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Tuesday, April 29, 2014

2048 - Evolution Edition!

Many of you may have noticed a game sweeping the internet recently; a game called 2048.

2048 - Classic
The premise is simple: combine similar numbers to advance. Two 2s make a 4; two 4s make an 8; and so on until you get the coveted 2048 tile.

The game has been so popular that it has spawned a whole list of parodies, including variants based on the Fibonacci sequence, Tetris, Pokémon, and even a website where you can make your own 2048.


So create my own 2048, I did!  I present: 2048 - Evolution Edition.
It's the same concept as the original, except combining like organisms advances you along an evolutionary lineage. Proceed all the way to the end to see the final product!

Mostly I created this for fun, but I hope that it can also be informative.  I've written up short descriptions to go along with each tile, for those who would like to learn (or teach!) as well as play.

Whatever you do with it, have fun!

TILE DESCRIPTIONS:

Choanoflagellates
Choanoflagellates are single-celled organisms very closely related to animals.  They look quite similar to the cells of modern sponges, and some even form small colonies.  A colonial choanoflagellate-like organism may have been the ancestor of true multicellular animals.

Sponge
Sponges are invertebrate animals whose cells are barely specialized, creating very simple bodies.  They represent some of the earliest animals: so simple they seem like little more than a colony of single-celled organisms. As they evolved, their descendants would develop more complex bodies.

Pikaia
Pikaia
has a body very different from most animals that came before it.  It has well-developed organ systems, a defined head and tail, and a flexible rod called a notochord running down its back.  Later relatives would use the notochord as the foundation for a true backbone.   

Astraspis
Astraspis
is one of the earliest fish, and among the earliest animals with bones, including a true backbone.  It has no jaws as fish do today, and its bones form mostly simple features.  Its descendants would develop many advanced bony structures.

Latimeria
Latimeria is a coelacanth.  Coelacanths are some of the most ancient fish, and are still around today.  They belong to a group called the lobe-finned fish.  Latimeria has true bony jaws and, unlike most fish, has a series of bones in its fins to give them strength as it swims.

Tiktaalik
Tiktaalik
is one of the first vertebrate animals to leave the water.  It has a neck separating its head from its body, lungs as well as gills, and a flat head for peeking out of the water.  The limb bones it inherited from its fish ancestors are developed enough for it to crawl around on land. 

Seymouria
Seymouria
has fully-developed limbs and lungs adapted for life on land.  It also has special traits that allowed it to live its whole life away from the water, unlike its amphibian ancestors.  Seymouria represents the transition between amphibians and reptiles.  

Tritylodon
Tritylodon inherited many land-dwelling traits from its ancestors, including the specialized amniotic eggs that it lays.  But it also has specialized teeth, inner ear bones, and other traits typically associated with its descendants, the mammals.

Aegyptopithecus
Aegyptopithecus
is a true mammal.  It gives live birth and feeds milk to its young.  It is also specialized for life in the trees, with long arms and grasping fingers and a great sense of balance.  Many of its descendants would stay in the trees, but others evolved to walk upright on the ground.

Australopithecus
Australopithecus
inherited its specialized arms and legs from its tree-dwelling ancestors, but unlike them it has no tail and stands erect, walking on two legs across the ground.  It has a large brain and dexterous hands, and might use simple tools like many apes do today. 

Homo sapiens
Homo sapiens is a multicellular animal with a defined head and backbone.  It has lungs for breathing air, and can live its whole life on land.  It has bony jaws with specialized mammalian teeth and gives live birth.  Its arms are great for grabbing and climbing, and it walks and runs upright on two feet.  

Watch the World Change

A slightly belated Happy Earth Day to everyone!

One of my jobs at the museum this month was to set up a bunch of interactive tables for our Earth Day celebration.  My favorite of the tables was labeled “The Changing Environment” and it featured a series of maps, on paper and on slide shows, showing how our planet has changed in recent years, largely due to human activities.  Maps are a great visual representation of the state of the planet, and some of the maps I found were quite powerful.  I thought I'd share them.

Global Forest Change
Habitat loss is one of the greatest dangers to natural ecosystems, and deforestation is one of the most widespread forms of loss.  A team at the University of Maryland compiled twelve years of satellite image data on global forest cover, and used this information to create an interactive map showing how our forests have been changing.

Let’s take a look at just a few of their images.

This is North America, showing areas where forest was gained from 2000-2012 (in blue),
and areas where forest was lost (in red).  Some areas have been experiencing both gain
and loss, but overall, losses dominate.
And this is the same data for South America.
This one is fairly terrifying.
There are many more settings the Global Forest Change map can display, and many more places on the globe to look.  You can play around with the map on your own here.

Global Temperature Anomalies
Despite the extensive political debating (at least in my country), there is absolutely no denying that the world is getting warmer.  NASA’s Earth Observatory collects global data on all sorts of information including precipitation, atmospheric components, snow, temperature, and more.  The map that caught my eye this Earth Day was their Global Temperature Anomalies map.

