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When family weddings all seem to coincide with one another, the phenomenon happens for a reason. An individual and their first cousins tend to be of a similar age, so their weddings usually happen in a similar time frame. But weddings for extended family members, say second and third cousins, tend to be more spread out. This is because the time between one generation to the next varies, meaning that families become more spread out from generation to generation.
A new study by University of Pennsylvania post-doc Farshid Jafarpour from the Department of Physics & Astronomy, who works in the lab of Andrea Liu, reveals that variations in generation times don't accumulate over multiple generations in single-celled organisms, like bacteria. He proposes a new theory, published in Physical Review Letters, that describes how factors that regulate the size of individual cells influence the growth rate of an entire population.
Animals - Plants - Bacteria - Size - Population
Unlike animals and plants, bacteria increase the size of their population simply by growing in size and then splitting in half to make two new bacterial cells. By studying bacteria when they are dividing on a regular basis, known as the exponential growth phase, Jafarpour was able to develop a model that mathematically describes this fundamental phase of population growth. "If you want to study the physics of bacterial growth, you really want to remove all the other parts that are not part of the growth phase," he says.
Jafarpour used a combination of math equations, computer simulations, and data from biology experiments that tracked the growth of individual bacteria cells. He was surprised to find that the model predicts that bacteria oscillate between slower and faster bursts of growth, in "synchronized bursts of divisions," instead of the population growing at a constant rate. These population-level oscillations in growth now provides a new, mathematical...
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