Absolute & Relative Growth Video Lecture | Biology Class 11 - NEET

hello friends this video on plant growth
and development part 6
yes brought to you by exam feel calm no
more fear from exam so we will discuss
about absolute and relative growth rate
now this is a very important concept
which we which you should understand
very clearly because we spoke about
growth in this growth rate was present
in case of both and meta crude and
geometric growth here we will introduce
these two notes to differentiate between
a linear growth rate and an exponential
growth rate so let us see what is
absolute and relative growth rate the
term absolute growth rate means total
growth per unit time now these are
similar to the terms which you have
learnt in your physics like absolute
velocity and relative velocity so
anywhere it is relative it is compared
to something else tonight and absolute
means it has to be it has something to
do with composition so absolute growth
rate is total growth per unit time
whereas when you talk about relative it
is growth of a particular system per
unit time so relative growth rate is
always expressed per unit the initial
parameter so I'll explain it to you with
the help of an example okay so let us
suppose you have something like a say
you have a leaf the leaf it is a very
young leaf and it is going to grow over
a period of time let us suppose
initially the leaf had an area of say
five centimeter square over a period of
time the area became ten centimeter
square so when you talk about absolute
growth rate you just talk about the
increase in growth over that period of
fact that's all but when you talk about
relative growth rate you talk about the
increase in growth with respect
to the initial sites so the increase in
size that is it increased its size by 5
centimeter square so how much did it
increase with respect to what it was it
was 5 centimeter square now it became 10
centimeter square so the growth rate is
the relative growth rate is 100 percent
so it became 100 percent it became 2
times when compared to the initial size
so whenever we will talk about relative
growth rate will have a comparison to
the initial size whether it is initial
size or initial length or initial area
or initial cell size whatever it is so
that initial parameter comparison has to
be done when it is relative growth rate
but no such comparison is done in case
of absolute growth rate therefore
absolute growth rate grows linearly so
it will be like with increase with time
whereas relative growth rate grows
exponentially because whenever you
compare it with the initial parameter
the growth rate is like more so that
increases exponentially so now we will
take the same example and suppose you
take a leaf and the leaf increases in
size so when you talk about relative
growth rate you will compare the
increase with the initial size now we
will take the same example of the leaf
in the slide and with calculations we
will actually show how do we calculate
absolute growth rate and how do we
calculate relative growth rate so let us
take an example of two leaves so let us
suppose this is leaf one and this is
leaf - right now as you can see in the
picture it is quite evident that both
the leaves have different sizes right so
let us suppose the initial size of this
leaf is let me write it here so this is
my leaf one and this L is mine leave -
there is suppose in one
if one the area of the leaf is initial
area is 10 centimeter square
now since the leaf 2 looks bigger so
obviously the initial area here will be
more and let us suppose that the initial
area is 50 centimeter square so these
are just data nothing to link with
reality right so these are the initial
areas of these two beams now let us
suppose that over a period of time both
the leaves have grown and now leaf one
has become this much big the light green
area actually shows how much it has
increased leave to has also increased in
size now let us suppose the final area
of leaf one is 20 centimeter square
similarly the final area of leaf 2 is 60
centimeter square right now we have to
calculate absolute growth rate and
relative growth rate for both of them
now when you calculate absolute growth
rate now what I said absolute growth
rate has nothing to do with the initial
parameter so it has nothing to do with
what was the initial area of them leave
it will just calculate the growth per
unit time right so what is the growth
growth is final area minus initial area
that is equal to 20 minus 10 which is
equal to 10 centimeter square so this is
the increase in area so when you say
absolute growth rate so that will be
equal to increase in area per unit time
now let us suppose that both of them had
shown this increase in the area say in 1
hour so that is the time
right so this will become ten by one now
I'm not considering the unit conversion
and although stuff so here this denotes
your absolute growth rate similarly if
you calculate the absolute growth in it
for this one leave two this will also be
a F minus a initial divided by time so
what is a F 16-50 by time so this is
also ten per unit time so basically both
of them have the same absolute growth
rate because the increase is same in
both the cases here also the increases
and centimeter square here also the
increase is ten centimeter square
therefore the absolute growth rate is
same for both leave one and leave two
but when you calculate the relative
growth rate you notice the difference so
let us calculate the relative growth
rate so what is relative growth rate
