IX Bio Record writing

1. EXPERIMENT 5
on of stainedtemporary1mount onion peel, and to record observations anddraw their labelleddiagrams.
( 4 )O B J E C T I V E
A I H :
P r e p a r a t i o
CONCEPTSs
A
cellis the structural and
functiona unit ofall living things.
2 Unicellular aEanisms (c.g. Amoeba) consist of a singic cell andnulticellular organisms consist of minions
o
cells(e.gorton, trees, human).
3. Acell can be
aenned as a mass of
protoplsm having a distinct nucleus and limited by plasmamembrane
4, The living parts ofa cell are nucleus, endoplasmic reticulum, mitochondria, Golgi body, ribosome,
ysosome
plastid, etc.
The non-living parts offa cell are cell wall, vacuoles, granules, etc.
6, Plant cells are
ditferentiated from animal clls on account of the presenicc of (i) cell wall, (ii) plastids,
(i) dictyosomes and (iv) large vacuoles.
7. In a mature plant cel, a large'permanent central vacuole occupying up to 90 per cent of the volume oT tne cell is
present.
Cell wall is a rigid, non-living boundary wall made up ofcellblose.
REQUIREMENTS
A medium sized onion, clean glass slide, cover slip, watch glass or petridish, a pair of scissors, a knife, needle,
brush, distilled water, giycerine, dropper, blotting paper, safranin solution, a high powered microscope.
PROCEDURE
1. Take a medium sized onion and cut it laterally into number of pieces [Fig. 1(a)] with the help of a knife.
2. Remove a scale leaf from one of the pieces.
3. Break the scale leaf gently from the middle and peel a small portion from the delicate epidermis (covering) that
covers the convex (outer) surface ofthescale leaf [Fig. 1(6)].
4. Cut 2-4 small pieces of the delicate epidermal peel with the help of a pair of scissors and place it in a watch glass
containing distilled water [Fig. 1(©)).
5. Put 2-3 drops ofsafranin solution in the watch glass. Wait for 2-3 minutes.
6. Transfer the peel to a watch glass containing water. This will remove the extra stain sticking to the peel.
1. Take aclean glass slide and pour in its middle 1-2 drops ofdilute glycerine [Fig. 24a)].
8. Transfer the stainedpeelon the glycerine placed on the slide with the help ofa brush. The peel may tend to curl
up. With the help ofneedle and brush flatten the peel.
9.Take adry and cleancover slipand hold it rom its edges with the left hand. Place the cover slip on the slide in
sucha way that one ofits edges comes in contact with the mount1ng material, ie.. glycerine. Lower the cover slip
slowly with the help ofneedle on the peel, such that no air bubble enters in it [Fig. 2(b) and 2(©)].
10 Remove the extra material surrounding the slide with the help of bloting paper.
11. Examine the slide at first under low power then under high power ofmicroscope.
(a) (b) (c)
Fig. 1: Removing the epidermis ipegiyfrom onion
41

2. Needle
Dropper
-
Cover slip
Plain glass slide
Glycerine
(a)
(c)
(b)
Fig. 2: Stages to show the niounting of an onion peel on a slide
OBSERVATIONS
CellIwall
1. A distinct cell wall is seen . **...
surrounding each cell.
2. A large vacuole is clearly
Cell membra
I : 1 :
* * w * *
seen in each cell.
**
3. So the celis underobserva
tion are the plant cells. It is
because, cell wall and large
vacuoles are found only in
plant cells.
1 1
4 **"
..... ** w.I*********
4 ******
L ' * * ' ' I 1
Nucleus
*****I2. ::1
**
ww.
******* *
1 * * * *
ANFERENCE -Cytoplasm
1. There are large number of
cells lying side by side with
distinct cell walls.
Vacuole
***** a
v*************
* * * * "
*******"
2. Adeeply stained nucleus is
present in the periphery of
cytoplasm.
*****.* 0JC:7
Fig.3: Cell structureof onion peel
3. Alightly stainedcytoplasm
1s present in the periphery of cell wall.
4. A prominent vacuole is the centre of each cell, surrounded by cytoplasm.
PRECAUTIONS
. Do not hold the peel with fingers. Use forceps, instead.
2. Use brush for transferring the material.
3. Staining should neither be too light nor too dark. Extra stain should be washed off in water.
4. Preparation of the glycerine mount should be done neatly.
5. The slide should be held by its edges.
6. Extra glycerine should be soaked with blotting paper.
7. Extra care should be taken to avoid entry of air bubbles.
(B) OBJECTIVE
ATM Preparation ofstained temporary mount ofhuman cheek cells, and to record observations and draw their labeld
diagrams.
CONCEPTSs
1. Animal cells, unlikeplantcells do not possess cell wall. Instead a thin semipermeable membrane (cell membrane)
surrounds the cytoplasm of the cell.
2. Aniunal cells, unlike plant cells, have a denser cytoplasm, which is more
granular and occupies most of the spate
ofthe cell.
3. Unlike plant cells, animal cells do not have vacuoles. However, ifsome animal cells have vacuoles, they are ver
small and temporary.
42

