Students session

Integrated Science : Active Transport, Diffusion, Osmosis, Practical Lesson SHS

TRANSPORT SYSTEM PRACTICAL SESSION

  1. The diagram below illustrates the set-up at the beginning and at the end of an experiment carried out by a science teacher to demonstrate a biological phenomenon to a class.

Previous Lessons 

Study the diagrams carefully and answer the questions that follows.

a)        i)   State the major difference between the set-ups at the beginning and at the end of the experiment.

ii) Explain what accounts for the difference you have stated in (i)

b)        i) What biological phenomenon was being demonstrated?

ii) Give one example of the phenomenon being demonstrated which occurs in

a)  Flowering plants

                   b)    Amoeba

c)             i) state the role which the yam cup plays

ii)     Explain what would be observed if a plastic cup is used in place of the yam cup.

Answers

 i) Difference between the set-up

The water level is higher than the level of the sugar solution at the beginning of the experiment while at the end of the experiment the water level is lower than the level of the sugar solution.

    ii) explanation

Water moved from the beaker into the solution in the yam cup. This caused the level of the solution in the yam cup to rise.

b. i)  The process of Osmosis

ii)   Examples of osmosis in flowering plants

  • Movement of water from the root hairs into the cortex.
  • Absorption of water from the soil by root hairs or through root hairs.

Example of osmosis in amoeba

Movement of (fresh) fresh water into the body of the amoeba.

Role of the yam

c) i. The yam cup served as a semi-permeable membrane.

If a plastic cup is used the levels of the water and sugar solution will remain the same. Plastic is impermeable to water.

2. The Diagram below illustrates a transverse section of part of a herbaceous plant. Study the figure carefully and answer the questions that follows.

i) Identify the part of the plant illustrated.

ii) Name the parts labelled I, II, III, IV, V, VI, VII and VIII

iii) State one function of the parts labelled I, III, IV

iv) Describe an experiment to show the function of the part labelled III

Answers

i) Transverse section of dicotyledonous stem

b.  i)             parts

I  – Epidermis

II – Cortex

III – Phloem

IV – Endodermis

V – Cambium

VI – Medullary rays

VII     – Xylem

VIII – Pith

 

b)    ii) Functions of parts

I – Protects the inner tissues of the stem

III – Transports or conducts manufactured food from the leaves to other parts of the plants.

V – meristematic or divides to form Xylem and Phloem.

c) experiment to show the function of part III

A ring of bark and associated phloem is removed from a tree using a sharp knife or blade. The tree is left for about a week. A swelling is seen above the ring. Contents of the swelling are analysed to be mainly organic food (sugars). This shows that food  move through the Phloem.

  1. In an experiment to determine a physiological phenomenon, a student peeled off strips of the epidermis of the leaf of Rheo discolour. The Strips were then placed in three solutions of different concentrations for about 30 minutes after which the strips were removed and examined under a light microscope. A, B, and C of strips from the three solutions. Study the cells carefully.

 

a) Name the parts labeled I, II, III and IV.

b) What physiological phenomenon did the student demonstrate?

c) Name Four materials the students needed for the demonstration.

d) i) State the three types of solution required for the demonstration.

ii) Match the different state of the cells A, B and C against the solutions you have stated.

e) What do the arrows in B represent?

f) Explain the results that would have been observed if red blood cells had been used for the experiment in place of the epidermal cells of Rheo Discolour

Answers

Parts

I. Cell wall

II. Cytoplasm

III. Vacuole

IV. Nucleus

b)    The student demonstrated plasmolysis or Osmosis

c) Materials needed: Petri dish, slide, cover slip, forceps or a pin, sugar or salt solution, distilled water.

i)         Solution required: Hypotonic solution or distilled water or weaker solution.

Isotonic solution or same concentration as cell sap.

Hypertonic solution or solution stronger than cell sap.

ii) Matching cells against solutions

Cell A – Hypertonic solution

Cell B – Hypotonic solution

Cell C – isotonic Solution

e) Arrows in B imply that the cell has become turgid or pressure is exerted on the cell wall or turgor pressure because water has entered the cell.

f) For Red blood cell

In hypertonic solution

The cell will shrink or crenation will occur.

In hypotonic solution

The cell will burst or haemolyis occurs due to absence of a cell wall and will cause the solution to become red in colour.

In isotonic solutions

The cell will maintain its original size and shape or will give a similar result as obtained for the plant cell.

 

 

Assignment

The figure below represents the beginning of an experiment to demonstrate osmosis in a living osmosis in a living cell using yam tissue.

a) Draw and label a diagram to illustrate what would be observed if the setup is allowed to stand for 24 hours.

b) What does the yam cup represent?

c) Explain the principle involved in the experiment

d) How would you set- up a control of the experiment above?

e) Give one example of the osmotic process in each of the following living things:

i. Flowering Plant

ii. Humans

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