Saturday, October 25, 2014
Saturday, October 4, 2014
Seasonal Habitat Change
If we rewind geological time regressively
And I could say the same for this hibiscus tree
And this lizard and this flea and this sesame seed
And if you still disbelieve in what your senses perceive
Then I could even use this rhyme as a remedy
‘Cause there’s so much variation in the styles in this industry
And differential survival when the people listening
Decide what they’re into and what really isn’t interesting
You could thrive like Timberlake on a Timberland beat
Or go extinct like Vanilla Ice and N’Sync
It’s survival of the fittest, but fitness is a tricky thing
It changes from place to place and from winter to spring
Baba Brinkman, Rap Guide to Evolution, "Natural Selection"
NOTE: Some adult lyrics in this rap
http://music.bababrinkman.com/track/natural-selection-20
Thursday, October 2, 2014
Birds of a Feather: Coloration, Evolution, and A Question
Lots of bird stuff in the news and on my mind lately. Among the biggest stories, a new study that helps show how birds evolved from non-avian dinosaurs.
And here's an interesting finding.
Peacocks gave Charles Darwin fits. He wrote to a friend that every time he saw one, he felt sick. Why? Their tails seemed to represent a real problem for his theory of evolution by natural selection. Of what survival use could a tail, however beautiful, be when it made its owner clumsy and slow? Eventually a "just so story" (a sort of fairy tale invented by Rudyard Kipling that pretends to explain why something is the way it is--like bears have no tails beause they tried to use them to ice fish and they froze off and their babies were born without them...that sort of thing) was concocted to try to reconcile the ornate pain-in-butt tail with the animal's need to fly away from predators fast.
It goes like this: Besides natural selection, there's such a thing as sexual selection. One partner, usually the female, has control over who she mates with, and she seeks the boys with th most desireable traits to be the dad to her babies. The biggest, the fastest, the healthiest, the most handsome. Whatever. Think of any trait and some animal somewhere will go "hubba hubba" over it.
In the case of peacocks, it was assumed that sexual selection occurred because if a male of the species ("peafowl" if you include the males and females) was able to survive with that heavy and ridiculous hing stuck to its butt, he must be strong and sassy. The peahens got a look at a big fancy tail like that and something in their tiny brains went, "He must be some special kind of bird to have all that weight strapped to his backside and still be able to get away from foxes. So I'd like that one there to be daddy to my babies, who will then get some of that super mojo in their genes."
Sounds plausible, yeah? Enough to let Darwin get some Zzzzzzs at night. Nothing like a pretty story to explain away an sticky problem. But as Thomas Huxley said, “Science is organized common sense where many a beautiful theory was killed by an ugly fact.”
And that's just what happened recently. Check out this edited news item:
Our final bird-related story has to do with flamingos, the pinkish wading birds that often stand in the water on one leg (for reasons not fully understood). Why is the flamingo pink? Can you think of a just-so story on that one? "Because it likes to soak in warm Strawberry Crush." "Because it's always a little embarrassed by it's skinny legs and big beak." Nope. And while the reason flamingos are pink might not be fully understood, the chemical they use to make that pink color is.
Flamingos need beta carotene to create that deep pink color. They get it from tiny shrimp that live in the water they eat from. Most zoos don't provide diets that are as rich in beta carotene as the birds eat in the wild, so they never develop such a deep shade of pink. They are light--from whitish to a much paler pink. Flamingos,then, are an excellent example of how the presence or absence of some ingredient in the environment has a profound impact on appearance that is not genetic.
By the way, beta carotene is a source of Vitamin A, which humans (and other animals) need for night vision, healing, and several other important functions. Do you know what's a great source of beta carotene? Its name is right there.
That's right: Carrots.
Final thought, related to the flamingo get its color from its diet. I was at the Como Zoo, in the tropics exhibit, and there was a tiny, brightly colored arrow dart frog--just walking around on the rocks! Not in a container of any kind, running free! I admit, I was a little freaked. These frogs are notorious for being very toxic. Some, I had heard, were even used to poison spear tips. I saw a docent (one of the volunteer educators) nearby and told him,"One of your poisonous frogs got out!" And he reminded me of something I should have rememebered on my own. These frogs do not produce their own toxins. This is from an online article about these frogs:
Because the frogs roaming free (intentionally--none had escaped) did not have access to the foods that would make them toxic, they were as safe as a Minnesota peeper.
The most comprehensive family tree of meat-eating dinosaurs ever created is enabling scientists to discover key details of how birds evolved from them.
The study, published in the journal Current Biology, shows that the familiar anatomical features of birds – such as feathers, wings and wishbones – all first evolved piecemeal in their dinosaur ancestors over tens of millions of years.
However, once a fully functioning bird body shape was complete, an evolutionary explosion began, causing a rapid increase in the rate at which birds evolved. This led eventually to the thousands of avian species that we know today.
