Biology practical-2

Experiment To Prove That Carbon Dioxide Is Given Out During Respiration

One of the basic and fundamental life processes that are carried out by living entities is
respiration. It is a catabolic process wherein complex organic molecules are broken down into
simpler molecules. The process releases energy either in the absence or presence of oxygen,
and hence respiration can be of two kinds:

Aerobic respiration – This kind of respiration takes place in the presence of oxygen, hence it
results in the complete glucose oxidation with the release of energy. It includes three stages –
namely, Krebs cycle, ETS and Glycolysis. All events relating to ETS take place inside
mitochondria while stages connected with glycolysis take place in the cytoplasm.
Anaerobic respiration – In this type of respiration, oxidation of food takes place in an
environment lacking oxygen supply. Less energy is released as a result of incomplete oxidation
of glucose.

Aim
To experimentally demonstrate that carbon dioxide is released during the process of respiration.

Principle/Theory
The process of respiration is biochemically carried out wherein food, glucose to be precise, is
oxidized and energy is released. In this experiment, gram seeds (moistened) are used. The
purpose of using these seeds is that they release carbon dioxide and are respiring actively. The
released carbon dioxide is consumed by the solution of KOH.

Material Required
Soaked gram seeds
U-shaped delivery tube
Conical flask
Blotting paper (moist) /cotton wool
Thread
Water
Beaker
Test tube
Rubber cork with a single hole
Freshly prepared KOH solution (20%)
Vaseline
Procedure
Germinate close to 25 seeds. This can be done by wrapping them in moist blotting paper or
cotton wool for around 3 to 4 days.
Set up the germinated or sprouted seeds in the conical flask. Spray some water into the flask to
dampen the seeds.
With the help of a thread, suspend the conical flask containing the test tube having a freshly
prepared 20% KOH solution.
Use the rubber cork to seal the opening of the conical flask.
One edge of the U-shaped glass delivery tube present in the conical flask should be inserted
through the hole in the rubber cork. The other edge should be placed into a beaker that is
saturated with water.
All attachments of the set-up should be sealed. This can be done using vaseline to create an
air-tight environment.
The initial water level present in the U-shaped delivery tube needs to be marked.
Leave the experimental set-up uninterrupted for 1 to 2 hours. Observe the fluctuations in the
water level in the tube.
Observation
Careful observation after a certain period of time reveals that the water level in the U-shaped
delivery tube has risen in the beaker.

Conclusions
The rise in level water indicates that carbon dioxide is released as a result of germinating gram
seeds during the process of respiration in the conical flask. The carbon dioxide that is released
in the process is absorbed or consumed by the KOH solution that is suspended in the test tube
in the conical flask, creating a vacuum or a void in the flask resulting in the upward water
movement in the tube. Hence, the water level in the tube changes.

Precautions
The seeds that are to be germinated need to be moistened
Air-tight environment for all the connections in the experimental set-up
The KOH solution that is used needs to be freshly prepared
Care needs to be taken to ensure that one end of the delivery tube is placed in the conical flask.
The other edge is submerged in the water of the beaker
The tube that contains the KOH solution needs to be suspended carefully
Viva Questions
Q.1. Why is the energy output of the anaerobic respiration lesser than aerobic respiration?

A.1. The process of anaerobic respiration produces 2 ATP. Aerobic respiration, on the other
hand, produces 38 ATP involving complete oxidation of glucose. In anaerobic respiration,
glucose is partially broken down.

Q.2. List the levels of aerobic respiration.

A.2. The following are the levels in aerobic respiration:

Glycolysis
Krebs cycle
Oxidative phosphorylation and ETS
Q.3. The cells’ energy currency is _________

A.3 Adenosine triphosphate (ATP)

Q.4. What happens when the photosynthesis rate is equal to the respiration rate?

A.4. When both are equal, it enters into a compensation point where there is no gross gas
exchange taking place.

Q.5. Can plants respire and take part in photosynthesis?

A.5 Yes, plants can respire in addition to taking part in photosynthesis during the day time.

Q.6. What is the purpose of keeping the seeds moistened in the experiment?

A.6. Seeds are required to be moist as water is required for growth to germinate. If they are not
moist enough, they may dry up resulting in a dip in the respiration rate.

Q.7. Can boiled seeds be used in place of moistened germinating seeds?

A.7. No, they cannot be used as boiled seeds cannot undergo respiration. The experiment will
show no result.

Q.8. State the significance of using KOH solution in the experiment.

