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BIOLOGY FOR CLASS IX
Class IX
Structural Organization Of Life
Content
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Microscope
 Light Microscope
 Electron Microscope
 Magnification And Resolution
Cell
 Cell Theory
 Cell Organelles
 Differences Between Animal And Plant Cells
 Types Of Cells
 Differences Between Prokaryotic And Eukaryotic Cells
 Cell Division
 Mitosis Stages
 Significance Of Mitosis
 Meiosis Stages
 Significance Of Meiosis
Organization Of Cells To Form Tissues, Organs And Organ System
 Plant Tissues
 Types Of Plant Tissue Systems
 Types Of Animal Tissues
 Unicellular Organism
 Multicellular Organism
 Brassica as multicellular organization, with root, stem, leaves, flower fruit and seed as their parts
 Frog as multicellular organization with digestive, respiration, circulatory, excretory, nervous and reproductive
organs and system
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Parts and Microscope:
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Eyepiece Lens: The lens at the top that you look through. They are usually 10X or
15X power.
Tube: Connects the eyepiece to the objective lenses
Arm: Supports the tube and connects it to the base
Base: The bottom of the microscope, used for support
Illuminator: A steady light source (110 volts) used in place of a mirror. If your
microscope has a mirror, it is used to reflect light from an external light source up
through the bottom of the stage.
Stage: The flat platform where you place your slides. Stage clips hold the slides in
place. If your microscope has a mechanical stage, you will be able to move the
slide around by turning two knobs. One moves it left and right, the other moves it
up and down.
Revolving Nosepiece or Turret: This is the part that holds two or more objective
lenses and can be rotated to easily change power.
Objective Lenses: Usually you will find 3 or 4 objective lenses on a
microscope. They almost always consist of 4X, 10X, 40X and 100X powers. When
coupled with a 10X (most common) eyepiece lens, we get total magnifications of
40X (4X times 10X), 100X, 400X and 1000X.
Rack Stop: This is an adjustment that determines how close the objective lens can
get to the slide. It is set at the factory and keeps students from cranking the high
power objective lens down into the slide and breaking things. You would only need
to adjust this if you were using very thin slides and you weren't able to focus on the
specimen at high power. (Tip: If you are using thin slides and can't focus, rather than
adjust the rack stop, place a clear glass slide under the original slide to raise it a bit
higher).
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1.
Light microscope
A light microscope uses focused light and lenses to
magnify a specimen, usually a cell. In this way, a
light microscope is much like a telescope, except
that instead of the object being very large and
very far away; it is very small and very close to the
lens.
Electron Microscope
 The
electron microscope is a type of
microscope that uses a beam of electrons It
is capable of much higher magnifications and
has a greater resolving power than a light
microscope, allowing it to see much smaller
objects in finer detail. They are large,
expensive pieces of equipment, generally
standing alone in a small, specially designed
room and requiring trained personnel to
operate them.
Magnification:

Magnification is the ability to make small objects seem
larger, such as making a microscopic organism visible.
Magnification is the process of enlarging something
only in appearance, not in physical size.
 By increasing magnification resolution is disturbed.
 Magnification improves with the focal length of lens.
Resolution:

Resolution depends on the distance between two
distinguishable radiating points.

Resolution is the capacity to separate adjacent objects.
In 1665, an Englishman by the name of Robert
Hooke examined thin slices of cork and observed
that it was composed of numerous little boxes,
fitted together like honey comb.
 Since these boxes resembled the compartment of
monastery he named them as cells.
 The cork cells studied by Hooke were really empty
boxes; they had lost their living matter, the
protoplasm.
 After his discovery, the protoplasm in living cells
was largely over looked due to its transparency.
 Today, with the help of special techniques, we are
able to see not only the protoplasm but also many
bodies inside it.
 A general outline of a plant cell is as follows:

Plant cells are surrounded by a non living and
rigid coat called cell wall. The cell wall is not a
living part of the cell.