A team of researchers examined the evolutionary links between ancient birds and their closest dinosaur relatives by analyzing the anatomical make-up of more than 850 body features in 150 extinct species, then using statistical techniques to analyze their findings and assemble a detailed family tree.
Based on their findings from fossil records, researchers say the emergence of birds some 150 million years ago was a gradual process, as some dinosaurs became more bird-like over time. This makes it very difficult to draw a dividing line on the family tree between dinosaurs and birds. [NOTE: This is the language of the press release related to this study, but because birds are dinosaurs, I wish they would have found a better way of expressing this. I suppose it's no different, though, than when people talk about humans and primates as if humans were not primates--which we of course are!]
Findings from the study support a controversial theory proposed in the 1940s that the emergence of [significantly] new body shapes in groups of species could result in a surge in their evolution.
The initial process is so gradual, said one researcher, that if you traveled back in time to the Jurassic, "you’d find that the earliest birds looked indistinguishable from many other dinosaurs.”
aAnother researcher added: “There was no moment in time when a dinosaur became a bird, and there is no single missing link between them. What we think of as the classic bird skeleton was pieced together gradually over tens of millions of years. Once it came together fully, it unlocked great evolutionary potential that allowed birds to evolve at a super-charged rate.”
And here's an interesting finding.
Peacocks gave Charles Darwin fits. He wrote to a friend that every time he saw one, he felt sick. Why? Their tails seemed to represent a real problem for his theory of evolution by natural selection. Of what survival use could a tail, however beautiful, be when it made its owner clumsy and slow? Eventually a "just so story" (a sort of fairy tale invented by Rudyard Kipling that pretends to explain why something is the way it is--like bears have no tails beause they tried to use them to ice fish and they froze off and their babies were born without them...that sort of thing) was concocted to try to reconcile the ornate pain-in-butt tail with the animal's need to fly away from predators fast.
It goes like this: Besides natural selection, there's such a thing as sexual selection. One partner, usually the female, has control over who she mates with, and she seeks the boys with th most desireable traits to be the dad to her babies. The biggest, the fastest, the healthiest, the most handsome. Whatever. Think of any trait and some animal somewhere will go "hubba hubba" over it.
In the case of peacocks, it was assumed that sexual selection occurred because if a male of the species ("peafowl" if you include the males and females) was able to survive with that heavy and ridiculous hing stuck to its butt, he must be strong and sassy. The peahens got a look at a big fancy tail like that and something in their tiny brains went, "He must be some special kind of bird to have all that weight strapped to his backside and still be able to get away from foxes. So I'd like that one there to be daddy to my babies, who will then get some of that super mojo in their genes."
Sounds plausible, yeah? Enough to let Darwin get some Zzzzzzs at night. Nothing like a pretty story to explain away an sticky problem. But as Thomas Huxley said, “Science is organized common sense where many a beautiful theory was killed by an ugly fact.”
And that's just what happened recently. Check out this edited news item:
A scientist took it upon himself to fill in the missing data points. He used high-speed digital video cameras to capture the take-offs of five peacocks with their tails; the experiment was then repeated after clipping off the birds’ tails with pruning shears. The peacocks would be induced to fly from a lower perch to a higher one by an experimenter clapping or rattling a stick at them. Filming the peacocks from different angles showed the birds’ rate of climb and acceleration—things that matter if you’re pursued by a predator—as they launched from their perches.
So, how much did dragging around a giant tail slow down the peacocks? Actually, not that much. According to the research, "a tiny amount."
Overall, the new find refines our understanding of sexual selection as it applies to the peacock, but it doesn’t shake the foundations of the larger evolutionary model.
“Organisms will go to extravagant lengths to produce structures and behaviors that take a lot of effort,” one researcher said. “However, if they win mates, apparently they are worthwhile to the organisms. If the organisms died overwhelmingly as a result of such effort, then maybe we’d have to rethink the phenomenon.”
Our final bird-related story has to do with flamingos, the pinkish wading birds that often stand in the water on one leg (for reasons not fully understood). Why is the flamingo pink? Can you think of a just-so story on that one? "Because it likes to soak in warm Strawberry Crush." "Because it's always a little embarrassed by it's skinny legs and big beak." Nope. And while the reason flamingos are pink might not be fully understood, the chemical they use to make that pink color is.
Flamingos need beta carotene to create that deep pink color. They get it from tiny shrimp that live in the water they eat from. Most zoos don't provide diets that are as rich in beta carotene as the birds eat in the wild, so they never develop such a deep shade of pink. They are light--from whitish to a much paler pink. Flamingos,then, are an excellent example of how the presence or absence of some ingredient in the environment has a profound impact on appearance that is not genetic.
By the way, beta carotene is a source of Vitamin A, which humans (and other animals) need for night vision, healing, and several other important functions. Do you know what's a great source of beta carotene? Its name is right there.
That's right: Carrots.