Let me explain what we’re seeing here.  This map identifies “normal” temperatures arbitrarily as the average of global temperatures between 1951 and 1980.  Average temperatures lower than that standard are shown in blue, and average temperatures warmer than that standard are shown in red.

The central map (1950s) is light since it is part of the chosen average range.  The years
before that tend to be colder, and afterward warmer, as the world gradually warms.
The full slideshow and explanation are available at the NASA Earth Observatory website, as well as a collection of other interesting maps of global data.

Google Timelapse
This is my favorite one.

Google and TIME partnered together to create Timelapse, basically, the same as Google Earth, but instead of showing satellite data for today alone, it scrolls through satellite data collected from the last 30 years, allowing you to watch the world change anywhere on the globe that you choose.  


These images are impressive, but still pictures don't really do the project justice - you need to see it in action.

Here’s a quick list of places on the map I’ve found to be fascinating.  Take a look!

Environmental damage:
-Aral Sea (The sea has been drying rapidly due to water diversion for irrigation)
-Latrobe Valley, Victoria Australia (Coal mining across the surface)
-The Amazon Rainforest (Extremely rapid deforestation)

Urban Expansion:
-Las Vegas
-Shanghai
-Dubai (Look at the coastal expansion!)

Climate change:
-Elephant Butte Lake, New Mexico (Drying due to drought)
-Lake Urmia, Iran (Drying due to drought and water diversion)
-Colubmia Glacier, Alaska (Glacial ice retreat)
-Greenland (Sea ice is disappearing along the coast)
-In fact, you ca see ice disappear all over the northern hemisphere.

Shifting environments:
-Ugayali River, Peru (The river shifts and changes course naturally over time!)
-North Carolina Outer Banks (The shoreline naturally changes slowly)

And there are tons of other places to look on the Timelapse map.  Search for yourself!  If you find something really cool, post it in the comments!


Earth Day is always a solemn day for me; in trying to celebrate the Earth, I am reminded of all the ways it is suffering.  I think the kind of information presented on these maps is fascinating, powerful, and informative.  Efforts are being made all over the world to better understand and better care for our lovely planet, and that, I think, is worth celebrating.

Happy Earth Day.

Sunday, January 12, 2014

News Trip! Science on the Ancient Seas

Happy 2014 everyone!  The year is barely two weeks old, and I’ve already seen a bunch of new research about ancient marine creatures.  Apparently, 2014 is a good year for studying the seas of the past.

For today’s post, let’s take a trip back in time, and make a few stops on the way to talk about some of the new science coming out on the old oceans.

Stop #1: The Dark Waters of the Mesozoic (and Paleogene)

Let me introduce you to three creatures that were swimming the seas a long time ago:
1. A fossil sea turtle from the Paleogene Period, 55 million years ago;
2. A fossil mosasaur, an aquatic relative of lizards, from the Late Cretaceous Period, 86 million years ago;
3. A fossil ichthyosaur, a dolphin-like reptile, from the Early Jurassic Period, 190 million years ago.
Each of these creatures left behind a fossil with a rare and special feature: an ‘organic film’ containing chemical leftovers of the skin and scales that used to be there.  If you know what to look for, this film preserves information about the shape and chemical structure of pigment molecules – the molecules that gave the skin its color.

Back in 2011, I waxed poetic about the exciting new methods that were allowing paleontologists to determine the colors of ancient animals – something that many generations of scientists said could never be done.  At that time, the studies were being done on the feathers of ancient birds and dinosaurs.  Now, using very similar methods, Lindgren et al. (2014) analyzed the remains of skin and scales on those three marine fossils, and what did they find?  Eumelanin, and lots of it, from all three fossils.  Eumelanin is a pigment that gives living tissue a black or brown appearance.  All three animals were dark in color.  The next question is: Why?

From top to bottom: sea turtle, ichthyosaur, mosasaur, now drawn in
evidence-based living color!
The researchers propose two main answers to that question.
First: camouflage!  Many marine creatures today, including some sharks, rays, and whales, exhibit counter-shading, being dark on top and light on the bottom.  Viewed from above, a counter-shaded animal blends in with the dark shadows below, but viewed from below, their light bellies blend in with the sunlit waters above. We don’t know for sure, but the mosasaurs and turtle might have been counter-shaded in the same way.  The ichthyosaur, however, has remains of dark-colored skin all over its body.  In this case, the scientists compare it to the sperm whale, which is also dark all over, possibly to help it blend in with the deep dark waters where it hunts.  It may be that this ichthyosaur was also a deep diver. 
Second: heating!  All three of these animals are reptiles, which means they need to warm up in the heat of the sun.  Being dark in color would let animals like these absorb plenty of sunlight and heat to keep warm in the cool ocean waters.

Most good features of an organism have more than one purpose, so camouflage and heat-absorption are both likely good explanations.  One way or the other, this trio of ancient sea-goers can now join the ever-growing list of prehistoric animals that can be drawn in color with real evidence to back it up!

