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DEPARTMENTAL SEMINAR PRESENTATION
DEPARTMENT OF BIOLOGICAL SCIENCES,
COLLEGE OF SCIENCE AND TECHNOLOGY,
COVENANT UNIVERSITY, OTA
TUESDAY 6TH FEBRUARY, 2018
01-May-18Pondering on Light: A friend or foe? - DedekeGA 1
PONDERING ON LIGHT-A
FRIEND OR FOE?DEDEKE, GABRIEL ADEWUNMI
Associate Prof. Eco-Physiology
Federal University of Agriculture, Abeokuta
01-May-18Pondering on Light: A friend or foe? - DedekeGA 2
Outline:
Answering the question “What is light and
its uses”
A look at the nature of light
What concerns an Ecophysiologist with
light?
Light Pollution
Some impacts of visible light on animals
Conclusion
01-May-18Pondering on Light: A friend or foe? - DedekeGA 3
All the fifty years of conscious brooding
have brought me no closer to answer the
question “What are light quanta” Of
course today every rascal thinks he
knows the answer, but he is deluding
himself – Albert Einstein
01-May-18Pondering on Light: A friend or foe? - DedekeGA 4
What is Light?
God said let there be light – Light
phenomenon has miffed man since
ancient times and all life is considered
to have emanated from light; light is
mysterious to us even till now
Light, in the modern age, has
contributed to further civilization and
improve our daily lives
01-May-18Pondering on Light: A friend or foe? - DedekeGA 5
Lights…
There are different kinds of light:
X-rays and Gamma rays, UV, Infrared –
Invisible to the eyes are also different kinds
of lights and visible rays
By wavelength classification, the shorter the
wavelength the higher the energy
(frequency) –
shorter wavelength rays (X-rays & Gamma-
rays) have 10,000 -100,000 times more
energy than visible rays01-May-18Pondering on Light: A friend or foe? - DedekeGA 6
Source:- AgriShift, 2014
Electromagnetic spectrum
01-May-18Pondering on Light: A friend or foe? - DedekeGA 7
Where does light come from…?
There are two kinds of radiation in luminous
phenomenon
1. Natural radiation – creates light by heated
bodies and by low pressure gases – neon, mercury
light
2. Induced radiation – creates a laser beam
In both mentioned above, it occurs when the energy
conditions of electrons inside the substances change.
The energy release then is the light and the
luminous phenomenon occurring in this way is called
natural radiation01-May-18Pondering on Light: A friend or foe? - DedekeGA 8
Induced emission of radiation is a matter of
creating coherent light by amplifying light
generated by the spontaneous emission from
electrons in the metastable state.
The amplification takes place when light is
reflected repeatedly between two mirrors, the
mirrors form a resonant light wave. Because the
light generated by the induced light process has
the same wavelengths and phases, it does not
diffuse even when projected over long distances.
Moreover, when this light is collected, we can get
energy of high density – laser beam.
01-May-18Pondering on Light: A friend or foe? - DedekeGA 10
Use of Light around us
X-ray can be
used to generate
images of the
sun to show
clear
distribution of
the temperature
and lines of
magnetic force
on its surface
01-May-18Pondering on Light: A friend or foe? - DedekeGA 11
X-rays and Gamma-rays are used among other things to investigate
the structure of substances, to control germination of plants and to
cure cancer by using the their high transmission ability and chemical
action
01-May-18Pondering on Light: A friend or foe? - DedekeGA 12
Computer
tomography (CT)
has revolutionized
the world of
medical diagnosis,
it makes a picture
by computer
analysis of the
transmittance of
x-rays01-May-18Pondering on Light: A friend or foe? - DedekeGA 13
Ultraviolet rays are used
for sterilization,
disinfection,
cultivation of plants,
phototherapy,
used in factories which manufacture electronic parts,
used in forensic investigation
aurora image sent by satellite are visible even in daylight when viewed by UV-light,
01-May-18Pondering on Light: A friend or foe? - DedekeGA 14
Infrared rays passed
easily through the air,
hence, are used
to send cloud
photograph captured by
a weather satellite,
for research of natural
resources in geology,
measuring
environmental
pollution,
their heat effect is
useful in medical and
industrial field and also
in many products,
analyzing ancient arts
and writing, 01-May-18Pondering on Light: A friend or foe? - DedekeGA 15
Thermography
converts
infrared rays
radiated
naturally from
the human body
into a picture
indicating the
distribution of
temperature
which is used in
the diagnosis of
diseases01-May-18Pondering on Light: A friend or foe? - DedekeGA 16
Nature of Light…Is light a wave?
