Well. it seems like we have covered everything about evolution that is possible. But, have we? We discussed Darwin and how he got his ideas and then microevolution. However, there seems to be just one thing we haven’t really dug into and that is Darwin himself and all his theories. I know, I know. You’re probably thinking I’m going to tell you everything you’ve already heard before. You must already know everything there is to know about Darwin anyway. He was that one guy way back when who did that one thing that affected all these other things, right? Wrong! My mission today is to tell you brand new things I learned about Darwin and his theories and to teach you something about evolution.
To bring you this blog post today, I sta through a 1 HOUR long lecture all about Darwin, and while I did learn a lot of interesting things, Iwould rather never do it again in the highschool computer lab (Many Mandi’s went insane in the creating of this blog post). Fans are just so loud. But, forgetting about me and going into the subject at hand, I watched a video about evolution, Darwin and his theories. It was given by a man named Sean B. Carroll. He recently wrote a book entitled “Endless Form Most Beautiful,” a quote from Darwin (P.S. I didn’t plagerize my title, source cited!). So, here we go (You have to say it like Peter Pan)!
Evolution is an idea that has become central to modern biology. Without the theory of evolution, we wouldn’t be where we are today in biology. We have our genetic make up today from things that have happened to humans in the past. Our medical lives are in constant evolution because we are evolving as well as other things. Evolution is a huge idea. Infact, there may be no bigger idea out there. But, all science has deep roots. Darwin’s ideas have been around, used and expanded upon for 150 years! Darwin gave many contributions to the scientific world. Sadly, Darwin’s key ideas tend to be greatly misunderstood. Let’s start at the beginning.
Darwin was headed for the medical field after school. He wanted to be a physician. However, he soon learned that surgery, blood and things in that category difinitely weren’t for him. He enjoyed natural history and love reading. After giving up on being a physician he started reading about scientist going and exploring the tropics. That always intregged him. But, his father, feeling like Darwin wasn’t doing anything with his life at the moment, decided Darwin was going to be a Clergy. So, he put him in religious school. While Darwin was studying to be a Clergy, he was offered to go on a voyage with the British Navy around the world. However, Darwin’s father refused to let him go, giving him several reasons for doing so. These were: it was a wild voyage, Darwin was not the first choice, he wouldn’t settle down after this voyage, it would be extremely uncomfortable and it would be completely pointless. But, Darwin decided he wouldn’t take no for an answer. So, he sat down and came up with an arguement for each of his father’s points and pursuaded him to let him go on this voyage.
This voyage was only supposed to be a two year trip around the world, but it ended up being five. Darwin was away from his family and everyone he knew for five years to go on this voyage. He had packed a lot of supplies to collect specimens and make observations and books to learn from as they traveled. Darwin had brought two books with him. The first was Lyell’s Principles of Geology and the second was the Holy Bible. The interesting thing is that Darwin brought a geology book. He was interested in geology and had a good understanding of it. This is what set him apart from the other naturalists. This is what helped him come up with his theories. It was critical knowledge for his success. In this book a new suggestion had come up and that was that landforms changes and became different over time. The other idea in this book is that the earth was much older than people orginally thought. Then you have the coral reefs. This is part of Darwin’s first theories. One question that was asked was how do coral reef form develop. At the time it was a popular belief that coral reefs were build on the edges of volcanic craters. However, Darwin questioned that. He just didn’t feel like that was likely and that was the actual answer. He figured that if landforms changed than coral reefs could change too. He figured coral reefs were all the same things, they were all just in different stages. When an island was first formed, a finging reef was formed around it. Then, when the island slowly sunk, it created a lagoon and then the reef acted as a barrier, getting the name a barrier reef (Australia). This was Darwin’s first great theory. When this theory was proven to be correct, it showed that Darwin had an ability to theorize. That when he thought hard and applied his knowledge, he could come up with amazing theories.
While Darwin was traveling on this voyage, he saw a lot of things. Many of those things were animals, both dead and alive. But, most importantly, he saw a lot of strange things he had never seen before. For example, he saw flightless birds. This amazed him because he had never seen a bird whose wings wouldn’t allow it to fly. He also saw interesting fossils. He found a huge, and I mean HUGE fossil of a ground sloth. And later, he realized that fossil wasn’t only much bigger than other sloths, it was much older. But, the place where he found the most interesting things would have to be the Galapagos Islands. He saw swinging lizards, giant tortoises, and seals that weren’t afraid of people. And, last but not least, Darwin’s legendary finches. A thought came to him; if land could change then can species’ change too? He did a lot of collecting of specimens and finally got to return home. When he arrived home, Darwin started connecting the dots but he still had so many questions. He studied everything he had very carefully and wanted to know what it all meant. He knew theorizing about these things was a great risk because everything he was theorizing went against the church and it’s beliefs at the time. So, he would theorize is special secret notebooks. And soon enough he was writing theories of how species’ formed. But, it would be a long time before people would read his theories.
At the time, Darwin had a huge amount of praise and attention for all of the fossils and specimens he had brought back to Europe. He knew that if he set forth his theories for how species came about, he was going to loose everything. Also, he married Emma and didn’t want to affect here religious devotion. Darwin conducted many experiments about this. He became a pigeon breeder and found from other breeders that you could make a fantastic variety of pigeons just by how you decided which two pigeons would breed together. He also heard that all the types of pigeons they had at the moment were all descendant from a white rock pigeon. More wheels were turning in his head to why other animals couldn’t do that too, or why that couldn’t happen on a larger scale. Then, there were the finches that Darwin collected from the Galapagos. The beak shape changed depending on the island. Darwin figured the bird had changed because of the food sources and it evolved to survive. This is about the time that Darwin came up with the idea that species are connected in a family tree. That one species gives way to another.
