention one of each type of change as it applies to your named ecosystem. Natural change: Flooding Artificial change: Deforestation References EncyclopaediaBrittanicia.co.uk EncyclopaediaBrittanicia.co.uk