1 Mrs Rola Sobhie

CAMBRIDGE AS BIOLOGY

PRACTICALS

9700/3

Mrs Rola Sobhie

Biology Coordinator

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AL NAHDA NATIONAL SCHOOL FOR GIRLS

BIOLOGY DEPARTMENT BIOLOGY PRACTICALS

Experiments for AS

1. Measuring microscopic objects using a stage micrometer and a graticule.

2. Observing plasmolysis in the cells of rhubarb epidermis, onion epidermis or

potato strips.

3. Using dialysis tubing as a model cell membrane to demonstrate osmosis

and diffusion.

4. Investigating how surface area affects the rate of diffusion

5. Carrying out biochemical tests for:

a) Reducing sugars

b) Non-reducing sugars.

c) Proteins.

d) Starch.

e) Lipids.

6. Carrying out a semi-quantitative Benedict’s test on a reducing sugar

7. Using Benedict’s test to estimate the concentration of reducing sugar in an

unknown solution.

8. Investigating the effect of temperature on enzyme activity.

9. Investigating the effect of pH on enzyme activity.

10. Investigating the effect of substrate concentration on enzyme activity.

11. Investigating the effect of enzyme concentration on enzyme activity.

12. Investigating the effect of inhibitors on enzyme activity.

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13. Investigating the action of catalase on hydrogen peroxide.

14. Measuring the rate of production of CO2 by yeasts during respiration.

15. Investigating the action of amylase on starch.

16. Investigating the action of proteases on proteins.

17. Investigating the action of lipase on lipids.

18. Investigating the action of urease on urea.

19. Immobilized enzymes.

a. Preparation

b. Advantages

c. Disadvantages

20. Using a potometer to investigate the effect of temperature, light intensity,

humidity and air movement on the rate of transpiration of a plant.

21. Practice the use of the equation C1 V 1 = C 2 V 2 in dilution problems.

22. Practice how serial dilutions can be carried out when given a stock

solution of a known concentration (e.g. diluting a solution to one half or one

tenth).

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AL NAHDA NATIONAL SCHOOL FOR GIRLS BIOLOGY DEPARTMENT BIOLOGY PRACTICALS

Data Presentaion and Analysis

1. Accuracy: The degree to which a measurement represents the true value

of something.

Simply put: How close a measurement is to the true value

Accuracy can be improved by using a better calibrated measuring instrument.

2. Precision: The ability of a measuring instrument to give the same reading

every time it measures the same thing.

Simply put: How close the measurements are to each other

Lack of precision is referred to as ‘random error‘.

3. Reliability: A measure of the degree of trust you have in the measurement

or how dependably an observation is exactly the same when repeated. It

refers to the measuring procedure rather than to the attribute being

measured.

Simply put: Will one get the same values if the measurements are repeated?

Reliability can be improved by:

a. Repeating the readings at least three times and calculating the mean

value.

b. Repeating using a wider range of values for the independent variable.

c. Removing anomalies

4. Estimating uncertainty in measurement:

a. Is half the value of the smallest division on the scale you are reading from.

b. If you make two measurements and your result is the difference between

them then the total error is the smallest division. For example, if you measure

a change in temperature or length using a ruler then you make two errors;

each is half the smallest division.

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5. Estimating the percentage uncertainty or error in a measurement:

To calculate the percentage error, divide the error in the measurement by the

measurement itself, and multiply by 100.

% error = uncertainty/ error X 100 Measurement

6. Tips for constructing a results table to display data

a. Draw a table with ruled columns, rows and borders.

b. Columns should be headed clearly with quantity and unit

c. Results should be organized in a sensible order, from lowest to highest

or vice versa

d. The independent variable should be in the first column and the

dependent variable in the second column

e. You should take at least three readings and calculate the mean value

f. Each measurement of the dependent variable should be taken to the

same number of decimal places

g. The calculated mean should be given the same number of decimal

places as the individual readings

h. If you get an anomalous reading then, do it again or ignore and don’t

use it in calculating the mean value

7. Tips for constructing a line graph

a. The independent variable goes on the x-axis and the dependent

variable on the y-axis

b. Each axis should be fully labeled, including the units

c. The scale on each axis should go up in equal intervals

d. The intervals chosen should make it easy to read intermediate values

e. The scales should cover the entire range of values to be plotted

f. The points are plotted as neat, carefully placed crosses

g. Each point should be joined to the next point with a ruled straight line

h. The line should not be extrapolated

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8. Constructing bar charts

A bar chart is drawn when you have a discontinuous variable on the x-axis

and a continuous variable on the y-axis

9. Constructing histograms

A histogram is drawn when there is a continuous range of categories on the

x-axis, and the frequency with which each of these categories occurs is

shown on the y-axis

10. Drawings

a. Diagrams should be drawn with clear, single lines

b. HB pencil and a clean ruler should be used

c. The proportions of the different components of the structures should be

accurate

d. No shading or coloring

e. Using most of thes pace provided

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AL NAHDA NATIONAL SCHOOL FOR GIRLS

BIOLOGY DEPARTMENT

BIOLOGY PRACTICALS Microscopic Slides for AS Biology

1. Dicot leaf (plan diagram).

a) Upper epidermis

b) Lower epidermis

c) Palisade mesophyll cells

d) Spongy mesophyll cells

e) Guard cells

f) Stomatal pores

g) Vascular bundle(xylem, phloem)

h) Drawing epidermis cells, mesophyll cells, spongy cells, guard cells and

stomatal pores.

