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BIOL 1000
Nicole Nivillac

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LIGHT AND LIFE 9/10/2012 6:23:00 AM
Evolution of Eyes:
Organisms from the same family but more complex eyes for each
Role of Light in Ecology and Behaviour:
Our planet we have diff environments (darkness to bright
Organisms that live there have to adapt
o Adapting to colouration
o Circadian Rhythm
Circadian Rhythms:
Biological clock
Behavioural patterns
CR is the behavioural pattern within a organism of a 24hr time
Controlled by an internal(endogenous)-natural clock
CR is a clock set by the photoreceptors you use according to light
and dark.
o Eg. Jet Lag:
If your on Canadian time and your on European clock,
sleeping schedule is not right
Because body is set to a certain time to wake up and
o Birds hibernating in winter and return in summer
Birds know the time of year
They know the weather and know when to fly back
Birds have a daily cycle as well as yearly cycles while
humans are 24hr clock only
Keeping track is important because they give a lot of info
o Plants are efficient because they make there enzymes at
night because they can absorb the energy during the day
They must do max photosynthesis during the day
DNA SYNTHESIS: we do it during the evening

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o Less risk to be damaged
o When we walk in the sun, it gets damaged so we do it during
the day
How does it work? (CR):
Clock is found in superchiasmatic nucleus of brain
o Light hits retina
o Gets photoreceptors
o Goes through optic nerve cells to the brain
o Sets biological clock in SCN
o Regulates other processes in body
o Also creates melatonin which is important in a human
Some ppl need to take synthetic melatonin
Melatonin production depends on the BIO CLOCK
Leaves are usually straight out during the day
At night the leaves drop so the save energy
ARCTIC circle people are exposed to artificial light
o Ppl who live in the dark, affects other issues
o The light helps with certain hormones and people may
becomes depressed/suicidal
Blind Mole Rate:
Still have photoreceptors so still can use natural light to set
biological clock
Same applies for blind people
Other factors help: sounds, outside temp
Avoiding Detection: Camouflage:
Helps disguise the animal from its predator
Blends in with its backround
Factories came up and trees were covered with sut
Light coloured moths were seen because sut was black
Later on black moths were eaten and lighter sut was there

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Predator must camouflage as well or prey might run away
Using Colour as Signals:
Eg. Skunks striped
Snakes make a sound to warn
Use colours to hide, attract, warn
Colourful Warning Examples:
Colours are there for other organisms NOT us.
Organisms use this to survive
Flower colour + Pollinator:
Flowers must be attractive for other organisms to come and
pollinate it
Birds pollinating flowers are usually red, yellow
Beetles: small, whitish or green
Perception that we see is different from what organisms see
o This is called CO-EVUALUTION
2 organisms evolve/trace simultaneously evolve/adapt
& those adaptions allow them to interact closely with
each other
Light in Aquatic Habitats:
If you go deeper into the ocean, red light cannot go that far
More at the surface, its brighter and wavlengths are able to
penetrate through the water
Fish in the deep water have silver bellies and black backs because
they try to camouflage: from the top they look like the bottom and
bottom up and they blend in with the light
Light Penetration?:
Organisms at the surface: better eyes and can see more colours
Bottom ocean: organisms have less developed eyes
Organisms always have what they need!
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