BIOLOGY DEPARTMENT PRACTICAL SEMINAR 2023

QUESTION 1. PHYSIOLOGY

Option 1.
You are provided with specimen A and hydrogen peroxide solution
Using a cork borer obtain 4 cylinders each measuring 3 cm long.
Label four test tubes as 1,2,3 and 4 and fill each test tube with contents as shown in table 1
below:
Test tube 1 2 3 4
3
Volume of H2O2 added (cm )
8 6 4 0
3
Volume of distilled water added (cm )

1) Using distilled water, top up the volume of solution in each test tube to a uniform volume
of 8 cm3. Record the volume of distilled water used in each case in the table 1 above.
(04 marks)
2) Place one cylinder from specimen A into test tube 1 and start a stop clock and after two
minutes, measure the height of the froth formed. Record it in table 2 below.
3) Repeat procedure 2) for the test tubes 2, 3 and 4. (04 marks)

Test tube 1 2 3 4
Height of froth
(mm)

a) Plot a graph of variation of height of froth with volume of H2O2. (06 marks)
b) Explain the variation of height of froth with volume of H2O2 added. (04 marks)
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c) From your results in 3), suggest what is being investigated. (01mark)

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d) Suggest the identity of the active substance in specimen A. (01mark)

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e) Explain why the cylinders were made of the same initial length. (01mark)
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Option 2.
You are provided with solution A and hydrogen peroxide solution.
Using a cork borer, obtain 4 cylinders each measuring 3 cm long.
Label 4 test tubes as 1, 2, 3 and 4.
To each test tube add 4cm3 of hydrogen peroxide solution.
Treat the cylinders obtained as follows:
To test tube 1, add one whole cylinder of A.
The second cylinder, cut into 3 equal pieces.
The third cylinder, cut into 8 equal pieces. The fourth cylinder, cut into 8 equal
pieces and the pieces boiled for 5 minutes.

a) Carry out the tests in the table below and record the height of the froth after 3 minutes.
(04 marks)

Test tube Treatment Height of froth (mm)

1 Add the whole cylinder
2 Add the 3 pieces of the second cylinder.
3 Add the 8 pieces of the third cylinder
4 Add the 8 boiled pieces of the fourth
cylinder.

b) Explain the observations in test tubes 1, 2, 3 and 4. (08 marks) `

(i) Test tube 1

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………………………………………………………………………………………………………….

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(ii) Test tube 2

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(iii) Test tube 3

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(iv) Test tube

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c) What factor is being investigated in the experiment. (01 mark)

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d) Identify the active substance in specimen A. (01 mark)

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Option 3.
You are provided with specimen A and hydrogen peroxide solution. Using a cork borer,
obtain four cylinders from specimen A and trim to a uniform length of 3 cm.
Treat the cylinders as follows:
Leave one cylinder intact.
Cut the second cylinder into three equal pieces.
Cut the third cylinder into smaller pieces and crush to a paste using a mortar and pestle.
Cut the fourth cylinder into smaller pieces and boil for 5 minutes. Label four test tubes as 1,
2, 3 and 4. Put 3 cm3 of hydrogen peroxide into each of the test tubes.

a) Then carry out the following tests (12 marks)

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 Test Observations Deductions

i) To test tube 1, put the

intact cylinder.

ii) To test tube 2, put the

pieces of the second
cylinder.

iii) To test tube 3, put the

pieces from the third
cylinder.

iv) To test tube 4, put the

pieces from the fourth
cylinder.

b) State two factors being investigated in the experiment. (01 mark)

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c) i) Compare the rate of reaction in test tubes 1 and 2. (02 marks)

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ii) Give an explanation for your answer in i) above. (02 marks)

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d) Explain the observation made in test tube 4. (02 marks)

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e) Identify the active substance in specimen A. (01 mark)

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…………………………………………………………………………………………………

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f) What is the importance of this reaction in the tissues of plants? (01 mark)

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Option 4:
You have been provided with specimen A, hydrogen peroxide solution and solution B.
Label four test tube as 1,2 3 and 4;
a) To each of the test tubes add hydrogen peroxide shown in table and top up with solution B
to make a total of 7 cm3 solution (02 marks)

Test tube 1 2 3 4
Vol of H2O2/cm3 2 3 4 5
Vol of B/cm3

b) Now peel specimen A and use a cork borer to obtain four cylinders and trim them to 4 cm
length, place each strip in the respective solutions in test tubes 1 to 4 for 5 min and record
the height of froth obtained using a ruler (04 marks)

Test tube 1 2 3 4
Height of froth/cm

c) Plot a graph of volume of B used against the height of froth obtained on the graph paper
provided. (06 marks)

d) Explain the trend of the graph above (06 marks)

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e) What was the above experiment testing for; (02 marks)

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PART 2. ANIMALS (Specimen K (Cockroach), Specimen L (Blowfly))

(a). Classification of the specimens.

