Friday, March 21, 2014

Darwin's Orchid

Part 1:

Evolution is not random.  (Take that, anti-reality people!)
Lady with pocket-rat.

People have turned one species of dog into hundreds of different breeds depending on their wants.  Want a larger dog?  Take advantage of natural differences in individual dogs.  Breed only larger dogs until you get a Wolfhound or a Great Dane.  Want a little yap-dog?  Breed only the smaller dogs until there are people walking around with dogs in their handbags (yuck).
Hamburgers, not milk from this breed

People have turned one species of cow into many different breeds.  Some produce more meat, some more milk.  The process is the same.  Take advantage of natural differences in individual cows, and breed the ones that have what you want.

Unless you hunt for meat or wild plants, everything that you eat every day has been modified over thousands of years by farmers.
Charles Darwin at the time
he traveled around the world

In the early 19th century, many scientists were puzzling over how evolution works.  There were several hypotheses (a hypothesis is an educated guess, based on observations).  Charles Darwin and many others came up with the theory (an explanation of facts based on testing) of natural selection - that nature chooses among individual differences.

In other words, nature does the same thing as any farmer or dog breeder.   Nature chooses among differences in individuals, based on their ability to survive and breed.

The faster antelope escapes the lion and lives to breed.  The sneakier lion gets the antelope and lives to breed.  The plant that can spread its seeds further has more babies.

The reason why Darwin gets credit for this explanation is that he had both the wealth (no need to work) to devote his life to research and the influential friends to make sure that his voice was heard above the others.

Part 2:
Conservatory at the NYBG

Yesterday I visited the orchid show at the New York Botanical Garden.  

Snowdrops, not snow!
There was no snow there, and spring flowers were blooming.

Orchids are fascinating.  There are an uncountable number of species, and they do some very kinky things.  Many orchids are shaped like and smell like female insects.  
What species of insect could love this "female"? 
Frustrated male insects fly from flower to flower, spreading pollen as they try to mate.

Most of the orchids at the show are hybrids, man-made versions of wild orchids (choose among the individuals that show some trait you want, and keep doing that over many generations until you get something you like).

But then there was Darwin's Orchid.

A scientific theory must not only explain what we have observed, it must also be able to predict what we will see in the future.  

For instance, Darwin would not be surprised that as we add antibiotics into the environment we get more and more bacteria that are resistant.

Darwin's Orchid, with a foot-long nectar spur
Some plants use sweet nectar to bribe insects into landing on them to spread pollen.  The nectary is where the nectar is kept and is usually at the back of the flower so that the insect has to crawl all over the pollen to get fed.

When someone showed Darwin an orchid with a very long nectary (that long green tube behind the flower in the photo), he predicted that there was an undiscovered moth out there with a foot-long tongue that could pollinate this orchid.

A moth with a foot-long tongue.  Photo from
Houston Museum of Natural Science
Darwin was right, and now we have Xanthopan morgani or the Morgan’s sphinx moth. This moth was not discovered until 1903, but proved Darwin’s theory and was originally named Xanthopan morgani praedicta in honor of his prediction. The moth has an unbelievably long tongue which can reach down into the flower to retrieve the nectar. In doing so, the moth rubs its head against the pollen producing organ of the plant and transfers the pollen to the next flower it drinks from.

That's what science does.

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