 Cell walls are significantly thicker than plasma
membranes. It is responsible for the shape of
plants and controls the growth rate of plant
cells.
 Walls are a layered structure, having three basic
portions: intercellular substance or middle
lamella, primary wall and secondary wall.
 The middle lamella cements together the
primary walls of two contiguous cells and the
secondary wall is laid over the primary. The
middle lamella is mainly composed of a pectic
compound which mostly appears to be calcium
pectate. The primary wall is largely composed of
cellulose and the secondary wall may be of
cellulose .

All living cells, prokaryotic and eukaryotic, have
a plasma membrane that encloses their contents
and serves as a semi-porous barrier to the
outside environment.
 The plasma membrane is permeable to specific
molecules, however, and allows nutrients and
other essential elements to enter the cell and
waste materials to leave the cell.
 Small molecules, such as oxygen, carbon
dioxide, and water, are able to pass freely across
the membrane, but the passage of larger
molecules, such as amino acids and sugars, is
carefully regulated.
 According to the accepted current theory, known
as the fluid mosaic model, the plasma membrane
is composed of a double layer (bilayer) of lipids,
oily substances found in all cells.
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 The
term cell nucleus was used by Robert
Brown for the first time in 1831.
 The nucleus is a highly specialized organelle
that serves as the information processing and
administrative center of the cell.
 This organelle has two major functions: it
stores the cell's hereditary material, or DNA,
and it coordinates the cell's activities, which
include growth, intermediary metabolism,
protein synthesis, and reproduction (cell
division).
Position:
 The location of nucleus varies in the cell
depending upon the species. Usually it is situated
in the centre of the cell surrounded on all sides
by cytoplasm
Shape:
 The shape of nucleus is variable according to cell
type. It is generally spheroid but ellipsoid or
flattened nuclei may also occur in certain cells.
Nucleoplasm.
 The semi fluid matrix found inside the nucleus is
called nucleoplasm. Within the nucleoplasm,
most of the nuclear material consists of
chromatin, the less condensed form of the cell's
DNA that organizes to form chromosomes during
mitosis or cell division.
Chromatin and Chromosomes:
 A dense string-like fiber called chromatin.
 The Nucleolus:
 The nucleolus is a membrane-less organelle
within the nucleus that manufactures
ribosomes, the cell's protein-producing
structures.
The Nuclear Envelope
 The nuclear envelope is a double-layered
membrane that encloses the contents of the
nucleus during most of the cell's lifecycle.
 Part
of plant cells outside the nucleus (and
outside the large vacuole of plant cells) is
called cytoplasm. The cytoplasm is about 80%
water and usually colorless. Cytoplasm is
often used to refer to the jellylike matter in
which the organelles are embedded
(correctly termed the cytosol). Most of the
activities in the cytoplasm are chemical
reactions (metabolism), for example, protein
synthesis.
 Some
important cytoplasmic organelles found
in eukaryotic cells.
 Endoplasmic reticulum (ER)
 Golgi Apparatus
 Mitochondria
 Plastids
 Centrioles
 Ribosomes
 Lysosomes
 They
are found in all eukaryotic cells and are
structurally continuous with the nucleus of
the cell. The ER is a complex network of
tubes. The lumen is filled with fluid. There
are two types of endoplasmic reticulum smooth ER and rough ER.
 Smooth
Endoplasmic reticulum - They are
tubes with a smooth surface as they lack
ribosomes. The smooth ER helps in calcium
sequestration and release and secretion of
lipids.
 Rough Endoplasmic reticulum - They are
tubes with rough surface as the ribosomes
are attached to its surface.
 The endoplasmic reticulum serves many
general functions, including the folding of
protein molecules in sacs
called cisternae and the transport of
synthesized proteins in vesicles to the Golgi
apparatus.
 The
Golgi bodies are elongated, flattened
structures called cisternae and they are
stacked parallel to one another.
 They are bound by a single membrane and
are found close to the nucleus.
