Topic 3 Assessment Booklet
Marks = 155 Time Allowed 202 minutes
Q1.(a) Explain two ways in which the structure of fish gills is adapted for efficient gas exchange.
1. _________________________________________________________________
___________________________________________________________________
2. _________________________________________________________________
___________________________________________________________________
(2)
(b) Explain how the counter current mechanism in fish gills ensures the maximum
amount of the oxygen passes into the blood flowing through the gills.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(3)
(Total 5 marks)
Q2.
(a) Binding of one molecule of oxygen to haemoglobin makes it easier for a second
oxygen molecule to bind.
Explain why.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
Page 1 of 52
, ___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
A haemocytometer is a special microscope slide which can be used to count the numbers
of blood cells in a sample of blood.
• The surface of the slide has many small, equal-sized squares marked on it.
• The depth of the liquid under each square is 0.1 mm
• When counting, cells that touch top or left lines are counted but cells that touch right
or bottom lines are not counted.
A doctor used a haemocytometer to determine the number of red blood cells per mm3 in a
blood sample. He diluted the original blood sample by a factor of 200 times before putting
some on a haemocytometer.
The diagram shows the distribution of cells in a typical small square.
(b) The doctor counted the red blood cells in many small squares.
The mean number of red blood cells per small square was 7
The original blood sample was diluted by a factor of 200 times.
Calculate the number of red blood cells per mm3 in the original blood sample.
Give your answer in standard form.
Page 2 of 52
, Answer = ____________________ red blood cells per mm3
(2)
(c) When counting, cells that touch top or left lines are counted but cells that touch right
or bottom lines are not counted.
Suggest two reasons for this rule.
1. _________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
2. _________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
The doctor also wanted to know how many white blood cells per mm3 there were in a
different sample of blood. To do this he first diluted the sample by a factor of 20 times. He
then made the white blood cells clearly visible by using a stain that makes nuclei appear
dark blue.
(d) When counting white blood cells, the doctor only diluted the blood sample by a
factor of 20 times, instead of 200 times when counting red blood cells.
Suggest why he only diluted the sample by a factor of 20 times.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(1)
(e) Explain how the stain allowed the doctor to count the white blood cells amongst all
the red blood cells.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
Page 3 of 52
, ___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(1)
(Total 8 marks)
Q3.
Under the correct conditions, new roots grow from the cut end of a plant stem. A scientist
investigated the effect of substance X on the growth of new roots.
She used a ringing experiment to investigate the movement of substance X in stems
taken from lemon plants. She cut out a length of stem from each plant. She then put a
small block of agar on the top of each length of stem. Some agar blocks contained
substance X.
The diagram below shows how she treated each length of stem.
She grew the lengths of stem in the same environmental conditions for 6 weeks, and then
found the number of roots per length of stem. Roots grew at the other end of the stem
from where the agar blocks were placed.
The table below shows the scientist’s results.
Mean number of roots
Treatment
per length of stem
D 5
E 11
Page 4 of 52
Marks = 155 Time Allowed 202 minutes
Q1.(a) Explain two ways in which the structure of fish gills is adapted for efficient gas exchange.
1. _________________________________________________________________
___________________________________________________________________
2. _________________________________________________________________
___________________________________________________________________
(2)
(b) Explain how the counter current mechanism in fish gills ensures the maximum
amount of the oxygen passes into the blood flowing through the gills.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(3)
(Total 5 marks)
Q2.
(a) Binding of one molecule of oxygen to haemoglobin makes it easier for a second
oxygen molecule to bind.
Explain why.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
Page 1 of 52
, ___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
A haemocytometer is a special microscope slide which can be used to count the numbers
of blood cells in a sample of blood.
• The surface of the slide has many small, equal-sized squares marked on it.
• The depth of the liquid under each square is 0.1 mm
• When counting, cells that touch top or left lines are counted but cells that touch right
or bottom lines are not counted.
A doctor used a haemocytometer to determine the number of red blood cells per mm3 in a
blood sample. He diluted the original blood sample by a factor of 200 times before putting
some on a haemocytometer.
The diagram shows the distribution of cells in a typical small square.
(b) The doctor counted the red blood cells in many small squares.
The mean number of red blood cells per small square was 7
The original blood sample was diluted by a factor of 200 times.
Calculate the number of red blood cells per mm3 in the original blood sample.
Give your answer in standard form.
Page 2 of 52
, Answer = ____________________ red blood cells per mm3
(2)
(c) When counting, cells that touch top or left lines are counted but cells that touch right
or bottom lines are not counted.
Suggest two reasons for this rule.
1. _________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
2. _________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
The doctor also wanted to know how many white blood cells per mm3 there were in a
different sample of blood. To do this he first diluted the sample by a factor of 20 times. He
then made the white blood cells clearly visible by using a stain that makes nuclei appear
dark blue.
(d) When counting white blood cells, the doctor only diluted the blood sample by a
factor of 20 times, instead of 200 times when counting red blood cells.
Suggest why he only diluted the sample by a factor of 20 times.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(1)
(e) Explain how the stain allowed the doctor to count the white blood cells amongst all
the red blood cells.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
Page 3 of 52
, ___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(1)
(Total 8 marks)
Q3.
Under the correct conditions, new roots grow from the cut end of a plant stem. A scientist
investigated the effect of substance X on the growth of new roots.
She used a ringing experiment to investigate the movement of substance X in stems
taken from lemon plants. She cut out a length of stem from each plant. She then put a
small block of agar on the top of each length of stem. Some agar blocks contained
substance X.
The diagram below shows how she treated each length of stem.
She grew the lengths of stem in the same environmental conditions for 6 weeks, and then
found the number of roots per length of stem. Roots grew at the other end of the stem
from where the agar blocks were placed.
The table below shows the scientist’s results.
Mean number of roots
Treatment
per length of stem
D 5
E 11
Page 4 of 52
