Role of light in Animals - Organisms & Population, Biology, Class 12 Video Lecture

hello friends this video on organisms
and population part 9 is brought to you
by exam for your form no more fear from
exam now not only plants light also
plays an important role in animals now
this might sound a little viewed at once
because you might think that how is
light directly impacting animals now I
will give you a lot of instances where
light directly affects animals so some
of the aspects in case of animals where
light plays an important role are
pigmentation animal movements the
production and photoperiodism so let's
discuss each of these one by one so
first let's talk about pigmentation so
when it comes to pigmentation the first
thing that we can think of is the
coloration of skin of animals which is
very strongly influenced by light so you
would have seen that if you stay in the
Sun for quite a few days what happens
your skin color tends to become darker
so what I mean what happened to your
skin color that's because under the
influence of light the pigments which
are responsible for a button skin color
so those pigments get affected in
presence of light and as a result the
the skin color becomes darker and
because of the same reason you would
have seen that humans living in the
tropical areas that is near the
equatorial region which receive more
light are darker our skin gets darker in
the Sun so if you compare somebody who
is living in India with somebody who is
living in say United States or say you
know so you would see a difference in
the skin color at this jet this happens
due to the exposure of light in
different regions let's look at some
examples like frog wall lizards they
often look light in color in
like sunlight so because sunlight has a
direct impact on the pigments which
imparts color to our skin
the next impact of light on animals are
with regards to their movements so a lot
of movements in animals are like
directly impacted by light so let's see
how specially this type of movement
specially happens in lower animals for
example you talk of euglena so you clean
up you talk of this animal you would see
that it will always move towards the
source of lights of available light is
coming it tends to move in that
direction similarly these type of
animals are known as positively
phototactic animals positively because
it is moving towards light so positive
photo is like tactic means it is like
attracted towards light so these are
four positively phototactic animals
similarly we also have negatively
phototactic animals and one such example
is earth on so earth warm always tends
to move away from the light source is
always wants to move towards darkness so
these are called negatively phototactic
animals so these type of movements are
also influenced by light you think of
reproduction even reproduction in a lot
of animals are influenced by light so in
many animals light activates the
breeding season for example specially in
birds they are more active for
reproduction activities during summer
than winter because light activates
their breeding activities
so therefore reproduction process
happens for a frequency giving summer
than winters now there exist different
types of animals based on their activity
in light like some animals are more
active during the day some animals are
more active during the night
so let us look at the different types of
animals so diurnal animals are those
which remain active during the day
so examples of such animals are the
birds butterflies there are diagonal
animals we talk about nocturnal animals
which are active during Bank the best
example would be the owl the bat they
remain active at night all are all
animals are those which are active
during dawn dawn is the early morning
time so examples could be the Belkis
which is a bird like as you can see on
the screen Vespa other animals are those
which are active during dusk that is the
time during the evening the time during
sunset so examples are rabbit so you see
different animals are at more active
during a specific part of the day now
what happens throughout the day so
during the daytime there is maximum
sunlight during night there is no light
during dawn again during dawn and dusk a
kitten's limited sunlight so depending
upon how much light is present the
activity of so many animals are impacted
so that means we can see that light
influences animals as well so if some
animals are influenced in their
movements some animals become more or
less active with presence or absence of
light some animals their skin color and
pigmentation are impacted by light thank
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