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A3
Homework
Cells and growth
HELP
1 a Copy and complete these sentences by choosing from
the words below.
small
smaller
big
All living things
bigger
grow
division
, which means they start
and get
process of cell
. They grow by the
.
b These sentences are in the wrong order. Copy them out
in the correct order to explain what happens during cell
division.
A The cell starts to divide into two.
B The nucleus divides into two.
C The cell finishes dividing and two new cells have
been produced.
D There are two copies of the nucleus in the same cell.
CORE
2 Cell division happens in three main stages, which are:
1 The nucleus divides.
2 The cell divides.
3 The new cells grow.
a Draw a diagram for each of these three stages, showing
what the cell or cells might look like under a
microscope.
b Suggest a reason why, after the cell divides, each new
cell grows before it can divide again.
c Only stage 3 increases the size of an organ. Suggest
what might happen to the size of the organ if all the cells
in it completed stage 3 at the same time.
© Harcourt Education Ltd 2003 Catalyst 1
This worksheet may have been altered from the original on the CD-ROM.
Sheet 1 of 2
A3
Cells and growth (continued)
Homework
EXTENSION
Read the passage about the cell division of cholera bacteria,
and then answer the questions about it.
Some illnesses are caused by bacteria, which multiply very
quickly. One example is cholera, which affects people who
are crowded together in very unsanitary conditions, such as
you might find in a refugee camp or in a hot country after an
earthquake. Cholera bacteria are swallowed when a person
drinks contaminated water or eats contaminated food. In their
digestive system, where the conditions are just right, the
cholera bacteria multiply prolifically. If it is not treated very
quickly, cholera causes death within a few hours.
3 The passage says that cholera bacteria can multiply
‘prolifically’. Use a dictionary to write a definition of the word
‘prolific’.
4 In the digestive system, a cholera bacterium can divide
every hour. Suppose you swallowed some water containing
1000 cholera bacteria. Assuming that none of them died,
how many would be in your digestive system:
a after 1 hour?
b after 5 hours?
c after 12 hours?
Show your working for each one.
5 Cholera is passed from one person to another when
bacteria from the digestive system get into water that the
second person drinks. Suggest how this might happen
easily in a crisis situation like a refugee camp or after an
earthquake. (Hint: think about any pictures of these events
that you may have seen and remember that the answer is
pretty unpleasant.)
6 Write a sentence or two to explain why it is very important,
during cell division, that the nucleus always divides first.
© Harcourt Education Ltd 2003 Catalyst 1
This worksheet may have been altered from the original on the CD-ROM.
Sheet 2 of 2