Class 10

LIST OF EXPERIMENTS

Sub- Biology

1. Preparing a temporary mount of a leaf peel to show stomata.

2. Experimentally show that carbon dioxide is given out during respiration.

3. Studying (a) binary fission in Amoeba, and (b) budding in yeast and Hydra with the help of prepared
slides.

4. Identification of the different parts of an embryo of a dicot seed (Pea, gram or red kidney bean).

Experiment No.1

Aim

To prepare a temporary mount of a leaf peel to show stomata.

Theory
Stomata mean ‘mouth’ which are pore found in the epidermis of leaves, stems and all other plant parts
found above the ground. Stomata permit the exchange of gases between the atmosphere and the inside
of the leaf.

Materials Required
Lily leaf, Watch glass, Slide, Cover slip, Safranin solution, Glycerine, Forceps, Dropper, Scissors or Blade,
Petri Dish, Filter Paper, Distilled water, Brush, Compound microscope

Procedure

Step 1: A lily leaf is taken and simply fold in the centre which gets broken into two pieces.
Step 2: One leaf piece is gently pulled and we got a transparent leaf peel.

Step 3: The leaf peel of lower epidermis is taken and cut with scissors or a blade into small pieces. These
pieces transferred with the help of paintbrush into a petri dish containing water. (Do not keep them
without water. They will dry)

Step 4: A piece of leaf peel is selected and transferred into another watch glass containing dilute
solution of safranin (a red stain).
Step 5: With the help of paintbrush specimen is transferred back into first water containing
petridish/watch glass to remove excess of stain.

Step 6: Specimen is transferred to slide with the help of brush.

Step 7: A drop of glycerine is put on the peel and it is covered carefully with a cover slip by using needle
to avoid air bubbles. Excess glycerine is removed with help of a filter paper.
Step 8: The leaf peel is observed under low power of microscope.
Step 9: For inner details, again the leaf peel is observed under high power (45x) of microscope.

Observation

1. A horizontal row of cells is seen.

2. The cells may be irregular or rectangular in shape, depending upon the leaf used for leaf peeling.
3. At certain places stomata are seen.
4. Each stoma is guarded by a pair of bean shaped cells that are guard cells.
5. The central pores/apertures are called stomata.
6. Inner wall of guard cell is thicker than the outer wall.

Precautions
1. The epidermal peel should be taken from a freshly-plucked leaf.
2. Take the epidermal layer from the lower surface of a leaf, as it has more stomata.
3. Always use a clean glass slide.

EXPERIMENT No.2

To show experimentally that carbon dioxide is given out during respiration - Science Practicals

Method -I : There are two methods to do this experiment. We are giving both of them. Students are
advised to perform any one based on the availability of the materials in their lab.

Aim

To show experimentally that carbon dioxide is given out during respiration.

Theory
Respiration is a catabolic process wherein food is oxidized to release energy for various life processes. It
is of two types:
(i) aerobic respiration that takes place in the presence of oxygen

(ii) anaerobic respiration that takes place in the absence of oxygen.

In aerobic respiration the breakdown of food (glucose) leads to the release of carbon dioxide gas, water
and energy in the form of adenosine triphosphate (ATP). Most organisms that we see around us
undergo aerobic respiration. Yeast and certain microorganisms and cells of skeletal muscles in our body
undergo anaerobic respiration.
The overall reaction mechanism of aerobic respiration involves the oxidation of carbohydrate and the
subsequent production of CO2, H2O and energy.

C6H12O6+6O2 → 6CO2 + 6H2O + Energy

Materials Required
Germinating gram seeds, KOH solution, petroleum jelly, a conical flask, (100 mL), a beaker (250 mL), a
single-bore cork, a clean delivery (bent) tube, a small test tube, a piece of thread, and a measuring scale.

Procedure

Step 1: About fourty germinating seeds are taken in a conical flask.

Step 2: The cork to the mouth of the conical flask is fixed and with the help of a thread, the tube is
suspended containing KOH solution.

Step 3: One end of a clean delivery tube is inserted in the conical flask through the cork. The other end
of the delivery tube is dipped in a beaker filled with water as shown. The water level inside the delivery
tube rises at the end dipped in the water due to capillary action which is marked. This is the initial
reading (h1) of water level in the delivery tube.