Thomas Young, an English Physicist, in 1807,
by his Interference experiment, asserted that
light has the properties of a wave
Further experiment using filters showed that
the region of strong beam consists of high
number of particles massing together while
the region of no light has sparse particles in
them.
01-May-18Pondering on Light: A friend or foe? - DedekeGA 17
Nature of Light…Is light a particle?
In 1905, Albert Einstein in his light quantum hypothesis now
a theory, succeeded in explaining the photoelectric effect
which had been unexplainable because light was considered
only as a wave.
He asserted that light is a particle containing energy
corresponding to their wavelength.
When blue light is irradiated on metal, it emits electrons from
it. However, when red light is used no electron emission is
observed – hence blue light is particles with high energy
capable of emitting electrons while red light is particles
containing low energy not capable of emitting electrons
Light is therefore, in this way, came to be called photons
(light quanta)- clusters of energy containing energy.
01-May-18Pondering on Light: A friend or foe? - DedekeGA 19
Light…is it a wave or particle?
The two observations showed that light has two
characteristics - a wave as well as particles.
It behaves as waves:
when it proceeds or propagated through space – light
propagation.
It behaves as particles:
when energy conversion is a concern such as in the
photoelectric effect, where light interaction with
materials occurred and light is absorbed and emitted.
The various properties of light, are due to the behavior of
extremely small particles called photons that are invisible to
the naked eye..01-May-18Pondering on Light: A friend or foe? - DedekeGA 21
The first ever
photograph of
light as a particle
and wave – Ecole
Polytechnique
Federale de
Lausanne (March
2, 2015)
01-May-18Pondering on Light: A friend or foe? - DedekeGA 22
‘…..we need to become more aware that “light isn’t just light; analysis of the spectral nature of light which we create, and fill our nocturnal world with, is critically important. …… spectral
quality plays a key role in every system………’(Anonymous).
For the rest of my life I will reflect on what light is – Albert Einstein
Should we be concerned with all these?
01-May-18Pondering on Light: A friend or foe? - DedekeGA 23
What concerns an Eco-Physiologist in all these?
Having established that light is more than just the one we
see, my focus will now be majorly directed at a tiny portion
of the electromagnetic spectrum - the visible light
We all are acquainted with the visible light. In some
immediate past, the cry of “up NEPA” and “aww! What’s
wrong with this NEPA?!” rends the air whenever power
outage occurs, especially at night.
The major reason for this uproar all the time, is that apart
from our dependence on electric power for several domestic
and industrial purposes, it is also our source of light in the
night.
The bottomline, light has profound effect on us and our
environment .01-May-18Pondering on Light: A friend or foe? - DedekeGA 24
Visible Light defined
Light in an optical radiation with a spectral power
distribution anywhere within the “visible region”
of the electromagnetic spectrum (approximately
380 nm to 730 nm) radiating from a source (Rea et
al., 2010).
From what has been said it is also evident, that the Whiteness of the Sun’s
light is compounded all the Colours wherewith the several sorts of Rays
whereof that Light consists, when by their several Refrangibilities they are
separated from one another, do tinge paper or any other white Body whereon
they fall. For those colours…are unchangeable, and whenever all those Rays
with those their colours are mix’d again, they reproduce the same white light
as before – Sir Isaac Newton
01-May-18Pondering on Light: A friend or foe? - DedekeGA 25
Seeing light in another light
An article I read on the sea turtles’ hatchlings
and the impact of light pushed me to see light
in another light.
I began to see light in another light from then
on; light has profound effects on us, other
animals and our environment than we ever
thought about of.
Then I also came across the term light
pollution01-May-18Pondering on Light: A friend or foe? - DedekeGA 26
The bright lights from coastal communities
Dave Armstrong 2012 01-May-18Pondering on Light: A friend or foe? - DedekeGA 27
What is light pollution?