Darwin was reading a book by Malthus (we learned a little about him earlier) and he had put something in his writings about the competition for survival. He suggested that the favorable traits in a species would be saved and that the not so favorable would be gotten rid of. This blossomed Darwin’s idea of natural selection.
Darwin kept working on his evidence until two events happened that convinced him to go public with his ideas. Darwin had 10 children and he was always at home to work and be with them. He was very close to his first daughter Annie. She got very sick and died. In Darwin’s mind he was thinking what could be worse than losing your daughter. That maybe he should tell everyone his theories. But he still didn’t, until he received a package from another scientist named Wallace. He had developed a theory of species formation and wanted Darwin to look at it and see what he thought about it. In that package, Darwin saw his whole life’s work and he was worried that someone was going to beat him to it. He didn’t want to wait any longer. That is when Darwin and Wallace went together to present the species evolve and natural selection is the force behind that. Then, after that Darwin completed his work of Origin of Species. In this work, Darwin put all of his evidence for evolution but he also showed the arguments against evolution. He wrote it very creatively and beautifully because he knew for people to read it and listen to it, he and to make it interesting and it had to appeal to the people.
At this point, in the video, people were allowed to ask questions. The first was if Wallace had published anything else after he presented with Darwin. Wallace did publish many more things, but, unlike Darwin, he was never able to really capture his audience of inspire others. That was why Darwin’s works were so popular. People enjoyed them, and for some, it inspired them and gave them ideas that they then wrote down. The other was what happened with Darwin’s family when he made his theories public? When Darwin publicized this, he was very careful about it. Emma knew and had read his theories before he make the announcement. Their relationship was great. What Darwin always worried would happen never did and his relationship with his family stayed the same.
Back into the lecture, Carroll continued to talk about the Origin of Species. In this work Darwin really stressed descent from other species along with modification. He said that everything has descended within it’s own class from common parents and has been modified in the course of descent. This idea that all life is connected has been said to be Darwin’s grandest theory. The way Darwin represented this idea was with the “Tree of Life.” The higher branches represented the new things and the bottom laid the way for the new species. He stressed that fossils were evidence for evolution. He found oyster beds 13,000 feet above sea level, proving that land changes and so does environment, so animals would have to change to cope with that. Fossils were a huge insight into that.
There are four sites in North America with amazing fossils. The first, and oldest is 505 million years old and is called Burgess Shale. They found Aysheaia and Trilobite fossils there, which were the earliest complex animals. The second is Dinosaur National Monument which is full of Jurassic deposits. There were huge stones found with amazing fossils in them. They were about 157 million years old. There was one rock with over 2,000 bones in it. They must have been washed down a river and then cemented into stone. The third is Fossil Butte. It is a very arid area and the rocks have horizons on them that are rich in fossil deposits. The rock are full of fossil fish from enormous lakes that used to cover the area. In that time, there would be massive die-offs in the lakes because of adjustments and then the fish would be covered in silt and fossilized. They have found 50 million year old fish kills. They also found a fossil of a 50 million year old palm tree, suggesting that this area was once tropical. The environment, land and animals have all changed. The last is the most recent, called La Brea Tar Pits. The have something called bone beds that are between 12,000 to 14,000 years old. They were really just piles of bones in pits, because they used to be tar pits and animals would get stuck in them. When predators came to get some food, then they would get stuck in the tar too, killing many animals. The good thing about the tar is that is was amazing preserver of the animals. They have found amazing mammoths and saber-tooth tigers inside these pits. But what do all of these places tell us?
- They tell us that the animals and plants have changed.
- They tell us that they had a huge time frame in which the change happened.
- Extinction is a fate for 99% of the species we have seen.
- The environments have changed immensely.
This shows that there are living things on a constantly changing surface. With all of the changing environments, the living things have to change to survive. So, we have proved now that evolution happens, but now the question is how? This is where natural selection comes in. Natural Selection is rejecting less favorable traits and preserving the more favorable traits. The equation for natural selection is variation, time and selective advantage.
Here is an example of an adaptation of a certain species called Rock Pocket Mice. They have 2 colors; sandy and dark. These two types of mice live in a sandy colored area, however, they have lava flows, which harden a blackish color. When the mice don’t blend in with their surroundings, then the have a smaller chance of survival. So, the mice color matching their surroundings. At first, all the mice were the sandy color. But, now, they have the possibility to change because of natural selection. All sandy mice have two copies of the light allele. The dark mice have one or two copies of the dark allele. This is the genetic basis for color difference. Now we have to find out how often a coat mutation arises. This depends on three things.
- Mutation rate
- Reproduction rate
- Population size
The mutation rate is 2 per billion, the possible mutation sites in the gene is 10 and the copies of gene in each mouse is 2. We have to multiply all of these numbers together and it gives you a 1 in 25 million shot at having an offspring with the mutation. Is this a long shot? Let’s continue and see. The reproduction rate is each female is having at least 5 babies and the population size is 5,000 females. The total offspring for the year is 25,000. These means that every thousand years, a spontaneous black mouse will be born. Considering how old the species is, this mutation could have happen a total of 1,700 times. So, it really isn’t a long shot.
To find our how long it would take for every mouse to be black you need the population size and s.
- s is the selection coefficient (the advantage)
- s is a relative measure of fitness
- s is product of reproduction and survival
Right now, the black mice have a .01 or 1% advantage. It would take 1,000 generations for 95% of the population to be black mice. If the black mice had a 10% advantage, then it would only take 100 generations for 95% of the mice to be black. Unlike most people believe, natural selection is a very rapid process and it spreads quickly.
A change in the environment an animal lives in is completely out of their control. But when the environment changes, the process of natural selection will happen. The environment changing is random, but natural selection isn’t.