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Lecture 2

BIOL 1000 Lecture Notes - Lecture 2: Phototaxis, Ommatidium, Arthropod Eye

Course Code
BIOL 1000
Nicole Nivillac

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How is light captured?
Light is captured by pigments, and the color that is expressed is the
wavelength that was not absorbed
All pigments are related by conjugated systems
Conjugated systems have alternating bonds (Double bond-single bond-
double bond)
Conjugated systems have delocalized electrons so that the photon can
easily be captured
Light is a source of information in the way of photoreceptor which is
a membrane protein with a non-proteins pigment bound to it (Retinal)
When light is absorbed by the pigment, it turns from a cis retinal to a
trans retinal
The change in retinal change causes the opsin to change in a process
called rhodopsin
Plants have eye spots that can sense light so that they can move
toward it called Phototaxis
Positive phototaxis is when an organism moves toward the light
while negative phototaxis is when an organism moves away from
the light
The eye is an organ that can sense light
Lens eye is the most complex
Occelus is the simplest eye which is a cup lined with about 100
photoreceptor cells
Compound eye is the second type are built with hundreds of
ommatidia. Each ommatidia has light focused on it, forming a mosaic
image which allows for a greater view of movement
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