3. 4. All animalcells have
centrosome with two centrioles.
5. All animal cells have prominent Golgi bodies present near the nucleus.
6. Compared to plant cells, the animalcells have more lysosomes in number.
7. Unlike plant cells, the animal cellsdo yot have plastids.
8. The number of
mitochondria present in aqimal cell depends upon its activity.
VREQU IREMENTS
Watch glass, clean glass slide, cover slip. needle, brush, cotton bud or toothpick, methylene blue solution, blotting
paper, high powered microscope.
ROCED RE
1. Take a clean glass slide and in the middle of it pour a drop of distilled water with the help of a dropper.
2. Take a clean cotton bud or a toothpick and use it to serap the inner wall of your cheek gently, so as to scrap the
epithelial tissue.
3. Mix the scrap on the cotton bud or toothpick in the drop of water placed on the glass slide.
Pour a drop of methylene blue solution on the mixture on the slide and mix it thoroughly. This will stain the epithelial
tissue. Spread the contents evenly on the slide.
5. After 2-3 minutes remove the excess water and methylene blue solution, evenly on the slide by using corner of a
blotting paper. Do it carefully, otherwise the material will also be removed.
6. Pour a drop of glycerine on the contents ofslide and spread it.
7. Take a dry and clean cover slip and hold it from its edges with left
hand. Place the cover slip on the slide in such a way that one of its
edges comes in contact with the mounting material, i.e., glycerine.
Lower the cover slip slowly with the help of needle so that no air
bubble enters it.
. : i .
*****
****
***
*
****
. * * .
:****.i
8. Remove the extra glycerine surrounding the slide with the help of a
blotting paper.
Epithelial cells
9. Examine the slide first under low power and then under high power
of microscope.
OBSERVATIONS
1. Large number of flat cells with iregular boundaries are seen.
2. Each cell has athin cell membrane (or plasma membrane).
- Nucleus
Cell
membrane
3.Adistinct deeply stained nucleus is seen in each cell.
Granular
4. Space between the plasma membrane and the nucleus is filled with
granular material called cytoplasm.
cytoplasm
individual epithelial cells
5. There are no vacuoles in the cells. Fig. 1: Cheek cells ofhuman be:ngs
No cell wallis visible.
KFERENCE
The examination of material on the slide suggests that these are animal cells, because cell wall and prominent vacuoles
are not seen in the cells.
PRECAUTIONS
1. Rinse your mouth with clean water before scrapping. Scrapping ofthe cheek should be done very carefully so that
no damage is done.
2. The cotton bud or toothpick should be washed thoroughly so that it does not infect the cheek with any foreign
body. Incaseof using a toothpick, serap with blunt or thick end of the toothpick.
3. The slide should be neatiy mounted with no air bubble and in just the right amount of glycerine used.
3

