BIO(Diversity)

    Diversity in Living Organisms

        

      There are many plants and animals

around us. We know very little about them.

Most of them belong to a world not visible

to the naked eye, as you have already studied

in the chapter on, ‘Microbial World’. The

types of organisms that we have studied so

far are also in lakhs, existing from mountain

peaks to deserts and plateaus to the deep

oceans, from extreme cold conditions to

extreme hot ones and many more, such

diversity is the symbol of nature.

Studying about diversity as it is, would

be a very chaotic and difficult task.

Moreover describing and naming each

organism individually without knowing the

organisms that might be sharing common

characteristics would be insignificant. Thus

people who have tried to study diverse

organisms in nature have tried to make

groups of them on the basis of differences

and similarities found among them. This

helped to identify largely varied and closely

related groups of organisms.

Thus our knowledge of the entire living

world depends on first making meaningful.

groups to carry out our study in a

systematic manner.

In this lesson we will try to study the

diversity present among several living

organisms, classify and appreciate nature's

miracle

Diversity in plants:

Here as we finish our activity we would have established some common characteristics of land plants- those having two seed leaves are called dicotyledons, while those having single seed leaf are

called monocotyledons.

They share some common

characteristics like venation (dicots have

reticulate/branched, while monocots have

parallel venation).

By doing the above activity we can

understand how grouping is done in biology

by observing the similarities and

differences among diverse groups in the

sample under study. We will do some

similar exercises with animals now.

Diversity in animals:

Observation of external characters of insects Collect housefly, mosquito, ant, dung beetle, butterfly, moth and cockroach from your surroundings. Observe them carefully. Take the help of a magnifying lens to get a closer view. Are all insects of the same size or shape?

What differences did you observe

with regard to legs?

What differences did you observe

with regard to wings?

Is there any relationship between

the number of wings and legs?

Did you find any two insects with same

characters? If yes, display in the class. If

no, note down the differences in your note

book.

Even though all these are insects and

you see that they show several differences.

Can you find at least one character that is

similar to the whole group, what is it?

How do you group insects? Would it

be based on number of body segments or

number of legs they have?

The examples of insects given above

are of different species. Hence they show

a lot of difference and we say they are

diverse. If we were to compare insects of

the same type that is to say two houseflies

we will be perhaps still find some

differences(try it out yourself) and these

would be variations.

Let us see some variations that are

present in human populations

Monera

Observe the given slides carefully and

say

How many cells are found in the

organism?

Do you find any nucleus in the

middle of the cell?

Are there any other cell organelles

found in the cell?

By observing the above characteristics

we conclude that Monerans are:

A. One-celled organisms

B. Cells have no membrane bound nucleus

C. Reproduce by splitting into two.

D. Absorb nutrients from outside their

bodies

E. They move with the help of

locomotory organs like flagella, cilia

or hair like structures present on them.

F. Some monerans cause diseases, but

others are helpful to people.

G. Examples: bacteria

        Nostoc

        Bacteria

Three major groups of organisms come under this group. They are archaebacteria (ancient bacteria present till date, some species found in hot springs come under this), eubacteria (streptococcus, rhizobium, e.coli etc) and cyanobacteria which are also called blue green bacteria as they appear similar to blue green algae externally but internally are more like bacteria(but they are not bacteria).

Protista (protoctista):

Observe the given slides carefully and

say

How many cells are found in the

organism?

Do you find any nucleus in the

middle of the cell?

Are there any other cell organelles

found in the cell?

Are there any locomotory organs

in them?

Characteristics of protists

A. Most are one-celled (unicellular),

but some have many cells.

B. Cells have a membrane around the

nucleus.

C. Some get nutrients and energy by

eating other organisms.

D. Some get energy from the sun, and

nutrients from the water around

them.

E. These live either solitary or in a

colony.

F. Some of the cell organelles are

present inside the cell.

G. Mostly reproduce by splitting into

two (Binary fission).

H. Examples are paramoecium,

amoeba, algae, etc.

              Amoeba

           Paramecium

Fungi:

Observe the specimen and diagrams

given below and answer the following

questions.

What is the colour? Can they

prepare their own food as green

plants?

