Module 12 Blog Post

Diseases of Civilization: Acne 

Acne is one of the most common diseases of civilization, occurring in most populations around the world. It may not be as deadly as others like cancer and heart disease but it can signal an unhealthy diet or illness. How it occurs: Acne forms when a hair follicle is clogged by dead skin cells and sebum. Bacteria may be trapped in the follicle too, producing puss and causing inflammation. You usually see the worst acne in teenagers, when they are going through puberty.

 Acne Vulgaris: A Disease of Western Civilization | Acne | JAMA Dermatology | JAMA Network

This article presents interesting data concerning the absence of acne in the Kitavan islanders, and Ache hunter gatherers in Paraguay, as well as anecdotal evidence from medical professionals that acne was absent in Inuit and islander populations. These populations eat mostly natural foods like meats, fruits, vegetables; which are also all low glycemic index foods. There's not a lot of dairy, grains, sugar, or oils in their diets according to this source. Interestingly though, the article mentions that 3/4 Kitavans are smokers. The Ache people were similar, a population of hunter gatherers that were contacted and introduced to western good like bread, sugar, and tea in the 1970s. Following the introduction of western diet, diseases associated with it did not become more common.

Is Acne Fed by the Western Diet? (webmd.com)

This resource is good if you want to read about how the western diet influences the hormones and metabolic processes in the body. More specifically, the high glycemic index foods that are in the western diet can increase levels of insulin and IGF-1. The increase of these hormones leads to more sebum being produced. A really interesting fact from this article states that teens are more susceptible to acne because when you're still growing insulin resistance is a natural part of tissue growth. The article talks about the Academy of Dermatology not being able to say that "food causes acne", mostly because of papers written in the late 1900s, like one paper that specifically tested whether or not chocolate was a cause (the experiment showed that it didn't cause acne)

Dairy and Acne: How They’re Connected, The Myth and the Science (dermcollective.com)

This source has links to quite a few different studies that support the claim that milk itself may not be to blame for acne. Yogurt and cheese don't have any conclusive studies yet. Skim milk is shown to cause more acne, probably due to added sugars and whey protein. Milk also has naturally occurring hormones which can affect IGF-1. Fermented dairy, according to this source, was also shown to be correlated with decreasing acne.

There's quite a bit of evidence that shows that the western diet mainly causes/exacerbates acne due to sugar and hormones.

Sources

Is Acne Fed by the Western Diet? (webmd.com)

Acne Vulgaris: A Disease of Western Civilization | Acne | JAMA Dermatology | JAMA Network

Dairy and Acne: How They’re Connected, The Myth and the Science (dermcollective.com)

The age-old problem of acne - ScienceDirect This article is pretty interesting, it just kind of goes through how acne was described in history

Module 11 Blog Post: Speciation

Speciation in Nature

Hybridization takes two species that are evolved to be adapted to a specific environment. If two species from different environments interbreed, this could cause those mixed offspring to be less adapted to both environments, and the fitness of the hybrid will be lower than the fitness of their parents.A lot of zoo animal type hybrids, who may never mate in the wild, give birth to offspring that have multiple medical issues, live shorter lives, or are not able to reproduce.The only example of successful hybridization a marine mammal is the clymene dolphin (maybe, there was conflicting evidence online). The sources I looked through said it was possibly a hybrid of the spinner dolphin and the striped dolphin, both of which have habitats that allow for them to interact with one another. Examples of mammals in nature were hard to find because it can be hard to tell whether or not an animal is a hybrid or not (cryptic species, hard to test). There are also records of bottlenose dolphin/ false killer whale hybrids that exist in nature and also a viable hybrid that lives in captivity; the hybrid had two offspring that both passed. The resource listed below concerning the study of clymene dolphin hybrids claims that the genetic diversity created by hybridization can be beneficial. It can introduce genetic variation and create new species to fill new ecological niches. There are more species of dolphins, whales, and porpoises breeding and having viable offspring but its not common. For the hybridization to be beneficial and create viable offspring, maybe its just somewhat up to chance and the separate evolutionary paths each species takes and the types of selection acting upon both.

Whale-Dolphin Hybrids - Cross Species Hybridization (google.com)

Sources

Wholphin / Wolphin - WHALE FACTS

Don't call it a wholphin: first sighting of rare whale-dolphin hybrid | Whales | The Guardian

Hybrid Speciation in a Marine Mammal: The Clymene Dolphin (Stenella clymene) (nih.gov)

Module 10: Sexual Dimorphism

Pipefish Courtship

Sexual dimorphism evolves for a few reasons but the main cause of these differences in males and females is due to the fact that each sex has a different roll when it comes to how they experience selection. Males can develop characteristics like horns, larger size, ornamental feathers...etc. due to competition with other males and the need to impress females and pass on their genes. Some of these characteristics/ competitions allow the animal to compete with others and in some cases, the ones with the best fitness will pass on their genes.