relative growth rate will be equal to
the increase which is AF minus ki
compared to the initial area so this
will be divided by E I that is the
initial area per unit time so what will
be the answer a F minus K is 10 divided
by 10 so this is equal to 1 per unit
time so if you want to calculate it in
terms of percentage so you have to
multiply it with 100 percent so this
would be hundred percent would be the
relative growth rate right now similarly
if you calculate relative growth rate in
case of leaf 2 that will also be AF
minus AI divided by the initial e I per
unit time so this will be n divided by
initial AI is 50 so 10 by 50 per unit
time that is equal to
one by five per unit time and one by 5
if you want to calculate it in
percentage this will be 20 so this would
be 20 percent so the increase the
relative increase in growth for leaf
wine is 100 percent because here it
became double but here the increase
relative increase was only 20 percent
because initially the leaf was already
50 centimeter square so even though the
increase is the same here also it is 10
centimeter square increase here also it
is 10 centimeters well increase but
since here the initial value was more
therefore percentage increase or the
relative percentage increases only 20
percent so the relative growth rate is
different for both of both these leaves
so now you understand the difference
between absolute growth rate and related
truthly these understand this because
this is very very important this is a
very important concept right so that is
how absolute growth rate and relative
growth rate differs from each other okay
so we have spoken quite a few things
about growth now let us talk about
something very important what are the
conditions that are required for a plant
to grow so what are the inputs which
have to be given to your plant so that
it can grow so what are they water the
first and the primary necessity of a
plant so whatever so I will talk about
the advantages of water in the life of a
plant
they are like numerous so water helps
and photosynthesis which is a basic
requirement for a plant photosynthesis
is the process by which they prepare
food so whatever is required for food
preparation what prevents dehydration
now every living organism on this earth
for if all of them dehydration to
overcome be hydration is a challenge
nobody wants to die
because the moment it'd be hydrates it
is going to die so all that remains
dehydration it acts as a medium for all
the reactions which take place inside
the plant body for example there are so
many enzymes which participate in so
many metabolic reactions so water acts
as a medium for those enzyme making
activities minerals are also provided to
the plants in the by dissolving it in
water so they're also water acts as a
medium it helped me it also helps an
enlargement of cells because cells can
absorb water and that's how they can
enlarge vincent's water also acts as a
medium which can dissolve all the waste
materials from the cells of the plants
and then throw them out of the plant
body so that means water it is like it
serves multiple purposes and it is
something which is very very essential
for a plant to grow next is mineral
nutrients when I say nutrients I'm
talking about both micro and macro
nutrients we have spoken about all these
in one of our previous lessons like
right minerals nutrition so here we both
micro as well as macro nutrients metals
the nutrients which are needed in small
amounts as well as those which are
needed in large amounts both of them are
necessary for the growth of a plant for
example nitrogen phosphorus sulfur
calcium sodium potassium so all of them
are required for plant growth oxygen of
course it is required because you learnt
about the processes of photosynthesis
and respiration right oxygen plays a
very important role there so you see it
is needed temperature now each plant
means a specific
Venetia to grow for example if you take
a plant which is generally found in
extremely cold areas or in the heat en
masse like the pylons or the day order
if you try to bring them at in a in an
area which is very hot and it is not a
heating area you would not see much of
growth of those plants
so each plant has a specific requirement
of temperature some grow well in higher
temperatures whereas some of the terms
grow well in lower temperatures so
temperature also plays a critical role
in the growth of a plant light of course
plant cannot survive without light light
play is one of the most critical role in
the process of photosynthesis the
pigment chlorophyll its main job is to
absorb some absorb some frequencies from
the visible light so light plays a very
important role light also effects the
flowering in a plant like some plants
need a large exposure to sunlight to
flowering in some plants need very
little exposure to sunlight to flower so
light also plays a critical role for the
growth of a plant gravity gravity again
when we talk about the Tropic movements
of a plant how plants grow you would
actually see that the role roots of a
plant always grow with inside the soil
they keep on going deeper and deeper
inside the soil and that their gravity
plays a role it is because they get
attracted towards gravity and because of
which they keep on growing towards that
so that also we will talk about when we
talk about the tropic movements in
plants so these are some of the
important conditions which are very much
required for growth of a plant thank you
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