biology organisation in living things
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BIOLOGY ORGANISATION IN LIVING THINGS
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Organisation in Living Things
Our world is made up of living and non-living things. There are many traits which help us to identify the
difference between them. Let us study a little more in detail about living beings.
Characteristics of Living Beings
The following characteristics can be observed in living beings only.
RESPONSE TO STIMULI
•The immediate reflex action or response to changes in the surrounding environment is observed only in living beings.
•For example, when you accidentally touch a hot vessel, you take your hand back immediately.
GROWTH
•Living things go through various stages of development and show growth, a characteristic which is not seen in non-living things.
REPRODUCTION
•Living things have a unique characteristic of producing offspring of their own kind.
NUTRITION AND
RESPIRATION
•Living beings require food and water for survival.
•They use oxygen to release the chemical energy stored in food.
LIFE SPAN
•All living beings have a definite period of life.
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Organisms are unicellular or multicellular. Organisms whose entire body consists of a single cell are
termed unicellular organisms (Amoeba and Paramecium) and organisms whose body consists of many
cells are termed as multicellular organisms (Mango tree, human being, cow etc.)
In a multicellular organism, different cells are present which perform different functions. Let us study the
levels of organisation.
Cell
The basic structural and functional unit of life.
Tissue
A group of cells specialised to perform a particular function.
Organ
Different tissues make up an organ.
Organ System
Several organs performing a related task make up an organ system.
Organism
Different organ systems make up an organism.
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Plant Tissues: Location and Function
Meristematic Tissue
Cells are small, polygonal shaped and arranged without intercellular spaces.
The cells have thin cell walls, dense cytoplasm and large nuclei.
Types of Meristematic
Apical meristems
These are found at regions such as tips of stems and roots, where they bring about an increase in
the length.
Lateral meristems
These are found along the entire length of the root and stem, where they bring about an increase in
the thickness.
Plant Tissues
Permanent Tissues
Dermal Tissues
Vascular Tissues
Xylem Phloem
Ground Tissues
Parenchyma Collenchyma Sclerenchyma
Meristematic Tissues
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Functions of Meristematic
The cells produce new cells resulting in the growth of plants which is evident from the increase in length
and thickness.
They produce different types of cells, each of which performs a particular function for the plant.
Permanent Tissues These tissues are made up of cells that do not divide. They are classified into the following categories:
Dermal Tissue: It is a simple tissue consisting of similar cells. It is the outermost protective covering of
all parts of the plant, such as root, stem and leaves. Cells are flat and rectangular in shape and lack
intercellular spaces. A waxy, water-proof covering called cuticle is produced by dermal tissue, except in
the roots.
Ground Tissue: It is a simple tissue consisting of similar cells. This tissue provides mechanical support
and forms the bulk of the plant body. It is further divided into
PARENCHYMA
•It has thin-walled round or oval-shaped cells with spaces between them.
•It is present in the stem, leaves, flowers, fruits and seeds.
•Most parenchyma contain leucoplasts and store food.
•Chloroplast-containing parenchyma are called chlorenchyma and are involved in photosynthesis.
•Parenchyma with large air spaces are called aerenchyma, which is found in aquatic plants.
COLLENCHYMA
•It consists of elongated cells with thick cell walls to provide mechanical strength.
•A mixture of cellulose and pectin makes up its cell wall.
•It is found in non-woody plants, leaf stalks and veins of leaves.
SCLERENCHYMA
•It is long, narrow, fibre-like cells pointed at both ends.
•Mechanical strength is provided by cell walls which are thick and contain lignin.
•It is usually found in patches.
•The fibres from jute and coconut are sclerenchyma.
•Cells which are oval or round in shape are found in fruits like pear; these are known as stone cells.
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Vascular Tissue: It is also known as conducting tissue. The different cells unite and perform a certain
function. Xylem and Phloem are vascular tissues. They run throughout the plant and are involved in
transport of materials within the plant. In the stem, xylem and phloem occur together as distinct bundles
called vascular bundles-where the xylem lies towards the centre and the phloem lies outside. They are
examples of complex tissue, i.e. tissue consisting of different cells.