Pregnancy is very costly for females of any species. Extra sustenance and is required due to the energetic costs of it. However, pipefish roles are reversed and the males gestate the offspring until birth. In pipefish, seahorses, and sea dragons, the females pass the eggs on to the males in a pouch or on their tails. Then the males fertilize the eggs in the designated pouch or tail, where they are kept until they hatch. Carrying offspring is a very costly and takes a lot of extra resources and stress on the body but the females of these fish only have to expend the energy it takes to make the eggs, which would usually be the males role. Instead the males take on the physiologically taxing role of carrying the offspring. Sexually dimorphic characteristics like the pipefish sail, antlers, and intricate peacock feathers are costly too so the roles in pipefish are generally reversed; the females court and the males carry young. Female courtship probably evolved in pipefish due to this reason. The males are able to choose a mate who they think will produce good offspring that are worth the cost to carry.

Similar to pipefish, male seahorses and sea dragons also carry offspring; but unlike pipefish, they have generally common sex roles in mating and courting. The males generally compete for female choice. Mating rituals involve mirror dancing and tail grabbing in seahorses. They are sexually dimorphic in some ways, like body and tail length, but they don't have flashy costly displays like the female pipefish. Maybe pipefish sail is a good indicator of health and that is how the female specific characteristic evolved. It also probably helps male pipefish make what they see as the best choice, to help choose the fittest female and have the fittest offspring.

Sources

BBC - Earth News - Ghostly 'dance of a sea dragon' - this short article explains the dancing courtship ritual of sea dragons and seahorses 

Module 9 Blog Post

Chinese Water Deer

The Chinese water deer has a teddy bear face fluffy ears and huge fangs. When we think of artiodactyls, we probably think they'll have horns or antlers, not fangs like a big cat. 

The teeth look to long to be any help in assisting with digestion, and the water deer is a ruminant, which means it has a four chambered stomach. The Chinese water deer's diet is herbivorous, however, a part of the ruminal physiology of the Chinese water deer is not well developed and they are not able to properly digest a diet of highly fibrous plant material.

Like most deer, the males of the species use these bony appendages to fight other males. These are solitary animals and the males will fight other males who come too close. I could not find if this was also a characteristic used in sexual selection, the territorial behavior only gets worse during mating season, so maybe that's something that should be studied in in the future. The males battle other males kind of like giraffes (that's how its described in the article at least, I tried to find a video of males fighting each other but I think I just found one where the male is trying to mate). They stand shoulder to shoulder and try to stab each other in the neck and back. Why are antlers more common tools for fighting in deer instead of fangs. The fangs are so cute :3

They have inguinal scent glands, which most other species of cervids do not posses. These glands are located in the area around their groin. The water deer lives in a place where tall grass and tall water plants grow. This is most likely an evolution that came about as advantageous for scent marking their territory, as they seem to be very territorial animals. Being solitary from members of their own species also probably helped facilitate this adaptation, they know that there are other deer in the area and the males know if they are intruding in another males territory.

Sources

ADW: Hydropotes inermis: INFORMATION (animaldiversity.org)

Bambi attacked by fanged buck - YouTube

Water Deer | NatureRules1 Wiki | Fandom

Why is Genetic Variation not Eroded Over Time?

 

Blog Post Module 8: Reflection 

There are several factors that keep genetic variation from eroding over time; some of which include non random mating, genetic drift, and gene flow.

Genetic drift: is a force of evolution that can cause random changes to a populations allele frequencies. 

Gene flow/Migration can affect a population in a few ways

    1) Migration can homogenize allele frequencies of multiple connected populations.

    2) Migration can create genetic diversity by introducing new alleles from one population to             another population.

Migration acts as a homogenizer but also introduces new genetic material to populations.

Crossing over and recombination: These events can increase genetic variation by allowing new allele combinations; from generation to generation, offspring have a greater chance of being genetically different from their parents.

Mutation causes a change in DNA sequencing, and in addition, creates new alleles to be passed on in a population

Depending on what kind of organism is being observed and what kind of non-random mating is exhibited, this force can create new genetic variation within a population. One type of non-random mating, inbreeding, decreases genetic variation. Another category of non-random mating, outbreeding, increases genetic variation. These opposite modes of non-random mating can be controlled by humans or occur randomly in nature.