Step 4: The conical flask is made air-tight by applying a thin smear of petroleum jelly so that the gas
evolved during the process of respiration by the germinating seeds does not leak out.

Step 5: This set-up is kept undisturbed for about forty five minutes in the bright sunlight.
Step 6: The final water level (h2) in the delivery tube is marked and recorded.

Observation
After two hours, the level of water has risen in the delivery tube at the end dipped in the beaker of
water.
Results and Discussion
1. The rise in the level of water indicates that CO2 is produced by germinating seeds during respiration.
2. The germinating seeds respire and produce CO2, which is absorbed by KOH solution which created a
vacuum in the conical flask.
3. The air present in the bent glass tube moves into the conical flask. This pulls the water in the bent
tube further up.

Precautions
1. Ensure that the experimental set-up is air-tight.
2. KOH is corrosive. Handle it carefully.

EXPERIMENT No. 3

To study binary fission in Amoeba and budding in yeast with the help of prepared slides

Aim

To study (a) binary fission in Amoeba, and (b) budding in yeast with the help of prepared slides.

Theory

Binary fission and budding are forms of asexual reproduction in lower organisms, like bacteria,
unicellular protozoans, and a few other animals. In binary fission, the parent cell divides into two
daughter cells by amitosis and each daughter cell grows into an adult. The division of nucleus is called
amitosis because the stages of a typical mitotic division are not observed in these cells. Budding is
commonly seen in yeast and Hydra. Hydra is a tiny freshwater organism which produces young ones
from its body laterally. Yeast is a unicellular organism which produces a chain of cells attached to the
parent cell.
Materials Required
A compound microscope, permanent slides of binary fission in Amoeba and budding in yeas

Procedure
Step 1: The slide is placed under compound microscope.
Step 1: The slide is focused under low power and later high power of compound microscope.
Step 2: The stages in binary fission and budding are observed carefully.

Observations

(a) Binary Fission in Amoeba

(i) In the beginning, the pseudopodia are withdrawn and the body becomes rounded.

(ii) Nucleus divides amitotically followed by the division of cytoplasm.

(iii) A furrow or constriction develops at the point of fission in the main body.

(iv) The furrow becomes narrow and finally two daughter-cells are formed.

(b) Budding in yeast

(i) A small outgrowth or protuberance is seen on the parent cell.
(ii) Nucleus divides and is later, seen in the bud.
(iii) Repeated budding forms a chain of cells.
Results and Discussions
The prepared slides show asexual reproduction in which only one individual is involved in the production
of new individuals.

Precautions
1. Focus the slides properly.
2. Study the slides first under low-power magnification and then under high-power magnification of the
compound microscope.
3. Draw diagrams as seen under the microscope.

EXPERIMENT No.4

To identify the different parts of an embryo of a dicot seed

Aim

To identify the different parts of an embryo of a dicot seed (Pea, gram or red kidney bean).

Theory

A seed is a small embryonic plant enclosed inside a seed coat. During sexual reproduction male gamete
fuses with female gamete and zygote is formed. After some rest period zygote divides, re-divides and
finally develops into an embryo. In the earlier stages of development of embryo there is no difference
between monocots and dicots, but their development differs in later stages. The process of
development of mature embryo from zygote is called embryogeny.

Materials Required
Permanent slides of dicot embryo showing different stages and a compound microscope.

Procedure
Step 1: Observe each permanent slide in sequence from early stages to maturity first under low-power
magnification and then under high-power magnification of a compound microscope.
Step 2: Draw diagrams and identify the different parts.
Step 3: Label the different regions of the embryo.
Observations

1. Zygote divides transversely forming a basal cell towards the micropyle and a terminal cell towards the
chalaza.

2. The basal cell divides by transverse divisions and finally forms 6-10 celled suspensors.

3. The uppermost cell of suspensor swells up to form a vesicular cell while the lowest cell of the
suspensor is called hypophysis. Hypophysis forms part of the radical and root cap.

4. The terminal embryonal cell divides by transverse and vertical divisions and forms 16-celled globular
embryo.

5. The globular embryo later becomes heart-shaped due to its differentiation into cotyledons.

6. The embryo and cotyledons become larger and curved.

Results and Discussions
The prepared permanent slides show successive stages of the development of dicot embryo. The young
dicot embryo is globular but changes to heart-shaped structure at maturity due to differentiation into
cotyledons.