MODELLING OF NATURAL SELECTION
MATERIALS
(Per Group)
Set of cards, 15 red, 15 yellow and 15 orange
Offspring selector disc (Four-sided)
Prey selector dice (Six- sided)
BACKGROUND
The following assumptions apply to the activity
 Only three variations of colour exist in the population.
 The original population consists of 30 individuals: 10 red, 10 yellow and 10 orange.
 Each year the cows will mate and produce one offspring.
 Sex of the parents and offspring is not relevant in this model.
 When different cows mate the following offspring are produced.
PARENTS
red x red
yellow x yellow
red x yellow
red x orange
yellow x orange
orange x orange



OFFSPRING
Red
yellow
orange
½ red: ½ orange
½ yellow: ½ orange
¼ red: ½ orange: ¼ yellow
Each year after the calves are born the farmer sells one third of the population. On
examination of the population the farmer sells cows in the following proportions 3 red: 2
orange: 1 yellow (Leaving three to be randomly selected using the die method)
At the end of the year 30 cows are left for random breeding for the following year.
No other factors cause population changes, including environmental.
METHOD
1. Copy this table into exercise book.
YEAR
1
2
3
4
5
RED
10
ORANGE
10
YELLOW
10
TOTAL
30
2. Take 10 cards of each colour. These will be your original population. The other cards are to
be put aside to later represent calves.
3. Shuffle cards and deal out 15 pairs. These are the random matings that occurred in your
herd.
4. Examine each pair and using the following information, determine the colour of the offspring
produced.
PARENTS
red x red
yellow x yellow
red x yellow
OFFSPRING
red
yellow
orange
Other combinations use the offspring selector disc and refer to table.
PARENTAL CROSS
red x orange
DISC STOPS ON
1 or 2
3 or 4
1 or 2
3 or 4
1
2 or 3
4
yellow x orange
orange x orange
COLOUR OF CALF
red
orange
yellow
orange
red
orange
yellow
5. Once colour of calf is determined, take cards from spare piles and add to original population
(herd).
6. Now your herd has a total of 45 individuals. (30 cows and 15 calves). Now the farmer will sell
15 individuals (one third of the population) for meat. In order to determine which of the
cattle the farmer sells, use the ratio and then roll the prey dice for the last three options and
remove the cow card as indicated by the colour on the dice.
Number on die
Colour
1 or 4
Red
2 or 5
Yellow
3 or 6
Orange
7. Repeat the selection processes (roll of the dice) 2 more times until 15 cows all up have been
removed.
8. Count the number of cows left in each colour of your population and record results in table
(including total number of animals). These remaining cows will be your breeding population
for the next year (year 2).
9. Repeat steps 3-8 until you have enough data for at least 5 years.
10. Sort cards back into 3 piles and place an elastic band around the entire set.
http://www.coloring kids.com/cows-coloring-book-pages.html
Brotherton, J. Mudie K, (2004) Heinemann biology activity manual, second edition, Heinemann hartcourt education pg 127-130
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