What happens when you ask a bunch of undergraduate students to contribute short pieces for a class blog on evolutionary topics (with the minor incentive of extra credit)? Turns out to be quite an educational experience, if you follow the links below! About half the students in the Spring '07 Evolution class here at Fresno State contributed a variety of essays on what they've been reading outside class, what they find fascinating and worth sharing in the world of evolutionary biology.
Having been unsure of what to expect, and frankly, being a bit nervous about this experiment, I am really glad I opened up the blog to students - what a way to get a small army to go out and find interesting tidbits from the frontiers of evolutionary biology! And gratifying to think that by the end of a seemingly long semester, one hasn't entirely killed their interest in the subject! (well, I might be flattering myself there - perhaps the interest remains despite my best efforts!) I think you will enjoy these diverse essays as much as I did - so if you know these students, pat them on the back (and you students can pat yourselves!).
So here's a list of all the essays contributed thus far:
- 28th Annual CCRS - a report
- Barn Swallows: Bringing sexy back
- Are chimps more evolved than humans?
- Gene links longevity and diet
- Language, Learning, Logic and the Chimp Genome
- To See Or Not To See: The Mexican Tetra’s Question
- Walking on eggshells... evolutionarily
- Corals more complex than you?
- From DNA analysis, clues to a single Australian migration
- Hollywood knows what's to come
- Why do ducks have big d..cks?
- Promiscuous females cause male zebras to have bigger testes and act all weird
- How the itch came about: Humans and Gorillas get intimately close
- Eat like a python = run like a horse? Or how digestive regulation has evolved
- Positive parasites?
- Sexual dimorphism and adaptive radiation
- Fascination of the cetacean cognition
I might have to try this again in future classes...
(PS: if you have submitted something but don't see it on this list, email me to make sure I haven't missed / lost it when my laptop hard drive crashed last week)
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Caribbean and Florida adventures offer several amazing encounters to interact with dolphins whose cognitive abilities excel the event. However, a new perspective on cetacean brains claimed that the cognition of cetaceans is merely a complexity associated with an increase in thermogenic neural cells as a result of climatic cooling in Eocene-Oligocene era. Nevertheless, countless laboratory exercises and research on communication, behavior, and social structures confirms that cognition is the principal factor of cetacean brain complexity, as reviewed in the latest issue of PLoS Biology.
Substantial evidence indicates cochlear and cortical modifications—attributed to the echolocation—within cetaceans’ brains around this Eocene-Oligocene transition. Contrary to the controversial report, cetacean body size became smaller during the Eocene-Oligocene transition. And with it a new dynamic altered the predation order of early cetaceans that may have contributed to behavioral changes. Independent cortical development occurred during the divergence of primates and cetaceans, yet convergent evolution is evident in many of the similar social and behavioral traits; especially limbic associations such as intuition, social awareness, and decision-making. An abundance of glial cells—crucial for axonal myelin— in the cetacean neocortex represents white matter that is exclusive to humans and cetaceans.
Many studies of bottle-nose dolphins in particular reveal cetacean understanding of self recognition, manipulation of mechanisms, and precision and memory of symbols and patterns. Cetacean dialect also has the capacity for advanced sound and recognition, discernment, and imitation as evidence for social learning in cognition. Bottle-nosed dolphins demonstrate an ability to communicate in conveying directional information (i.e. target exercises) and comprehending human gestures and pointing in interactions. Furthermore, cultural aspects such as ‘alliances within alliances’—a social behavior even rare to humans—are continually being researched within cetacean communities. Studies have proven evidence of meaningful relationships and cultural acquistions of direct teaching such as Killer Whale methods of cruising the incoming waves to catch prey on shorelines.
Cognitive similarities in social behavior with humans reveal that cetacean complexity is more related to function than body size. Incorporation of structured vocals and visual behaviors in communication indicate higher order cognition. Most notably, echolocation illustrates the remarkability of cetacean cognition; utilization of this cetacean feature is even being pursued in naval counter-terrorism efforts. So, if you get a chance to interact with these fascinating cetaceans, understand they may not be that far down the food chain from humans.
Reference:
Marino, L. (2007). Cetaceans Have Complex brains for Complex Cognition. PLOS Biology: Online Peer-reviewed journal. Volume 5: Issue 5 (e159)
--contributed by Jerome Lewis
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Caribbean lizards have strong sexual dimorphism (that's a female Anolis lineatopus on the left, and male on the right in the above image). Their degree of sexual dimorphism has led them to use resources in different habitats that limit competition between the opposite sexes of the same species. Scientists from Harvard University, the University of Hawaii, and Washington University in St. Louis, studied the role of sexual dimorphism in evolutionary diversification among anole species during their well-known adaptive radiation.
