plan, choose equipment or resources and perform a first-hand investigation to model natural selection
A simple but useful investigation that you might use is ‘Stick-bird’: Within a hypothetical population of ‘worms’ (toothpicks) that inhabit a predominantly green-coloured environment (green grass), there are two colour variations; cream and green. The worms are food for a predator known as a ‘stick-bird’ (students).
Possible hypothesis: In a predominantly green coloured environment, green worms have a greater chance of survival and therefore reproduction due to their ability to blend in with the background.
Toothpicks are mixed and scattered randomly over a measured grassed area. Stick birds (students) are later brought to that area and remain outside a ‘fence’. They are told to prey on the ‘worms’ in the field (collect as many toothpicks as they can) in a given time. After 3 minutes, the ‘stick-birds’ are driven from the field by the ‘farmer’ (teacher). They escape back to the classroom
Tally and compare the numbers of green and cream toothpicks recovered. Calculate percentages recovered of each colour.
Consider the numbers of toothpicks and students that will be needed for valid and reliable data to be collected in the investigation. You may need to modify the procedure in light of your considerations.
A possible conclusion
It would be expected that fewer green worms would be collected as they would have a selective advantage over the cream worms due to camouflage effect. Thus the environment has selected the better adapted worms who will go on to reproduce in greater numbers, over time the green worms will become the more prevalent phenotype within the ‘worm’ population.