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IA- Practical IDeas-from external colleagues

Page history last edited by Jay 14 years, 7 months ago

Table 1: Titles of the investigations related to different topics


Topic in the Biology guide/Syllabus assessment statement number?

Title of the investigation

Web-site with experiment details (optional)

3.6 Enzymes

Investigating protein enzymes in fruits


Different fruits used are papaya, pineapple, apple, avocado, orange etc. Gelatin (protein) can be used for making jelly and the effect of different fruit extracts can be investigated. Refer to the sites for procedure & ideas:







Stomatal distribution & density in the leaves



My students use different types of leaves like dicot, monocot. Apply a thin layer of transparent nail varnish and peeled off when dry. It takes beautiful impression of epidermal calls and stomata, and can be observed under high power. Refer to the sites:




2 enzymes

Investigating a factor affecting the activity of the enzyme in Beano (a pill that prevents flatulence by converting oligosaccharides into glucose)


Human physiology



The effect of sugar intake on blood glucose level




Karyotyping to identify patient conditions due to chromosome anomalies



Cell theory

2.1.6—explain the importance of SA to volume ratio as a factor limiting cell size

To study the conductivity of Nacl agar cubes of different SA to vol ratios

Got it from a workshop by Linda Round in Mumbai. Works very well

Topic 6.6


Topic 11.4

Sea urchin gametes.


Sea urchins are readily available on the Peruvian coast and can be made to ejaculate (with an injection of KCl). The gametes can be seen under a microscope and give great images of sperm fizzing around eggs. The students are fascinated. Useless for evaluation of the moderated criteria but manipulative skills can be observed.


ption D: Evolution

(Esp. D3.5)

Skulls lab.


The students have (about 20) photos and drawings of prehistoric human and chimp skulls. Each student traces 1 or 2 and they all make a number of measurements from all the images and calculate indices, plotting these against age of fossil.


Excellent for the DCP and CE criteria and very interesting




1 Statistics

Statistical Analysis of Students’ Physical Data


1 Statistics (just used this for DCP introduction but it is a lab directly related to topic 2.4 – Membranes)

When Cells Freeze Over” from The Science Teacher, 1998.

http://12knights.pbworks.com/PSOW [click on the link to the PDF titled, “When Cells Freeze Over”

2.4 Membranes (and IA intro to microscope drawings)

Microscope drawing of Elodea Canadensis in hypotonic and hypertonic solutions


2.4 Membranes

Investigate one factor that may affect the process of diffusion


2.4 (membranes)

Effect of temperature on diffusion through a membrane.

We do this very early on as a AfL exercise so they get FAR too much help to use it towards their real marks. We use beetroot placed in water at different temperatures, take samples of this water and do colorimetry to see how much of the pigment has diffused out of the beetroot. It is great for early discussion of controlling variables and uncertainties and errors. It gives good results too – an initial steady increase in diffusion as you increase temp followed by a sudden jump at the point when the membrane begins to break down. You could also use it for surface area to volume by keeping the same volume of beetroot, but cutting it into smaller and smaller cubes/cylinders to increase the surface area – haven't tried that as we usually use agar with creosol red indicator and HCl diffusing into it.

2.3 (enzmes)


We do 3 main experiments with enzymes – all from natural sources as they are difficult to get and keep here in Perú.

One to introduce t-tests is to compare the height of the froth produced using the same mass/volume of liquidised liver to liquidised potato tissue. Everyone in the class does 3 readings each and then they pool class data and calculate the mean, stDev and t-tests to see if the difference is significant. Again it is an early prac. so it is used for discussing ideas and to practise writing up, rather than a 'real' lab.

A second is to think of other ways of measuring activity other than height (or volume) of froth. We cut thin discs of potato and use different concentrations of H2O2 and time how long it takes for the discs to produce enough oxygen to make them rise to the surface. This is great for discussing errors and uncertianties. You can modify this by using discs of filter paper which have been soaked in a solution of liquidised potato to make it easier to control the surface area and thickness.

We also do an experiment with salivary amylase. This involves first constructing a standard curve for the absorbance shown by known concentrations of starch/iodine solution. Students then compare the activity of their saliva with other members of the class by reacting the same volumes of starch/saliva and calculating how much starch is left after a certain amount of time and then calculating the rate of the reaction. If they take readings every 2 mins until there is no starch left they can also look at how the rate of the reaction changes with time.

Students can then design their own enzyme experiment having seen a variety of different methods for measuring the rate of the reaction and without having looked at the 2 main factors of temperature and pH!


Mitosis virtual lab

http://www.biology.arizona.edu/cell_bio/activities/cell_cycle/cell_cycle.html students sort cells and then work out how much time is spent in each stage of mitosis.

Topic 2.4 - Membranes

Effect of surface area to volume ratio on diffusion rate using cresol red jelly and dilute HCl.


Topic 6.2

Investigate any one factor that affects the heart rate



Light dependent reaction

(For HL


Crush 1 gram of spinach leaves using a pinch in distilled water and obtain the leaf extract which would contain chloroplast. Find the OD of the leaf extract. Now, take two ml of leaf extract and 1 ml of DCPIP (1% dichlorophenolindophenol) in a cuvette and find immediately its optical density by spectrophotometer and then expose it to light for one minute. Check and record its OD after every minute. DCPIP is blue is colour and when it gets reduced, turns colourless. (When leaf extract is mixed with DCPIP it appears dark blue-green, but as its DCPIP undergoes reduction it slowly turns lighter and finally original green colour of leaf extract is restored). It functions as NADP in light dependent reaction. Wrap another cuvette having same contents and check its OD every minute as a control. Process can be repeated with fresh contents. Plot the graph taking Time as independent variable and Optical Density as dependent.

Expected results:

In control cuvette very little or no change should be observed due to absence of light. Cuvette exposed to light shows decrease in its OD



Rate of anaerobic respiration using yeast and glucose mixture

Set the apparatus as shown in figure:


You need to fill the small bottle (Eye drops bottle is suitable for this experiment)

You need to fix the bottle using plasticine as it might float. Count the number of bubbles per minute. You can perform this investigation at different temperatures. Different types of sugars can be used

6.2 / H5

Factors that affect the heart rate of Daphnia

While I state this is one of my favourite experiments I haven’t done it since I left the UK due to problems getting live specimens in Jamaica. It teaches the students a lot of patience, microscopes techniques - dealing with live specimens and is open to many variables, from changing temperature, to changing caffeine and alcohol concentrations.


Factors the affect rate of transpiration

Another experiment that test patience in setting it up without bubbles


Length of mango leave

This I found by accident I had a grade 8 class and I wanted to improve graphing skills and data manipulation. I sent groups off to 6 different mango trees and got them to measure 100 leaves from each tree – choice of leaf had to be random.

Frequency graphs were then drawn and it was found that while the sizes of leaves from each tree followed a normal distribution, different species of mango had different ranges of leaf size. I have since used this with t-tests to compare populations

3.7, 8.1, and Option H

Gas Analysis (data logging)

The lab includes capturing expired gases at different activity intensities and mearsuring CO2

3.1, 3.2, 3.6

Vitamin C content of fruit juice






















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