Evo Devo

Evolutionary Developmental Biology (a.k.a Evo Devo) is a growing field of biology that stands at the interface between evolutionary biology and developmental biology. With an ever increasing knowledge base, the literature on the topic is becoming increasingly difficult to wade through. I hope this blog can highlight the important findings in the field that anyone, scientist or layperson, may find interesting and enjoyable.

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currentsinbiology:

An Unexpected Engine of Evolution (Wired)
It’s often thought that evolution is fueled by competition, with red-in-tooth-and-claw dynamics generating new, better-adapted forms and species. But sometimes — perhaps frequently — new species just happen!
Above and at right is a map of greenish warbler distribution, color-coded according to local genetic signatures, around the Tibetan plateau. The warblers are what’s known as a ring species, occupying a horseshoe-shaped range; as neighboring populations intermingle, genes flow around the horseshoe, but populations at its tips no longer interbreed and eventually become different species.
At left is a computational model of this process. According to the model, no adaptations or differences in reproductive fitness are necessary to produce new species. Rather, they seem to arise as a function of time and space; evolution itself is a generative, diversifying force.
Citation: “Evolution and stability of ring species.” By Ayana B. Martins, Marcus A. M. de Aguiar and Yaneer Bar-Yam. Proceedings of the National Academy of Sciences, March 11, 2013.

currentsinbiology:

An Unexpected Engine of Evolution (Wired)

It’s often thought that evolution is fueled by competition, with red-in-tooth-and-claw dynamics generating new, better-adapted forms and species. But sometimes — perhaps frequently — new species just happen!

Above and at right is a map of greenish warbler distribution, color-coded according to local genetic signatures, around the Tibetan plateau. The warblers are what’s known as a ring species, occupying a horseshoe-shaped range; as neighboring populations intermingle, genes flow around the horseshoe, but populations at its tips no longer interbreed and eventually become different species.

At left is a computational model of this process. According to the model, no adaptations or differences in reproductive fitness are necessary to produce new species. Rather, they seem to arise as a function of time and space; evolution itself is a generative, diversifying force.

Citation: “Evolution and stability of ring species.” By Ayana B. Martins, Marcus A. M. de Aguiar and Yaneer Bar-Yam. Proceedings of the National Academy of Sciences, March 11, 2013.

New theory uncovers cancer's deep evolutionary roots

pitchforking:

A new way to look at cancer – by tracing its deep evolutionary roots to the dawn of multicellularity more than a billion years ago – has been proposed by Paul Davies of Arizona State University’s Beyond Center for Fundamental Concepts in Science in collaboration with Charles Lineweaver of the Australian National University. If their theory is correct, it promises to transform the approach to cancer therapy, and to link the origin of cancer to the origin of life and the developmental processes of embryos.

Davies and Lineweaver are both theoretical physicists and cosmologists with experience in the field of astrobiology – the search for life beyond Earth. They turned to cancer research only recently, in part because of the creation at Arizona State University of the Center for the Convergence of Physical Science and Cancer Biology. The center is one of twelve established by the National Cancer Institute to encourage physical scientists to lend their insights into tackling cancer.

The new theory challenges the orthodox view that cancer develops anew in each host by a series of chance mutational accidents. Davies and Lineweaver claim that cancer is actually an organized and systematic response to some sort of stress or physical challenge. It might be triggered by a random accident, they say, but thereafter it more or less predictably unfolds.

Their view of cancer is outlined in the article “Exposing cancer’s deep evolutionary roots,” written by Davies. It appears in a special July issue of Physics World devoted to the physics of cancer.

“We envisage cancer as the execution of an ancient program pre-loaded into the genomes of all cells,” says Davies, an Arizona State University Regents’ Professor in ASU’s College of Liberal Arts and Sciences. “It is rather like Windows defaulting to ‘safe mode’ after suffering an insult of some sort.” As such, he describes cancer as a throwback to an ancestral phenotype.

The new theory predicts that as cancer progresses through more and more malignant stages, it will express genes that are more deeply conserved among multicellular organisms, and so are in some sense more ancient. Davies and Lineweaver are currently testing this prediction by comparing gene expression data from cancer biopsies with phylogenetic trees going back 1.6 billion years, with the help of Luis Cisneros, a postdoctoral researcher with ASU’s Beyond Center.

But if this is the case, then why hasn’t evolution eliminated the ancient cancer subroutine?

“Because it fulfills absolutely crucial functions during the early stages of embryo development,” Davies explains. “Genes that are active in the embryo and normally dormant thereafter are found to be switched back on in cancer. These same genes are the ‘ancient’ ones, deep in the tree of multicellular life.”

The link with embryo development has been known to cancer biologists for a long time, says Davies, but the significance of this fact is rarely appreciated. If the new theory is correct, researchers should find that the more malignant stages of cancer will re-express genes from the earliest stages of embryogenesis. Davies adds that there is already some evidence for this in several experimental studies, including recent research at Harvard University and the Albert Einstein College of Medicine in New York.

“As cancer progresses through its various stages within a single organism, it should be like running the evolutionary and developmental arrows of time backward at high speed,” says Davies.