Vascular Tissue
Xylem
Conducts water and minerals
from the roots to the leaves.
Consists of tracheids and
vessels; however, both of
these are dead cells.
Phloem
Transports food materials in
both upward and downward
directions.
Consists of living cells,
primarily sieve tube cells and
companion cells.
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Animal Tissues – Location and Function
They are broadly classified into epithelial tissue, connective tissue, muscular tissue and Nervous tissue.
Let us learn in brief about each.
Type of Tissues Characteristics Location Function
Epithelial Tissue
Epithelial tissue
1. It consists of closely
packed cells.
2. The cells form a
continuous layer.
3. What the skin is to
the potato, the
epithelium is to an
organ.
1. Covers the whole
body surface.
2. Forms the external
and internal lining
of many organs as
well as cavities of
the body.
1. Protection
2. Reproduction
3. Absorption
4. Secretion
5. Sensory
perception
Types of Epithelial Tissues
Squamous epithelium
1. Cells are large,
extremely thin and
flat.
2. The cells are placed
on a thin basement
membrane and have
central nuclei.
The lining of blood
vessels, alveoli of
lungs and inner lining
of cheek.
1. Transports
substances
through a
selectively
permeable
membrane.
2. Protects the body
from infection,
e.g. skin.
Columnar epithelium
1. Cells are tall and
cylindrical and are
arranged like pillars.
2. The height of cells is
greater than their
width.
3. Nuclei are found at
the base of cells.
They are oval in
shape.
Found where
absorption and
secretion occur, as in
the inner lining of the
stomach, intestines
and gall bladder.
1. Secretes
digestive
enzymes.
2. Absorbs nutrients
from digested
food.
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Ciliated columnar epithelium
Cells possess fine hair-
like outgrowths called
cilia on their free
surface.
The inner lining of the
wind pipe or trachea,
lungs, respiratory
system and buccal
chambers.
In the respiratory
tract, the cilia move
and their movement
pushes the mucus
forward to clear it.
Cuboidal epithelium
1. Cells are cube-
shaped and are
placed on a
basement
membrane.
2. It is composed of a
single layer.
1. Secretive or
absorptive tissues.
2. The lining of the
salivary glands and
thyroid glands.
1. Helps in the
absorption of
useful material
from urine,
before it is
passed out.
2. Helps in the
secretion of
saliva.
Connective Tissues
Connective tissue
1. They have large
spaces between
them which are filled
up with fluid or solid
secretion products of
the cell.
2. Hence, a matrix is
formed which may be
soft, hard or liquid
and may contain
fibres to increase the
mechanical strength
of tissues.
1. Found in deeper
parts of the body in
between skin and
muscles.
1. Connects various
organs and
keeps them in
proper place.
2. Provides support
to organs.
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Types of Connective Tissues
Connective tissue proper
Encloses all organs
and body cavities.
Binds and supports
structures within the
body.
Loose (areolar) connective
tissue
1. The matrix is soft.
2. Matrix consists of
scattered irregular
cells.
1. Found beneath the
epithelia.
1. Fills the space
inside the organs
and supports and
strengthens the
internal organs.
2. Helps in repair of
tissues.
Dense connective tissue
1. It contains more
fibres than the loose
connective tissue.
1. Tendons
(connecting
muscles to bones)
are dense
connective tissues
containing only
fibroblasts and
collagen fibres.
2. Ligaments
(connecting the end
of bones in a joint)
contain both
collagen and elastic
fibres.
Provides flexibility to
ligaments and tendons
which help in
movement.
Specialised Connective Tissues
Adipose tissue
1. Cells are filled with
fat globules, situated
in a large central
vacuole of a cell,
pushing the
cytoplasm and the
nucleus to the
periphery.
2. A loose framework
of areolar tissue
supports these cells.
1. Found beneath the
skin, between the
coils of the
intestines, around
the kidneys.
1. Stores energy in
the form of fats.
2. Protects the
internal organs.
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Cartilage
1. It is a supporting
tissue.
2. Deposition of
inorganic salts such
as calcium hardens
the matrix.
1. Lies mostly in
groups within
special spaces
called lacunae.
2. Present in the nose,
external ear etc.
