biology organisation in living things

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.



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.



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



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.



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.



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.



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.



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.



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.



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.



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



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.



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



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



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.



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



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.



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.

biology organisation in living things

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