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Welcome to The Visible Embryo, a comprehensive educational resource on human development from conception to birth.

The Visible Embryo provides visual references for changes in fetal development throughout pregnancy and can be navigated via fetal development or maternal changes.

The National Institutes of Child Health and Human Development awarded Phase I and Phase II Small Business Innovative Research Grants to develop The Visible Embryo. Initally designed to evaluate the internet as a teaching tool for first year medical students, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than one million visitors each month.

Today, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than 1 million visitors each month. The field of early embryology has grown to include the identification of the stem cell as not only critical to organogenesis in the embryo, but equally critical to organ function and repair in the adult human. The identification and understanding of genetic malfunction, inflammatory responses, and the progression in chronic disease, begins with a grounding in primary cellular and systemic functions manifested in the study of the early embryo.

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Pregnancy Timeline by SemestersFetal liver is producing blood cellsHead may position into pelvisBrain convolutions beginFull TermWhite fat begins to be madeWhite fat begins to be madeHead may position into pelvisImmune system beginningImmune system beginningPeriod of rapid brain growthBrain convolutions beginLungs begin to produce surfactantSensory brain waves begin to activateSensory brain waves begin to activateInner Ear Bones HardenBone marrow starts making blood cellsBone marrow starts making blood cellsBrown fat surrounds lymphatic systemFetal sexual organs visibleFinger and toe prints appearFinger and toe prints appearHeartbeat can be detectedHeartbeat can be detectedBasic Brain Structure in PlaceThe Appearance of SomitesFirst Detectable Brain WavesA Four Chambered HeartBeginning Cerebral HemispheresFemale Reproductive SystemEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterSecond TrimesterFirst TrimesterFertilizationDevelopmental Timeline
CLICK ON weeks 0 - 40 and follow along every 2 weeks of fetal development
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Home | Pregnancy Timeline | News Alerts |News Archive Nov 7, 2013

 

Chlamydomonas reinhardtii is a single celled green alga about 50 micrometres in diameter that swims with two flagella. It has a cell wall made of hydroxyproline-rich glycoproteins, a large cup-shaped chloroplast, a large pyrenoid, and an "eyespot" that senses light.

Image Credit: Wikipedia







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Solved origin of biologic complexity

Scientists have puzzled for centuries over how and why multicellular organisms evolved the almost universal trait of using single cells, such as eggs and sperm, to reproduce.

Now researchers led by University of Minnesota College of Biological Sciences (postdoctoral fellow) William Ratcliff and associate professor Michael Travisano, have set a big piece of that puzzle into place by applying experimental evolution. They have transformed a single-celled algae into a multicellular one which reproduces by dispersing single cells.

"Until now, biologists had assumed that the single-cell bottleneck evolved well after multicellularity, as a mechanism to reduce conflicts of interest among the cells making up an organism," says Ratcliff. "Instead, we found that it arose at the same time as multicellularity. This has big implications for how multicellular complexity might arise in nature. We show that this key trait, which opens the door to evolving greater multicellular complexity, can evolve rapidly."

In an article published in the journal Nature Communications, researchers described how they produced a multi-celled algae strain by repeatedly selecting and culturing Chlamydomonas reinhardtii algae. After 73 rounds, they found that algae in one of the test tubes had become multicellular.


Observing the new algae form, Ratcliff and Travisano discovered that the multicellularity was produced by actively breaking up and shedding single cells — which grow into new multicellular clusters.

They then developed a mathematical model to explain the reproductive benefit of this single-celled strategy.

Their mathematic model predicted reproduction from single cells is more successful in the long run — despite single cells being less likely to survive than groups of cells. That disadvantage is compensated for by the sheer number of single celled life forms.


Ratcliff and Travisano are collaborating with Matthew Herron and Frank Rosenzweig at the University of Montana, to find the genetic basis for multicellularity and continue experimenting with evolving even greater complexity.


"Understanding the origins of biological complexity is one of the biggest challenges in science. In our experiment we reordered one of the first steps in the origin of multicellularity, showing that two key evolutionary steps can occur far faster than previously anticipated.

"Looking forward, we hope to directly investigate the origins of developmental complexity, or how juveniles become adults, using the multicellular organisms that we evolved in the lab."

Michael Travisano, associate professor, University of Minnesota College of Biological Sciences


Several years ago, Travisano and Ratcliff made international news when they evolved multicellularity in yeast. Their new work takes their previous findings further by initiating multicellularity in algae which has never had a multicellular ancestor.

Their success provides a new theory for evolutionary origins of the single-cell bottleneck in the history multicellular life cycles.

Abstract
The transition to multicellularity enabled the evolution of large, complex organisms, but early steps in this transition remain poorly understood. Here we show that multicellular complexity, including development from a single cell, can evolve rapidly in a unicellular organism that has never had a multicellular ancestor. We subject the alga Chlamydomonas reinhardtii to conditions that favour multicellularity, resulting in the evolution of a multicellular life cycle in which clusters reproduce via motile unicellular propagules. While a single-cell genetic bottleneck during ontogeny is widely regarded as an adaptation to limit among-cell conflict, its appearance very early in this transition suggests that it did not evolve for this purpose. Instead, we find that unicellular propagules are adaptive even in the absence of intercellular conflict, maximizing cluster-level fecundity. These results demonstrate that the unicellular bottleneck, a trait essential for evolving multicellular complexity, can arise rapidly via co-option of the ancestral unicellular form.

Original press release: http://www1.umn.edu/news/news-releases/2013/UR_CONTENT_461547.html