Another Miracle of Science!

The New York Times has a piece on the latest in science successes.  For only the 2nd time in history, the United Nations is calling a disease completely eradicated from the face of our planet. And like the first, smallpox, this one is a major killer.  Unlike smallpox, though, you probably haven’t heard of it.  It’s called rinderpest, which is German for “cattle plague,” and is a cousin of the measles virus.  The last case was seen ten years ago in a buffalo in Kenya.  You can read more about the monumental undertaking of eradication and more about  the thousand-year old rinderpest itself by reading the entire article.

Energy!

This post has the most monstrous image I’ve made to date.  I hope it will become more popular and useful than my current heavy hitters the cell and even Louis Pasteur’s experiment of spontaneous generation, which I’ve seen make the top ranks of both Google and Bing image search!

In this image, I’ve covered energy as it passes from the sun in the form of light to the chloroplast of plants. In the chloroplasts, there are structures called thylakoids where the magic happens. This is where photosynthesis takes place in two parts, 1) light-dependent reactions and, 2) Calvin Cycle.

The waste products here are eliminated and the useful products are then sent to the mitochondria.  The first step is 1) glycolysis, followed then by 2) the Krebs cycle (also called the Citric Acid Cycle) under aerobic conditions OR, 2) fermentation (under anaerobic conditions)

There’s a LOT of stuff that happens here. These are the basics.  This stuff can get extraordinarily complicated–the guy the Krebs cycle is named for won a Nobel prize for his work!

I’ve never, personally seen an image that attempted to go from the sun to photosynthesis to cellular respiration but I tried to keep it as simple as possible. That said, if you feel something’s missing, its probably because it is. Some steps weren’t explicitly mentioned for simplicity’s sake.

One final note: ATP gives you a burst of energy. If you need energy to do anything for longer than about a minute and a half, you want sugar. Sugars provide longer-lasting energy.  ATP (which makes up about a half-pound of your total body weight) doesn’t store, in other words, it gets used shortly after it’s made. ATP actually gets recycled over 1,000 times a day by humans!

Energy path thumb

Click for full size

But AmoebaMike, what else do I need to know about taxonomy and evolution?

In order to standardize names of organisms, back in the the 1700s, a Swedish botanist named Carl Linnaeus developed a two-name system. Referred to as, binomial nomenclature, it is the system with which we use–even still today–for naming organisms.

Carl von Linné, Alexander Roslin, 1775.
Scientific Hottie
Carl Linneaus,
Image via Wikipedia

The word binomial means “two names.” So it is by using two names that we fully name each organism, in the same way that you have both a first and a last name. In binomial nomenclature, the first of the two names indicates the genus name. A genus is a group of closely related species. The second name is the species name; often it is a Latinized version of a word that describes a trait of the species, a location where the species can be found, or even an influential person in the discovery or science of that particular species. See the accompanying image.

Click for full size

Finally, you need to know how organisms are classified. Scientists try to make maps, or trees, called cladograms to show the relationship between different species. It used to be that organisms that were organized in cladograms based on physical similarities the species shared with one another. For example, as the name implies, the horseshoe crab looks like a crab.  In fact, it’s actually more related to spiders than it is to crabs!

Now that science has advanced greatly in the past half-century or so, cladograms are built using information scientists gather from DNA and RNA sequencing.  We’re finding out that like the horseshoe crab, some things we thought were related aren’t really all that close!  Have you ever heard of a panda or a koala being referred to as panda bear or koala bear?

Bears are members of the family Ursidae.  The bears you think of when you hear the term “bear”, like the grizzly bear and the polar bear are in genus Ursus.  Ursus is one of the genera of family Ursidae. Pandas are members of family Ursidae, but their genus is Ailuropoda. So they’re technically bears!

Koalas share the same class as the bears, Mammalia.  That’s as close as they’re related.  Koalas aren’t bears any more than dogs or whales are bears.

One last note: as you see in the image, the proper way to discuss a species is using the full name and italicizing it. The genus name gets capitalized, but can also be abbreviated by the first initial. For example, koalas would be Phascolarctos cinereus or P. cinereus and pandas would be Ailuropoda melanoleuca or A. melanoleuca.

Scientists finish a 53-year-old classic experiment on the origins of life

Harold Urey, circa 1963

Urey, circa 1963. Image via Wikipedia

Sometimes an article is so well written that you can do nothing to better it.  Ed Yong is the type of writer to consistently put out articles of that quality-level.

And so all I can do is send you to his blog, for you to read for yourself.

It concerns the Urey experiment on possible origins of life, meticulous science, and more than 50 years of advances around undisturbed samples.

Read all about it here.

Evolution

We recently covered Taxonomy here at AmoebaMike.  Taxonomy, a way of classifying organisms, fits very well with evolution.

There is of course an issue with evolution: the hot topic that pits “religion vs science”.  That of course is hogwash as the Pope (more than one) came out and said that evolution is not some fad hypothesis. But then of course, plenty of other Christians really dislike Catholics so that’s not enough for some people.  It’s an argument that probably takes over 6% of the internet already, and I won’t replay it here. I just wanted to point out that it is a hot button issue.

So moving past the issue of man being created in the image of God, evolution can actually tell you a lot. It shows how different species are related to each other. For example, did you know that you have more in common with a whale, than a whale has in common with a shark?

While sharks and whales both live in the ocean, sharks are actually a type of fish that doesn’t have bones. Whales, on the other hand, are mammals. And like humans, which are also mammals, whales suckle their young. Sharks are cold-blooded and whales are warm-blooded. Sharks breathes through their gills underwater and whales breathe air through their lungs.

