Blog Post: Module 3

 Measuring Fitness

I believe fitness is the ability of an organisms genetics to survive and be passed on to further generations. The ability of an organism to pass on its genetics also depends on the environment the organism currently lives in and has lived in.

Some mammals experience a change in coat color when the seasons change in winter and summer. Arctic hares and arctic foxes are good examples of this. Coat color in animals like the arctic hare tends to vary depending on the region and the variability of snowfall. A link below goes to an in-depth article about animals that change coat colors in the summer and winter and explains the genetics and physiological processes that are affected by it. The article states that there are variations in the change of coat color between seasons; some animals change from a full white coat in winter, to a brown coat in summer. Others only have pachy or incomplete appearing changes; some have brown and white patchy coats and others get grayish or blueish coats.The animals that grow fur a coat color inbetween brown and white seem to usually live in regions where snowfall is variable and does not occur at the same time every year. The article also states that it seems like the animals that do not adapt a coat color that accurately reflect the rate of snow fall at a given time is possibly less likely to survive.

One way that we can probalby quantify fitness is by looking at birth and death rates of a population of hares of a specific phenotype. If someone were to pick a certain phenotype of an animal, like an arctic hare and followed a population of them for a few generations (maybe a decade or longer), they could possibly see correlations between the environment and the phenotypes passed down. If the organisms phenotype is considered to exhibit fitness in its environment, then they would see that phenotype passed down. If another phenotype persists more than the others, those phenotypes may work better than others in the given environment, like a hare developing a grayish-brown coat color instead of a full white or full brown coat. Mathematically, this could be done by calculating phenotypic, genotypic, and allelic ratios and observing them throughout time.

Cute bunnies :)

Sources

https://onlinelibrary.wiley.com/doi/10.111/brv.12405?__cf_chl_jschl_tk__=pmd_nZ_BiLldamzFzrvETjaZIk5K7_U.ytU3UHNsNrYm5OQ-1632529904-0-gqNtZGzNAeWjcnBszQdR

coolantarctica.com 

https://ejphoto.com/arctic_hare_page.htm

Blog Post 4

Blog Post 4

The circumstances that high and low mutation rates might be adaptive are in places where the ecosystem or habitat is constantly changing around a species or where the environment around a group of organisms stays fairly constant. There are parts of the DNA that code for reparation and replication; this means there is a way for the rate of mutation to become heritable. 

Darwin's postulates say that individuals are varied in the traits that they exhibit; which probably means the mutation rate of individuals is also varied, due to the different genetic makeup in the regions of the DNA that code for reparation and replication. If the rate of mutation is possibly different quantitatively from individual to individual, then from species to species, it must differ greatly. Do large organisms have a higher or lower rate of mutation than smaller animals? Do viruses and bacteria have higher mutation rates than higher order organisms?

Another one of Darwin's postulates is that survival and reproduction of offspring is directly influenced by the traits they inherit from their parents. To what point in an organisms development can we test mutation rate for? Only organisms with mutations that are beneficial or only slightly hindering are able to be seen. Lethal mutations are probably not easily observed in a nature setting, and therefore may not be considered when calculating mutation rate. Environmental factors must play a part in the way mutations occur and are passed on, as they can directly affect the DNA. Environments with high levels of environmental chemical exposure or sun exposure would mostly likely increase mutation rates within a population.

Heritability would probably have to be calculated in order to get a quantitative look at how genes that directly affect mutation rates are inherited from generation to generation.

Here is an interesting scientific article regarding mutation rates in E.coli 

High mutation rates limit evolutionary adaptation in Escherichia coli (plos.org)

Information from the chapter 3 reading assignment in module 3 was used in this post

Module 2 Blog Post: Compelling evidence of evolution

                                            Good Old Earth

    Earth is around 4.6 billion years old. We can figure this out by analyzing and comparing objects in space and the light they emit, and radiometric dating, which measures the amount of decay a uranium isotope has experienced. Scientists can tell decay has happened by looking for elements that result from the decay like radium and radon isotopes. By knowing how long an object takes to decay means we can measure time from observing this object; kind of like knowing how old food hiding in your fridge may be by looking for new products and decay that results from the passage of time. This live science article (How is Earth's Age Calculated? | Live Science) has quite a few interesting facts concerning the different calculations of earths age and the universes age in the past 200 years. According to the article, a geologist named Arthur Holmes, in the early 1900s, proposed that the earth was around 1 billion years old and was later confronted by a large amount a disagreement from the low estimate. The universe was also quite young apparently; about 1.8 million years old as was proposed in the 1920s. Today, scientists propose the universe is more than double the age of Earth. The large margin of error could be due to differences in technology and techniques used to measure decay and detecting specific materials.

    Species on average seem to last around 1 million years (How long do most species last before going extinct? | Live Science). With all the changes that the Earth's climate has been through composition and temperature wise; life would have had to change to some degree (sometimes a severe degree) to become viable. Many forms of life today require oxygen to live, but oxygen was not abundant on the planet until certain life forms came about and produced it as a by product, like plants and microbial life. The Smithsonian article mentions the debate scientists have over the current extinction rate and the different real world factors that make it difficult to measure. Some of those factors include, a sparse species being difficult to find or animals that are extinct in the wild but kept in a zoo. Some species may last a couple million years according to the article.

    After comparing the rate of these two values; the earth being billions of years old and the average rate of time a species lasts before going extinct (a few million), there has to have been changes that allowed life to carry on. The life that did carry on had millions of years to adapt to changing temperatures, air and water composition, and changes in their ecosystems (life evolving alongside each other).

 How Old Is Earth? | EarthDate

(This is a fragment of meteorite found in the Canyon Diablo that helped scientists create a method to radioactive dating)

This resource also includes the fact that it is easier to find undisturbed samples on the moon, as the moon does not have plate tectonics.

Module 1 Blog Post: What is Evolution?

                          What is Evolution? (In Your Opinion)

    An old biology teacher of mine used to tell the class that evolution was a change over time, and that everyone experienced evolution everyday. It might be a slightly simplified definition of evolution, which is defined in one way as descent with modification. Our teacher was probably just trying to fit in a motivational speech to us in the lecture. Evolution is what turned primitive single-celled life into millions of multicellular organisms. Organisms evolved to live all over the planet in extreme places like the deep ocean, and in places with extreme temperatures, hot and cold. 

    A scientific theory is something scientists have spend a good amount of time running experiments and gathering data for. The data will always have room to improve with advances in the technology used to record it and the understanding of the subject. With this in mind, the theory is still something we can see is happening, we just need data and concrete evidence for it to be a fact. I believe that evolution has to be a fact. Evolution can be seen through observing creatures that exist currently and in the distant past of years ago. The observations that scientists find giving evidence to evolution include fossils, human artifacts, ancient art, and the layers of sediment where the past is buried under. The layers of earth can be examined for carbon dating and depending on what substances are found in the ground, we can see what the composition of life and land in the area was and how it changed. Fossils give us an opportunity to see what life forms existed in the past and how the organisms present today came to be. by looking at genetics, physiology, composition, and many other variables, scientists and create a tree to map out the path of evolution a species took through the past 4-5 billion years. There are many different explanations as to how the process of evolution occurs. An interesting idea that is not supported by scientific evidence is Lamarck's ideas about inheritance; if an animal loses a limb, the offspring of the animal will now be born without that limb. Gregor Mendel left behind detailed and thorough data collected from breeding pea plants. The mechanism of genetic inheritance of certain traits in pea plants has been very influential in the field of genetics; which is the most important component of evolution. In conclusion, evolution is a fact the way we know what color the sky is; we just need to find evidence and data that can explain how it happens.