 The vesicle formed from the ER fuses with
the membrane of the Golgi apparatus.
 The
cavity of the Golgi body is has vessel
proteins that are modified for export.
 The main function of the Golgi apparatus is
sorting, packaging, processing and
modification of proteins. It also forms
lysosomes and peroxisomes.
 Lysosomes
are single membrane
bound structures.
 They are tiny sac like structures and are
present all over the cytoplasm. The main
function is digestion. They contain digestive
enzymes. Lysosomes contain digestive
enzymes that are acid hydrolases.
 They
are responsible for the degrading of
proteins and worn out membranes in the cell
and also help degradation of materials that
are ingested by the cell.
 Lysosomes that are present in the white
blood cells are capable of digesting invading
microorganisms like the bacteria and viruses.
 During the period of starvation the lysosomes
digest proteins, fats and glycogen in the
cytoplasm.
 They are capable of digesting the entire
damaged cell containing them; hence, the
lysosomes are known as "suicide bags" of the
cell.
 Peroxisomes
are found in liver and kidney
cells.
 Peroxisomes have enzymes that are
responsible to get rid of the toxic peroxides
from the cell.
 Ribosomes
are the site for protein synthesis
of the cell.
 It is composed of two subunits, a small
subunit and a large subunit.
 The
ribosomes subunit acts as an assembly
line where the RNA from the nucleus is used
to synthesize proteins from amino acids.
 Ribosomes are found freely floating or bound
to a membrane or attached to mRNA
molecules in a polysome.
 Centrosomes
are the cytoskeleton organizers.
 Centrosomes
are composed of two
centrioles, they separate during cell division
and they help in the formation of mitotic
spindle.
 Mitochondria
are of various shapes and sizes
and are numerous in the cytoplasm of all
eukaryotic cells.
 Mitochondria are double membrane
bound. The inner membrane is folded into
numerous cristae.
 Mitochondria
are the power generators of the
cell.
 They are capable of self-replication as they
possess their own DNA.
 The main function of mitochondria is to
produce energy through metabolism.
 In the mitochondria sugar is finally burnt
during cellular respiration.
 The energy released in this process is stored
as high-energy chemicals called adenosine
triphosphate (ATP).
 The energy is used by the body cells for
synthesis of new chemical compounds.
Plastids are cellular organelles found only in the plant cell.
Plastids are of three types - chloroplasts, chromoplasts and
leucoplasts.
•Chloroplasts are elongated disc shaped organelles which
contains chlorophyll. Chlorophyll is present in green plants
which helps them make food by the process of photosynthesis,
which uses energy from the sunlight is converted into chemical
energy.
•Chromoplasts are plastids which are found in
fruits and are yellow, orange and red in color.
•Lecuoplasts are colorless plastids. They found
in roots, seeds and underground stems.
Animal cell
Plant Cell
Animal cells are usually smaller is size.Plant cells are usually larger in size.
Cell wall is completely absent.
Presence of cell wall is a characteristic
feature of plant cell.
Cellulose in any form is not present.
Cell wall is made up of cellulose.
Cytoplasm of animal cells is dense,
more granular and
it occupies most of the space in the
cell.
In a plant cell, cytoplasm is pushed to the
periphery of the cell.
The cytoplasm forms a thin lining against
the cell wall.
Vacuoles are absent usually. If present, Vacuoles are prominent and large
they
are
small
organelles, organelles
in
the
plant
cell.
they are temporary and they serve One or more vacuoles may be present.
as organelles for excretion or secretion. The central space in the cell may be
occupied by a large single vacuole.
Plastids are absent.
Centrosome is present.
Plastids are present. They may of three
types chromoplasts, chloroplasts and
leucoplasts.
Centrosome is absent in plant cells.
Instead
of
centrosome,
there are two small clear areas called
polar caps are present.
Golgi complex is prominent and highly
complex;
Golgi apparatus is present in form
it is present near the nucleus of the subunits called dictyosomes.
cell.
