Light and life
[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
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:
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
Plantscontain phytochrome. Phototaxis
Many organisms exhibit phototaxis (movement in
response to light).
• Positive phototaxis - move towards a light
• 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
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