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level: Distribution of Organisms

Questions and Answers List

level questions: Distribution of Organisms

QuestionAnswer
what is a biotic factorliving things that affect the distribution of organisms eg competition for resources, grazing, predation, food availability and disease
what is an abiotic factornon-living things which affect the distribution of organisms eg temperature, humidity, and light intensity
describe this predator prey interaction graphthe population of predators always lags behind the prey population at low prey populations the predators cannot find enough prey to eat so the predator population will stay low at higher prey populations the predators find more prey, eat them and the prey population will decrease because they have eaten more, the predator population can reproduce more and their numbers will increase lower prey populations limit how many prey can be found and eaten by predators so predator numbers will decrease this pattern will continue giving a distinct graph
what effect does predation have on biodiversitypredation can increase biodiversity for instance, predation can kill one species, which is in competition with a different species. This can allow the different species to gain resources they may not be able to if their competitors weren't killed, therefore increasing biodiversity
describe what occurs at different levels (low, intermediate and high) levels of grazingat low levels of grazing the slower growing plant species die because they are out competed for resources by a small number of vigorous grass species which will hen dominate the habitat at intermediate grazing levels some of the vigorous growing plants are eaten allowing the slower growing species to gain more of the resources to survive. This therefore results in a mixture of slower and more vigorous growing plant species so increasing biodiversity. at high grazing levels, overgrazing could damage all of the plant species present and very few grow
what does food availability refer tothe availability of edible vegetation, eaten by herbivores or the availability of prey eaten by predators
name 5 abiotic factors affecting an organisms distributionlight intensity temperature soil moisture pH humidity
what instrument is used to measure soil pHpH meter
what instrument is used to measure light intensitylight meter
what instrument is used to measure temperaturethermometer
what instrument is sued to measure soil moisturesoil moisture meter
what instrument is sued to measure oxygen concentrationoxygen meter
name a possible source of error & its solution for when using a light metercasting a shadow over the light meter to overcome this error do not stand between the sun and the light meter
name a possible source of error and its solution for when using a pH or soil moisture metermoisture from previous reading left on the probe to overcome this error wipe the probe dry between measurements
name methods of sampling live organismspitfall traps: to sample organisms living on the soil surface tullgren funnel: used to sample organisms living in the soil branch/tree beating: used to sample small organisms living in bushes or trees quadrat: used to sample low growing plants or slow moving animals, eg snails
what is meant by replication of samplingthe samples taken of an ecosystem must be representative or that ecosystem, therefore an appropriate number of samples should be taken. this should provide more reliable results which are more representative or the ecosystem
what are sampling techniques used for?find out which plants and animals live in an ecosystem find out how common or rate plants and animals are in a given ecosystem investigate the reasons why the plant or animal lives there
describe how to sample using quadratsa quadrat is used to mark off an exact area of the ground so that the organisms in that area can be identified and counted in order to improve the reliability of the results: - quadrats should be placed randomly - multiple samples should be taken and average results calculated
what is the purpose of placing quadrats along a transect lineto assess species distribution in relation with any abiotic factor that varies across a measurable distance
name possible sources of error and solutions with pitfall trapsorganisms may not be able to climb into container: make sure container is in line with soil surface trapped organisms may be eaten by birds: cover trap with a raised stone or leaf trapped organisms may eat each other: use a preservative such as 50% ethanol in the traps and check the traps regularly
name possible sources of error and solutions with quadratsquadrats are not placed randomly: ensure quadrats are thrown at random some plants that are partly in the quadrat are included and others are not: establish a rule for plants that are partially included and apply consistently do all quadrats in the study
what is a paired statement keya key made up of pairs of statements to help identify an organism
what is an indicator speciesspecies that by their presence or absence indicate environmental quality/levels of pollution
name one example of indicator specieslichens are often used as indicators of air pollution shrubby lichens are not capable of growing in areas of high air pollutions whereas crusty lichens are capable of growing in areas of moderate to high levels of air pollution