Prokaryotic
Eukaryotic
Nulear membrane is absent A double nuclear membrane is
therefore prokaryotic cells doing present. They have well defined
not possess distinct nucleus.
mucleus.
They do not have many of the They have membrane bounded
membrane bound structures e.g. structure (organelles).
Mitochondria,ER,Golgi bodies
Ribosomes are of small size and Ribosomes are of large size and
freely scattered in cytoplasm.
present either on endoplasmic
reticulum free in cytoplasm.
Nucleoplasm is absent.
Nucleoplasm is present.
Single chromosome is found.
Proper chromosomes in diploid numbers
are present.
Respiratory enzymes are located on the Respiratory enzymes are present in
inner surface of the cell membrane.
mitochondria.
These cells are simple and comparatively These
cells
are
complex
and
smaller in size i.e. aveage 0.5 -10nm in comparatively larger in size i.e. 10diameter.
100nm in diameter average.
Bacteria and cyanobacteria are examples Fungi, Algae, Animals and Plants are
of prokaryotes
examples of Eukaryotes.
Cell
Cell is the basic unit of life.
Cell Theory
1. All living things are made up of cells.
2. Cells are the basic units of structure and
function in living things.
3. Living cells come only from other living cells.
Cell Division
 Cell
division is the process by which
a parent cell divides into two or
more daughter cells.
1. Mitosis
2. Meiosis
 Prophase
 Metaphase
 Anaphase
 Telophase
 This
division produced having the same amount
and type of genetic constitution as that of the
parent cell.
 It is responsible for growth and development.
 The
number of chromosomes remains the
same in all the cells produced by this
division. Thus, the daughter cells retain the
same characters as those of the parent cell.
 It helps the cell in maintaining proper size.
 Mitosis helps in restoring damaged or lost
part, healing of wounds and regeneration of
detached parts (as in tail of lizards).
 It is a method of multiplication in unicellular
organisms.
 Meiosis
I
The first meiotic division is more important
than the second division because it is the
reduction division. In this, four sty ages can be
differentiated.
 Prophase I
 Metaphase I
 Anaphase I
 Telophase I
 (a)Leptotene
or Leptonema (leptos=thin)
This is the first stage of meiosis following
interphase. The chromosomes at this stage
appear long, thread-like structures. On the
entire chromosome, characteristic bead-like
structures, called chromomeres can be seen. In
animal cells, the centrioles divided and move
towards opposite poles.
 (b)
Zygotene or Zygonema (Zygone=adjoining)
 This
stage is characterized by the pairing of
homolosgous chromosomes. This phenomenon is
known as synapsis. The pairing starts at the
centromere or at any other position. The paired
chromosomes are called bivalents or dyads.
They gradually become thick and short.
 (c)
Pachytene or Pachynema (Pachus=thick)
 Each
chromosome of a bivalent splits
longitudinally into two sister chromatids so that
the bivalent becomes a tetrad or quadrivalent.
The two nonsister chromatids, one from each
bivalent (one paternal and the other maternal)
partially coil around each other and exchange
their genetic material. On each of the nonsister
chromatids of the tetrad, transverse breaks occur
which are followed by interchange and final
fusion. This process is known as crossing over and
the point where the crossing over takes place is
called chiasmata (singular, chiasma). Due to
coiling, the paired chromosomes become thicker
and short. The nucleolus still persists.
(d) Diplotene or Diplonema (Diploos=double)
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At this stage, homologous chromosomes start at the
centromere and moves towards the ends. The type of
separation from centromere towards the end is
known as terminalization. This separation makes the
dual nature of a bivalent chromosome distinct and
hence the name of the stage is diplotene. As the
terminalization proceeds, the chiasmata (points of
genetic exchange) move towards the ends of the
chromosomes but the chromosomes are held together
at the chiasmata. It should be remembered that
crossing over always takes place between nonsister
chromatids of homologous chromosomes. Chiasmata
are not the cause but are only the consequence of
crossing over. The number of chiasmata per bivalent
varies and is dependent upon the length of the
chromosomes. Nucleolus and nuclear membrane start
disappearing at this stage.
