Unit 3 - Key Area 2 - Distribution Of Organisms Flashcards
What is a biotic factor? Give examples
Biotic factors are interactions associated with living organisms. They can also influence the distribution of organisms in an ecosystem.
Biotic factors can be :
• Competition for environmental resources
• Disease
• Food Availability
• Grazing
• Predation
What is an abiotic factor? Give examples
Abiotic factors are non-lining variables that can influence where organisms can live. Abiorc factors can be : • Lignt intensity • Moisture • pH • Temperature
How would you measure light intensity? What are the sources of error?
Light meters can be used to measure light intensity. The meter is held at the soil surface and pointed in the direction of the maximum light intensity, and then the meter is read.
Errors can be made when measuring light intensity by accidentally shading the light meter. The reliability of the results can be checked by taking many samples
How would you measure moisture and pH? What are the sources of error?
Soil moisture and soil pH meters are also available, Both are used by simply pushing the probe into the soil and reading the meter
Errors can be made when measuring pH and soil moisture when probes are not cleaned between readings. The reliability of the results can be checked by taking many samples.
How would you measure temperature? What are the sources of error?
The temperature of the air can be measured with a thermometer. The temperature of the soil can be measured with a temperature probe
Errors can be made when measuring temperatures when probes are not cleaned between readings. The reliability of the result can be checked by taking many samples.
What is a quadrat used for and how is it used?
A quadrat is used to sample plants and slow moving animals. It marks off an exact area so that organisms in that area can be identified and counted.
Quadrats should be placed randomly so that a representative sample is taken
What are the limitations and sources of error of quadrats?
There are some limitations of using a quadrat. Human judgement can be an issue when using a quadrat for example, some plants may be partially inside/outside a quadrat so there are basic rules that scientists follow to reduce the chance of human Judgement affecting results.
What is a pitfall trap and how is it used?
Pitfall traps are often used to sample the small invertebrates living on the ground.
The top of the container should be level with the soil surface. Cover the trap with a piece of wood to make it dark and to stop birds eating your catch. Use a large number of traps at random to make results more reliable.
What are the limitations and sources of error of pitfall traps?
The traps must be checked often to avoid the animal escaping or
being eaten before they are counted.
What are biological keys?
Organisms can be identified using biological keys.
There are a two different types of keys
• Branching keys
• Paired Statement Keys
What effects do biotic and abiotic factors have?
When factors change in an ecosystem it can cause an increase in numbers of one population but a decrease in numbers of another population.
Give an example of an effect.
An increase in lignt intensity can increase the number of buttercups which provide more food for rabbits. Rabbit numbers will increase. Fox numbers increase as rabbits increase.
Increased rabbits and foxes leads to an increase in disease. Populations then decrease
What is pollution?
Pollution is the addition of substances to the environment that cause harm to organisms.
What is an indicator species?
An indicator species help indicate levels of pollution/environment quality either by their presence or absence.
As pollution levels increase biodiversity decreases. Lichens can be used to determine air. Organic waste decreases the level of oxygen.