Make a sketch of the main parts of the

body

Do you find root like structures?

Guess why?

Characteristics of fungi

A. Most are many-celled (multi

cellular) and some are one-celled

organisms.

B. Eukaryotes with well defined

prominent head (you usually see

them propping out from the ground

or on barks of trees during rainy

season).

C. Get nutrients and energy by

absorbing/ digesting the surface

they live on through root like

structures which are fine thread

like parts of their body.

D. Most of these reproduce by spores.

E. Examples are yeast, mushrooms,

bread moulds, and lichens.

Plantae:

Several plants grow around you. Do

all of them produce seeds?

Think if grass produces seeds

(hint:compare with rice plants and

think).

Name some plants that produce

seeds.

Which part of the plant produces

seeds? Where is it located?(recall

structure of plant parts studied in

earlier classes)

Do all plants have a definite

structure to produce seeds?

Plants are diverse in nature. The basis

of classifying them is the way they acquire

their food, the type of reproductive

structures they have and the way they

reproduce. They are multicellular,

eukaryotic with cell walls. They are usually

autotrophs and use mainly chlorophyll for

photosynthesis.

The first level of classification among

plants depends on whether the plant body

has well differentiated, distinct parts.

The next level of classification is based

on whether the differentiated plant body has

special tissues (vascular tissues) for the

transport of water and other substances

within it. Further classification looks at the

ability to bear seeds and whether the seeds

are enclosed within fruits.

Let's look at some plants like moss and

ferns more closely.

            Funaria

Activity:

Observation of moss plants through

hand lens.

You can collect mosses from the

greenish velvety growth on bricks during

the rainy season. Scrap a bit of this greenish

growth over a slide and observe with a hand

lens or under a dissection microscope. 

These are not exactly flowers but

structures that contain seed like structures

called spores. Spores contain very little

food while the seed stores a lot of it.

Moreover where seeds are produced from

ovule of flower, spores are produced within

structures called as sporangium in a

different manner.

 Sporophylls of Cycas & Fern

Coelenterata/Cnidarians:

These are aquatic forms showing more body design differentiation when compared with Poriferans. There is gastrovascular cavity in the body. The body is made up of two layers of cells: one forming the outer layers while the other forming the inner layers. Some
live in colonies ,like the corals that are tiny nearly 3 to 56 mm but their colonies where we may find several types of them which
form coral islands huge as say an island (1800 sqkm ), is called coral reefs while others like hydra, jellyfish and sea anemones are common examples.

Hydra

Platyhelminthes:

The body of animals in this group is far

more complexly designed than in the two

other groups we have considered so far. The

body is bilaterally symmetrical, meaning

that the left and the right halves of the body

have the same design. There are three layers

of cells from which differentiated tissues

can be made, that is why such animals are

called triploblastic. This allows outside and

inside body linings as well as some organs

to be made. There is thus some degree of

tissue formation. However, there is no true

internal body cavity or coelom, in which

well developed organs can be

accommodated. The body is flattened

dorsoventrally, from top to bottom, that is

why these animals are called flatworms.

They are either free living or parasitic.

Some examples of free living animals like

planarians or parasitic animals like

liverflukes and tapeworms.

        Tapeworm

     Nematoda

The nematode body is also bilaterally symmetrical and triploblastic. However, the body is cylindrical rather than flattened. There are tissues, but no real organs, although a sort of body cavity or a

pseudocoelom is present. These are very familiar as parasitic worms causing diseases, such as the worms causing elephantiasis (filarial worms) or the wormsin the intestine(roundworm or pinworms).

Annelida (Segmented Worms):

Annelida animals are also bilaterally

symmetrical and triploblastic, but in

addition they have a true body cavity. This

allows true organs to be protected in the

body.

There is, thus, extensive organ differentiation. This differentiation occurs in a segmental fashion, with the segments lined up one after the other from head to tail. These animals are found in a variety

of habitats– fresh water, marine water as well as on land.