Specimen Specimen K (Cockroach) Specimen L (Blowfly)

1. Kingdom Animalia
Reasons:
• Have well developed sense organs for
sensitivity
• Have well developed mouth parts for
heterotrophic nutrition.
• Have legs for locomotion

2. Phylum Arthropoda
Reasons
• Have exoskeleton
• Have jointed legs
• Segmented body

3. Class Insecta
Reasons
• Have 3 main body divisions
• 3 pairs of legs
• 3 thoracic segments

Habitat of the specimens

Specimen Habitat

K (cockroach) Cracks / crevices in walls/buildings

Reason: Dorsal ventrally flattened body
L (Blowfly) Decomposing or rotting rubbish

Diet of the specimens

Specimen Diet

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 K (Cockroach) Solid plant material
Reason for diet: Serrated mandibles for cutting food
L (Blowfly) Fluid materials
Reason for diet: Has proboscis that is expanded at the tip to
increase surface area for sucking fluids

ii) Describe the structural features of specimen K (cockroach) and specimen L (Blowfly).

(a) Cockroach

Observable features on; Description

1. Head of specimen K (cockroach) - Has a pair; of long; segmented antennae tapering

towards the end away from the head;
- Has a pair of compound eyes;
- A pair; of mandibles with serrated edges;
- A pair of maxillae;

2. Thorax of specimen K - Has 3 segments;

(cockroach) - Each segment has a pair of legs/ has 3 pairs of
legs;
Has 2 pairs of wings;

3. Abdomen of specimen K - Has many segments;

(Cockroach) - Has a pair; of hairy; anal cerci which taper
towards the tip;

(b) Blowfly

Observable features on; Description

4. Head of specimen L (Blowfly) 1. Eyes

• Three small simple eyes
• Oval shaped • A pair of large compound eyes
• Hairy • The compound eyes are oval shaped
• The eyes are dorso-laterally located on the head
2. Antennae
• Has a pair of antennae that are short, segmented
with hair like bristles
3. Mouth parts
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 • Proboscis is expanded at the tip/funnel shaped A
pair of maxillary pulps which are hairy and short
5. Thorax of specimen L
(Blowfly) i) Wings
• Made up of three • Has a pair of wings that are network veined,
segments short and membranous ii) Legs
• Hairy • Has six legs that are jointed;
• Has strips on the • The legs are hairy with glandular pads between
dorsal side two claws;
• Has two short • Have curved claws;
halteres attached on • The hind limbs are long;
the third thoracic
segment

6. Abdomen of specimen L Is segmented; hairy; tapering towards the posterior

(Blowfly) end;

Adaptations of the specimens to their habitat/ mode of life

Qn. Describe the adaptations of the specimens K and L to their different habitats/modes of life
Specimens Adaptations

K - Has 2 long antennae for increased sensitivity

- Has 2 large compounds to provide a large field of view for increased
sensitivity
- Has pointed spines of the legs for defense against enemies
- Segmented body for increased flexibility during locomotion
- Dorsal laterally body shape to easily hide in crevices and cracks
- Dull colored body for camouflage
- Serrated mandibles for easy cutting of food

L - Hairy body for carrying germs to other areas

- Has 2 wings for swift movement leading to easy escape from enemies
- Has 2 large compounds to provide a large field of view for increased
sensitivity
- Has proboscis that is expanded at the tip to increase surface area for
sucking fluids
- Has hairy antennae for increased sensitivity
- Has a pair of halters for balance during flight

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Qn. Observe the head/ thorax/ abdomen of the specimens. Compare the observable structures Hint:
Give both the similarities and differences (Refer to the tables above)

Some Drawings

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Revision Questions (refer to notes above for answers)
You are provided with specimen K (Cockroach) and L (Fly).