This could provide clues to future treatments. For example, when life took the momentous step from single cells to multicellular assemblages, Earth had low levels of oxygen. Sure enough, cancer reverts to an ancient form of metabolism called fermentation, which can supply energy with little need for oxygen, although it requires lots of sugar.

Davies and Lineweaver predict that if cancer cells are saturated with oxygen but deprived of sugar, they will become more stressed than healthy cells, slowing them down or even killing them. ASU’s Center for the Convergence of Physical Science and Cancer Biology, of which Davies is principal investigator, is planning a workshop in November to examine the clinical evidence for this.

“It is clear that some radically new thinking is needed,” Davies states. “Like aging, cancer seems to be a deeply embedded part of the life process. Also like aging, cancer generally cannot be cured but its effects can certainly be mitigated, for example, by delaying onset and extending periods of dormancy. But we will learn to do this effectively only when we better understand cancer, including its place in the great sweep of evolutionary history.”

candidscience:

Visualizing vertebrate skeletal bone formation

Mesenchyme tissue condenses to form cartilage.  The cartilage is later replaced by bone; although, there are some structures that remain permanently cartilage and do not ossify, such as the cartilage of the trachea and articular cartilage of the joints. Alcian Blue/Alizarin red staining is ideal for revealing the cartilaginous skeleton of developing embryos. The cartilaginous skeleton is stained dark blue by Alcian Blue, the bone is stained with Alizarin Red, and the other embryonic tissues are “cleared” using benzyl alcohol/benzyl benzoate (BABB). Here are some examples:

1.  Alcian blue staining of a Stage 17 BAT (Carollia perspicillata) embryo. This image was taken by Lingyu Wang and Ketty Lee.  http://thenode.biologists.com/tag/mouse/

2.  This remarkable image shows the forming skeleton of an embryonic CHICKEN, stained to differentiate between hardened bone (in red) and the still-unossified cartilage model (in blue). http://www.vetmed.vt.edu/education/curriculum/vm8304/lab_companion/histo-path/vm8054/labs/Lab8/Examples/chickbon.htm

3.  A MOUSE embryonic skeleton, with bone stained Alizarin Red and cartilage stained Alcian Blue. [Credit: Jacqueline Norrie, graduate student, Institute for Cellular and Molecular Biology]  http://www.utexas.edu/know/2013/09/30/science-visualized/

4.  Alcian blue staining of an advanced CORN SNAKE embryo to show the skeletal anatomy. 

http://www.sciencedirect.com/science/article/pii/S0012160609002784

5.  Alcian blue staining of a WHIPTAIL LIZARD..Image(s) by Andrea Wills (2007 Woods Hole Embryology Course)

 http://www.sdbonline.org/index.php?option=com_content&task=view&id=105

6.  The image shows the ventral surface of the SKATE RAJA prepared by alcian blue and alizarin red staining for cartilage and bone. (With additional staining of the ampullary canals surrounding the face.) It was taken by David Gold (University of California, Los Angeles), Lynn Kee (University of Michigan), and Meghan Morrissey (Duke University). http://thenode.biologists.com/skate-wins-cover-contest/photo/

7. 40-day old CAT fetus shows its cartilaginous skeleton stained with alcian blue. The specimen was also stained with alizarin red, which stainscalcium.

 http://chickscope.beckman.uiuc.edu/explore/embryology/day14/dev2.html

8. Lateral view, fetal HUMAN head (12 weeks) stained for bone (alizarin red) and cartilage (alcian blue). http://php.med.unsw.edu.au/embryology/index.php?title=File:Fetal_head_lateral.jpg

jtotheizzoe:

Every Embryo
In the neighborhood of 600 million years ago, the embryos of the animal kingdom branched into several distinct arms based on how that little ball of cells that’s created after fertilization begins to pattern and fold itself into what will one day become a fully grown adult. 
Think about this: If you go far enough back in evolution, the common ancestors of all of these various families of organisms, from vertebrates to insects to sea slugs, had the same set of genes to call upon in order to make a three-dimensional animal. Very quickly, and quite beautifully, the diversity of life’s forms exploded. 
Much of the amazing variety you see among animals today begins with the patterns laid down in the earliest stages of development, and this represents the crossroads where they all began their journey to the modern age. 
(From Wired’s Best Scientific Figures of 2012)

jtotheizzoe:

Every Embryo

In the neighborhood of 600 million years ago, the embryos of the animal kingdom branched into several distinct arms based on how that little ball of cells that’s created after fertilization begins to pattern and fold itself into what will one day become a fully grown adult. 

Think about this: If you go far enough back in evolution, the common ancestors of all of these various families of organisms, from vertebrates to insects to sea slugs, had the same set of genes to call upon in order to make a three-dimensional animal. Very quickly, and quite beautifully, the diversity of life’s forms exploded. 

Much of the amazing variety you see among animals today begins with the patterns laid down in the earliest stages of development, and this represents the crossroads where they all began their journey to the modern age. 

(From Wired’s Best Scientific Figures of 2012)

mucholderthen:

SCIENTIFIC ILLUSTRATION:  NucleosomeThe Mediterranean Institute for Life SciencesSplit, Croatia
High resolution ray-traced model of a nucleosome, isolated on black.