Protochordata:

These animals are bilaterally

symmetrical, triploblastic and have a

coelom. In addition, they show a new

feature of body design, namely a

notochord, at least at some stages during

their lives. The notochord is a long rod-like

supporting structure (chord=string) that

runs along the back of the animal separating

the nervous tissue from the gut. It provides

a place for muscles to attach for ease of

movement. Protochordates may not have a

proper notochord present at all stages in

their lives or for the entire length of the

animal.

Protochordates are marine animals.

Ex. Herdmania, Amphioxus.

 Herdmania

Amphioxus

BIO(Plasma Membrane)

                  Plasma Membrane

 Activity-1:

Get in-go out

Let us look at the substances in the

table. Some are used by the cells while

some are discarded by the cells.

Preparing Solutions:

To prepare sugar solution we need sugar

and water. In a sugar solution sugar is the

solute and water is the solvent. Sugar

dissolves in water forming sugar solution.

Preparation of saturated solution :

Take 100 ml of water in a beaker.

Add sugar/salt. Stir till it is dissolved.

Repeat it till little amount of it is left at

the bottom of the beaker which will not

dissolve. This is the saturated solution of

sugar/salt (in cold water).

Which one is more concentrated

solution?:

Take three beakers with one hundred ml.

of water in each. Add half teaspoon of sugar

to the first beaker, one teaspoon to the

second and one and a half teaspoon to the

third. Compare the three solutions and

answer the following. The solution of

which beaker will be most sugary? What is

the reason? Can we convert the solution of

beaker I into solution of beaker III?

How? How can we make the solution of the

third beaker indicated to that of the

first? How much water should we add to the

solution in the third beaker to make it

similar to solution of the first beaker?

Solutions with different amount of solute

dissolved in them are solutions of different

concentrations. The amount of sugar present

in the 100 ml of water is the concentration of the sugar.

Which beaker has the most concentrated solution?

Lab Activity:

Aim : Observation of material in different

solutions

Material: 1. Two beakers 2. Tap water

3. Sugar 4. Dry grapes or kishmish

Procedure: Take 100 ml of water in a

beaker. Keep dry raisin (kishmish) in it.

 Kishmish kept in tap water

Leave it for one hour. Observe what has

happened. Take it out and compare it with

the dry raisin. Is there any change in the

size of kishmish. (You may try the same

activity with slightly dried carrots and other

such vegetables) Did you ever observe that

your mother dipped wilted vegetables in

water. Can you identify the reason.

Then take 100 ml of saturated solution

of sugar in a beaker, which was already

prepared.

Swollen kishmish kept in tap water

Keep swollen kishmish of the previous

activity or fresh grape or carrot in it.

Leave it overnight. And observe in the

next morning what happens. Do you find

any change in the size of kishmish.

In the lab activity - 2a, water is

moving from …...............…… to

………….............

In the lab activity - 2b, water is moving

from …....……..… to ………......….

Let us think how water goes in and

comes out of Kishmish. Does the layer

permits water to pass through?. How does

it works? The cells in the outer layer of

kishmish permit water to pass through.

Learn more about the process. Let us

do the following activity.

Lab Activity:

Osmosis

Materials needed: One raw potato,

beaker / bowl, two pins, Water, Sharp knife.

Procedure: Take the raw potato and boiled

potato. Peel off the skins. Cut cube shaped

cups from them as shown in the figure (you

could make some other shapes as well).

Prepare a few amount of saturated sugar

solution.

Pour the sugar solution in the potato

cup to a level as shown in the figure.

Mark the level of sugar solution by

piercing the pin.

Keep the potato cup in the bowl/beaker

    scoop to make a cup

       

Pour water in the beaker / bowl to half

of the height of the potato cup. Ensure that

the potato cup does not float or submerge

in water.

Leave the arrangement for half an hour

and note your observations

Repeat the above experiment by taking

sugar solution in the beaker and water in

the potato cup. Note your observation and

compare with that of your previous one.

By comparing potato and kishmish

activities, do you find anything in common

among them? What is it?

From your observations you can

conclude that water always moved towards

the sugar solution. What might be the

reason? Such process, in which water moves

towards sugar solution is called Osmosis.

(In Greek Osmos means pushing).

We see that the movement of water

through membrane in osmosis i.e. from

less solute concentrated to more solute

concentration. To understand how materials may be

moving in and out of cells through the cell

membrane, let us do the following activity.