Light pollution is defined as any alteration of the
natural quantity of light due to the introduction of
artificial light, in particular if this light is dispersed off
the horizontal plain and/or induces negative effects on
living organisms”( Elena and Paolo, 2010).
Light pollution is also defined as the alteration of
natural light levels in the night environment produced
by introduction of artificial light (Fabio et al., 2011).
01-May-18Pondering on Light: A friend or foe? - DedekeGA 28
Types of Light pollution
Three types of light pollution as identified by
Longcore and Rich (2010) are:
Ecological light pollution- “artificial light
that alters the natural patterns of light and
dark in ecosystems.”
Astronomical light pollution - light that
interferes with the view of the night sky.
Aesthetical disruptive light – light that
affects animal physiology01-May-18Pondering on Light: A friend or foe? - DedekeGA 29
Sources of Artificial light pollution
Sports facilities,
Commerce,
Retail,
Agriculture,
Buildings,
Monuments,
Mineral extraction,
Airports,
Sea ports,
Roads,
Streets,
Junctions,
Pedestrian paths and
Parking areas
Significant sources of light pollution as identified by Department for
Communities and Local Government, London (1997) include;
01-May-18Pondering on Light: A friend or foe? - DedekeGA 30
Animals are affected by HPS lighting interference
Dave Armstrong 201201-May-18Pondering on Light: A friend or foe? - DedekeGA 31
Effect of Artificial light pollution
Interrupting Dormancy in animals
Alteration in Activity levels
Disruption of bioluminescent behavior
Altering effect on Migration
Alteration of reproductive cycle in animal
Disruption of orientation in animals01-May-18Pondering on Light: A friend or foe? - DedekeGA 32
Behaviour of Loggerhead Sea Turtles on an
Urban Beach II: Hatchling Orientation
Artificial lights, both from nearby or from distant sky glow, can confuse the hatchlings and cause them to crawl onto roads or into communities, often leading to fatal exhaustion, dehydration, predation or even being crushed by cars.
Source: Michael Salmon, Melissa G. Tolbert, Danielle P. Painter, Matthew Goff and Raymond
Reiners (1995). Journal of Herpetology, 29 (4): 568-576 Department of Biological Sciences,
Florida Atlantic University, Boca Raton, Florida.01-May-18Pondering on Light: A friend or foe? - DedekeGA 33
Ecological Impacts of Light Pollution on Wildlife:
Amphibians as Models1. Chronic exposure of Plethodon cinereus to artificial night lighting limit
foraging opportunities, which leads to reduced growth and reproductive
output, survival during winter hibernation, and population size and
distribution.
2. One study examined the effect of artificial night lighting on foraging activity
of common (European) toads, Bufo bufo, at Walton Lake, Milton Keynes, U.K.
3. Artificial light was found to reduce the number of calls and movements by
males of Rana clamitans compared to the control. This may affect selection
of mates (mate choice) by females which may cause changes in the
population dynamics of frogs exposed to artificial night lighting.
4. Night light exposure was found to delay metamorphosis in Xenopus laevis
therefore decreasing their chance of escaping a pool before it dries or cools,
which would increase tadpole mortality.
Source: Wise, S. (2007). Presentation at the International Conference in Defense of the Quality of the Night Sky and the Right to Observe the Stars Starlight -- La Palma, April 19-20, 2007 Department of Biology. Utica College of Syracuse University, Utica, NY U.S.A.
01-May-18Pondering on Light: A friend or foe? - DedekeGA 35
Effects on Artificial Night Lighting on Moths
Artificial night light was found to impair the following:
Flight Activity
Vision
Predisposition to predation by Bats
Crypsis (disrupt their camouflage) and easy prey by Birds
Defense Against Other Predators
Courtship and Mating – interferes with hormonal production
Oviposition
Dispersal and Migration
Circadian Rhythms
Trauma
Source: Frank, K.D. (2006) Ecological Consequences of Artificial Night Lighting.
