Category Archives: genes and genetics

Evolution: A Quest for Change

Posted on by
Reply

Contributed by Mark Jedrzejczak

https://www.youtube.com/watch?v=IVCmoPcqdEI

Ever since Morgan Freeman’s success on the Science network’s program, “Through the Wormhole” the actor has been much sought out for his iconic narrative voice and style. We are proud to present the first episode of his* most recent documentary series on the topic of macroevolution, “Evolution: A Quest for Change”.

(* well, someone that sound like him, anyway.)

The title reflects a little tongue-in-cheek on the part of the producers, since evolution is not really a quest, since quests involve a mission with an end goal. Instead, evolution is more like a knight going doing a bunch of random missions and after some time, he starts to choose those missions that get him the most princesses. Similarly, evolution is a process driven by the nonrandom selection of heritable traits that impart the best fitness. This ends up changing the gene frequencies in a population over time. On a macroscopic level, this is characterized by the evolution of a species’ gene pool as a whole, often leading to divergence and speciation. The process of macroevolution is responsible for the existence of all the organisms that ever were and will be inhabiting our pale-blue dot, planet Earth.

This documentary presents the topic of large-scale evolution, the main mechanisms that drive macro evolution, and what evidence exists for the process. At the same time, the documentary helps highlight the importance of scientific literacy, critical thinking, and smart science teaching, especially for today’s youth. Research done by Hayat Hokayem and Saouma BouJaoude (2008) on college student’s perception of evolution underscores the importance of understanding the student’s perspectives on the theory of evolution. In addition, their research suggests that accepting and working with an individual’s “cultural milieu” or worldview is the most effective method of conveying scientific ideas. An instructor simply handing a student a stack of scientific information is not good enough, especially when the latter starts reading the information with a set of presuppositions. These biases should to be understood and used as building blocks, and should not be seen as pieces that instructors need to be tear down.

A more effective way of teaching is to build upon student’s misconceptions…and also not to even use the word misconception. One study by April Cordero Maskiewicz and Jennifer Evarts Lineback (2013) advocates using students’ incorrect ideas about science as a resource for refining teaching strategies.

This documentary addresses a few of these “misconceptions”, especially a couple that were highlighted in the Maskiewicz and Lineback study. These were that ‘natural selection is trying to give what the organisms need.’ The video clearly discusses that evolution and the process of natural section have no goal or “finish line.” Another incorrect idea, taken from the “MiTEP List of Common Geoscience Misconceptions Organized by the Earth Science Literacy Principles”, that biases new students in the field of evolutionary biology, is the “young Earth” model, and this too is addressed in the video.

For more information, see:

Age of the Earth. U.S. Geological Survey. 1997. Archived from the original on 23     December 2005. Retrieved 2006-01-10.

Oberthür, T, Davis, DW, Blenkinsop, TG, Hoehndorf, A (2002). Precise U–Pb mineral ages, Rb–Sr and Sm–Nd systematics for the Great Dyke, Zimbabwe—constraints on late Archean events in the Zimbabwe craton and Limpopo belt. Precambrian Research 113 (3-4): 293–306.

Carlin, J. L. (2011) Mutations Are the Raw Materials of Evolution. Nature Education Knowledge 3(10):10.

H Su, L-J Qu, K He, Z Zhang, J Wang, Z Chen and H Gu. (2003) The Great Wall of China: a physical barrier to gene flow? Heredity. 90, 212–219.

Liman, R., Sheehy, B. & Schultz, J. (2008) Genetic Drift and Effective Population Size. Nature Education 1(3):3.

Macroevolution. Understanding Evolution. 2014. University of California Museum of Paleontology.

Hokayem, H. and BouJaoude, S. (2008), College students’ perceptions of the theory of evolution. J. Res. Sci. Teach., 45: 395–419.

April Cordero Maskiewicz and Jennifer Evarts Lineback Misconceptions Are “So Yesterday!” CBE Life Sci Educ September 4, 2013 12:352-356.

MiTEP List of Common Geoscience Misconceptions Organized by the Earth Science Literacy Principles. http://mitep.mspnet.org/media/data/MiTEP_List_of_Common_Geoscience_Misconceptions.pdf?media_000000007297.pdf

Survival of the Fittest: Monarch and Viceroy Butterflies

Posted on by
Reply

By: Chris Frey, Griffin Murphy, Jason Shah, Mick McColl

Darwin’s Theory of Evolution was a groundbreaking advancement, explaining how natural selection results in the inherited biological change within a population. This is evolution. Biological fitness is central to this theory, and although many people understand that the fittest survive, not all understand what this truly means.  Biological fitness is measured by the ability of an organism to reproduce and successfully pass on its genes to future generations. Misconceptions arise when individuals perceive the largest, strongest organisms within a population to be the most biologically fit. To demonstrate fitness in the context of evolution, one need only look at butterflies.  They come in all shapes, sizes and colors, sometimes adopting another species’ physical characteristics in a process known as mimicry.  Mimicry comes in several varieties, including Batesian mimicry, which is when a palatable organism mimics a species that is unpalatable to predators. Consequently, they are avoided by predators, increasing their fitness.

A vivid example of Batesian mimicry is depicted by Viceroy and Monarch Butterflies. Monarch butterflies are unpalatable due to toxic milkweeds they consume as larvae, which results in low levels of predation in their natural environment.  Viceroy butterflies have wings emblazoned with similar shape and color schemes, ostensibly reducing the predation rate. Colors must be matched very closely as avian predators have some of the most developed eyes in the animal kingdom (for more information, see paper from 2012 by Stoddard and colleagues listed below).