 (e)
Diakinesis (Dia=across)
 The
chromosomes undergo further
contraction and shortening. During this stage
the nucleolus and nuclear membrane
disappear. Centrioles reach the opposite
poles of cell and start forming spindle
apparatus.
Interphase
The interphase is a brief period here. Sometimes it
may be absent. There is no duplication of
chromosomes at this stage which is a different
condition from that of mitosis.
The second meiotic division is essentially a
mitotic division and is sometimes termed as
meiotic mitosis. It can be studied under the
following four stages.
1. Prophase II
In both the cells the nuclear membrane and
nucleoli disappear . The centrioles duplicate
and migrate towards opposite pole. Each set of
centriosles is surrounded by aster rays. The
formation of spindle starts. The shortening of
chromosomes begins.
2. Metaphase II
 The chromosomes arrange themselves on the
equatorial plane and centromere divides.
Each chromatid gets attached to spindle
fibres by its centromere.
3. Anaphase II
 Spindle fibres attached to the opposite faces of
cenromeres shorten in length. This causes a pull on
the centromere. As a result, the centromere splits
along the longitudinal axis and the chromatids are
pulled to the opposite poles.
4. Telophase II
 The chromatids (now the chromosomes)
reach their respective poles. They uncoil and
form the chromatin network. Nucleolus and
nuclear membrane reappear. At the end of
this phase, four haploid (n) nuclei are
produced in each cell.
It maintains the same chromosome n umber in the
sexually reproducing organisms. From a diploid
cell, haploid gametes are produced which in turn
fuse to form a diploid cell.
 2. It restricts the multiplication of chromosome
number and maintains the stability of the species.
 3. Maternal and paternal genes get exchanged
during crossing over. It results in variations among
the offspring.
 4. All the four chromatids of a homologous pair of
chromosomes segregate and go over separately to
four different daughter cells. This leads to
variation in the daughter cells genetically.
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Tissues are made up of groups of cells that all have
a similar function and structure. Some examples of
tissues include muscles, bones, skin and the lining
of the stomach, lungs and intestines. The lining of
the stomach is just one of the many tissues that
have joined together to form the organ, as it also
contains muscles, mucus membrane tissue and
many other tissue types.
 Plants
do have a higher level of structure
called plant tissue systems. A plant tissue
system can be defined as a functional unit,
which connects all organs of a plant. Like
animal tissue system, plant tissue system is
also grouped into various tissues based on
their functions.
 They
are the tissues, which covers the
external part of the herbaceous plants.
 They are composed of epidermal cells, which
secrete the waxy cuticle.
 Waxy cuticles are responsible for protecting
plants against water loss.
 Dermal tissue consists of Epidermis and
periderm.
 They
are the outermost layer of the primary
plant body, which covers roots, stems,
leaves, floral parts, fruits and seeds.
 They are one layer thick with cuticle.
 They are composed mostly of unspecialized
cells- parenchyma and sclerenchyma.
 They include trichomes, stomata, etc.
•They are the outermost layer of stems and roots of
woody plants such as trees. They are also called as
barks.
•They replace epidermis in plants that undergo
secondary growth.
•They are multilayered structures.
•They include cork cells, which are nonliving cells that
cover the outside of stems and roots.
•The periderm protects the plant from injuries,
pathogens and also from excessive water loss.
 They
synthesize the organic compounds and
support the plants by storing the
produced products.
 They are composed of parenchyma cells and
also include collenchyma and sclerenchyma
cells.
 They
are the general cells of plants, which
are circular in shape and have very thin wall.
 They are present in all plant cells.
 They have very large vacuoles and are
frequently found in all roots, stem, leaves
and in fruits.
 Parenchyma
cells help in synthesizing and
storage of synthesized food products.