Final thought, related to the flamingo get its color from its diet. I was at the Como Zoo, in the tropics exhibit, and there was a tiny, brightly colored arrow dart frog--just walking around on the rocks! Not in a container of any kind, running free! I admit, I was a little freaked. These frogs are notorious for being very toxic. Some, I had heard, were even used to poison spear tips. I saw a docent (one of the volunteer educators) nearby and told him,"One of your poisonous frogs got out!" And he reminded me of something I should have rememebered on my own. These frogs do not produce their own toxins. This is from an online article about these frogs:
Poison frogs derive their toxins from the spiders, beetles, ants, centipedes, termites and other insects that make up their diet.
Because the frogs roaming free (intentionally--none had escaped) did not have access to the foods that would make them toxic, they were as safe as a Minnesota peeper.
Monday, September 8, 2014
Archer Fish Superstar
I go to the Como Zoo & Conservatory (http://www.comozooconservatory.org) every Sunday morning that I have free. There is always something new to see. For example, I had always hoped to see the archerfish, housed in a tank in the marine house (with the penguins and puffins and seahorses!), use their amazing shooting ability to hunt for bugs.
And one morning a few Sundays back, I got my wish. The zoo staff member feeding the fish was placing grasshoppers (I think) on the rocks a couple of feet higher than the fish in the tank, and the fish were “spitting” jets of water at them, knocking them into the water to eat. It was spectacular. And the family near me watching the spectacle was not sure that they were really seeing what they were seeing. “What’s going on?! Are they jumping up so fast we can’t even see them?!”
It’s one of those awkward moments, right? You know something, but you don’t want to look smart-alecky. But I was so excited I couldn’t contain myself, and I explained a little about how these fish hunt, how they have special eyes, brains, and mouths that allow them to do this amazing thing. And then I sort of caught myself and said, “Sorry to go off there…these are just some of my favorite animals.” Fortunately, the mom said, “No, no…I’m really glad you did! That is fascinating.”
So it’s not always a bad thing to show off a little of what you learn, outside the classroom, I guess.
Coincidentally, a study just a week or two later in the Cell Press journal Current Biology on September 4 said that archerfish are even more skilled than had been realized. Using water as they do includes them in the fairly exclusive club of tool-using animals (although that club seems to grow every year, doesn’t it?). What makes it tool use—and not JUST tool use, but SKILLFUL tool use—is the way the fish change the hydrodynamic properties of the jet of water from their mouths.
One of the scientists who conducted the archerfish research said that this high level of accuracy probably evolved because where the fish are located, “there is very little to actually shoot at, so it’s important for the fish to be efficient.”
Paper authors Schuster and Gerullis trained some archerfish to hit targets from 20 to 60 centimeters from a specific location, and measured the water jet variables produced. This led to the discovery that archerfish are able to adjust the jet, in ways that compare with how human throw projectiles at targets. Schuster said that this ability requires “precise time control of movement.”
The scientists speculated that what they have learned about water jet control from the fish might find application for human products, including in medicine.
Archerfish, because of their unique hunting adaptation, have sometimes been used as an example of an organism that could not have evolved by Darwinian means. The number of “moving parts”—in the mouth, brain, and eyes—needed to produce such an amazing adaptation really is dizzying. In that way it reminds me of the mimic octopus, which has such a near-perfect ability to imitate its surroundings, camouflaging itself into almost any background by means of color, pattern, and even texture, that it seems more like magic than biology.
How great for science that such challenging puzzles abound! Using the tools of science in the natural world, what discoveries might we make in our efforts to answer such puzzles that contribute to our understanding of the natural world, and maybe make our lives better? Anyone who had the mad skillz of a mimic octopus or an archerfish would be a superhero to rival Mystique or Hawkeye.
Beautiful Bugs
I recently started reading a great new book on insect evolution, Planet of the Bugs: Evolution and the Rise of Insects, by Scott Richard Shaw. It's highly readable for smart sixth graders on up, and is filled with fascinating information presented in a friendly, conversational tone.
Below I quote from a few of the facts I've learned so far in Bugs:
...Keep in mind that given the current rates of new discoveries, description, and publication, it could take an estimated 500 more years just to provide names and morphological descriptions for the remaining insect species.
Insects are cold-blooded animals, and since blood flows through the veins in the their wings, insect wings work very well as little solar panels for warming up on cold mornings.
Small size has promoted insect species diversity by allowing bugs to divide the world into exceedingly small niches.
For as long as 150 million years, insects were the only animals that could fly, and that gave them great advantages in terms of their ability to escape predators and to disperse and colonize new areas.
Over the past 120 million years, insects have coevolved and explosively diversified in tandem with the angiosperms--the dominant forms of plant diversity in modern ecosystems. They are essential as pollinators and seed-dispersers for most of the flowering plants, whose communities would be vastly diminished if all plant-associated insects were eliminated.
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