Unicellular and Multicellular Organisms (Easy Explanation) Video Lecture - Class 9

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now we will look at the classification
of organisms based on the number of
cells now how many cells are present
inside the body of a living organism now
just now I was telling that we human
beings we are made up of many cells so
how do we know which organisms are made
up of how many cells now based on the
Lampoon of cells present in a living
organism organisms are divided into two
categories unicellular organisms and
multicellular organisms now I don't
think I really need to explain
unicellular is made up of one cell
multicellular is made up of many sense
so these are the two broad categories of
organisms so let us quickly have a look
at the unicellular organisms let us look
at water unicellular organisms so one
cell constitute the entire organism so
let us look at some of the you know here
in these organisms there is just one
cell so all the life processes for
example the processes which take place
inside a be every any living organism
whether it is digestion or excretion or
respiration so everything is taken care
by this one cell so single cell performs
the basic functions that are
characteristic of the organisms so how
to get food how to digest the food how
to absorb the food everything is done by
that single cell so one such example is
amoeba there are any other examples so
to start with anybody if you look at
amoeba they are shapeless they do not
have a specific shape it is a
microorganism very small in size
they are generally found in marine
regions where there is water for example
the decaying bottom vegetation of
freshwater lakes or ponds so that is
where you generally see them so amoeba
is one such unicellular organism where
this particular organism which you see
that is nothing but one cell so this
cell will manage to do everything cell
has changing shape this next example
would be chlamydomonas this is a green
algae so I'll give you generally would
have seen this on the surface of water
you often see that there is a green
layer which is formed so that is nothing
but algae so Chlamydomonas is an example
of one such algae which is again
unicellular made of one cell so this is
how the structure of chlamydomonas looks
like this is just one cell and inside
the cell you have a nucleus you have a
chloroplast you have the flagella for
movement so these are the different
structures inside the cell the third
example would be Paramecium they have
Syria for locomotion they are also a
type of protozoa we again we find the in
general in freshwater ormaline
environments they are often termed as
slipper animal too because of the their
shape which resembles a slipper again
the most important unicellular organisms
with bacteria they are they come in a
variety of shapes and sizes they are
considered amongst the first life-forms
on earth it is said that all of the life
forms evolved from bacteria you find
them in a number of cases they are C
found in water soil inside the body of
plants or animals so they are found in
quite a few places so that was about
unicellular organisms let us now talk
about multicellular organisms now what
happens in those organisms
too many scents and present so many says
constitute the organism best example
would be tunings now one important
characteristic feature of multicellular
organism institution of label I don't
think I need to explain it because I
think I have explained it quite a number
of times in the previous lessons but
still just a short recap division of
labour is that concept where all the
cells in the living organism do not
perform the same function a group of
cells perform one function another group
of cells perform another function and so
on so it is like the entire task is
divided into sub tasks and each sub task
is assigned to a particular group of
cells so that is known as division of
labor so this concept comes into picture
only in case of multicellular organism
because that is quite obvious for
unicellular there is just one cell so
where do you divide the work there is if
there is one person in the team that
person has to take care of all the work
but if there are ten members in the team
you can divide the work amongst them so
similar is the case here so some
organisms or have sense of various kinds
our examples of multicellular organism
is human being now in human being only
we can see that inside our body we have
so many cells but all cells are not
alike all the cells are not similar just
think of all these cells think of the
blood cells the white blood cells and
the red blood cells even all of them are
not similar some are round in shape some
are by concave in shape some have
amoeboid shape irregular shape you think
of the nerve cell it has got a very
different shape all together it is quite
long and then it has branches think of
the bone cell osteocyte again it has a
different appearance the smooth muscle
fibers they are low with tapering ends
again that is very different the fat
cell or the adipose cell so they have a
different appearance the sperm cell or
the egg so all the cells they
I mean I have not taken example of all
the cells present inside the human body
but some of them have been shown in this
screen and you see that they differ from
each other in so many ways so one
organism can have cells of many
different kinds no all good cells can
have different shapes because they are
to perform different function they might
have different sizes again depending
upon their location and their function
so that means in case of a multicellular
organism many cells when present there
many cells will be present in the
organism but there will be the concept
of diffusion of Labor one new group of
cells will perform one function and
another group will take up another
function and so on and also the variety
of cells will also be huge and you saw
that all the cells has to be similar
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