Geologic Timeline Reflection

The Cambrian Explosion is a sudden appearance in the fossil record of complex animals that had mineralized skeletal remains. This is considered to be the most important evolutionary event in the history of life on Earth. 96% of species became extinct after the Permian mass extinction. There were at least two or more phases of extinction over the span of millions of years. This was the the insect population's one and only mass extinction. This tragic event may have been caused by an asteroid impact or a drop in oxygen levels. 65 million years ago, the dinosaurs died in Cretaceous mass extinction. This mass extinction may have been caused by flood basalt eruptions affecting the world's climate, and a drastic fall in sea level.

The Earth is approximately 4.543 billion years old. The Silurian Extinction happened 439 million years ago. Dinosaurs lived between 230 and 65 million years ago in the Mesozoic Era. This was millions of years before the first homo sapien appeared. Modern humans evolved 200,000 years ago. Compared to the Earth, humans are a relatively new species. If the timeline of Earth was based off a one year calendar with the Big Bang occurring on January 1, humans have only been around for about five minutes. I was surprised that we have impacted the world so much in the five minutes that humans have been on the Earth.

The last 200,000 years have been mainly dominated by humans. In the past 50 years, humans have burned tons and tons of fossil fuels. The human society has also dumped massive amounts of trash into landfills and oceans. With all the technologies we have created to change the Earth for the better, we have dumped so much waste that the Earth might never recover.

My question is "How do scientists know what happened in every mass extinction?"

Earth life in 24 hours

Unit 8 Reflection

This unit was about constant change. Variation is any difference in traits within a population such as height or eye color. Variation exists because of crossing over, meiosis, mutations, and sex. Artificial selection occurs when humans select traits from a population's variation that they want, and only mate individuals with those traits. Darwin discovered that evolution is caused by natural selection. He came p with for observations and two conclusions explaining how populations can change or evolve over time because of natural selection. A gene is a section of DNA that gives instructions for a trait. An allele is different variations of a gene that give different variations of that trait. Genetic variation is stored in the gene pool, and these gene pools can change over time. Allele frequency is how common an allele is in a population. Evolution acts on a population, as natural selection acts on an individual. A species is a group of individuals that can reproduce and have fertile offspring. Speciation is the rise of two or more species from one existing species. Embryology is the similar stages of embryo development that suggest common ancestry. Gene flow is moving alleles from one population to another. Natural selection selects for traits advantageous for survival. The 4 eras are: Precambrian Era, Paleozic Era, Mesozoic Era, and Cenozoic Era.

This is a picture of my graph from the Hunger Games
 Lab. It shows the gene flow in the population.

This is an image of gene flow. It shows how
the alleles move from one population to another.

I want to learn more about the rate of evolution because it is very slow for some populations and not for others. I would like to know how to increase the rate of evolution because some species have a very slow rate of evolution. Since my reflection on Unit 7 ( https://monicabio9.blogspot.com/2017/03/unit-7-reflection.html ) I have tried to focus more on not being so passive agressive. I have tired to consider both sides of the argument and not be mad about which was the argument went.