Catherine Rich & Travis Longcore (eds). Island Press. Pages 305-344.01-May-18Pondering on Light: A friend or foe? - DedekeGA 36
A common sight of moths being attracted by a floodlight Source:- Catherine and Travis, 2006
01-May-18Pondering on Light: A friend or foe? - DedekeGA 37
Sea squirts like Botrylloides leachi were significantly
reduced in areas polluted by artificial light01-May-18Pondering on Light: A friend or foe? - DedekeGA 38
Source: Catherine and Travis, 2006
Thousands of mayflies
carpeted the ground
around a security light
at Millecoquins Point in
Naubinway on the
Upper Peninsula of
Michigan representing
another huge loss of
reproductive potential
for the species.
Light has three effects on
insects:
Fixated or capture effect
Crash barrier effect,
Vacuum cleaner effect
01-May-18Pondering on Light: A friend or foe? - DedekeGA 39
Effects of light colour and oscillator frequency on earthworm bioactivity
Owa et al.(2008) concluded that
1. The level of performance of the experimental worms (under all the light treatments) was a lot higher; in terms of surface cast production, than that recorded for earthworms in the wild.
2. Of the four light treatments and the control used in this experiment, Hyperiodrilus africanus responded best under the red light treatment, in terms of cast productivity and tolerance.
3. The order of preference for the different light treatments shown by the earthworms, in terms of cast productivity, is red, blue and green in descending order. The white (mixed) light and control (dark) had significantly less stimulating effects on the productivity of the worms.
4. H. africanus is less likely to emigrate from an area, farm or vegetation, where they are exposed to red light or an oscillator of the frequency band about 44 KHz.
Owa, S. O., Peters, S., Dedeke, G. A. and Aladesida, A.A. (2008). African Journal of Agricultural Research Vol. 3
(1), pp. 029-036, Available online at http://www.academicjournals.org/AJAR ISSN 1991-637X01-May-18Pondering on Light: A friend or foe? - DedekeGA 40
Haemolymph Electrolytes, Acetylcholinesterase and Melatonin Activities of Giant
African Land Snail (GALS) (Archachatina marginata) exposed to Monochromatic
Lights.
Exposure to varying wavelengths of light
elicited varied responses in the haemolymph
electrolyte concentrations of GALS.
Exposure to red light and total darkness
enhanced the activities of acetylcholinesterase
and melatonin in the haemolymph but were
suppressed by blue and yellow light.
Dedeke, G.A., Okulaja, Y., Ogunnaike, M., Awesu, A. and Kehinde, F.O. (2017). Haemolymph Electrolytes,
Acetylcholinesterase and Melatonin Activities of Giant African Land Snail (GALS) (Archachatina marginata) exposed to
Monochromatic Lights. Journal of Molluscan Research 3:81-90. Published by Research Network on Giant African Land
Snails (NetGALS).
01-May-18Pondering on Light: A friend or foe? - DedekeGA 41
Impact of exposure to light spectral on fruitfly, Drosophila melanogaster
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
AMBIENT BLUE RED WHITE YELLOW
PER
CEN
TA
GE (
%)
LIGHT TREATMENTS-10
0
10
20
30
40
50
60
70
1 2 3 4 5 6 7 8 9 10 11 12 13 14
CU
MM
ULAT
IVE F
REQ
UEN
CY
DAYS
TREND OF MORTALITYAMBIENT
BLUE
RED
WHITE
YELLOW
Source: Dedeke, G.A., Emuze, A.J. and Kehinde, F. Impact of exposure to light spectral
on Drosophila melanogaster (Unpubl Data -2018)
The trend of mortality of Drosophila on
exposure to different light spectra
The percentage mortality of Drosophila on
exposure to different light spectra
01-May-18Pondering on Light: A friend or foe? - DedekeGA 42
Potential of light spectral in the control of mosquito
Dedeke, G.A., Rasak, I.B. and Kehinde, F. The use of light spectral in the control of
mosquito (Unpubl Data - 2018)
AMBIENT BLUE GREEN RED WHITE YELLOW
-20.0
0.0
20.0
40.0
60.0
80.0
100.0
LIGHT TREATMENTS
PE
RC
EN
TA
GE
ADULT
MORTALITY
UNDEVELOPED
Percentage of mosquito larvae that developed into adult, larvae mortality, and undeveloped pupae on
exposure to light of varying wavelength for fourteen days