3. Present between
bones
1. Smoothens the
bone surface at
joints, allowing
smooth movement
of these joints.
2. Provides shape,
support and
flexibility to the
body parts such
as nose and
external ear.
Bone
1. It is harder than the
cartilage and has a
hard matrix.
2. Matrix contains
large quantities of
phosphates and
carbonates of
calcium and
magnesium.
3. A large number of
Haversian systems
make up the bones;
each system has a
central Haversian
canal containing
blood vessels and a
number of lacunae
arranged around it
in concentric circles.
Bone cells are located
within the lacunae
which are
interconnected
through canaliculi.
1. Provides support to
the body.
2. Helps in movement.
3. Protects the
internal organs.
Blood
1. It has a liquid matrix
to transport nutritive
materials,
respiratory gases,
excretory materials
and other
substances.
2. It consists of 55%
plasma and 45%
blood cells.
3. The plasma is
strawberry coloured
and watery
Present throughout
the body.
Connects different
body parts and
establishes continuity
within the body.
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containing about
90% water, the rest
is salts and proteins.
4. RBCs (Erythrocytes)
are circular,
biconcave discs
lacking nucleus and
containing
haemoglobin.
5. WBCs (Leucocytes)
are shapeless,
lacking any pigment.
They protect the
body from diseases.
6. Platelets
(Thrombocytes) clot
blood when vessels
are damaged.
Muscle Tissues
Muscle tissue
1. Consist of
elongated, narrow,
muscle cells called
muscle fibres.
2. As muscle cells are
drawn into long
structures, they are
also called muscle
fibres.
Mostly attached to the
bones.
Help in contraction
and relaxation, which
facilitates movement
of the body.
Types of Muscle Tissues
Voluntary muscles
1. Voluntary muscles
are under our
conscious control.
2. Each cell is long,
cylindrical and has a
number of nuclei
placed along its
outer edge.
3. The cells are
bundled up and
enclosed in
connective tissue
sheaths which
continue as a
tendon connecting
1. Found attached to
bones.
2. Because these
striated muscles
are attached to the
skeleton, they are
termed as skeletal
muscles.
Help in voluntary
muscle movement and
locomotion.
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these muscles with
bones.
4. They are also known
as striated muscles.
Involuntary muscles
1. They consist of
spindle-shaped
cells, each with a
centrally located
long nucleus.
2. A sheet of muscle
tissue is formed by
the arranged cells.
3. They are not under
the control of one’s
will and hence
termed as
involuntary muscles.
1. Ureters
2. Digestive tract
3. Urinary bladder
4. Iris of the eye
5. Internal organs
1. Carry out
movements which
cannot be carried
out by our
conscious will, e.g.
movement of food
in the alimentary
canal, blinking of
eyes, breathing etc.
Cardiac/heart muscles
1. The cells are
arranged end to end
and branch and
unite to form a
continuous network.
2. Each cell has a
single centrally
located nucleus.
Found only in the
walls of the heart.
1. Rhythmic
contraction and
relaxation of
cardiac muscles
help to pump and
distribute blood to
various parts of the
body.
Nervous Tissues
Nervous/neural tissue
1. Highly specialised
cells called neurons
make up the
nervous tissue.
2. Neurons transmit
messages within the
body.
3. There are two sets
of fibres - axons and
dendrites. Axons
maybe naked or
covered by a fatty
substance.
Components of the
nervous system,
including the brain,
spinal cord and
nerves.
1. Nerve cells
mediate the
transmission of
messages from
the brain to
different parts of
the body and vice
versa.
2. The dendrites
transmit the
messages towards
the cell body, while
the axon carries
them away from
the cell body.
3. Nerve impulses
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allow the
movement of
muscles.
Organs in Animals and Plants
A group of tissues working together and performing a common function makes up an organ. A
multicellular organism has several organs.
Certain organs perform a single function, e.g. eyes are concerned with sight. However, some organs have
multiple functions. The liver produces bile, destroys worn-out red blood cells and so on. The roots of
plants absorb water and minerals along with fixing the plant in the soil. The leaves help in photosynthesis,
transpiration and exchange of gases.