 Parenchyma cells also controls plant's
metabolism like photosynthesis, respiration,
protein synthesis.
 They also play a vital role in wound healing
and regeneration of plants.
 Collenchymas
are a specialized parenchyma
tissue, which are found in all green parts.
 Collenchyma cells are elongated with
unevenly thickened walls.
 They are alive during the cell maturity.
 Collenchyma cells controls the functions of young
plants.
A collenchyma cell provides a support
to plants by not restraining growth,
which is caused due to their absence
of secondary walls and hardening
agent in their primary walls.
 They
are rigid, non-living cells.
 They have thick, lignified secondary walls
and lack protoplasts at maturity.
 They provide strength
A
sclerenchyma cell also provides a support
to plants with the help of hardening agent
present in their cells.
 Sclerenchyma cells are of two types:
 Sclereids:
They are short, irregular in shape
and have thick, lignified secondary walls
 Fibers: They are long, slender and are
arranged in threads.
 They
are specialized cells with transport of
water, hormone and minerals throughout the
plant.
 They contain transfer cells, fibers in addition to
xylem, phloem, parenchyma, cambium and other
conducting cells.
 They are located in the veins of the Leaves.
 The
term Xylem is derived from the Greek word
meaning Wood.
 They are dead with hollow cells, which consist of
only cell wall.
 They play a vital role in transporting water and
dissolved nutrients from the roots to all parts of a
plant.
 They transport the nutrients in the upward
direction .i.e. from the root to the stem, leaves
and flower.
 Xylem is also called as water-conducting cells.
 The
term phloem is derived from the Greek word
meaning Bark.
 They are live cells, which lack nucleus and other
organelles.
 They transports dissolved organic food materials
(sugars) from the leaves to all parts of a plant.
 They transport the nutrients in the downward
direction .i.e. from the leaves to the different
parts of the plant.
 Phloem is also called as sugar-conducting cells.
 The
structure of the cell varies according to
its function. The tissues are different and are
classified into four types:
 Epithelial
tissue
 Connective tissue
 Muscular tissue and
 Neural tissue.
 Epithelial
tissue is commonly referred to as
epithelium. The epithelial tissue forms the
outer covering or lining for some part of the
body.
 An epithelial tissue forms the surface of the
skin, lines many cavities of the body and
covers the internal organs.
 These
tissues have cells and fibers that are
loosely arranged in a semi-fluid ground
substance.
Areolar tissue - It is present beneath the
skin, it serves as a framework support for
epithelium.
Adipose tissue - This type of tissues is
specialized to store fats.
 Fibres
and fibroblasts are packed compactly
in dense connective tissue. Tendons are
dense regular tissue that attaches skeletal
muscle to bones and ligaments attach bone
to other bones. Collagen is the dense
irregular tissue present in the skin.
 Muscle
tissues are made of long cylindrical
fibres, arranged in parallel arrays. These
fibres are composed of fine fibrils known as
myofibrils. The contraction and relaxation of
moves the body to adjust to the changes in
the environment. Muscles are of three types
skeletal, smooth, and cardiac.
 Cardiac
muscle tissue is a tissue present only
in the heart. Cell junctions fuse the plasma
membranes of cardiac cells. Communication
junctions allow the cells to contract as a
unit.
 Neural
tissues control the body's responses to
the changing conditions. Neurons are the
units of neural system, they are excitable
cells. Glial cells and neurons are the cells
that form the nervous system.
 Organ
is a group of tissues in a living
organism that have been adapted to perform
a specific function in animals. e.g.,
the esophagus, stomach, and liver are organs
of the digestive system.
 The
main function of this system is to
transport nutrients and gasses
to cells and tissues throughout body. This is
accomplished by the circulation of blood.
 Cardiovascular:
 This system is comprised of the heart, blood,
and blood vessels. The beating of the heart
drives the cardiac cycle which pumps blood
throughout body.