Activity-2:

Filtration

       

To perform this activity we need the

following materials:

Two beakers, Funnel, Filter paper,

Retort stand, Sugar, Iodine and Wheat / rice

flour, 500ml plastic bottle, cotton cloth.

Procedure :

1. Arrange the filtering apparatus as

shown in the figure (4a) or the

alternative method as in figure (4b).

2. Prepare wheat or rice powder

solution in a beaker by adding one

tea spoon of powder in 100ml of

water.

3. Add a drop of tincture iodine to the

solution.

4. Now pour the solution into the

funnel.

Then observe,

What remains on the filter paper or

the cloth?

What did the filter paper/ cloth

allow to pass through?

Which substance is not allowed by

the filter paper to pass through?

Why are certain substances not

allowed to pass through the filter

paper? Guess.

Cells also act in the same way while

allowing the substances to pass through the

plasma membrane.

With the understanding of above

activities let us try to understand the nature

of the Plasma membrane.

a) It allows water to pass through it.

b) It allows certain materials dissolved in

water to pass through.

c) It will not allow certain materials to

pass through it.

Allowing materials to pass through is

called permeability.

In the previous activities we have

observed the movement of water and

materials in plants.

To know more details about plasma

membrane or cell membrane, let us go

through the following paragraphs.

The outermost, extremely delicate,

elastic and membranous covering of the

cell that separates its contents from the

external environment is called plasma

membrane. Protoplasm of a cell consists

of two parts, cytoplasm and nucleus.

Plasma membrane is selectively

permeable because it allows entry of

certain substances, exit of some

substances while preventing passage to

remaining substances. Plasma membrane is

a living flexible membrane.

Functions of plasma membrane

Shape: It provides a definite shape to semi

fluid contents of the cell.

Mechanical Barrier: It functions as a

mechanical barrier that protects the internal

contents of the cell.

Selective Permeability: The membrane

determines what substances are to be

allowed entry or exit from the cell.

Endocytosis: The flexibility of the

membrane enables the cell to engulf food

and other substances (foreign particles)

from its external environment by

endocytosis. Amoeba acquires its food by

this process.

Recognition: It has substances over its

surface which function as recognition

centres and points of attachment. They help

in tissue formation, distinction of foreign

substances and defence against microbes.

Flow of Information :Helps for flow of

information amongst different cells of the

same organism.

Osmosis: It occurs due to presence of tiny

water channels in the plasma membrane.

Cell Continuity: At places plasma

membranes of adjacent cells become

continuous to form plasmodesmata and cell

junctions.

Specialization: Plasma membrane gets

modified to perform different functions,

e.g. absorption in microvilli.

Diffusion

There are other ways in which materials

move in a medium. Let us study one such

process by the following activity.

If a bottle of scent is opened in one

corner of a room, what will happen?

How do we feel? Its smell spreads in

the entire room. Let us think of the

following.

How does the smell spread in the

entire room?

Is the smell spreading uniformly in

the entire room?

Can you reach the scent bottle if

you are blind folded?

When blind folded how you are

able to locate the scent bottle?

Can you give any other such

examples?

There are other processes in which

substances move in a medium. Let us study

another such process by the following

activity.

Activity-4:

Diffusion with coffee powder

Experiment with coffee powder. Let us

Take half bowl of water. Prepare a small

ball of coffee powder. Slowly put it in

water. Observe what happens. Write a note

on what you observed.

Do this activity as many ways as you

could like.

Putting the pinch of coffee powder

first and adding water slowly.

Pouring hot water on the pinch of

coffee powder etc.

Note your observations for each situation

and write down what you infer.

Let us see whether other substances

also behave in the same manner.

Activity-5

Keep a small Crystal of KMnO4

(Potassium permanganate) in the

centre of the Petridish with the help

of a Forceps.

Carefully fill the Petridish with

water. (It is better to use filler or

dropper)Observe the movement of Pink

Colour in the Petri dish everyminute.

Also observe the spreading of colour

from center to periphery.

Repeat the experiment with other

substances (E.g.: copper sulphate) and

compare the result.