This is an interesting article concerning populations recovering from bottleneck effects:

Bottlenecks and rescue effects in a fluctuating population of golden-mantled ground squirrels (Spermophilus lateralis) | SpringerLink

 File:Golden-mantled ground squirrel - Bow Lake.jpg - Wikipedia

They study involved researchers trying to find real life evidence of a rescue effect in a population of these ground squirrels. The researchers studied a population of the squirrels that had bottle neck effect that lasted about four years. The results of the genetic analyzation showed that while less than ten squirrels in the population remained, the effect of immigration kept the allele frequency from reaching a point of 100% heterozygosity (which usually happens in bottle necks. Also, the results of the study showed that there wasn't really a loss of fitness in the population. 

Genes seem to mix and change continuously in a way that they keep somewhat of an equilibrium.

This study implies that outbreeding/gene flow can increase genetic diversity. Out breeding is also something zoos do with their breeding animals, in order to keep the genetic material of the animals in captivity diverse.

sources

Outbreeding - an overview | ScienceDirect Topics

Bottlenecks and rescue effects in a fluctuating population of golden-mantled ground squirrels (Spermophilus lateralis) | SpringerLink

Module 7 Blog Post: Reflection

 

Reflection

    In my first blog post, I wrote about what my high school biology teacher told us about evolution; that its a change over time and that we change every day. I thought she was trying to say it in an inspirational way, not in the scientific way. Throughout this class, I learned what the actual definition of evolution is, how it occurs, and the mechanisms that facilitate it. Mechanisms such as selection, fitness, epigenetics, mutation, mutation rates, and Hardy-Weinberg assumptions. Definitions of these words were taught in other classes but we were not exactly taught how to show them visually and quantitatively like we do in the R exercises. One important concept I personally did not understand was how mutation rates can change and more importantly, how do they change. Now I know that DNA polymerase; which copies the DNA during replication, can become mutated which in turn can change mutation rates. That was one of the most interesting concepts. My view of evolution has changed in the way that, not only do we know the math that goes into these terms, but we are also learning how to read and create visual representations of these concepts. Evolution has a lot of depth to it, and there are so many interdisciplinary concepts that tie into the theory.

Taking genetics was a prerequisite to take this class, so I think all of us have a good background when going through the different mutation types, the Hardy-Weinberg assumptions and mathematically learning how to compute frequencies but we learning how to model it was not taught. I personally have trouble with the models on R exercises, mainly the cave molly and modeling different scenarios involving heritability of standard length and eye size.

I think learning more about the coevolution of pathogens and humans and how it occurs or evolutionary epidemiology would be interesting to learn more about. How and what about these concepts are modeled and what can we learn from it theoretically and realistically. 

Module 6

Chinchilla inbreeding

Most pet chinchillas in the United States are probably descended from 11 chinchillas that were brought into the country from Chile in 1923. They were most likely almost hunted to extinction for fur in the 1800s and 1900s. Today, there are probably only around 10,000 individuals left in the wild. With only 11 individuals to work with, pet chinchillas were most likely the result of severe inbreeding. A lot of pet chinchillas today suffer from malocclusion, which is considered a polygenic trait.

Of course captive chinchilla breeding is not natural and usually involves selectivity, non-random mating is not really possible to observe. Malocclusion is a misalignment of the teeth and because chinchillas are rodents, this is a life-threatening medical condition for them. With inbreeding, or facilitative assortative mating, breeders can breed chinchillas with the cute characteristics everyone loves; thick fur in a variety of colors, a cute squirrely tail, and a stocky body. Captive breeding with this method could also give fur collectors what they want without assisting in extinction of the wild chinchilla. 

Wild chinchillas are generally a yellowish gray color to help them blend in with their native habitat in the mountains. Through domestication and selective breeding, chinchillas now come in colors like white, black, blue-gray, violet, and pearl. Some colors are recessive, some are dominant, and some are expressed by dosage and incomplete dominance. Some of these colors most likely arose and were kept in circulation by some degree of inbreeding. 

Assortative mating resulting from inbreeding in the wild could be beneficial for the remaining population of chinchillas to select for the traits that were most beneficial for survival in their changing environment (maybe?).

Disassortative mating stemming from inbreeding could also be beneficial for the remaining chinchilla population for keeping unhealthy phenotypes in check, such as a different fur color that does not blend in or malocclusion (if it occurs in wild chinchillas (possibly?). 

Sources

Chinchilla Colors - Pet Ponder color genetics

Chinchillas.com Chinchilla Malocclusion

Fun Facts About Chinchillas | Live Science