Page 61 - Science Coursebook

3 End of unit questions

3.3 Pedro wants to breed strawberry plants that have larger fruits.
He chooses five of his strongest strawberry plants and plants them in the same
part of his garden. When they produce fruits, he collects the fruits and finds the
mean mass of the fruit from each plant.
These are his results.

Plant A Plant B Plant C Plant D Plant E
Mean mass of 23.8 24.2 21.3 26.2 25.9
one fruit / g

a Explain why it was important for Pedro to plant all five plants in the same
part of his garden. [2]
b Describe how Pedro could find the mean mass of one fruit on Plant A. [2]
c Which two plants should Pedro breed together? [1]
d Pedro breeds the two plants together by taking pollen from one of them
and brushing it onto the stigma of the other one. Explain why he does this. [3]
e Suggest what Pedro should do next. [3]

3.4 A bacterium called Staphyloccus pneumoniae is a major cause of a serious infection
of the lungs, called pneumonia. The graph shows the percentage of cases of
pneumonia in which the bacteria were resistant to penicillin (an antibiotic).

20
18
16

percentage 14
of cases of 12
penicillin-
resistant 10
pneumonia 8
6
4

2
0
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
year

a What is an antibiotic? [1]
b Describe the trend shown in the graph. [1]
c Suggest how natural selection has caused this trend. [3]

3 Variation and inheritance 59