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(a). Observe the specimens carefully with a hand lens, using observable characteristics, state
the phylum and class to which the specimens below and give reason(s) in each case.
(06marks)
(i) Phylum:
Reason(s)

(ii) Class: Reason(s):

(b) State how specimen L adapted as vector. (04 marks)

(c) Using a hand lens, State the differences between specimen K and L. basing on the
observable features on the, (04marks)
i) head
ii) thorax

(d) Place specimen L on its dorsal side, cut off the wings with a razor blade. Using a hand
lens, draw and label the dorsal view of its head and thorax. (07
marks)

(e) Carefully cut the hind limb of specimen K from the point of attachment to the body.
Draw and label. (07 marks)

(f) How are the specimens adapted for survival in their habitats.
i) Specimen L
ii) Specimen K

(g) Cut off the outer wings and inner wings of specimen K. State the differences between the
hind (inner) and fore(outer) wings. (04marks) PART
3. PLANTS (X (Black jack), Y (Bean pod), Z (Orange))

Qn. (a). Identify, with reasons the specimens X, Y and Z

- Fruits

Reason. Have 2 scars

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 (b) Identify each of the specimens giving a reason in each case.

Specimen Identity

X Achene
Reason:
- Dry pericarp which cannot split
Y Legume
Reason:
- Dry pericarp with many seeds
- Presence of 2 sutures
Z Before cutting After cutting

Succulent fruit Reason: Berry

- Has fleshy Reason
pericarp - Has many seeds

Observable features of the specimens

Qn. (a) Using a hand lens, observe specimen X and Y. Describe the observable external
features on the specimens

Specimen Observable features

X Cylindrical; elongated; non hairy; fruit with 4; short
hooks; at one end

Y - Many seeds;
- non-hairy; dry; pericarp
- 2 sutures/lines of weakness;
- short fruit stalk;

Trial question

State three structural differences between Y and Z

(b)(i) Open specimen Y longitudinally along one suture to expose the internal structure.
Describe the structure

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Has many seeds; arranged in one locule; in a row; with each seed attached to the placenta
by a short funicle;

(ii). Using a knife, cut specimen Z transversely and describe the internal structure.

- Has a fleshy pericarp;

- The epicarp is thin;
- The mesocarp is thin, spongy;
- The endocarp is thick; has numerous hairs;
- The endocarp is divided into locules/chambers;
- Each locule has one seed; projecting outwards; attached to placenta by a short
funicle;

Placentation of the specimens

Qn. Cut specimen Y longitudinally and specimen Z transversely. Observe carefully and
describe the arrangement of the seeds in each specimen

Specimen Description of arrangement of seeds/

placentation
Y Few seeds arranged regularly in one locule in a row along the
placenta located near the edge of the pericarp

Z Numerous small seeds projecting outwards in chambers from a single

central placenta

Qn. State the type of placentation of each of the specimens X and Y. Give a reason in each
case

Specimen Type of placentation Reason

Y Marginal placentation Seeds situated along the margin of the pericarp

Z Axile placentation Seeds arranged in chambers originating radially
from a single central placenta.

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You are provided with specimens X (Bidens Pilosa), Y (Bean pod) and Z (Orange).
a) i) Identify the plant structures;
Fruits;
Reasons:
Have two scars
Have a pericarp

ii) Identify each specimen giving one reason; Specimen

X:
Identity: Achene Reason: has one seed surrounded by a soft
fibrous pericarp.

OR
Dry indehiscent Reason(s):
Has a dry pericarp.
Has no lines of weakness/sutures.

Specimen Y:
Identity: Legume Reason: Has two
longitudinal sutures.

OR
Dry dehiscent fruit
Reason(s)
Has a dry pericarp
Has sutures

Specimen Z:
Identity: Berry

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Reason: Has fleshy pericarp.
Has many seeds.

b) Differences between any two specimens.

Cut specimen Z transversely and open Y longitudinally.
(i)
X (Bidens Pilosa) Y (Bean pod)

(ii)
X (Bidens Pilosa) Z (Orange)

(iii)
Y (Bean pod) Z (Orange)

c) Describe the arrangement of seeds in:

(i) Specimen Y:
Seeds are arranged in line, attached to the placenta located at the margin of the fruit wall.

(ii) Specimen Z: Seeds are radially arranged and attached to a

central placenta.

e) Drawings of specimens X, Y and Z

(i) Drawing of specimen X

(ii) Drawing of longitudinal section of specimen Y.
(iii)Drawing of transverse section of specimen Z (iv)
Drawing of longitudinal section of specimen Z

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