Field Investigations
Field investigations
Measuring population size of a common species in a habitat using sampling techniques to investigate the species.
This is a two-part investigation in which students are required to measure the population size of a plant species using random sampling and then investigate the e4ect of a factor on plant distribution using a transect line. Light intensity is a good factor to measure using a light meter. An outdoor survey area of around 400m² is required for a class of students and should be prepared by marking out a 20M x 20M square for each group using string and a trundle wheel or tape measure. Students should also be familiarised with the identification of the plants which are being counted.
Equipment (per pair of participants)
• 1 x quadrat
• 1 x tape measure or 1 x trundle wheel
• 1 x light meter
• 1 x clipboard
• 2 x bags of numbers 1M-20M
Method
Basic
- Before the practical session, mark out a 20M X 20M square using a trundle wheel and string.
- The students then collect one number from each of the two number bags (these could be colour-coded in order to help with returning them to the correct bag).
- Using the numbers as co-ordinates, one member of the group should walk that distance in metres along the bottom of the 20M square and stand beside it.
- Another member of the group should then measure the distance from the second number up the side of the 20M square and stand beside it.
- The third member of the group then places the quadrat so that it is in the area where the two other members of the group meet in the middle, inside the 20M square.
- Students should then put the numbers back into their appropriate bags and count and record the number of individuals of a chosen plant species within the placed quadrant.
- The light intensity at each spot can also be measured using a light meter and recorded.
- The process is then repeated for ten quadrants.
- The equation to use for estimated population size is as follows:
Transect line method
- Identify to students a species of plant they are going to study.
- Using the tape measure, students should extend this over 30M in a line from the base of a tree.
- A quadrat is then placed against the measuring tape with one corner lined up with the zero mark on the tape measure.
- The number of the specified plant species within the quadrat is counted and noted in a suitable table. Light intensity at this spot should also be measured using a light meter.
- The quadrat is then moved along the tape measure in a set increment (for example 2M or 5M). The number of plants of the specified species is counted and the light intensity is measured again.
- The process is repeated through the 30M length of the transect line.
Technician tips
• The 20M square can be marked out for the students just before the start of the lesson to save time.
• The two bags of numbers could be made from different coloured paper, in order to assist with the students returning them to the correct bags
To do this practical you will need
Need some Biology inspiration and help?
Measure and sample species in a habitat for GCSE Biology practicals by using our required method and sampling equipment. For students to do this practical they will need grid quadrats, tape measures, trundle wheels, light meters and clipboards. Browse and explore our site for more science equipment ideal for schools or lab experiments.
