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Lecture 2

Lecture 2 Jan 9, 13.pdf

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York University
BIOL 1000
Nicole Nivillac

Light and life Chapter 1 [Chapter PDFs are posted in Moodle] What is light? • The visible region of the electromagnetic spectrum that humans can detect with their eyes. • Light is described according to its wavelength but it behaves as particles called photons. How does light interact with matter? 1. Reflected off the object 2. Transmitted through the object 3. Absorbed by the object Pigments Pigments Photosynthesis Vision Light and Life – Chapter 1 • How do you think light and life are linked? Also see figure 1.9 textbookin your A photosynthesizing organism could be: A. Green B. Red C. Brown D. Purple E. Any of the above colours (A-D). F. Only two of the above colours (A-D). Many organisms use light as a source of information Photoreceptor:light sensor Chlamydomonas eyespot (contains rhodopsin). Plantscontain phytochrome. Phototaxis Many organisms exhibit phototaxis (movement in response to light). • Positive phototaxis - move towards a light stimulus. Dugesia • Dugesia (a tiny flatworm) exhibits negative phototaxis. The eye • An organ used to sense light. • Important for vision, which distinguishes it from the eyespot. • Vision requires the brain to interpret signals sent to the brain from the eye. Eyes Evolution of the camera eye What good is ‘half’ an eye? Suboptimal Eyes? Simple Complex Eyes Eye spot – e.g., Euglena Eye cup – e.g., Dugesia Pinhole eye – e.g., Nautilus Primitive lens – e.g., Box jellyfish Evolution of Eyes Sl
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