Distribution of organisms Flashcards
What is meant by a niche?
Every organism has its own niche i.e. the role an organism plays within a community. This includes the resources it requires in its ecosystem, such as temperature, light and nutrient availability and its interactions with other organism e.g. competition and predation, in the community. Therefore interactions with other organisms and levels of particular resources can influence where organisms live (their distribution) and how many of them there are (biodiversity).
What are the factors which can affect an organisms distribution?
Biotic factors and abiotic factors.
What are biotic factors?
Biotic factors are living things that affect the distribution of organisms e.g. competition for recourses, grazing, predation, food availability and disease.
What are abiotic factors?
Abiotic factors are non-living things which effect the distrubution of organisms e.g. temperature, humidity, pH and light intensity.
What are the five biotic factors affecting an organism’s distribution?
Competition for resources Predation Disease Grazing Food availability
What is competition?
Competition is the struggle between individuals when recourses are in short supply/limited e.g. food, light, water etc.
What are the effects of competition on an organisms distribution?
The effects of competition include more successful species increasing in number and less successful species decreasing in number.
What is meant by predation and how does it affect an organisms distribution?
A predator is an animal that hunts and eats other organisms therefore it can influence where particular prey live and ultimately the biodiversity of an ecosystem.
Which population is greater: Prey or Predator.
The population of predators always lags behind the population of prey.
What is the affect of predation on biodiversity?
Predation can increase biodiversity.
Why is disease a biotic factor?
It is a biotic factor because diseases are caused by living microorganism.
What is the affect of disease on an organisms distribution?
Disease has a similar effect to predation, controlling the number of organisms in a population.
Describe low levels of grazing.
At low levels of grazing, the slower-growing plant species die because they are out competed for recources by a small number of vigorous grass species which will then dominate the habitat. (Interspecific competition).
Describe intermediate levels of grazing.
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. Intermediate grazing levels therefore results in a mixture of slower and more vigorous growing plant species so increasing biodiversity.
Describe high levels of grazing.
At the high grazing levels, over grazing could damage all of the plant species present and very few grow.
Describe how food availability can affect the distribution of an organism.
Food availability can involve the availability of edible vegetation, eaten by herbivores, or it can involve the availability of prey, eaten by predators.
Name 5 abiotic factors.
These are the climate/environmental factors which can effect where an organism lives (distribution): Light intensity Temperature Soil moisture pH humidity
What measurement instrument can measure the abiotic factor:soil pH?
pH meter
What measurement instrument is used to measure the abiotic factor: Light intensity?
Light meter
What measurement instrument can be used to measure the abiotic factor: Temperature?
Thermometer
What measurement instrument can be used to measure the abiotic factor: soil moisture?
Soil moisture meter.
What measurement instrument can be used to measure the abiotic factor: Oxygen concentration?
Oxygen meter
Describe how a light meter is used.
Light intensity is measured using a light meter, the sensor is held upwards and a reading is taken from the scale.
What is a source of error when measuring light intensity
A source of error would be casting a shadow over the light meter.
How can we overcome a source of error when measuring light intensity?
To overcome this error do not stand between the sun and the light meter.
Describe how a moisture meter or a pH meter are used.
soil moisture and pH are measured using a moisture meter or a pH meter, the probe is inserted into the ground and a reading is taken from the scale.
What is a source of error which can occur when measuring soil pH and soil moisture?
For both these abiotic factors a source of error would be moisture from previous reading left on the probe.
How could you overcome the source of error which could occur when measuring soil moisture or soil pH?
To overcome this error, wipe the probe dry between measurements.
What methods can be used for sampling plants and animals?
The following methods can be used for sampling live organisms: Pitfall trap Tullgren funnel Branch beating Quadrat
What is a pitfall trap used for?
Used to sample organisms living on the soil surface.
What is a tullgren funnel used for?
Used to sample organisms living in the soil.
What is branch beating used for?
Branch beating is used to sample small organisms living in bushes or trees.
What is a quadrant used for?
Used to sample low growing plants or slow moving animals e.g. snails.
How can reliable results be provided when sampling plants and animals?
The samples must be a representative of the ecosystem therefore an appropriate number of samples should be taken. This should provide more reliable results.
What are sampling techniques used for?
Sampling techniques are used to:
Find out which plants and animals live in an ecosystem.
Find out how common or rare plants and animals are in a given ecosystem.
Investigate the reasons why the plant or organism lives there.
How do you sample using quadrats?
A quadrat is used to mark off an exact area of the ground so that the organisms in that area can be identified and counted.
How can we improve the reliability of the results when sampling quadrats?
Quadrats should be placed randomly
Multiple samples should be taken (& average results calculated).
Why should quadrats be placed along a line (transect)?
Quadrats can be placed along a line (a transect) to asses species distribution in relation with any abiotic factor that varies across a measurable distance.
Give three possible sources of error when sampling using a pitfall trap.
Organisms may not be able to climb into container.
Trapped organisms may be eaten by birds.
Trapped organisms may eat each other.
How can we minimise the possible source of error: organisms may not be able to climb into the container?
Make sure that the container is in line with soil surface.
How can we minimize the possible source of error: Trapped organisms may be eaten by birds?
Cover trap with a raised stone or leaf.
How can we minimise the possible source of error: trapped organisms may eat each other?
Use a preservative such as 50% ethanol in the traps or check traps regularly.
What is a possible source of error which can occur when using a quadrat?
Quadrats are not placed randomly.
Some plants that are partly in the quadrat are included and others are not.
How can we minimise the error which may occur when sampling using a quadrat: Quadrats are not placed randomly.
Ensure that the quadrats are placed at random.
How can we minimise the possible source of error: Some plants that are partly in the quadrat are not included and others are not?
Establish a rule for plants that are partially included and apply consistently to all quadrats in the study.
What is a possible source of error which can occur with both a pitfall trap or a quadrat?
The numbers and types of organism may not represent the whole ecosystem.
How can you minimise the error which may occur when measuring biotic factors using a quadrat or a pitfall trap?
Take several samples to make results more reliable.
What are some human activities which can have an impact on biodiversity?
Human activities (another biotic factor) can also have an impact on biodiversity. These include: Land and water usage overexploitation climate change Pollution Invasive species.
What are indicator species?
Indicator species indicate the quality of the environment/level of population by their presence or absence.
What are lichens often used as indicators of?
Lichens are often used as indicators of air pollution.
What are the three types of lichen?
Hairy lichen
Leafy lichen
Crusty lichen
Describe the tolerance of hairy lichen.
Hairy lichen cannot tolerate sulfur dioxide at all and are not capable of growing in areas with high levels of air pollution.
Describe the tolerance of leaf lichen.
Leaf lichen can tolerate moderate levels of sulphur dioxide and therefore is capable of growing in areas with moderate levels of air pollution.
Describe the tolerance of crust lichen.
Crusty lichen can tolerate high levels of sulphur dioxide and therefore is capable of growing in areas with high levels of air pollution.
What are aquatic indicator species used for?
Invertebrate species in water tend to be used as indicator species to determine the quality of water by their presence or absence.