Do you find any relation between

Time and Movement?

For better understanding, the

movements of molecules in water, observe

the following activity.

                

BIO(Animal tissues)

             Animal tissues

 Activity-1:

Collect the substance lining the mouth

by using wooden spoon and observe this

under the microscope. Draw the diagram

that you have observed in the microscope,

in your note book.

How are the cells arranged?

Are there any inter cellular spaces?

The epithelial tissue, extremely thin

and flat, form a delicate lining. This is called

as squamous epithelium. We find this type

of epithelium in oesophagus, lining of

mouth, lining of blood vessels, lung alveoli

where transportation of substances

selectively occurs through permeable

membrane (you will learn about

permeability in the next chapter of

“Transport across Membrane)”.

The epithelial cells in skin are arranged

in the form of layers. This is called as

stratified squamous epithelium.

Think, why are the epithelial cells

in the skin are arranged in the form

of layers?

If you drink hot tea or chilled cool

drink, how do you feel?

If your skin burns or is wounded

which tissue would get effected?

Activity-2:

Take a permanent slide of cuboidal

epithelium from your laboratory slide box

and observe under the microscope. Draw

the picture in your note book. How are the

cells arranged?

      

These are the cuboidal epithelial cells

which form the lining of organs or tubules

like ureters or other parts and provide

mainly mechanical support to salivary glands.    

Activity-3:

Take a permanent slide of columnar epithelium from the slide box and observe it under the microscope.

Draw the figure that you have

observed under the microscope

How are the cells? Do you find any

hair like projections on the outer

surface of epithelial cells.

This types of cells are present where

ever absorption and secretion occurs. Try

to think where is this type of epithelial

tissues present in your body?

Do you know?The skin is also a kind of

epithelial tissue. Where does nails, and hair

grow from. The scales of fishes, reptiles

and feathers of birds also grow from

epithelium. These are modified epithelial

tissues. You learn more about them in the

chapter: Adaptations in different

Ecosystems.

Connective tissue:

If you tilt your body to any side of your body, what will happen to your internal organs? Is there any displacement? The internal organs are located at specific places without any displacement in organs

due to connective tissues. The tissueconnect organs and muscles. These tissuesare called connective tissue.

Connective tissues help in binding the

other tissues and organs together and

provide a frame work and support to various

organs in the body. These tissues also play

a major role in the transport of material

from one tissue to another. They also help

in the body defence, body repair and

storage of fat. There are different types of

connective tissues, each performing a

different function.

How do glasswear items carry for

longer distance?

Areolar tissue is one type of

connective tissue which joins different

tissues. It helps in packing and helps to keep

the organs in place. These cells are called

fibroblasts. These are the major

components in this type of connective

tissue. These cells secrete fibrous material

which holds the other tissue in position.

These cells also help in repair of the tissues

when they are injured.

           Areolar Tissue

The muscles in our body are attached

to the skin and bone by this type of tissue.

We can see this type of tissue around blood

vessels and nerves.

Why do old people shiver more in winter when than youngsters? Is there any special arrangement to prevent the escape of heat

energy during winter? Fat storing adipose tissue is found below the

skin and between internal organs. The cells of this tissue are filled with fat globules. Storage of fat also acts as insulator. Are all tissues in our body smooth and soft? Which tissue gives definite shape to

body of vertebrae? Bone is another type of connective tissue; it forms the frame work that supports the body. It is a major component of the skeletal system of several vertebrae

(except some fishes like sharks).

Cartilage is a type of connective tissue

found in the joints of bones, tip of ribs, tip

of the nose, external ears and in trachea.

Embryos of several vertebrae do not have

bone but have cartilage. The entire skeleton

of fishes like sharks is made of cartilage.

Cartilage is hard but not as hard as bone

How two bones are connected at joints?

Ligament is yet another type of

connective tissue that connects bones at

the joints and holds them in position. It is

made up of large number of fibres. These

fibres are made up of a protein called

collagen. This is very elastic in nature.

Activity-4:

Invite a scientist or doctor to your

place. Record an interview about blood

structure and its functions. It is important

to make a questionnaire inorder to conduct

interview. After completion of interview,

prepare a booklet about blood and keep it

in the class room library or display it on

the bulletin board.