A.8. The solution is known to absorb carbon dioxide that is released during the process of
respiration of germinating seeds, thereby creating a slight vacuum in the flask hence increase in
the water level. The rise in water level indicates the occurrence of the process of respiration.

Q.9. List one circumstance under which there would be no rise in the water level in the
apparatus.

A.9. If the test tube holding the KOH solution is discarded from the experimental setup, the
carbon dioxide produced during the respiration process shall not be consumed hence there
would be no inflation in the water level.

Q.10. In the experiment, what is the purpose of using Vaseline?

A.10. It is used because it is used to seal all the apparatus, hence securing the set-up air-tight.

Q.11. Can you think of an alternate method to depict the release of carbon dioxide during the
respiration process?

A.11. In the same apparatus, water could be replaced by lime water as lime water tends to turn
milky in the presence of carbon dioxide.

Q.12. What are respiratory gases?

A.12. Carbon dioxide and oxygen are involved in the process of respiration, and hence are
known as respiratory gases.

Practical-3

Identifying the Different Parts of a Dicot Seed Embryo

Male and female gametes fuse to form the zygote during sexual reproduction. The zygote
further undergoes division to evolve into an embryo. Monocots and dicots do not differ in the
initial stages of development but they differ in the later stages of development.

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

Principle/Theory
The process of fertilization in plants leads to the formation of fruits which forms the ripened
ovary. The seed can be one or many which form the mature ovule.

What does a seed consist of?

A seed consists of the following parts:

Hilum – It is a scar that is located on the seed coat, associated with the stalk of the plant
Seed coat – Forms the exterior covering of the plant, supplying with nourishment and protection
to the seed inside
Endosperm – It is the tissue containing nutrients for the growth of the embryo
Embryo – Several divisions of the zygote gives rise to this structure.
What does the embryo consist of?
It consists of the following parts:

Radicle
Plumule
Cotyledons
How are seeds classified?
On the basis of cotyledons in the seed, angiosperms can be classified into the following:

Monocots
Dicots
What is germination?
Germination is the process wherein the micropyle present in one part of the hilum takes up
water. which under favorable conditions, such as suitable light, temperature, air, etc, it uses up
for the seedlings to develop into tiny, immature embryonic plants from the seed coats.

Germination involves the following steps:

Seeds swell, plumules develop into shoots
From the radicle of the seeds, the roots arise
Formation of cotyledons(one in monocots and two in dicots)
Material Required
Seeds of red kidney bean/gram
Forceps
Magnifying glass
Cloth
Petri dish
Water
Procedure
Soak a few seeds overnight
Next morning, drain the excess water out
Now wrap the seeds in a clean and a moist cloth for a day, allow it to dry
Next, carefully peel the seed coat
With the help of forceps, dissect the seed so as to get two equal halves
Examine with the help of a magnifying glass. Carefully identify and locate different parts of the
seed
Sketch out the interior of the seed you examined labeling all the parts as shown in the diagram.
Diagram
Dicot Seed

Observation
The bean seed resembles the shape of a kidney. It has a convex and a concave side
A scar known as the hilum is observed on the slightly darker side of the concave side
A tiny pore known as the micropyle is located just adjacent to the hilum
The seed is enclosed by a seed coat
The embryo possesses two distinct and large cotyledons that resemble the shape of a kidney
and are white in color
Lateral attachment of the cotyledons to the curved embryonal axis is observed
Radicle is examined. It is the rod-shaped and lightly protrusive lower end of the embryonal axis
that is found placed towards the micropylar end.
The upper end of the embryonal axis exhibits the plumule
Hypocotyl is observed which is a section of the embryo axis found in between the radicle and
adjunct of cotyledon leaves
The epicotyl is also observed which is the section of the embryo axis between the adjunct of
cotyledon leaves and plumule
Conclusion
Three principle parts of the embryo of dicot seeds are observed, they are:

Cotyledons
Plumule
Radicle
Precautions
Care needs to be taken while dissecting the seed as it may damage the seed
The cloth that is used to wrap the seeds needs to be moist
Viva Questions
Q.1. How is a soaked seed different from a dry seed?

A.1. In comparison with a soaked seed, a dry seed has a wrinkled and a hard seed coat. The
soaked seed has a softer seed coat that can be peeled easily

Q.2. In this experiment, why are seeds soaked overnight?

A.2. Seeds are soaked in order to assist the cotyledons for water absorption so as the embryo
turns active

Q.3. What is the purpose of covering the seeds in the moist cloth?