Anolis lizards originating in the West Indies have evolved independently in Cuba, Hispaniola, Jamaica, and Puerto Rico. Each species on each island has evolved traits that have allowed them to fit specific habitats through adaptive radiation. Past studies on adaptive radiation has focused primarily on males but it is important to consider both sexes because the study of sexual dimorphism helps explain the importance of male and female contribution to the population’s survival.
Marguerite Butler, Stanley Sawyer, & Jonathan Losos studied 15 different species of Anolis lizards and found that only 14 percent of niches were occupied by both sexes of the same species. 45 niches were covered by females and 36 percent of niches were occupied by males. By occupying different niches, males and females can decrease competition. For example, the sexes in hummingbirds have different lengths in beak size. This allows them to obtain nectar from different flowers which eliminates competition for food. By reducing competition between males and females of the same species, individuals increase their chances of surviving which leads to a higher fitness level of the whole population
--contributed by Jemimah Corpuz
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Recent research has discovered that parasites can evolve fairly quickly to become helpful instead of harmful. Parasites have long been famed to be harmful to their hosts with some harmful enough to even kill their host. In the case of a parasite known as Wolbachia, present in nearly one fifth of all insects, harmful affects are typically in making females less fertile; but scientists have now discovered that Wolbachia can boost female/host fertility instead of lessen it in order to spread themselves in nature. Insects can only get Wolbachia from their mothers and additional effects from this bacteria include, turning males to females, causing infected females to reproduce without males and triggering vicious cycles of increasing female promiscuity and male sexual exhaustion. The presence of these parasites also often carries a toll on their victims, for instance, cutting down the number of eggs that females produce. Despite these effects, researchers have found that in span of just 20 years, this bacteria has evolved means of boosting offspring production to better spread itself in a laboratory setting by 10%. Initially a 20% decline in offspring production was observed.
But what about the idea of a positive parasite?
It is still unknown how Wolbachia lead to a boost in fertility, but experts suggest it is due to a nutritional benefit. In that rapid evolutionary span, Wolbachia have been concluded to be heading in the direction of being needed for host survival. This developing mutually beneficial relationship has been compared to the symbiotic relationship of mitochondria within cells. Wasps for example need Wolbachia to generate eggs in order to reproduce. This research sheds light on the symbiotic theory and shows that a dependant relationship between host and parasite can evolve in a very short time span.
--contributed by Stephen Rettig
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A few weeks ago, Prof. Stephen Secor from the University of Alabama visited Fresno State to speak in the Department of Biology seminar series. Professor Secor lectured on his studies of the regulation of digestive systems as an evolutionary response. His study subjects were pythons who tend to fast for long periods of time between feedings. His finds show that the upregulation of the digestive system in short bursts is more energetically favorable to species that tend to fast for long periods of time. Upregulation is the process where a body system goes from a complete state of dormancy to fully functioning with a matter of hours and then goes dormant once the necessary function has been carried out. Examples of upregulatory animals are pythons, boas, and hibernating animals to an extent. This is atypical of other digestive systems that tend to idle between meals instead of complete shutdown. Signs of expatiated upregulation are increased nerve activity, increased blood flow to system, increased heat, and production of bodily fluids like stomach acid. His ideas were to prove that the quickened upregulation is an evolutionary response. The quickened upregulation save an animal more energy than constantly idling the body system. This reduces the necessary amount of food intake and reduces the need for the animal to hunt down prey. The lecture was very informative and interesting.
--contributed by Mark Garcia
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While researching hominid evolution I came across this interesting article on the Discovery channel webpage by Jennifer Viegas, titled “Lice Passed from Gorillas to People,” that commented on a study done by David Reed and team, on the evolutionary history of anthropoid primate lice.
According to the study, humans have two genera of lice invading our bodies. These are the body and head lice, Pediculus and Pthirus. The latter, found only on pubic hair, was derived from a common ancestor with the louse found on gorilla. Since louse is very host specific it is possible to analyze the evolution of the host with that of the parasite. Therefore, the study done by Reed and team was in search of discovering the evolutionary history of the human lice. They did this by extracting DNA from both the the species found on gorilla and those found on humans. The study involved the use of PCR studies, alongside phylogenetic and cophylogenetic analyses.
Figure 1. Phylogenetic trees for primate lice and their vertebrate hosts. Trees are shown as cladograms with no branch length information, and are based on molecular and morphological data. Dashed lines between trees represent host-parasite associations. Humans are unique in being parasitized by two genera (Pediculus and Pthirus). Photo credits: J. W. Demastes, T. Choe, and V. Smith. (click on image for larger version).
