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Posts Tagged ‘evolution’

On Wednesday, we asked about examples for teaching evolution.  Confusedious talked about the lineage of whales–a wonderful illustration of the way evolution is not necessarily linear.  The pressures of survival can encourage adaptations that bring a species out of the water, and then eventually send them back again.  Some of the interim forms are… startling.  The alligator-like Ambulocetus natans doesn’t look like anything you’d want to get close to, even with binoculars.

MASI’s own Henderson linked to a piece on the rapid evolution of a lizard species, after being transplanted to a new environment.  Although evolution can also take place gradually, punctuated equilibrium suggests that faster change isn’t at all uncommon.

J. B. S. Haldane (he of the pre-Cambrian rabbits) was once asked what his studies of evolution had taught him about the Creator. Haldane gave the question due consideration, then announced: “He has an inordinate fondness for beetles.”  They make up about a quarter of all the species on Earth, so he had a point.  An Inordinate Fondness is a monthly blog carnival that covers beetles in all their glorious variation. Unrelated to the blog, there is also a book and a Flickr set. Researchers at Harvard are working on putting together the full beetle family tree–click through for the stunning photos on the first page, if nothing else.

The Evolving Planet Exhibit at Chicago’s Field Museum is one of the best places to get a feel for the scale and pattern of evolution.  It’s set up as a story, walking you from the origin of life through its many eras and extinction events, all the way up to the development of modern humans.  The Burgess Shale animation in Thursday’s post is from that exhibit.  The whole thing starts with this plaque:

That would make a great business card, convenient for handing out to people who think “theory” means “vague hunch.”  Or maybe it belongs on stickers, for putting inside the covers of high school biology texts.

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Post by Ruthanna Gordon

Evolution is one of the most well-supported theories in science. It draws on many types of evidence, most notably the millions of datable fossils gathered by researchers from all over the world. At times, fossils can seem almost mundane: small ones dot any marble floor, and slightly larger ones go for a few bucks in museum gift shops. It can be a shock to realize how spotty the fossil record really is.

Most living organisms never become fossils. They live and die in open air or water, and their bodies eventually decompose without a trace. A species is lucky to leave any remnant at all. The infamous Tyrannosaurus rex, for example, probably once roamed in the tens of thousands. We have about 30 skeletons in various stages of incompleteness, and one footprint. For comparison, scientists estimate that the current population of North American Homo sapiens may leave between 0 and 2 fossils.

We have fossils from about 300,000 species, far less than 1% of the total that have ever walked, squirmed, or swum the earth. Of these, most preserve only hard materials such as bone and shell. On rare and fortunate occasion, we are able to find fossils of soft tissue. These treasures provide a cornucopia of information about their original owners.

One example: About 500 million years ago, multi-cellular organisms went from tentative experiment to wildly successful profusion. The Cambrian Explosion (which predated the Cambrian era and took several million years) is best documented at the Burgess Shale in British Columbia. Here, regular mudslides covered the sea floor, burying marine animals and preserving their every detail—for a few wormlike creatures, we can still see the contents of their stomachs. The Shale includes some of the earliest recorded ancestors of modern life, families that thrived for several million years before dying out, and a few strange lineages that vanished almost as soon as they appeared.

Trilobite from the Field Museum's fossil collection

Pikaia gracilens doesn’t look much like you, although it’s certainly related. Trilobites lasted until the mass extinction at the end of the Permian. But you won’t find anything close to a Hallucigenia wandering around today—a pity, in my opinion.

Another example: Last year, scientists managed something previously considered impossible. They discovered the color of a dinosaur. Exceptionally well-fossilized feathers, including pigment structures, were compared to the pigments in modern birds. What they found was something like a chicken-sized, flightless woodpecker. White stripes on the arms and legs stand out against a black coat. An orange crest tops the whole ensemble. The remake of Jurassic Park may feature impressive levels of accuracy—or you can check out the models at your nearest science museum.

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Open Question: Evolution

Evolution takes place over millions of years.  Change on that scale can be hard to convey.  What are the best illustrations of evolution?  Do you have a favorite museum exhibit?  Are you inordinately fond of beetles (as an example of biological diversity)?

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Post by Henderson

Evolution, simply put, is change over time.

Most of us have little trouble tracing our past.  We can look to our parents and ask them questions about our grandparents.  We can look to historical records and see where we may have come from.  And even now, we have the ability to trace our lineage back generations via a DNA ancestry test (the findings from my own place my family as coming from Liberia).

But reconstructing more than just a single lineage is a bit more difficult.

From Darwin and Wallaces 19th century discovery of evolution, researchers have been piecing together how organisms changed over millions of years.  From a single cell to the complex ecosystem that surrounds us today, these scientists are explaining how organisms arrived at their current incarnation and answering questions as to what effects migration and environment had on the new traits they inherited.

Remember that from high school?

No?

Well here are a few videos to jog your memory.

Turn up your speakers on this one.  Let the techno music guide you through some awesome video of how fish increased in size and complexity and made their way onto land.

Why must every rational person accept evolution? Don Exodus tells us in this video.

Richard Dawkins describes stages to the evolution of the eye.  From a single-celled organism with an eye-spot sensitive to light to the eyes you are using to read this post.

In evolutionary terms, sex may be more important than life.  But there is a species of lizard that may beg to differ.

Here’s a little humor for you.  A conservative cartoon host debates evolution.

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