Distribution of organisms

• Biodiversity in an ecosystem is affected by a variety of factors, which can be classified as biotic and abiotic.
• Wrong temperature reading can be caused by a shadow over the light meter.
• pH and moisture readings can be the same if the probe is not cleaned and dried before and after each use.
• Time is needed for the temperature to reach the correct temperature.
• The probe should not cast a shadow over the light meter.
• A 'biotic factor' is any living component that affects another organism, including food availability, disease, competition for resources, predation, grazing, and others.
• Lynx and hare are examples of predator-prey interaction.
• The peak for the lynx population always comes after a peak for the hare population.
• Water pollution is caused by the discharge of harmful substances into rivers, lakes and seas.
• Many aquatic invertebrate animals cannot survive in polluted water, so their presence or absence indicates the extent to which a body of water is polluted.
• Level of pollution can be determined by the presence or absence of indicator species.
• Indicator species include mayfly larva, freshwater shrimp, water louse, rat-tailed maggot and sludge worm.
• Lichens can be used as indicator species to indicate air pollution.
• For the populations to survive, there will always be more hares than lynx.
• Abiotic factors include temperature, soil moisture, light intensity, pH, and others.
• Abiotic factors can be measured using instruments such as a light meter, soil pH meter, thermometer, and moisture meter.
• Errors in measuring abiotic factors can be minimised by ensuring all observers are standing to one side of the light meter to avoid casting a shadow over the sensor, wiping the probe with a tissue before taking a reading, and others.
• Pitfall traps are used to sample small invertebrate species living on the soil surface.
• Species fall in and are unable to climb back out again so they can be measured after a period of time.
• The pitfall trap should be camouflaged to ensure that the invertebrate species are not harmed and that the cup does not overflow with water.
• The cup needs to be level with the ground so invertebrate species would fall in to ensure that the species identified at the end are a better representation of the species found in the sampling area.
• Repeating an experiment ensures that the results taken are reliable.
• Invertebrate species can eat each other! (Predation)
• Species can be misidentified.
• Some pitfall traps are never found again.
• Paired-statement keys are used to identify organisms from a sample.
• If conditions in an area are not suitable for the needs of an organism then that organism will not be found in that area as it cannot survive there.
• The temperature is too cold for many species to survive in the arctic.
• Some plant species prefer particular pH ranges.
• An increase in acidity in ponds can kill fish species.
• Species are adapted to specific temperature ranges.
• A change from the norm can kill species.
• Sulphur dioxide and nitrogen dioxide are released into the air when we burn fossil fuels.
• These gases dissolve in the water contained in clouds forming dilute acids and fall to the earth as acid rain.
• Acid rain damages the leaves of plants which reduces their ability to photosynthesise.
• Acid rain lowers the pH of freshwater.
• This can kill individual species of fish who can’t tolerate acidic pHs.
• Carbon dioxide released during the burning of fossil fuels acts as a greenhouse gas.
• These gases form a heat trapping layer in our atmosphere and cause global warming.
• Global warming is responsible for melting the polar ice caps and is also thought to be responsible for causing floods.