2. Xerophytic leaf (adaptations).

a) Thick waxy cuticle.

b) Folded leaf.

c) Tiny hairs (trichomes) in the lower epidermis.

d) Sunken stomata in grooves deep in the epidermis

e) Plan diagram

f) Examples: marram grass and nerium

g) Xerophytic adaptation.

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3. Transverse section of a root (plan diagram & labelling)

a) Epidermis

b) Cortex

c) stele

d) Endodermis

e) pericycle

f) xylem

g) Phloem

4. Longitudinal section of a root tip

a) Plan diagram

b) Annotated diagram

c) Root cap

d) Region of cell division

e) Region of cell elongation

f) Identifying the stages of mitosis in a root tip (prophase, metaphase,

anaphase, telophase).

g) Identifying cells in the prophase.

h) Comparison between cells in the region of cell division and cells in the

region of cell elongation

5. Transverse section of a monocot or dicot stem (plan diagram &

labelling).

a) Epidermis

b) Cortex

c) Vascular bundles(xylem, phloem, cambium)

d) Pith

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6. Transverse section of a hollow stem.

a) Plan diagram

b) Epidermis

c) Cortex

d) Vascular bundles

e) Air space (hollow pith)

7. Transverse section of a vascular bundle.

a) Xylem

b) Cambium

c) Phloem

8. Longitudinal sections of xylem and phloem.

a) Xylem

b) Phloem

c) Arrangement of lignin in xylem (spiral, annular, articulate or perforated).

d) Identifying sieve plates in phloem.

e) Identifying companion cells.

f) Preparing a section through the xylem of a rhubarb stem.

9. Transverse section through an artery, vein and capillary.

a) Tunica externa

b) Tunica media

c) Tunica intima (endothelium)

d) Lumen

e) Comparison between an artery and a vein.

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10. Human Blood smear

a) Identifying RBC’s, phagocytes and lymphocytes.

b) Drawing diagrams of RBC’s, phagocytes and lymphocytes.

c) Comparing WBC and RBC.

d) Using a graticule to find the ratio of the diameter of one

cell to the other e.g. phagocyte: RBC.

f) Using a graticule to estimate the diameter of any blood cell.

11. Frog blood smear

a) Identifying RBC’s, phagocytes and lymphocytes.

b) Drawing diagrams of RBC’s, phagocytes and lymphocytes.

c) Using a graticule to estimate the diameter of any blood cell.

12. Comparison between RBC’s of a human and a frog

a) shape

b) size

c) presence of a nucleus

13. Transverse section through a lung

a) Alveoli (squamous epithelial cells, surfactant cells, macrophages)

b) Blood vessels

c) Bronchiole

d) Bronchi

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14. Transverse section through a trachea

a) Plan diagram

b) Outer connective tissue

c) Cartilage

d) Smooth muscle

e) Inner connective tissue

f) Ciliated epithelium

g) Goblet cells

h) Blood capillaries

i) Lumen

j) Drawing cartilage cells, ciliated cells and goblet cells

k) Comparing cartilage cells to ciliated epithelial cells

15. Transverse section through a bronchus

a) Plan diagram

b) Cartilage

c) Smooth muscle

d) Ciliated epithelium

e) Goblet cells

f) Blood capillaries

g) Lumen

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Dicot Leaf

Plan Diagram of a leaf

Spongy mesophyll

cells

Palisade mesophyll

cells

Air Space

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Vascular Bundle

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Xerophytic Leaf

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Marram Grass

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Vascular Bundles

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Transverse section of a monocot or dicot stem

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Plan Diagram of a stem transverse section

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Plan Diagrams of root TS and stem TS

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In the stem vascular bundles are arranged in a cylinder for support. In the root the xylem and phloem are in the center.

Pith

Xylem

Phloem

Xylem, phloem and cambium form vascular

bundle

Endodermis Epidermis

Phloem

Cambium

Cortex

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Root Tip

Region of

cell division

Region of cell

differentiation

Zone of differentiation

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Telophase

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1. Interphase (a) 4. Anaphase (d)

2. Prophase (b) 5. Telophase (e)

3. Metaphase (c) 6. Cytokinesis

Onion root tip undergoing mitosis

3 4

2

1

5

6

d

e

c

a

b

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Cytokinesis in animal cells

(g) Cytokinesis (f) Telophase (e) Anaphase

(a) Interphase (b) Prophase (d) Metaphase (c) Late Prophase

Late Prophase

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Blood Smear

Lymphocyte Phagocyte Platelet Red blood cell (Neutrophil) (Thrombocyte) (Erythrocyte)

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Frog Blood Smear

RBC WBC

Parts of

RBC

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Phagocyte RBC Lymphocyte

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Artery and Vein

Tunica externa

Tunica media

Tunica intima

Lumen

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Tunica

media

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Aorta

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Plan Diagram of a trachea

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Cartilage

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Bronchiole under high power

Smooth Muscle

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Alveolar duct