Zebrafish Heart – 3 Days Old

Here is the developing zebrafish heart at 3 days post-fertilization. Unlike mammals, which have four chambers, the zebrafish heart consists of only two: a single ventricle (left) and a single atrium (right). Despite the difference in the number of chambers, the heart is the first organ to form in both mammals and zebrafish. Can you guess why? The developing embryo needs nutrients and as its … Continue reading Zebrafish Heart – 3 Days Old


These images show cross sections of the different compartments of the developing gut in a chick embryo: esophagus (top), small intestine (middle), and large intestine (bottom), at days 6, 8, 10, and 14 (left to right). As the chick develops, the shape of the gut changes from a simple tube to a more complex form with specific surface folding patterns. The way the surface is … Continue reading Tubular

What large ants tell us about variation in complex human traits

Traits that exist along a continuum, such as height, size, and behavior, vary significantly from person to person. The genetic and environmental interactions that cause these characteristics have long stumped scientists. In a recent study by Alvarado et al., ant larvae were exposed to an environmental factor that regulated adult ant size. The scientists were able to generate large and small ants just by changing … Continue reading What large ants tell us about variation in complex human traits

Pigments: Patterning the Living World

The natural world displays an incredible amount of innate beauty, from snow-covered mountain peaks to exotic tropical reefs. For scientists and non-scientists alike, one of its most mesmerizing features is the pigmentation and coloration of living organisms. Biological pigments, found in animals, plants, and even bacteria, are compounds that absorb certain wavelengths of light and reflect others. This combination of light absorption and reflection gives … Continue reading Pigments: Patterning the Living World