4. EXPERIMENT 6
OBJECTIVVE
ldentificaion of parenchyma, collenchyma and sclerenchyma tissues in plants, striped, smooth and cardiac
muscle fibres and nerve cells in animals from prepared slides. Drawing of their labelled diagrams.
CONCEPTS
1. Tissue: A group ofcells similar in stricture, having a common origin and performing similar functions is
called a tissue.
2. Tissue system: Several tissues, which may be structurally similar or different, may collectively perform the
same function. This grouping of tissues gives rise to tissuc system.
3. Meristematic tissues: The plant tissues consisting of undifferentiated,actively dividing cells are meristematic
tissues.
4. Permanent tissues : The marure plant cells incapable of division are known as permanent tissues.
5. Parenchyma, collenchyma and sclerencliyma are simple permanent tissue whereas xylem and phloem are
complex permanent tissues.
6. Parenchyma is a primitive, simple tissue widely distributed throughout the plant body.
7. Collenchyma, being a strong and flexible tissue, is a strengthening tissue of growing organ.
8. Sclerenchyma is also a mechanical tissue. It consists of fibres and sclereids.
9. Four basic types of animal tissues are epithelial, connective, muscular and nervous tissues.
10. Muscular tissues are ofthree typesstriated, unstriated and cardiac muscles.
11. Striated, skeletal and voluntary muscles are attached to the bones and help in body movement.
12. Striated muscles occur in the limbs, body wal, face and neck.
13. Nervous tissue is a very specialised tissue for receiving stimulations and sensations and transmitting
messages.
14. Nerve cell or neuron is one of the most important elements of the nervous tissues.
REQUIREMENTS
Prepared slides of different types of plant tissues and animal tissues and compound microscope.
PROCEDURE
Observe the slides one after the other under low power of microscope. Draw sketches and label them. Observe
the differences among them.
OBSERVATIONS
PLANTTISSUES
(a) Parenchyma
1. The slide shows numerous cells.
2. The parenchymatous cells are isodiametric. From isodiametric, it implies that almost all cells are equal in length
and width.
3. Intercellular spaces are present at the comers ofthe cells.
4. Each cell possesses a large central vacuole.
5. Each cell has thin cell wal.
47

5. INFERENCE
. Parenchymatous cells make simple tissues.
h e s e cells are present in the soft areas ofplants, such as stems, leaves, roots, flowers and fruits.
. Ihe important function ofthese cells is photosynthesis, storage and to help in fHoatation.
Parenchymatous cells are living cells and are precursor ofallother cells.
Vacuole
Nucleus
- Intercellular-
space
(a)
Transverse section
(b)
Longitudinal section
Fig.1:Parenchyma
b) Collenchyma
. These are isodiametric or elongated living cells.
2. The intercellular spaces are generally absent.
3. Each cell has a large central vacuole, peripheral cytoplas1n and a prominent nucleus
4. The cells are iregularly thickened at the comers.
5. These cpHs are present below the epidermis in petiole, leaves and herbacious dicot stems.
INFERENCE
Since collenchyma cells are flexible in nature, they prevent tearing of leaves and stems. They also providemec
strength, store food and photosynthesise.
Vacuole
Thickening
at the corners
Nucleus
(a)
Transverse section
(b)
Longitudinal secton
Fig.2:Collenchyma
8

