Unit 8 Reflection

This unit was about evolution; we looked at how populations evolve and how life on Earth originated. Evolution happens because genetic variation exists in populations. Variation is due to sexual reproduction, meiosis, and crossing over which happens during meiosis. Humans breed animals for both work purposes and for food, and this is called artificial selection. They select individuals with the trait they want and only mate individuals with this trait. A selection process also occurs in nature, natural selection. Nature favors certain phenotypes which are advantageous for survival and these individuals have a better chance of surviving, reproducing, and passing on their genes. The population evolves to look like these "winners", which was one of Darwin's conclusion about the evolution of populations. This principle was illustrated in The Hunger Games Lab where each there were three phenotypes, and the ones that were better for picking up enough food survived, and those who couldn't gather sufficient food fast enough died and didn't pass on their genes. The initial population in this lab did evolve, as we could see by the change in allele frequency.

Allele frequency change in the Hunger Games Lab

We can tell if a population evolved by looking at if the allele frequency has changed. Allele frequency is how common an allele is in a population. Natural selection can favor one extreme phenotype, in which case the normal distribution bell curve will shift towards that extreme. This is called directional selection. In stabilizing selection, nature favors the intermediate phenotype, and in disruptive selection, nature favors both extreme phenotypes. Disruptive selection can lead to speciation, where two new species arise from one. They are considered two new species if they can no longer mate with each other. Speciation occurs when groups are reproductively isolated, either geographically, behaviorally, or temporally.

http://www.bio.miami.edu/dana/pix/selection_modes.jpg

Evidence of evolution can be seen in many ways, from the analogous and homologous structures in organisms to embryology to vestigial structures, which are evolutionary left-overs. These all indicate a common ancestry. Scientists use fossils as evolutionary evidence as well, although fossil evidence can be biased because organisms which have shells or bones fossilize the best. Earth's history, which is 4.6 billion years long, is divided into 4 eras (precambrian, paleozoic, mesozoic, and cenozoic), which are further divided into periods.

I am curious to learn more about the ways that current populations in the world are changing now.
I am working to become more assertive in group settings (rather than passive or aggressive). I am doing this by voicing my opinions, but also coming up with compromises and incorporating others' opinions as well.