Distribution of organisms Flashcards
What is a habitat?
A habitat is the place where an organism lives
What do we mean by the term ‘distribution’ in relation to organisms?
The distribution of an organism is where an organism is found
Give three environmental factors which can affect where an organism is found.
Any of the following; temperature, availability of water, availability of oxygen and carbon dioxide, availability of nutrients or amount of light.
Why might there be more of a particular organism in one area than another? E.g. in a field you might find more daisies in the open than under trees. Why?
It depends on the environmental factors. In the example it is due to amount of light.
Explain two ways that you can study the distribution of organisms.
You could measure how common an organism is in two areas (using quadrats) and compare them or you could measure the change of distribution across an area (using a transect)
Here is a method for measuring distribution of organisms using quadrats. Fill in the gaps.
Place a 1m2 quadrat on the ground at a ______ point within the sample area. Count the ______ within the quadrat. ______ steps 1 and 2 as many times as you can. Work out the _____ number of organisms per quadrat within the area. Repeat steps 1-4 in a ______ sample area. Finally, ______ the two means.
random, organisms, repeat, mean/average, different, compare
How do you work out population size?
Work out the population size of an organism per 1m2. Then, multiply the mean by the total area (in m2) of the habitat
What is a transect?
A transect is a piece of rope or string (or anything else that makes a line) that gos through a habitiat.
Describe briefly how you would use a transect and quadrat to measure the distribution of organisms along a habitat.
Mark out a line in the area you want to study using a transect. Place quadrats down along this line in a set patten (to the right of the line, to the left of the line, alternating sides, every 2m ect.) and count the organisms that you are investigating.
What must you remember about collecting data along a transect when not using quadrats?
To only count the organisms that touch the line.
How can you make your results more reliable? Why must you do this?
To make your results more reliable you need to take a larger sample size so that it is a closer representative of the whole population.
How can you make your results more valid?
You must contol all of the variables apart from the one that you want to investigate. This is so that you know that your results are due to the environmental factor that you are investigating and not due to chance.
