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Chapter

ENVS 2210 Chapter Notes -Arthropod Eye, Aqueous Humour, Trichromacy

by

Department
Environmental Sciences
Course Code
ENVS 2210
Professor
Ernesto Guzman

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ENVS Unit 07 pages 191-223
Senses: Bees’ Perceptions of the World
- Honeybees brain 850 000 cells, gets info from sensory array
- Five eyes have photoreceptive tasks, the ocelli are little more than light metres
- Compound eyes need bright light to gather info on images: colour, colour
patterns, sizes, shapes, symmetries, edges, and movements
- Compound eyes have tiny facets of compound that can receive three wavelengths:
ultraviolet, blue, green
- Sense polarization of daylight
- Smell and taste = chemical sense
o Most tasting done in mouthparts but antenna can taste as well as smell
- Sensillae are microscopic sensors
- Several generic types respond to types of stimuli: chemicals, touch, heat,
humidity, carbon dioxide, vibration
o Senses of touch and vibration mediated by mechanoreceptors
- Proprioception: providing info to central nervous system about relative body parts
- Bees can tell and measure time
- Bees sensitive to magnetism and electricity, but we don’t know how
Vision and Light
- Light sensed in diff ways:
o Presence )above certain threshold) or absence (below that threshold)
o Discrim. Of wavelengths, repped by colour vision
o Disc. Of images (shapes and sizes) through sharpness of vision
o Polarization angle that light rays diff pass through a medium (usually
air or water)
o Speed of reaction of optical sensors that allow for sensing movement
- 3 simple eyes (ocelli) in honeybee located top of head, can monitor light intensity,
period of exposure to light, and wavelength
o Each had one lens for the entire retina and can refract to about 800
photoreceptor cells
- Camera eye (human beings)- light enters eye through cornea and aqueous
humour, goes through lens etc. to retina and ya
o Rod and cone cells, trichromatic receptors very exiting
o Visual pigments: rhodopsin and iodopsin, breaks down pigment cell and
excited nerve cell, nerve impulses go to dendrites to axons to brain
o Colour is visual perception associated w/ various wavelengths in visible
portion of electromagnetic spectrum of light
o Red green and blue are the primary colours (trichromatic), achromatic
vision = no colour (nocturnal animals)
o Honeybees and all insects have two compound eyes that has many facets,
like a mosaic, large picture of relatively small tiles so total picture cant be
seen
Ability to see detail is resolving power
Depending on colour, object of that size isn’t recognized by
honeybee until about 1 metre or less from it (196)
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