So what happened? Well the studies showed that the human
Pthirus diverged from the gorillas species a lot more recent than the actual divergence of human from gorillas. Humans and gorillas separated about 7 million years ago, while the
Pthirus species has a common ancestor at about 3 million years ago. It is a well known fact that pubic lice are introduced by sexual contact - does this then imply that humans were having sex with gorillas 3 million years ago? As impossible as this may sound, it is a potential hypothesis, but there are others as well that can explain the relatively recent divergence of the two species. Such as host switching, duplication and extinction among the lice. Overall, this study is an example of coevolution among parasites and their host. How exactly the human host came to acquire pubic lice from gorillas is still an open question, and somewhat impossible situations cannot necessarily be ruled out completely.
--contributed by Patricia Torres
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This article (from 1990) examined the differences in male zebra mating behavior and testicular size as influenced by polyandrous and monandrous zebra mares. The study focused on comparing the plains zebra (Equus burchelli) with Grevy’s zebra (E. grevyi) in northern Kenya. Plains zebras reside in herds consisting of several females and a single stallion. Females are considered monandrous as they will stay and mate with the same male for 9 – 26 months. This is the same type of mating behavior seen in wild horse populations. Grevy’s zebra females are generally polyandrous and typically travel in small groups without a male. These groups of females may travel through the territories of up to four different stallions each day. This polyandrous behavior is also seen in female asses (E. asinus) in wild populations. When mating, the polyandrous mares will stay with the stallion for only 1 – 48 hours. After giving birth, a normally polyandrous mare may become monandrous and stay with a male for 3 – 59 days. This longer association with the male provides that mare and her newborn with protection and allows the stallion a chance to mate with the mare.
The promiscuous mating behaviors of female Grevy’s zebras have caused the males to evolve in ways that would help to improve their reproductive success. Grevy’s zebra stallions that are mating with polyandrous females will exhibit more mating behaviors such as calling and mounting and will mate with the female more frequently than stallions with monandrous females. Polyandrous mares also exhibit a shorter estrous than monandrous mares, thus decreasing the amount of time that she will be receptive to the stallion and requiring him to mate often to increase chances of conception. The frequent mating requires greater stores of sperm and has led to the evolution of larger testes in the Grevy’s zebra. Larger testicular size enables the stallion to breed more frequently and also allows him to produce greater volumes of sperm to help improve his reproductive success.
--contributed by Abigail Hall
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A post-doctoral researcher at Yale University, Dr. Brennan, has recently made some interesting findings in her studies on duck genitalia. The observations have both answered and raised questions about the co-evolution of waterfowl species, particularly, ducks.
The findings of Dr. Brennan’s study, published in this month’s journal, PLoS One, give us a better understanding of not just the mating practices of ducks, but also the physiological aspect and how it relates to the co-evolution of sexes in these species. For example, of 16 species of ducks and geese caught, Dr. Brennan found that the size of the male phallus was matched to fit the size of the female oviduct. As Dr. Brennan put it “When you dissected one of the birds, it was really easy to predict what the other sex was going to look like.”
What was fresh in this area of study is that Dr. Brennan examined the female anatomy of waterfowl, an area that has been overlooked. Through the study of the female genitalia, Dr. Brennan was able to observe that not only did the female genitalia range in size and shape, as their counterpart male, but that females are capable of expelling male sperm, perhaps as a defense when they are forced to mate, as is the case often. This argument comes from “studies on some species that have found that forced matings make up about a third of all matings. Yet only 3 percent of the offspring are the result of forced matings. ‘To me, it means these females are successful with this strategy,’” said Dr. Brennan.
This article is very interesting and sheds light on the co-evolution of waterfowl species. The findings from the proceeding study also raises questions such as, “Why does the male phallus return and disappear every year?” This is a great read for any ornithologist!
--contributed by Danny Tovar
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Yes, the blog lives, at least until I have shared all the last minute student submissions so you can all enjoy reading them during / after finals week!
So why did I move here? Well, basically, blame Apple! Yes, the makers of my beloved laptop (oh awright... go ahead and snicker, all those of you who were laughing at me as I fumbled with the ugly Dell laptop for my last lecture) have so far overlooked a rather serious flaw in their iWeb application, which I was using to create the lovely old class blog! So when the hard drive crashed last week, one of the files that got corrupted was the iWeb file for the class blog. And wouldn't you know it - this was just when I had made a number of recent updates but had not backed up the disk in some weeks! Well, having recovered most of the other data over the weekend, and cursed and shaken my fists at Apple for not allowing me to easily update the blog without having to recreate most of the old posts, I finally turned to Google's Blogger, which has proved more reliable and robust for my other class blog.
So here we are... and I'm posting the remaining student submissions in this place now. I will also post a running index of all student articles, from both the old and new locations so they are all available through one place. If you've sent me something, but don't see it pop up here, do let me know as I may have lost your email amid all this shuffling around!
Enjoy reading!
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