This system breaks down food polymers into smaller
molecules to provide energy for the body.Digestive
juices and enzymes are secreted to break down the
carbohydrates, fat, and protein in food.
 This
system regulates vital processes in the body
including growth, homeostasis, metabolism, and
sexual development. Endocrine organs secrete
hormones to regulate body processes.
 Endocrine structures: pituitary gland, ovaries,
testes, thyroid gland
 This
system protects the internal structures of
the body from damage, prevents dehydration,
stores fat and produces vitamins and hormones.
 Integumentary structures: skin, nails, hair,
sweat glands
 This
system enables movement through the
contraction of muscles.
 Structures: muscles
 This
system monitors and coordinates
internal organ function and responds to
changes in the external environment.
 Structures: brain, spinal cord, nerves.
AMOEBA
An amoeba is a type of unicellular organism usually
found in water around decaying vegetation, in wet
soil and in animals such as humans.
Multicellular organisms are those which are made
up of many cells. Humans are multicellular.
Multicellular organisms can be much larger and
more complex.
 Brassica
 Brassica
campestris is the botanical name of
mustard (sarsoun). You are very familiar with this
plant since its oil (mustard oil) is used for cooking
and its leaves are used as vegetable (saag).
 Vegetative
parts
 1) Root: The root is that part, which grows
under the soil and develops from the radicle of
the seed. The first part of the root to arise
from the radicle is known as the primary root.
 Internal structure
 This
part of plant develops from the plumule
of the seed and grows away from the soil. It
bears branches and flowers. The point, on
the stem or on a branch, which gives rise to
leaf, is known as the node.
 Internal structure
 Leaves
grow out on the stem and its branches from
the nodes. Generally, the leaf of Brassica consists
of two parts. The lower stalk like part is the
petiole and upper green expanded portion is the
lamina.
Internal structure
 Flower
With growing age, Brassica plant bears small,
yellowish flowers. Flowers are the most beautiful
and important parts of the plant. They are arranged
on young branches in a special way. This special
arrangement of the flowers on the stem is called
inflorescence.
Parts of the flower
1.Calyx
2.Corolla
3.Androecium
4.Gynoecium
 The
frog lives both in water as well as on land.
 There is a membranous skin between its toes
which helps in swimming.
 There are five toes in each foot but the hand has
only four fingers because the thumb is
rudimentary.
 In male frog the first finger is thicker than the
others.
 Frog
has neither a neck nor a tail.
 As the head is directly attached to the trunk
frog cannot move it as we can.
 The conical head has two large bulging eyes.
Behind each eye is a circular area called
tympanic membrane.
 These membranes help in hearing.
 At the tip of the snout it has two openings
called external nostrils by which frog
breathes.
 The skin of the frog is loose and slippery. It
is slippery due to secretions produced by
glands present in it.
DIGESTIVE SYSTEM
Buccal cavity
Food enters into the buccal cavity through mouth. The upper jaw has a
row of weak but pointed teeth.
 Pharynx
The buccal cavity opens into a short but narrow pharynx, which leads
into a wide tube,, the oesophagus. Immediately behind the tongue on
the floor of the pharynx is a slit like opening, the glottis, which opens
into the lungs.

Oesophagus and stomach
Pharynx opens into a wide tube called
oesophagus or gullet; It transports food into the
stomach.

Intestine
The intestine is a long narrow coiled tube. It is
divisible into small and a large intestine. The
partially digested food from the stomach enters the
small intestine through pyloric end, where its
digestion is completed.
Liver and pancreas
The liver is a large reddish-brown gland located
adjacent to the stomach. Its secretion is known as
bile. Between the lobes of the liver is a rounded
pouch called gall bladder, which stores bile. A
bile duct arises from it. On its way, this duct
passes through pancreas and joins the pancreatic
duct. The pancreas lies between stomach and
duodenum, the first part of small intestine. Its
secretion, pancreatic juice, is carried by the
pancreatic duct. The pancreatic duct and the bile
duct join to form a common hepato-pancreatic
duct, which then opens into duodenum. The bile
and the pancreatic juice help in the complete
digestion of the food in the small intestine

 Energy
is required by every organism to carry on all
the life activities. It is produced by the oxidation
of food specially glucose.