You are even more closely related to a sea anemone than the sea anemone is to an oak tree despite the fact that they pretty much just stick around in the same place.

How do you determine who you’re closely related to?

The same way you do with people!

Let’s take person A.  You’re related to person A.  How do you know is person A is your sibling? Look at your parents. Do you share parents? No? Do you share grandparents? If yes, person A is either an uncle/aunt or a cousin!

Looking at other organisms, primates like chimps are closely related to humans because a long time ago (a very, very long time) they shared a common ancestor.  Even further back, we share a common ancestor with a cat. Further in the past, we share a common ancestor with a jellyfish. And still further, we share an ancestor with a rose plant.

Does that mean you came from a chimp? a cat? a jellyfish? a rose plant? Of course not!  You didn’t come from any of those organisms any more than you came from your cousin or your uncle just because you share a common grandparent!

Through much hard work, including gene sequencing, a giant family tree is being constructed. Only it’s not like Geni where you can how closely you’re related to President Obama; it’s actually a tree of all life.  Fittingly, it’s called the Tree of Life. Check it out!

See also:

Another Use For Breasts in Humans

Being a post-pubescent male, I have an appreciation–an affinity even–for female breasts.  Perfectly natural and normal for me to feel this way.  Breasts in humans have the function of providing nourishment to young, as is the case in all mammals.  But unlike other mammals, human female breasts stay engorged full-time after puberty.  Other mammals’ breasts simply enlarge for the benefit of their young.

Scientists aren’t completely sure of why humans are different.  A female human’s breast size is not indicative of their ability to produce milk.  One very popular theory is that breasts evolved as humans began to walk upright.  Instead of having, say an engorged or colored butt like some primates, a bipedal woman’s breasts would be more noticeable to an upright man.

You may say, “but I like big butts.”  And while that may be the only thing you have in common with Sir Mix-a-Lot, there’s no arguing that in a face to face situation, no matter how much “junk in the trunk” she has, you’re going to notice a woman’s breasts before her butt.

And while women like Kim Kardashian and Jennifer Lopez are popular, in part, due to their posteriors, it turns out that men are willing to go above and beyond for a woman with large breasts that needs something.

courtesy Simon Howden

In a study published in 2007, a woman was put on a French road and stuck her thumb out.  Scientists recorded how many people stopped.  They did this and adjusted her apparent breast size.  As her breast size went up, so did the number of men who stopped to offer a ride (A cup to C cup went from 15% to 24%). -hat tip

Some may think that’s an obvious result, but just like they don’t play football games in the papers, it takes real observation to make science.  Somewhat surprisingly, the rate at which woman stopped stayed more or less consistent.  We’d expect that in a show of competition, women would be less likely to help if the hitcher had larger breasts.

In another study, the same scientist also found that hair color of the hitchhiker affects frequency of stops in cars–turns out, smiling also does.

In the unfair world we live in, if you ever need help with something your best luck is if you are blonde, smiling, and have large breasts.

Just please don’t take it as far as Heidi Montag.

Not Just Dominance & Recessiveness

One of the foundations of genetics is that some traits are dominant and some are recessive.  It’s a great way to start the discussion, but it’s not the whole story.  The most basic genetic options are dominant and recessive, but there is also co-dominance, incomplete dominance, and polygenic traits (plus more variations!) that account for lots of genetic variability.  I’ll briefly touch on these so you get a better understanding of just how quickly predicting genetic outcomes can get tricky.

In the case of co-dominance, there are actually 2 dominant phenotypes that can be displayed.  A better way to grasp this is to picture your alleles as being R = red and R’ = white.  If the genotype is RR, the flower is red. If the genotype is R’R’, the flower is white. But if the genotype is RR’,  the phenotype is actually both red and white!

Using red and white flowers again, I’ll move onto incomplete dominance.  In this case, when both alleles are present, neither one is really dominant over the other.  So the alleles would be designated as R = red and r = white.  When the genotype is RR, the flower is red and when the genotype is rr, the flower is white.  But, when the flower is heterozygous and has a genotype of Rr, the flower is pink!

Polygenic traits are traits you have that are actually composed of many genes.  For example, eye color isn’t one color or another, it can be: black, dark brown, light brown, hazel, green, blue, gray, amber or varying combinations.  Skin color is another excellent example of a polygenic trait in humans.

As a bonus, because I’m feeling particularly science-y today, I’ll tell you about sex-linked genes too.   Sex-linked dominance is the presence of a gene on the sex chromosomes.  Since the sex chromosomes in humans are designated as X and Y, any gene that sits on the X or Y is considered sex-linked.  Because females have 2 X chromosomes, they will have a different phenotypic ratio than males that have 1 X and 1 Y.  An example is some forms of color-blindness are located on the X chromosome, but it’s recessive.  So girls are less likely to have 2 copies of the recessive allele.  If a boy gets the recessive allele, he has the color-blindness, because there’s no copy on the Y chromosome to “overpower” his recessive allele on his X.  So the phenotypic ratio for girls is 3:1, but for guys, it’s 1:1–meaning there’s a 50/50 chance of having color-blindness, whereas, for girls it was only a 25% chance. In a sex-linked dominant scenario, girls would have a 75% chance and boys would still have a 50% chance.

It can all get a little confusing, but don’t worry, as along as you keep your Punnett  square handy, you should be able to work through any scenario.

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