It differs from other types of

connective tissues. There are different

types of cells in blood and each one has a

different function. All the cells in the blood

float freely in the plasma. Extra cellular

space is filled with fluid called plasma.

There are no fibres in blood.

Blood:

Blood is also a tissue which is having

different components. Let us know more

about blood.

There is a red stream that flows in

closed canals in our body. Think what is it?

The red stream that flows in closed tubes

in our body is blood. It is also a type of

connective tissue. Blood explains many

things about us. Blood is the source to

identify our wellness or illness. It is very

interesting to know about the blood current

in our body. There is highly sophisticated

and well developed mechanism to circulate

the blood to the entire body. Our heart pumps

nearly 36 thousand litres of blood to a

distance of nearly 20 thousand kilometers

in the time period of 24 hours. Blood is red

in colour. Do you agree with the statement

that all animals carrying red blood are your

blood relatives? The blood is always not red

in all animals. The cockroach has white

blood where as there is blue coloured blood

in snail. It is really a wonder that blood

appears in different colours.

Normal adult human beings have about

5 litres of blood. A chief component in

blood is water, which is stored in the

plasma.

Besides water, it also has several

nutrients such as glucose, amino acids,

proteins, vitamins, hormones, required for

the body and also excretory products such

as lactic acid, urea, salts etc. Plasma also

contains factors responsible for blood

clotting. Heparin helps to prevent blood

clotting in blood vessels.

Cells present in blood are corpuscles.

They are three types 1. RBC, 2. WBC,

3. Blood platelets.

Red blood cells also known as

erythrocytes which are red in colour. They

have red coloured protein called

haemoglobin. Because of haemoglobin

blood is red in colour, which helps in the

transport of oxygen and carbon dioxide 1ml

of human blood has about 5 millions of red

blood cells which live for 120 days in

blood.

Taking blood of an adult we can make a

chain of red blood cells around the earth at

equator with 7 circles. When you are in

your mother’s womb your RBC are formed

in the liver and spleen. After your birth

these RBC are generated from the bone

marrow of long bones. In mammals, mature

red blood cells are without nucleus.

Muscle Tissue:

If you are wounded deeply, a deep scar

would form at the place of wound? If we

are wounded on skin, a lighter scar would

form. Why? For the reason, that the skin

cells have regenerating character. Think

about the muscle cell. Will they get

regenerated like epithelial cells?

Muscles are responsible for the

movements of hands and legs and also of

several internal organs such as intestine and

heart. Small amounts of muscle tissues also

present in blood vessels. These helps in

increasing or decreasing the diameter of

the blood vessel and thus the blood flows.

Heart is made of only one type muscle cells

and they help in pumping the blood.

         Striated muscles

     Non-Striated muscles

How do muscles contract and relax?

Muscular tissue consists of elongated

cells called muscle fibres. This tissue is

responsible for movement in our body.

Muscles contain special protein called

contractile proteins which contract and

relax to cause movement.

During winter, body shivers. Why?

When the body is exposed to cold air,

we shiver. During shivering muscles

contract and relax producing large amount

of heat. This keeps the body hot.

Based on their structure, location and

function, muscles are three types. They are

striated muscle, non-striated muscle,

cardiac muscle.

We can move some muscles by our

conscious effort. For example the muscle

present in inner limbs move according to

our wish and will Such muscles are called

voluntary muscle. These muscles also

called as skeletal muscles as they are

mostly attached to bones and help in body

movement; these muscles show alternate

light and dark bands or striations. As a result,

they are also called striated muscle. The

cells of this tissue are long, cylindrical, un

branched and have many nuclei in the

cytoplasm (multi nucleated).

Nervous Tissue:

If you put your fingers in a glass of hot

water, how do you feel?

How would you know the water is hot

or cold? If you put your leg on a sharp edged

stone while walking, how will you feel?

The feelings like the above situations

is because of specialized mechanism in our

body. It works like electric current passing

through wires. Brain, spinal cord and nerves

play active role in this mechanism.

