Geologic Timeline Individual Reflection

The first major event in Earths history was the beginning of photosynthesis in cynobacteria. This is important because it increased the oxygen content in the atmosphere which led to the rise of eukaryotes and later plants and animals. Animals cannot survive without enough oxygen so we would not be here if it had not been for this event.

The second major event was the Permian extinction at the end of the Paleozoic Era. It was the largest mass extinction in Earth's history killing 80% of all life. This loss of life was necessary for the explosion of new life that happened afterwards. The absence of many species allowed dinosaurs to occupy the empty niches and start the era of Dinosaurs.

The third important event happened in the tertiary period when birds, mammals and flowering plants began to dominate. This happened when the dinosaurs went extinct after the cretaceous and the evolution of mammals led to the first humans. Without this event humans may not exist or be much different than what we are today.

The scale of Earth's history is incredibly massive. It surprised me looking at the timeline that all the eras and periods we talk about are all in the span of only about a meter. The Earth was barren with little to no life for most of history. When reading about it it seems that all the eras and periods are roughly the same length but looking at it you can see that the Precambrian Era is most of Earth's history.

Humans have had such a great impact on Earth in just a few hundred years. And most of our impact has happened in the last hundred. We are destroying ecosystems that took hundreds of millions of years to evolve in just years. Humans have existed for just a few thousand years, and have done more in a blink than any other species has done in millions of years.

Some questions I have are why did it take so long for life to take off and start evolving? Why did some species go extinct? Where there intelligent species in the past that went extinct? Why did the planet evolve the way it did?

20 Time Project Update

I am still set on the path I  identified in my last blog post. I am on track for working with Mr. Fitzgerald to help him in his garden. I further researched native plants and how to grow them in a greenhouse (Mr. Fitz plans on having a greenhouse built soon). Also, a possible project on building a worm bin may be available for me so I researched that too. Basically, I have been doing a lot of reading and research to learn more about my topic and be prepared when its time for me to take the next step in my project.

Unit 8 Reflection

Unit 8 was about evolution and how and why species evolve. Evolution can be measured as a change in the frequency of an allele in the gene pool. The gene pool is the the total number of genes in a population. One of the main forces that sparks change in the gene pool is natural selection,  the theory that the "winners," or individuals with better traits survive and reproduce to pass their genes on while the individuals with traits that don't help survival die and take their genes with them. We explored this in the Hunger Games Lab. When we tested this, the individuals with traits that helped them pick up food increased in population while the individuals with bad traits nearly died off. The allele frequency was graphed and showed the allele frequency change, showing that evolution was occurring.

The type of natural selection exhibited in this lab was directional selection, where one extreme phenotype, in this case the pincher, was favored so the phenotypes shift towards that. Stabilizing selection is where the average phenotype in the middle are favored and extremes are not. This keeps the population from changing. Disruptive selection is when both extremes are favored and the graph splits in two. This is often the beginning of speciation.

http://www.course-notes.org/biology/topic_notes/33_behavioral_ecology/fecundity_selection

Natural selection is not the only thing that can change allele frequency. Genetic drift is when random acts kill random members of the population, eliminating them from the gene pool. This can be harmful because it lowers genetic variation. Gene flow is movement of alleles between populations, and mutations can also change allele frequency. Sexual selection traits are traits that increase chance of mating but do not help an individual survive.

New species are created in a process called speciation. When a species is reproductively isolated, they begin to drift apart until they are two different species. They become different species in a process called evolution. There is evidence to prove evolution exists. There are certain traits that modern day organisms have that are useless but would have been useful to ancestors. Also, similarities between species point to a common ancestor in the distant past.

Earths vast history is split up into eras, periods, and epochs. Mass extinctions mark the end of many of these. Each time period has different characteristics.

This unit was not a very difficult unit, but the scale of the Earth's timeline is hard to comprehend. Some questions I have are how did unicellular organisms turn into multicellular organisms and then plants and animals. Also how did asexually reproducing organisms evolve and become sexually reproducing.

I have had a chance to be more assertive in the geological timeline project. I have realized that there is a time to be a leader and be slightly more aggressive for the better of the group, but also a time to sit back more passively to better the group. But mostly, I have been assertive by leading with clear logical steps and listening to the ideas of others.