though sea urchins don’t have eyes, they are covered in photoreceptors which collectively act as a retina, effectively making their entire bodies one big compound eye. sea urchins, one of the few marine organisms to have their genome sequenced, have about 23,000 genes (like a human), several of which are associated with sight, including those that govern the development of animal eyes.

"comparing all the genes of the sea urchin, it’s actually quite similar to humans," said george weinstock, who led the sequencing project. they are one of the few invertebrates on the human branch of the evolutionary tree. yet interestingly, they seem to be the only example of a deuterostome to have the rhabdomeric light sensors associated with protostomes, suggesting that rhabdomeric light detectors have been the norm for eyes throughout much of the animal kingdom’s history.

"we think of animals that have a head with centralized nervous systems and all their sense organs on top as being the ones capable of sophisticated behavior, but we’re finding more and more some animals can do pretty complex behaviors using a completely different style," notes sönke johnsen, a marine biologist at duke university who conducted the study on sea urchin vision.

the way that urchins apparently carry out eyesight - with a diffuse nerve net, where no region looks like a central processing unit - reflects how scientists are now often designing robots. “they’re finding it might be a lot better with a distributed system with many little processors and simpler sensors and simple rules, which end up creating fairly complicated behaviors as emergent properties.” [see: starlings post]”

photos of sea urchin tests up close by paul richman. when alive, tube feet would be seen coming from the holes, which the sea urchin uses primarily for sight, with the smaller dents seen in the tests, also containing photoreceptors, used for shading and blocking light. text sources.



Earth Sheltered Homes

The earth sheltered house uses the ground as insulating blanket which effectively protects it from temperature extremes, wind, rain and extreme weather events. An earth sheltered home is energy-efficient, quiet, freeze-proof and low maintenance. Aesthetically an earth sheltered home blends in with the natural environment, leaving more yard space and more space for wildlife.

Fifteen feet below ground the soil maintains a fairly constant temperature equal to the annual average temperature of the area’s surface air. If the average temperature in your area is 55, that means the soil temperature at 15 feet is 55 degrees and in the winter you will only have to bring the temperature inside your earth sheltered home up thirteen degrees, to bring it up to a comfortable 68 degrees. Versus bringing up the inside temperature 68 degrees, if your home is above ground and the outside windchill is 0. In the summer, that 55 degree soil will also keep your home much cooler than an above ground home. Many earth homes incorporate passive solar designs lessening even further the need for fuel for heating or cooling…

(read and see more: Inspiration Green)