Geological Timeline Reflection

We recently did a project where we created a timeline that represented the events that happened in Earth's history. This timeline went from the Hadean era to the present.

There were many important events over Earth's history, but some are more important than others. The three most important events are the creation of life, the mass extinctions, and the evolution of humans. It is rather self explanatory why the creation of life is important, because it led to every living thing on Earth. Life was created sometime during the Precambrian era, where the oldest prokaryotic fossils were found. It isn't known how life was created, but there are various theories and hypotheses, such as that the first amino acids came on a meteorite. Without life being created, the Earth would be a barren rock like some of the other planets. Like the creation of life, mass extinctions completely changed the Earth. They killed off lots of species, and caused new species to become dominant. In the Cretaceous period, half of plants and animals were killed off from a meteor. Humans may not have become the dominant species if this didn't happen. Humans have changed the Earth dramatically in the short time we have been here, which makes the evolution of our species one of the most important events in Earth's history. We have increased global temperatures, destroyed ecosystems, and are the cause of the next mass extinction. Without humans, none of this would have happened, and the planet would be in a lot better shape.

When we learned how long the Earth had existed, I had trouble picturing how long of a time it actually was. Most of the time on Earth was spent without life on it, and humans have been around for an extremely short time compared to the rest of Earth's history. What surprised me is how long Earth really has been around, about 4.6 billion years. This is a third of the universe's 13.7 billion year old existence. I found it interesting that the Earth was that old compared to the universe.

A diagram showing the events in Earth's history

As mentioned previously, humans have greatly impacted the Earth in the short time we have been here. We are causing the 6th mass extinction. We need to stop harming the planet, because even in the short time we have been here, we have drastically changed the Earth. For more detail on the issues facing the planet, check here. We have quickly become the dominant species on our planet, and have started changing other species to benefit us. We have bred animals to create different breeds, and we have genetically modified species to do many different things, like plants that are resistant to insects. A certain type of bacteria evolved to decompose plastic created by human activity. Despite the minuscule time we have been on the planet, we have changed a lot.

The only remaining questions that I have are ones that can't be answered. How was life created on Earth? If it came from a meteor, how was that life created? Someday, these questions may be answered, but we can only hypothesize until then.

Hunger Games Lab

In this lab we simulated different phenotypes of a population competing for food. The different phenotypes were "stumpy," "knuckler," and "pincher." The stumpy phenotypes could only pick up food with its wrists, the knuckler could only pick up food with the knuckles of its first and second fingers, and the pincher could only pick up food with it's thumb and first finger. It simulated natural selection, because traits that didn't allow the individual to collect more food died out.

The pincher phenotype was the best at picking up food. It was able to collect the most food with each grab, and was able to store it somewhere the quickest. The stumpy phenotype was unable to collect food well, and took a long time to store it. The knuckler phenotype was in the middle, not as slow as stumpy but not as fast as pincher.

We asked the question, "Do populations evolve?" We determined that the population did evolve. Evolution is defined as the change of allele frequency over time. The alleles we measured are the allele for how the individual can collect food. All alleles started off at about the same amount, but after one "year," the "a" allele frequency decreased dramatically, because all the stumpy phenotypes died. The allele frequency went from 48% A allele and 52% a allele to 31% A allele and 69% A allele. This was a change in allele frequency, so the population evolved. The allele frequency continued to change, so the population continued to evolve.

Allele Frequency Over 7 Years

In this lab, like in nature, some things were random, while others were not. The placement of food was random, sometimes spread evenly, sometimes in piles, and once all in the same spot. This made the survival random and linked to whether you were close to the food. Another random aspect was offspring. The alleles selected from offspring were a 50-50 chance. At the same time, offspring weren't random. You could choose your mate and possibly guarantee a certain phenotype, which increased the frequency of that allele.

The results of this lab would have been very different if the food was a different size. Making the food smaller would have made it a lot harder for the already struggling stumpy phenotype, and would have helped both knuckler and pincher phenotypes. Making the food larger would have helped the stumpy and pincher phenotypes, but would have immensely harmed the knuckler phenotype, causing a disruptive selection pattern.

If there was no incomplete dominance, meaning the knuckler phenotype wouldn't exist, then there would eventually be no more stumpy phenotype, and that means no more A allele. After one year, there was no more stumpy phenotype, and if there was no incomplete dominance, then any individual with the A allele would be a stumpy, and then die.

Natural selection lets the best phenotypes survive, and makes them more common, which changes the allele frequency. Because the allele frequency is what determines if a species evolves, that means natural selection causes evolution.

There were many different strategies to increase survival and reproduction. One was to go where there was the least competition, so no one would steal food. Another was to have easy storage for food, like the hood of a hoodie sweater. Another strategy was cheating and not using the phenotype they had. Because everyone had access to at least one of these strategies, it meant that whoever had an advantage no one else had would survive, and the pinchers had that advantage. In nature, the species with the best phenotype will win, but the strategies don't get passed down unless they are genetic. This means that if someone is very aggressive in food collection, their offspring might not be.

In evolution, populations evolve, not individuals, because individuals can't change their genotype. Natural selection acts on the phenotype of an individual, deciding whether it will survive or not. This is because the phenotype is the physical thing that helps or harms the organism, not the genotype.

Bird Beak Lab Conclusion

In this lab, we simulated different types of bird beaks with tweezers, binder clips, spoons, and scissors, and attempted to collect food, which we represented with rubber bands, toothpicks, paper clips, and macaroni, and the amount we collected determined how many offspring we had each year. The first simulation was normal, but then we had an environmental change to make collecting food different. Out environmental change was that we only had 10 seconds to collect food.
We verified that the individuals with the better traits would have more offspring. The tweezer beak was able to collect the most food, and therefore had the most offspring, 22 compared to 8 offspring from the spoon beak, 11 from the binder clip beak, and 15 from the scissor beak. This also verifies our second claim, which is that populations begin to look more like the "winners," or the most successful genotype. At the beginning, we were the only four birds, so tweezer beaked birds made up 25% of the population, or 1 out of 4. After several years, and several offspring, there were 22 out of 56 total offspring, making 39% of the population tweezer beaks, which is more than any other type of beak. This happened because the tweezer beak was able to collect food more effectively than the other beak phenotypes, so had the most offspring. The other birds had less offspring, so the tweezer beak made up more of the population.

After testing Darwin's conclusions, we asked what would happen if a disease affected the species. To simulate them having less energy, we reduced the time to collect food to 10 seconds. We found that with less time, all phenotypes produced less offspring, but tweezers and scissors produced the most. This is because the disease affected everyone equally, so all phenotypes collected less food.

While we tried to make this lab accurate, we did have some errors. We had different people collecting food with the different beaks at the same time. This means that someone may have been better at collecting food than someone else, making the data lean towards whoever was best at collecting, not necessarily what beak was best at collecting. We could have solved this by rotating beaks and having each person try out each beak. Another error we had was that the scissors were slightly magnetic. This made the collection of paper clips slightly easier, and some of the contact between the tweezers made them very slightly magnetic, but that made no difference because the attraction was so weak. This error could have been prevented by testing all metal "beaks" against each other to see if they were magnetic.

This lab was done to demonstrate how evolution can take place over a short period of time. From this lab I learned how Darwin's conclusions affect species with different phenotypes, which helps me understand the process of natural selection. Based on my experience from this lab, I could artificially select certain traits from a population to make a specific type of organism.