Stop #2: A 310 Million Year-Old Shark Nursery

The prehistoric 'spoonbill' shark,
Bandringa.
This time, we’re stopping to visit a prehistoric shark called  BandringaBandringa lived during the Carboniferous Period, had a ‘spoonbill’ similar to a modern sawfish, and apparently raised its babies in Illinois. 

Bandringa fossils have been found at three fossil sites in Illinois, Ohio, and Pennsylvania.  Past studies have identified two different species of this shark: B. rayi and B. herdinae.  A recent study by Sallan and Coates (2014) took a close look at all of these fossils, and found two surprising things:

First, it looks like there is actually only one species of Bandringa.  What past scientists had thought were different features of two species were caused by taphonomy – the way in which the fossils were buried and preserved.  Becoming fossilized in different environments gave some of the fossils a very different appearance, but when these researchers looked past those taphonomic differences, they found that the two supposed species are actually one and the same.
Second, it looks like all of the Bandringa fossils from the Illinois site are young sharks, while the Ohio and Pennsylvania fossils are all adults.  Also interesting is that the Illinois site was formed in an ancient river delta – where a river emptied into the ocean – while the Ohio and Pennsylvania sites both represent upstream parts of the ancient river.  Coincidence?  These paleontologists think not.

In modern times, there are several species of fish, including sharks, which live their adult lives in one place, but travel to a designated ‘nursery’ to lay eggs or give birth.  This can lead to some pretty awesome migrations.  Atlantic salmon are famous for this: they typically live their adult lives in the open ocean, but swim upriver to breed in the freshwater streams of Europe and North America. 

It looks like Bandringa may have done something similar, but in reverse, giving birth in the estuarine (freshwater + saltwater) environment of the ancient Illinois delta, then swimming upstream to live its adult life in the prehistoric freshwater rivers of Ohio and Pennsylvania.  On top of finding all the juvenile sharks living in the estuary, the researchers also found fossilized egg casings which may have belonged to Bandringa, or possibly to other fish also using this site as a nursery.  Not only does this give us some really remarkable insight into the life of this prehistoric shark, but this is also the oldest evidence of shark migration!

Stop #3: The Great Fish Divide, 450 Million Years Ago

About 450 million years ago, before there were any sharks or salmon, there lived some of the earliest gnathostomes (vertebrate animals with jaws).  Around this time, that ancient group split into two lineages: the bony fish (Osteichthyes), which would give rise to most modern fish, as well as all land-dwelling vertebrates; and the cartilaginous fish (Chondrichthyes), which gave rise to the sharks, rays, and chimaeras. The biggest difference between these two groups is right there in the names; one group has skeletons made mostly of bone, the other made mostly of cartilage.  But we are left with the ever-present question: Why?

To get at answering that question, Venkatesh et al. (2014) peered far back in history, not by looking at 450 million year-old fossils, but by looking at a modern animal, and the 450 million year-old clues in its genome.  Yep, it’s another new full-genome sequence, and this time, it’s the first fully sequenced cartilaginous fish: the Elephant Shark (Callorhinchus milli), a chimaera (close relative of true sharks and rays) which lives off the coast of Australia and New Zealand.

Callorhinchus milli, the Elephant Shark or
Australian Ghost Shark.  Adorable. 
To figure out what makes bony fish bony and cartilaginous fish not so much, the researchers first compared the genes of C. milli to genes from bony vertebrates.  They found that the Elephant Shark is missing a particular set of genes that all bony animals have: the SCPP gene family.  When a vertebrate embryo develops, much of its skeleton starts out as cartilage, which is then converted into bone; the SCPP genes are a big part of that process.  These researchers were even able to show that if the SCPP genes are removed from a developing zebrafish embryo, the fish will show a significant reduction in bone growth.  Clearly an important set of genes.

The SCPP gene family is thought to have developed over time through the duplication of an older gene, Sparcl1, which itself arose through duplication of an even older gene, Sparc.  When the researchers compared the genes of C. milli to genetic material from two other cartilaginous fish (a catshark and a skate), they found that all three have Sparc and Sparcl1, but are missing the SCPP genes.  It seems all Chondrichthyes lack that gene family.  On top of that, they also looked at the genes of a lamprey, which belongs to an evolutionary lineage that branched off before the big fish divide, and found that the lamprey is also missing SCPP genes.  Apparently that gene family is unique to the bony vertebrates.

Putting all of this together lets us embellish a bit on the story of the earliest jawed fishes.  About 450 million years ago, some of the earliest gnathostomes were swimming the seas, and they diverged into two major modern lineages.  The first lineage inherited their ancestor’s cartilaginous bodies, but in the second group, the Osteichthyes, some of the genes they inherited from that same ancestor mutated over time to give rise to the SCPP gene family, and as a result, much of their cartilage would harden into true bone.  This trait would then be passed on to all the bony fish of today, and all of the land-living vertebrates, including you and me.

Now, there is surely much more to this story, but this is a fascinating new piece.  It’s incredible what you can learn about the past by studying the clues in the creatures of the present!

Thanks for joining me on my journalistic journey!  2014 is already proving to be a very cool year in science.  Here's looking forward to another eleven months of exciting research!