A vivid example of Batesian mimicry is depicted by Viceroy and Monarch Butterflies. Monarch butterflies are unpalatable due to milkweed they consume as larvae, which results in low levels of predation in their natural environment.  Viceroy butterflies have wings emblazoned with similar color schemes, ostensibly reducing the predation rate. Wing shape plays an important role in mimicry too (for more information, see paper from 2013 by Jones and colleagues listed below).

Monarch and Viceroy butterflies serve as a model organism for mimicry and the evolutionary concept of survival of the fitness. Similar mimicry models have been recently exposed within a microbiological context. A bacterial pathogen has been discovered that mimics the structure of some of its intended hosts’ carbohydrates. This structural mirroring results in a reduced innate immune response by the host (for more information, see paper from 2009 by Carlin and colleagues listed below). In essence, the bacterium mimics the structure of the host species in order avoid immune detection and thus increase its chance of survival.

A visual explanation of Monarch and Viceroy mimicry has been provided below:

 

In addition, listed below are some articles on mimicry

Carlin, Aaron, et, al. 2009. Molecular mimicry of host sialylated glycans allows a bacteria pathogen to engage neutrophil Siglec-9 and dampen the innate immune response. Blood Journal. 2009.

Holmes, B. 2010. Accidental evolution: the real origin of species. New Scientist 205: 30-33.

Jones, R.T. 2013. Wing shape variation associated with mimicry in butterflies.        Evolution 67: 2323-2334.

Matthews, E.G.  1977. Signal-Based frequency-dependent defense      strategies and the evolution of mimicry. The American Naturalist 111: 213-222.

Rowe, C. C. Halpin. 2013. Why are warning displays multimodal. Behavioral Ecology and Sociobiology 67: 1425-1439.

Stoddard, M.C. 2012. Mimicry and masquerade from the avian visual perspective. Current Zoology 58: 630-648.

Williamson B.G., C.E. Nelson. 1972. Fitness set analysis of mimetic adaptive strategies. The American Naturalist 106: 525-535.

Yahner, R.H. 2012. Additional adaptations against predation. Wildlife Behavior and Conservation 55-64.

 

Convergent Evolution

Posted on by
Reply

Contributed by Greg Fricker and Geoffrey Welch

Have you ever thought how similar butterflies and bats are in taking to the skies? Looking around, we see that both of these creatures use wings for flight; however, butterflies are insects, and bats are mammals, like you and me. If we imagine the tree of life, these organisms would be on distant branches, having distinct lineages, but they have similar characters. Convergent evolution is this phenomenon where similar characters evolve independently in multiple lineages. This seems like a counter-intuitive process initially, as similar features are often associated with relatedness. As evolution is all about favorable hereditary traits being passed on to future generations, how then do the same traits arise in completely separate lineages?

The answer lies in the selection pressures organisms face. When a certain trait is so remarkably important for organisms in a particular environment, it can be expected to arise in multiple different species. For example, consider underwater foraging birds. Cormorants, penguins, puffins, and gannets, each with minimal relatedness to the others, have evolved to have a “pygostyle” tail, which is straight and elongated.  This pygostyle tail is vitally important to these birds, as it acts like a “rudder,” allowing for enhanced steering in water, just like the rudder on a sailboat. This rudder is so beneficial for these underwater foraging birds in finding food–and thus surviving and having offspring–that we see it arise multiple times. When the random mutations occurred separately in these four species, the advantage provided by this “rudder” tail ensured that the pygostyle phenotype would be passed along to future generations.

Yet another example can be seen in echolocation, or the ability of an animal to use vocalizations to locate objects and better “see” its environment.  It might be easy to dismiss instances of convergence within the birds previously stated due to the fact that all four cases are aquatic birds, and thus seem as though they would be at least somewhat related. In that case, consider bats and dolphins. Despite the fact that they are both mammals, bats and dolphins would be expected to share little in common, as they both evolved in drastically different environments.  However, both utilize echolocation. Not only did they both evolve the same physical trait, but it has been determined that the two groups converged on a genetic level as well. Three separate genes that play a role in echolocation, including a protein associated with inner ear hair formation, have been shown to have converged among three separate groups–dolphins and two groups of bats. Echolocation provided such a substantial fitness benefit in the two separate environments of caves and marine life that natural selection drove the evolution of it in these rather unrelated lineages.

For more information, check out the video below:

https://www.youtube.com/watch?v=_Qx2ZE7tKv4

Also, check out some of the recent research on convergence:

Parker et al. 2013. Genome-wide signatures of convergent evolution in echolocation mammals.  Nature. 502: 228-231.

Shen et al. 2012. Parallel evolution of auditory genes for echolocation in bats and toothed whales.  PLoS Genetics.  8(6): e1002788.

Liu et al. 2010. Convergent sequence evolution between echolocating bats and dolphins. Current Biology. 20 (2): 53-54.

Jones, G and MW Holderied.  2007.  Bat echolocation calls: adaptation and convergent evolution.  Proceedings of the Royal Society B. 274: 905-912.

Felice, RN and PM O’Connor. 2014. Ecology and caudal skeletal morphology in birds: the convergent evolution of pygostyle shape in underwater foraging taxa. PLoS One.  9(2): e89737.

Alerstam et al. 2011. Convergent patterns of long-distance nocturnal migration in noctuid moths and passerine birds. Proceedings of the Royal Society B. 278(1721): 3074-3080.

Gleiss et al. 2011.  Convergent evolution in locomotory patterns of flying and swimming animals.  Nature Communications. 2: 352.