6. (c) Sclerenchyma
1.
Sclerenchymatougcells are dead cells.
2. They have evenly thickened hard cell wals.
3. They have very little or no
protoplasm.
4. They have hard lignified secondary walls.
5. They can be divided intotwo types: () Sclerenchyma fibres (i) Sclereids
Lumen
Lumen
Pit
canal
Lignified
Thickened
cell wall
wall
Pit
(a)
Transverse Section (b)
Longitudinal Section
(c)
Sclereids (Stone Cells)
Fig.3: Sclerenchyma
() Sclerenchyma fibres
) They are highly elongated (I cm to 90 cm), narrow and spindle shaped, with pointed end walls
i) Adjacent fibres have simple oblique pits.
(i) The only function they perform is to provide mechanical strength. Otherwise these fibres are empty and dead.
() Sclereids
(i) They are highly thickened, dead sclerenchymatous cells which have very narrow cavities.
i) They may occur singly or in groups and are isodiametric innature
(ii) They are sometimes called grid or stone cells. They provide stiffness to the plant, wherever they occur. They
are found in pears, raw guava, shells of nuts and drupes (cherries and plums).
INFERENCE
The sclerenchymatous cells, being thick walled and having deposition oflignin give mechanical strength to the plants.
ANIMAL TISSUES
(a) Unstriated/Unstriped muscle fibres
Muscle
fibres
1. These are smooth and spindle shaped cells. These are
not enclosed by the sarcolemma.
Myofibrils
2. These are involuntary muscles i.e. they do not work
under the control of our will. So they work continuously
without getting tired.
3. The cells are uninucleate i.e. each cell has a single
nucleus. The nucleus is surounded by cytoplasm called
sarcoplasm.
4. Myofibrils are found in sarcoplasm.
Nucleus
Sarcoplasm
INFERENCE Fig 4:1rsttiatet ruscies
They are involuntary muscles found in the alimentary canal, blood vessels, urinary bladder, etc.
49

7. Sarcolemma
(b) Striated muscles/striped muscle fibres
Striation
The slide shows large number oflong cylindrical fibres that
are enclosed in a membrane called sarcolemma. Myofibril
Nucleus
2. The fibres are non-tapering and wide.
.The fibres are coenocytic, i.e., they are multinucleated. Ihe
nuclei lie towards the periphery of thefibres
4. The cytoplasm of each fibre is called sarcoplasm. It is
divided into large number of myofibrils.
5. Each myofibril bears alternate light band (1-band) and
dark band (A-band). Thus, the cells show longitudinal and
Lightband
( band)
Dark band
(A band)
(a)
Muscle fibres
under low power Muscle fib
under high po
Fig.5:Striatedmuscles /
transverse striations.
6. The cells are surrounded and held by connective tissus.
INFERENCE
The observations of slide shows the presence of striated muscles. It is because they are
long cylindiela
having myofibrils which make striations tightly packed.
The muscles give contractibility and strength to the voluntary muscles. These muscles (voluntary) work acar
our will. They get tired when overworked.
Intercalated
disk
(c) Cardiac Muscles
1. Cardiac muscles are
composedof branching and anastomosing Cröss-strationis .
(Connected and communicated betweeh) network of fibres.
2. They have centrally located one or two nuclei and transverse
striations with light and dark bands. So they show characters
of both striated and unstriated muscles.
3. Special electrical junctions called intercalated discs are
present at intervals in the fibres. Each fibre is surrounded
by sarcolemma.
Nucleus
4. They are richly supplied with blood and show rhythmic
contraction.
5. They do not work under the control of one's will.
INFERENCE
They are
involuntary muscles found only in the heart of our body. They keep on
performing throughout lie.
du
are found in the walls ofthebeart,they create an eficiant pumping action of the heart.
Fig.6: Cardiacmus
Sint'
(d) Nerve Cells
Nucleus
1. The nerve cell or a neuron has a
large body called cyton.
2. The cyton has a
prominent nucleus.
3. Cyton has cytoplasmic projections called dendrites.
4. One of the dendrites is long and is called axon.
5. A group of axons held together by a
conncctive tissue is
called a nerve.
Dendrites
Cell
body
Axon
Neurolemma
6. The axons are covered with
medullary sheath or
myelin Myelin
sheath
sheath.
7. At the nodes of Ranvier, the myelin sheath is absent. Node of
Ranvier
Unipalar
Neuron
8. A membrane called neurolemma surrounds the myelin
sheath.
9. The nerve endings are attached to muscles. Nerve'endings
Fig.: Nervecol
50

8. INFERENCE
From the above observation it is clear that a nerve cell has a largecyton, with a
prominent nucleussuch that
cyton has
cytoplasmic projections calleddendrites. One of the dentrites becomes long and is calledaxon. The axons pack together to
make a nerve fibre for the transport of nerveimpulse.
Differecs detmcen pon-striated.striatedan eard1a te
Featnres