Life Under the Sun

participation

What the Critics are Saying ...

"extraordinary little volume ... held my attention right to the last page ... virtuoso review of fungi, amoebae, slugs, butterflies, bacteria, and a host of other organisms"
- Gren Lucas, New Scientist

"Like the writings of Stephen Jay Gould, Oliver Sacks, and Lewis Thomas, Ensminger's work combines hard science and entertaining prose..."
- David Pitt, BookList

"This is a quick read, full of fascinating scientific stories by an accomplished writer. Readers will put this book down enlightened and satisfied that their time with this elegant exposition of light and its biological and medical effects was enjoyable and well spent."
- Albert D. Carlson, Quarterly Review of Biology

"Life Under the Sun is vibrant and illuminating ... and is strongly recommended for general readership and specialists alike"
- Alex Waller, Biologist

explanation

Preface
I wrote Life Under the Sun to share with people who have an enthusiasm for science in general and biology in particular my own fascination with the animals, plants, fungi, and microbes that respond to light. I hope that this book will appeal to professional biologists as well ...

Preface, Introduction, Chapter 1
( PDF )

Several figures from Life Under the Sun:

The Organisms of Life Under the Sun.

Daylight Spectrum.

Levels of Light on Earth and Biological Responses.

explanation

1. Vision at the Threshold
A rod cell in the retina of the eye can sense the absorption of a single photon. Absorption of photons by about six different rod cells allows perception of a light flash.

Two figures from the Appendix show the structual changes in retinal that follow light absorption:

Photoisomerization of rhodopsin.

Light and dark activation of rhodopsin.

explanation

2. The Five Percent Solution to Vision
The Eyeless Shrimp (Rimicaris exoculata) lives near hydrothermal vents two miles deep in the Atlantic ocean. Its eye-like organs may allow it to see the heat generated by these deep sea geysers.

Several books by Cindy Lee Van Dover, whose research is featured in this chapter, are highly recommended:

The Octopus's Garden: Hydrothermal Vents and Other Mysteries of the Deep Sea (1996, Perseus Press).

Deep-Ocean Journeys: Discovering New Life at the Bottom of the Sea (1997, Perseus Press).

The Ecology of Deep-Sea Hydrothermal Vents (2000, Princeton Univ. Press).

Explanation

3. A More Delightful Vision
Mantis shrimps, which live in tropical coral reefs, have eyes with more than a dozen different types of photoreceptors - many more than humans or any other animal.

The Lurker's Guide to Stomatopods is a comprehensive resource on mantis shrimps, with many beautiful color photos and several digital videos.

A recent paper discusses the ecological significance of trichromatic vision: Dominy N, Lucas PW, 2001 [PubMed ].

Explanation

4. A Burning Issue
Recent research has shown that long wavelength ultraviolet radiation (UV-A), formerly considered rather benign, can cause skin cancer and other health problems in humans.

A figure from the Appendix shows the most common type of UV radiation-induced structural damage to DNA: Cyclobutane pyrimidine dimer.

The USDA UVB Monitoring Program provides information on the geographical distribution and temporal trends of ultraviolet-B radiation in the United States.

A recent paper describes the topical application of an enzyme for reversal of DNA damage: Stege H, et al, 2000 [PubMed ].

Explanation

5. A SAD Tale
Many people experience Seasonal Affective Disorder (SAD) during the winter due to lack of sunlight. This disease can be treated by daily exposure to a bank of bright fluorescent bulbs.

A figure from the Appendix shows the synthesis of melatonin, a pineal hormone important in circadian rhythms: Melatonin synthesis.

The Michigan State University Counseling Center provides information about SAD: SAD Information Search .

Recent studies indicate that melanopsin from the retinal ganglion cells is the visual pigment that sets the human circadian clock: Hattar S, et al, 2002 [PubMed ]; Berson DM, et al, 2002 [PubMed ].

Explanation

6. The Purple Disease
Variegate porphyria, a disease in which porphyrins accumulate and make a person's skin photosensitive, may have afflicted King George III and other members of the Royal family of England.

A figure (Final steps of heme synthesis) and a table (Metabolic basis and characteristic features of the porphyrias) from the Appendix show the metabolic bases of the different forms of porphyria.

Purple Secret: Genes, 'Madness' and the Royal Houses of Europe (1998, Rohl J, Warren M, and Hunt D, Bantam Press) is highly recommended.

Explanation

7. A Novel Method of Weed Control
Farmers may be able to reduce their dependence on herbicides by applying a new method to control the germination of photosensitive weed seeds.

A figure from the Appendix shows the structure of the light-absorbing chrompohore of phytochrome: Photoisomerization of phytochrome.

The Weed Science Society of America promotes the development of weed science and technology.

Explanation

8. Light and Beer
When beer is exposed to sunlight, there is a chemical change in certain chemicals that are derived from hops. This can give the beer a skunky odor.

The Appendix shows the chemistry of the Sun-struck reaction and the structures of Photostable hop compounds.

Skunk Defensive Secretion has information on the chemistry of skunk odor and describes the use of household chemicals to neutralize this odor.

Explanation

9. Phycomyces - The Fungus that Sees
Physiological reactions in the fungus Phycomyces and in the visual systems of humans allows adaptation to a 10 billion fold or more change in ambient light level.

The Appendix shows the structures of riboflavin and roseoflavin.

The Phycomyces Web Site is a comprehensive resource for information about Phycomyces.

Explanation

10. Phycomyces - The Fungus that Sees
Physiological reactions in the fungus Phycomyces and in the visual systems of humans allows adaptation to a 10 billion fold or more change in ambient light level.

The Appendix shows the structures of riboflavin and roseoflavin.

The Phycomyces Web Site is a comprehensive resource for information about Phycomyces.

Explanation

11. Phycomyces - The Fungus that Sees
Physiological reactions in the fungus Phycomyces and in the visual systems of humans allows adaptation to a 10 billion fold or more change in ambient light level.

The Appendix shows the structures of riboflavin and roseoflavin.

The Phycomyces Web Site is a comprehensive resource for information about Phycomyces.

Explanation

12. Phycomyces - The Fungus that Sees
Physiological reactions in the fungus Phycomyces and in the visual systems of humans allows adaptation to a 10 billion fold or more change in ambient light level.

The Appendix shows the structures of riboflavin and roseoflavin.

The Phycomyces Web Site is a comprehensive resource for information about Phycomyces.

Explanation

13. Phycomyces - The Fungus that Sees
Physiological reactions in the fungus Phycomyces and in the visual systems of humans allows adaptation to a 10 billion fold or more change in ambient light level.

The Appendix shows the structures of riboflavin and roseoflavin.

The Phycomyces Web Site is a comprehensive resource for information about Phycomyces.

Explanation

14. Phycomyces - The Fungus that Sees
Physiological reactions in the fungus Phycomyces and in the visual systems of humans allows adaptation to a 10 billion fold or more change in ambient light level.

The Appendix shows the structures of riboflavin and roseoflavin.

The Phycomyces Web Site is a comprehensive resource for information about Phycomyces.

Explanation

15. Phycomyces - The Fungus that Sees
Physiological reactions in the fungus Phycomyces and in the visual systems of humans allows adaptation to a 10 billion fold or more change in ambient light level.

The Appendix shows the structures of riboflavin and roseoflavin.

The Phycomyces Web Site is a comprehensive resource for information about Phycomyces.