            Nerve cell

 

Cell body or cyton has a large nucleus

and cytoplasm. The cytoplasm contains

granular structure called Nissal’s granules.

There are some projections arising

from cell body. These are called dendrite.

They are sharp, branched, more in number.

One projection of the cyton is somewhat

longer than remaining projections.

This is called axon. Some nerve cells have axon

covered with sheath like structure. This

sheath is called as Myeline sheath. Gas or

nodes present at regular intervals on

myeline sheath are known as Ranvier

Nodes.

Axon of a nerve cell is connected with

Dentrites of a near by nerve cell to form a

web like structure throughout bod

BIO(Plant tissues)

              Plant Tissues

         Plants that we observe around us are

usually multi-cellular. They perform

several life processes such as growth,

respiration, excretion, etc, similar to those

performed by animals. In addition to these

they can perform photosynthesis and

prepare food not only for themselves but

also for all the other living organisms dependent on them, either directly or indirectly. Let us recall the information about different parts of the plants and the functions they are associated with.

Activity-1:

Parts of the plant and their

functions.

We have studied about the functions of

the parts of the plant in the earlier classes.

Read the functions given below and write

the names of the parts involved in

performing the respective function.

    Function Name of the parts:

1. Absorption of water from soil

2. Exchange of gases (air)

3. Photosynthesis

4. Transpiration

5. Reproduction

Activity-2:

Cells in onion peel

- Take a piece of an onion peel.

- Now place it on the slide.

- Put a drop of water and then a drop of

glycerine on it.

- Gently cover it with a cover -slip.

- Observe it under the microscope.

- Draw and label the diagram that you

have observed under the microscope.

Compare your drawing with figure-1 to

find out labelled parts.

Are all the cells similar?

How are the cells arranged?

Activity-3:

Cells in a leaf peel.

- Take a betel leaf or Tradescantia or

Rheo leaf.

- Tear it with a single stroke. So that a

thin edge be seen at the torn end.

- Observe the thin edge where the leaf

has been torn under the microscope

in the same manner as you had

observed the onion peel.

Draw a diagram of what you have

observed and compare it with figure-2.

Are all the cells similar?

Is there any difference in their

arrangement?

What can we infer from the above

activities?

Have you noticed that the cells are in

groups in both the activities?

Compare and write a note on the

arrangements of the cells that you have

observed in both of the activities.

You may have observed that the cells are

present in groups with certain

arrangement. With the help of the

following activities we shall try to find out

whether these arrangements have special

roles to play in the plant body.

Activity-4:

(a) Cells in root tip

- Are the cells in the root similar to that

of a leaf. Let us find out how the cells

are arranged in the root. For this we

need onion root tips.

- Take a transparent (plastic/glass) bottle

filled with water. Take an onion bulb

slightly larger than the mouth of the

bottle.

- Put the onion bulb on the mouth of the

bottle.

- Observe the growth of roots for a few

days till they grow to nearly an inch.

- Take the onion out and cut some of the

root tips.

- Take an onion root tip.

- Place it on the slide.

- Put a drop of water and then a drop of

glycerine on it.

- Cover it with a cover-slip.

- Remove excess water with the help of

blotting paper.

- Tap the cover-slip gently and press with

the blunt end of the needle or brush to

spread the material.

- Observe the structure and arrangement

of the cells.

- Draw the diagram of that you have

observed under the microscope.

· Are all the cells similar?

· How is the arrangement of cells?

       Cells in Onion roots tip:

Activity-5:

(b) Growing roots

- Take the onion used in the previous

activity and mark the cut end of the

roots with a permanent marker.

- Put the onion bulb on the mouth of the

bottle in the same way as you did in the

previous activity.

- Leave the set up aside for at least four

to five days. Take care that there is

enough water in the glass so that the

roots are submerged.

Did all the roots grow in a same manner?

What happened to the roots which had

been cut off?

Write down your findings, regarding the

cut roots and those that were not?

We observe that by removing the tip of

the onion root, having a particular

arrangement of cells, the growth of the root

in length is stopped.

You have observed that cells are present

in groups. Cells in groups which are nearly

similar in structure perform similar

functions. Such groups of cells are called tissues.