 This entire process called respiration, divided into
two phases.
 a) Gaseous exchange or Extra-cellular respiration
 b) Cellular respiration.
 Frog has three types of respiration on the basis of
organs involved in the gaseous exchange. These
are:
PULMONARY RESPIRATION
 The
gaseous exchange, which takes place in
lungs is called pulmonary respiration. The
frog has two lungs, which are balloon like
structures. Their outer surface is smooth but
their inner surface has numerous folds which
increase the area for gaseous exchange. The
lungs are richly supplied with blood vessels
.
Each lung has a bronchus at its upper end.
The two bronchi open into a larynx. The
glottis opens into the larynx. During
respiration air is taken in by the external
nostrils. It passes into the buccal cavity
through the internal nostrils. From here it
enters the glottis, passes through the larynx
and bronchi finally reach the lungs. In the
lungs, exchange of gases between air and
blood takes place i.e. oxygen is taken up by
the blood and CO2 is given out, which leaves
the body through same route.
BUCCAL RESPIRATION
 The
lining of buccal cavity is thin, moist and richly
supplied with blood capillaries. Here also exchange
of gases takes place between the air and blood.
This type of respiration is called buccal respiration.
CIRCULATORY SYSTEM
 Heart-
strong muscular pumping organ.
 ii) Three kinds of blood vessels:
 (a) Arteries － Which carry blood away from
heart.
 (b) Veins － Which return blood to the heart.
 (c) Capillaries － Exchange material between
tissues and blood.
HEART
 Heart
is a conical, muscular pumping organ,
located in the anterior region of body cavity. It is
enclosed in a membrane called pericardium. It
contracts and expands continuously throughout the
life. This contraction and expansion of heart is
called heart beat, due to which blood circulates
continuously in the body. Frog heart consists of
three chambers.

 (i)
Right auricle or Atrium.
 (ii) Left auricle or Atrium.
 (iii) Ventricle.
The truncus arteriosus originates from ventral
side of
the ventricle and divide into two branches
each of
which divides into three arches (arteries).
A
blood vessel, which carries blood away
from heart to the various body parts is called
an artery. The arterial system can be simply
stated to comprise of the following three
main components.
 Pulmocutaneous arteries
VENOUS SYSTEM
The oxygenated blood from the lungs is collected
by pulmonary veins, which bring it to the left
auricle of the heart.
(ii) The deoxygenated blood from head and fore
limbs is collected through several veins, which
join together to form one major precaval vein, on
each side.
(iii) Blood from all the lower parts of the body such
as stomach, intestine, liver, pancreas, genital
organs, muscles, hind limbs etc, is collected
through veins, which join together and form one
major vein called post caval. Both the pre-cavals
and the post-caval open into the sinus venosus
from where the blood is pumped into the right
auricle of the heart.
EXCRETORY SYSTEM OF FROG
In frogs, waste materials are excreted out in many ways e.g.
skin, lungs, liver.
Digestive system. etc. It is the set of organs
involved in the process of excretion--that is, the removal of
metabolic waste- matters from the body.
Besides these organs.
Nitrogenous waste materials are excreted through
two kidneys, which are attached to the dorsal wall of the
body cavity These are elongated in shape and composed of
urinary tubules.
Urinary tubules combine to form collecting ducts,
which open into ureter.
The urine collected by the kidneys comes into
ureters.
Each ureter starts from the edge of each kidney of
its side and opens into cloaca.
From here, the urine is excreted or stored in
urinary bladder which is
passed out of the body from the cloacal aperture.
Carbon dioxide and water are excreted through
skin and lungs while undigested
food and some waste materials are excreted
through liver and digestive system.