01-May-18Pondering on Light: A friend or foe? - DedekeGA 43
Potential of light spectral to control damage of stored beans
by the bean beetle, Callosobruchus maculatus
Light
Treatment
N
(Replicate)
No of beans
per
Replicate
Mean Number
of Perforated
Beans
Percentage
Damaged
Beans
CONTROL 3 702 124.67±16.56d 17.76
BLUE 3 702 16.67±1.53a 2.38
GREEN 3 702 61.00±17.44b 8.69
RED 3 702 17.33±4.51a 2.47
WHITE 3 702 13.67±3.79a 1.95
YELLOW 3 702 96.33±6.66c 13.72
0
2
4
6
8
10
1 2 3 4 5 6 7 8 9 10
NU
MB
ER
DAYS
WHITE
GREEEN
RED
BLUE
YELLOW
CONTROL
Source: Dedeke, G.A., Popoola, I. and Kehinde, F. Potential of light spectral to control damage of
stored beans by the bean beetle, Callosobruchus maculatus (Unpubl Data – 2018)
Trend in daily mortality of beans weevils housed with beans on
exposure to light of varying light spectral for ten days
Percentage Damaged beans by the bean beetle during exposure to
light of varying spectral for ten days
01-May-18Pondering on Light: A friend or foe? - DedekeGA 44
Likely Neurophysiologic Pathways…
There following are likely proposed pathways
through which light elicits the different effects in
animals
Light impinges on the retina – Retinal ganglion
cell - the Optic nerve – pituitary gland – temporal
lobe – occipital lobe of the brain –
informing the conscious centre of our brain of our
surrounding without interprepration
Direct connection of additional nerve bundles
from the retino-hypothalamic tract (RHT) –
affect the ANS01-May-18Pondering on Light: A friend or foe? - DedekeGA 45
Likely neurologic pathways cont’d…
A side branch of the RHT to the amygdala directly
bypassing the hypothalamus – colour sensitivity –
each frequency in the colour spectrum produce its own
specific neurological and psychological effect
A fourth nerve connection from the retina via the
lower optic tract (not used for vision) reaches the
transpeduncular nucleus (midbrain) (light and
colour sensitive) –
signal travels via the superior cervical ganglion back via the
brain stem to the pineal gland – this is responsible for the
circadian day-night rhythm and melatonin production in the
pineal gland when it gets dark01-May-18Pondering on Light: A friend or foe? - DedekeGA 46
Pathway cont’d…
Through the subconscious mind, immune system,
the limbic system, the nervous system.
Light – charge particles (travelling in the lymph and
blood as well as in nerve axons) like albumin which
was found to be able to be charged by coloured
light and able to deliver this charge to tissues far
away from the site of exposure.
Through the outer skin layer,
light also affects pigments, fluorescent particles in
the body fluids and inside the cells, that travel in
the blood and lymph01-May-18Pondering on Light: A friend or foe? - DedekeGA 47
Likely Neurophysiologic Pathways… ipRGC – Retinal-
ganglion cell
SCN – Suprachiasmatic Nucleus
PVN – Paraventricular Nucleus
DMN - Dorsal Medial Nucleus
LH -Lateral hypothalamus
SPZ -Subparaventricularnucleus/zone
VLPO - Ventrolateral preoptic nucleus
OPN - Olivary pretectal nucleus
EWN - Edinger-Westphal nucleus
ipRGC
SCN
PVNDMN
of the
hypothalamus
intergeniculate
leaflet
LH
OPN
VLPO
SPVZSplanchnic
and vagus
Nerves Amygdala and
lateral
habenula EWNPineal
gland
01-May-18Pondering on Light: A friend or foe? - DedekeGA 48
Conclusion Light has profound effect on the body’s metabolism; it has profound
effect on the hormone system, the emotions, stress levels, sleep, brain
function…Its different wavelengths elicit remarkable changes in the
concentrations of neurotransmitters such as melatonin, norepinephrine,
serotonin, beta-endorphin, cholinesterase…in the cerebro-spinal fluid of
animals. All these will in turn result in the physical, chemical and
behavioural changes which take place in animals.
Has light affected us, the animals, and our
environment in a tremendous way? Yes it has.
Is our life intertwined with light in an
inextricable manner? Yes our life is.
Is light then a foe or friend? I leave the answer
to that question to you. 01-May-18Pondering on Light: A friend or foe? - DedekeGA 49