      Growth on roots in onion bulb

Types of plant tissues:

There are four basic types of tissues in

the plants. They are

Tissues that bring about overall growth

and repair are called Meristematic

tissues.

Tissues that form outer coverings are

called as Dermal tissues.

Tissues that form the bulk of the plant

body, helping in packing other tissues

are called as Ground tissues.

 Tissues that help in transport of

materials are called as Vascular tissues.

You have already observed some types

of tissues. To observe various types of plant

tissues we need to know some techniques

for preparing slides and cutting sections.

See annexure for the same.

1. Meristematic tissues:

Observe the given figure of a stained

section of a shoot tip

From the above figure you can infer

that meristematic tissues are present on

the tip, sides and in between layers of other

tissues. Meristematic tissues at the

growing tip that bring about growth in

length are called as apical meristematic

tissues.

Tissues present around the edges in a

lateral manner and giving rise to growth in

the girth of stem are called lateral

meristematic tissues.

Areas from which branching takes place

or a leaf or a flower stalk grows, we find

a kind of meristematic tissue called

intercalary meristematic (also called

Cambium) tissue.

Activity-6:

Dicot Stem tissues

Prepare a temporary mount of the TS

of a dicot stem.

Observe it under the microscope.

Draw and label the diagram.

Compare it with figure given below

       Dicot stem (TS) - Tissues

What are the similarities between the

tissues in root and in shoot as shown

in the above figure?

Are all the cells similar in shape and

structure?

Activity-7:

Rheo leaf - Dermal tissue. 

- Take a fresh leaf of Rheo or Betel plant

- Tear it in a single stroke, so that a thin whitish edge can be seen at the torn end.

Slowly remove it and observe that peel

under the microscope (by preparing a

temporary mount).

See the arrangement of cells .Are all

cells similar? Are there any spaces

between the cells?

This activity shows a part of the dermal

tissue of the plants.

Dermal tissue (Dermis) usually consists

of a single layer of cells showing variations

in the types of cells on the basis of their

functions and location. These tissues are

divided into three different types. They are

epidermis (outer most layer), mesodermis

(The middle layer) and endodermis (the

innermost layer).

The walls of the cells of dermal tissue

are comparatively thicker than the cells of

meristematic tissues. In desert plants it may

be even more thick and waxy. Small pores

are seen in the epidermis of the leaf, called

stomata. They are enclosed by two kidney

shaped cells, called guard cells. Cells of

the roots have long-hair like parts, called

root hair.

        Parenchyma:

The cells of the parenchyma are soft,

thin walled and loosely packed. The

Parenchyma which contains chloroplasts is

called “Chlorenchyma”. The Parenchyma

which contains large air cavities or spaces

is called “Aerenchyma”. The Parenchyma

which stores water or food or waste

products is called “Storage Tissue”.

Collenchyma tissues have thick walled,

longer cells when compared with parenchyma. In the sclerenchyma the cells are thick walled and tightly packed without spaces. So when compared with dermal tissue, the ground tissue is of various types. And some of the ground tissues help in photosynthesis. Let us observe the ground tissue of some other stems.

Activity-8:

Take permanent slides of Chlorenchyma, Arenchyma, Storage Tissue from your laboratory and observe them under the microscope. Find out the characteristics differences and record them in your notebook.

       Chlorenchyma

             Arenchyma

          Storage Tissue

      Vascular Tissue:

We know that roots can absorb water

from the soil and send it to other parts of

the plant. The leaves and other green parts

prepare food and supply it to all the parts

of the plant.

Let us study the tissues involved in

transportation.

We have done an experiment on

transportation in class VII, in the chapter

on plant nutrition. We have observed that

when a plant is kept in red coloured water,

Some of the parts of the plant turned red.

Do the same experiment again by keeping

a small plant (with roots) in red coloured

water. Leave it for two hours. Now cut a

T.S. of the stem and observe it under the

microscope.

Which part of the plant is responsible

for this transport?

Draw a rough sketch of that part and

mark the part that appears red.

What do you conclude from your observation?

The tissues involved in transportation are vascular tissues. They are composed of different

types of cells which show specific arrangements.