A nucleosome is the basic unit of DNA packaging in eukaryotes, consisting of a segment of DNA wound in sequence around four histone protein cores.  This structure is often compared to thread wrapped around a spool.
Nucleosomes form the fundamental repeating units of eukaryotic chromatin, which is used to pack the large eukaryotic genomes into the nucleus while still ensuring appropriate access to it.  In mammalian cells approximately 2 m of linear DNA have to be packed into a nucleus of roughly 10 µm diameter.  
Nucleosomes are folded through a series of successively higher order structures to eventually form a chromosome; this both compacts DNA and creates an added layer of regulatory control, which ensures correct gene expression.
(Nucleosome - Wikipedia)

mucholderthen:

SCIENTIFIC ILLUSTRATION:  Nucleosome
The Mediterranean Institute for Life Sciences
Split, Croatia

High resolution ray-traced model of a nucleosome, isolated on black.

A nucleosome is the basic unit of DNA packaging in eukaryotes, consisting of a segment of DNA wound in sequence around four histone protein cores.  This structure is often compared to thread wrapped around a spool.

Nucleosomes form the fundamental repeating units of eukaryotic chromatin, which is used to pack the large eukaryotic genomes into the nucleus while still ensuring appropriate access to it.  In mammalian cells approximately 2 m of linear DNA have to be packed into a nucleus of roughly 10 µm diameter.  

Nucleosomes are folded through a series of successively higher order structures to eventually form a chromosome; this both compacts DNA and creates an added layer of regulatory control, which ensures correct gene expression.

(Nucleosome - Wikipedia)

rhamphotheca:

Fossil Fish With “Limbs” Is Missing Link, Study Says

by James Owen, Apr., 2006

Fossil hunters may have discovered the fish that made humans possible.

Found in the Canadian Arctic, the new fossil boasts leglike fins, scientists say. The creature is being hailed as a crucial missing link between fish and land animals—including the prehistoric ancestors of humans.

Researchers say the fish shows how fins on freshwater species first began transforming into limbs some 380 million years ago. The change was a huge evolutionary step that opened the way for vertebrates—animals with backbones—to emerge from the water.

“This animal represents the transition from water to land—the part of history that includes ourselves,” said paleontologist Neil Shubin of the University of Chicago.

Shubin was co-leader of a team that uncovered three nearly complete fossils measuring up to nine feet (3 m) long on Ellesmere Island in 2004. The new species, Tiktaalik roseaehad a flattened, crocodile-like head and strong, bony fins…

(read more: National Geo)                  

(image: T - Shawn Gould, Nat. Geo.; BL - Univ of Chicago; BR - Graham Roberts, NY Times)

_______________________________________

read more:

http://en.wikipedia.org/wiki/Tiktaalik

http://tiktaalik.uchicago.edu/index.html

http://evolution.berkeley.edu/evolibrary/news/060501_tiktaalik

(via justanexcuse2watchbridesmaids)

theecolologist:

Wednesday’s WTF!?!: The Surprising Snaps Of A Tropical Tiny…

They might look like weird little surprised specters, but these cartoonesque caspers are most definitely of our own earthly realm…Well, our aquatic realm, at least. They are, in fact, the larvae of everyone’s favourite tropical fishtank friend - the zebrafish. 

Zebrafish (Danio rerio) are tropical freshwater fish native to the streams of the southwestern Himalayan region, being found in parts of India, Pakistan, Bangladesh, Nepal, and also Burma. These fish display remarkable regenerative properties and their embryos - which are large, robust and transparent - develop at a rapid pace; this, among other things, makes them a popular model organism for research. 

These photos, depicting two-day-old (top) and four-day-old (bottom) larvae, were taken with a scanning electron microscope by researchers at the Max Planck Institute for Developmental Biology. The mouths of these larvae are already well formed and recognisable. However, what appear to be little lashed eyes in the area above the mouths are actually the future olfactory organs. In the bottom picture, you can see that the lower jaw of the larva on the left is smaller than that of the others. This is the result of the alteration of a gene which plays an important role in oral development. By analysing the zebrafish mutants with this abnormal jaw development it is hoped that some light can be shed on the development of spinal malformations in humans. 

Pretty neat, huh. But yes, I know what you’re thinking; even now that you know what they really are, you still think theyjust look like surprised little ghosts…

Aspiring Biologist: Mammals evolved to survive the dinosaurs...

imprettymuchabiologist:



Recent studies of jaw and ear function in primitive mammal-like reptiles indicate that the larger angular bone, which later became the tempanic ( bone of the skull, partially enclosing the middle ear and supporting the eardrum ) may have supported an eardrum while still part of the…

Iqbal Selvan: Chimpanzee geniuses also exist

iqbalselvan:

A perfect storm of abilities seems to come together to create the Einsteins of the animal kingdom. While testing intelligence, one chimp, named Natasha, had scores that were off the charts in comparison to other chimps. Is she like an ape genius?

Certain apes appear to be much smarter…

(via iqbalselvan-deactivated20130111)

goforgold93:

Bill Nye “Creationism isn’t for kids”