Organs System
Several tissues make up an organ, and several organs together make up an organ system. A single organ
cannot perform all the necessary functions in the body. The heart works with organs such as arteries,
veins and capillaries. It functions well in pumping the blood and keeping it in circulation. Hence, the heart
and the related organs together form an organ system called the circulatory system. An organ system
consists of a group of different kinds of organs working together to perform related functions. Let us study
the different organ systems in the human body.
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Circulatory System
- Consists of the heart, arteries, veins,
capillaries, blood, lymph and lymph vessels
- Transports materials throughout the body
Respiratory System
- Consists of the respiratory passage and
lungs
- Exchange of respiratory gases during
breathing
Muscular System
- Consists of different types of muscles
- Movement of different body parts
Skeletal System
- Consists of bones and cartilage
- Provides the body with a definite shape
- Protects the internal organs of the body
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Digestive System
- Consists of mouth, oesophagus, stomach, digestive
glands, intestines and rectum
- Breaks down food to simpler forms that can be
utilised by the body
Endocrine System
- Consists of pituitary, thyroid and adrenal glands
- Hormones produced by these glands influence
growth and other activities
Reproductive System
- Consists of testes in males and ovaries in
females
- Responsible for the continuation of species
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Excretory System
- Consists of the kidneys, urinary bladder,
ureters and urethra
- Removes the waste products from the
body
Integumentary System
- Includes the skin, hair and nails
- Keeps the germs out of the body and
protects the organs from mechanical
injuries
- Regulates the body temperature and is
involved in excretion in a small way
Root System in Plants
- Consists of main and branched roots
- Helps in fixing plants to the soil
- Absorbs minerals and water
Shoot System in Plants
- Includes all the parts above the soil like
stem, leaves etc.
- Involved in transportation of materials,
preparation of food etc.
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Higher Levels of Organisation
We have studied the lower levels of organisation. Let us now look at the higher levels.
A brief explanation about each level is given below.
Population Level
An organism needs to associate with other individuals of the same species for survival and continuity of
its own race. The individuals of the same species resemble each other in appearance having only
minor differences.
Community Level
An example of the community is a garden. It includes a variety of flowering plants, different kinds of
insects, birds and rodents. Hence, the population of different kinds of species found together constitute
a biotic community.
BIOSPHERE
The sum of all the existing ecosystems on our planet
ECOSYSTEM
The community along with physical space and conditions under which they exist
COMMUNITY
The population of different species found in a particular place
POPULATION
All the organisms of the same species living in a particular locality
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Ecosystem Level
The living communities in an area interact with the non-living environment. Two or more communities
together constitute an ecosystem. Examples: Forest, mountain, a paddy field, a pond etc. However, an
aquarium is an artificial ecosystem.
Biome
A group of ecosystems taken together in a geographically localised area with the same type of climatic
conditions. In simpler terms, it is a big-sized ecosystem with the same climatic condition. Few common
examples of biomes are the Thar Desert in India, the Sahara Desert in Africa, evergreen forests,
alpine forests, seas, huge lakes etc.
Biosphere Level
It includes the entire inhabited part of the earth, the water, the atmosphere and its living and non-living
components. The biotic components include plants, animals and microbes and the abiotic components
include the physical environment, soil and atmosphere. The biosphere surrounding the earth is divided
into three parts:
o Hydrosphere
It includes the water bodies on earth such as oceans, seas, rivers, streams and ponds. Life
exists up to 5 km below the sea level.
o Lithosphere
It represents the solid bedrock of the earth’s crust such as rocks, soil and nutrients.
o Atmosphere
A layer of gases envelopes the hydrosphere and the lithosphere on the earth, which is known as
atmosphere. Organisms exist up to 7–8 km in the air above the sea level.
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Principles of Biological Organisation
The unit of higher level is formed by the smaller units in the lower
level of organisation.
The system becomes more complex in terms of structure and functions as one goes higher in
the level of organisation.
The unit of level or organisation is independent in its mode of
existence and activity.
Each level of organisation has its own specialised structure and
function.
Every step of organisation combines the lower level making
a more complex system.
Any damage done at the higher level may not have any effect on the lower levels, however, any damage done at the lower level
will affect the higher level.