A.3. It is for the growth of the baby plant furthermore.

Q.4. What does the cotyledon hold?

A.4. It provides nourishment for the growing plant.

Q.5. What is the significance of the seed coat?

A.5. During the dormant period, the seed coat shields the embryo and the cotyledons

Q.6. What does the radicle part of the embryo turn in the future?

A.6. The radicle goes on to develop into the root system

Q.7. List some of the conditions that are required for the seed to develop into a complete plant.

A.7. Following are the conditions required:

Oxygen
Water
Suitable temperatures

Practical -4

Studying Binary Fission In Amoeba And Budding With The Help Of Prepared Slides
One of the basic characteristics exhibited by living entities is the reproduction. It is a process in
which organisms produce more of its kind by passing genetic information. The process can
either involve two parents or a single organism can reproduce individually, hence there as two
types of reproduction, asexual reproduction, and sexual reproduction.

Asexual reproduction is the process wherein a new offspring is produced without gamete
formation. In sexual reproduction, both female and male gametes are involved. Asexual
reproduction is commonly observed in lower animals and lower plants. New organisms are
produced rapidly and are genetically identical to their parents.

Asexual reproduction can be of different types, namely:

Budding
Binary fission
Multiple fission
Fragmentation
Sporulation
Vegetative propagation
Aim
To study about (a) Binary Fission in amoeba and (b) Budding in yeast with the help of prepared
slides

Principle/Theory
Budding and binary fission are types of asexual reproduction observed in lower organisms such
as bacteria, unicellular protozoans and some other entities.

What is binary fission?

In this type of reproduction, the parent cell divides or is split into two daughter cells through
mitosis wherein each daughter cell develops into an adult. Amitosis is the division of the
nucleus.

Define budding?
It is a kind of asexual reproduction wherein a new organism develops from a bud or an
outgrowth due to the process of cell division at a particular site.

Can you give an example of an organism that carries out budding?

A freshwater entity such as hydra.

Material Required
Compound microscope
Permanent slides of budding in yeast and binary fission in amoeba
Procedure
Place the slide under a compound microscope
Focus the slide, first under low power and later under high power of the compound microscope
Various stages of budding and binary fission can be carefully examined
Diagram
Binary fission in amoeba

Budding in yeast

Observation
(a) Binary fission in Amoeba

Initially, the pseudopodia are retrieved. The body of amoeba is coiled and becomes round
Amitosis is observed, the division of the nucleus takes places which are followed by splitting of
cytoplasm
At the point of fission in the body of the amoeba, a constriction starts to develop.
The constriction or furrow turns deeper resulting in the formation of two daughter cells
(b) Budding in yeast

Protuberance or a tiny outgrowth is observed on the parent cell

Division of the nucleus is observed which is later seen in the bud
Repetitive budding leads to the formation of a chain of cells
Conclusions
The prepared slides display asexual reproduction. One individual is involved to produce a new
offspring of its own kind.

Precautions
Slides need to be aligned and focused accurately
Sketch out your observation that is observed under a microscope
The slides first need to be examined under a low-power magnification of the compound
microscope and then under high-power magnification.
Viva Questions
Q.1. Name the cell division type that is observed in binary fission.

A.1. Amitosis

Q.2. In binary fission, mention the number of daughter cells that are formed?

A.2. Every binary fission results in the production of two daughter cells

Q.3. Why are budding and binary fission types of asexual reproduction?

A.3. In both of the processes, there is involvement of one parent only. Female and male
gametes do not fuse to form the zygote.

Q.4. Why are budding and binary fission faster processes in comparison to sexual
reproduction?
A.4. Yes, they are faster compared to sexual reproduction as there is no formation of the
zygote, fertilization and the various stages of embryonic development.

Q.5. Which division occurs first in binary fission? The division of cytoplasm or nucleus?

A.5. First, the division of the nucleus takes place which is followed by cytoplasmic division.

Q.6. Which organisms have better chances at survival? The ones produced as a result of sexual
or asexual?

A.6. Sexual reproduction produces organisms that have a better chance of survival.

Q.7. Where can we look for samples to prepare a slide of an amoeba?

A.7 Lakes, freshwater ponds, etc.

Q.8. What is the difference between the reproduction of yeast and hydra though reproduce
through budding?

A.8. Buds that are formed in unicellular organisms such as yeasts may or may not detach from
the parent body but in multicellular organisms such as hydra, buds detach from the parent body
that appears as branches, thereby living as independent individuals.