This unit was about evolution. We first studied gradual change. We learned about variation, which is any difference in traits within a population. It exists because of crossing over, meiosis, mutations, and sex. Variation in a species allows people to artificially select certain organisms with traits they want, like color or size. This is called artificial selection.
Then we studied Charles's Darwin's observations and conclusion. His observations where that all sexually reproducing species have high genetic variation, traits are inherited from parents to offspring, all species are capable of producing more off springs than the environment can support, and competition makes it so that only certain offsprings can survive and reproduce due to limited resources in the environment. His conclusions were that there are winners and losers in nature, and that population will start to look like the winners.
The next thing we studied was how evolution is measured. We first learned about the gene pool, which is the total of all alleles in a population, and allele frequency, which is how common an allele is in a population. The steps to determine allele frequency is to first add up the total of all alleles, then add up total for each type of allele, and finally, for each type of allele, divide the number by the total. We learned about how the gene pool slowly evolves. As frequencies change due to natural selection, the gene pool starts to have a higher number in winners. Although, lethal alleles that are recessive can hide in a population, which is why we still see them today.
Then we learned about speciation, which is the rise of 2 or more species from one exiting species. Speciation is caused by reproductive isolation, which is when a population is split into two and eventually the two populations cannot reproduce anymore. Three forms of this are behavioral isolation, which is caused by changes in mating behaviors, geographical isolation, which is caused by barriers in the environment, and temporal isolation, which is when timing prevents reproduction between populations. There are two patterns of speciation, gradualism, which is when speciation occurs slowly, and punctuated equilibrium, which is when new species arise suddenly.
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| https://commons.wikimedia.org/wiki/File:Punctuated-equilibrium.svg |
We then studied the supportive evidence for evolution. Evo-devo, which is the study the evolution of development processes in multicellular organisms, shows that embryos look very similar to each other in early stages of development, which shows that we have a common ancestor. Also, vesgital structures, which are adaptions that benefited ancestors, but are no longer needed and fossils are proof for the theory of evolution. Lastly, homologous structures, which is the same structure but different function, analogous structures, which is the same function but different structures, and convergent evolution, which is a process where unrelated organisms evolve similar structures or analogous structures independently.
We also studied evolving populations. Directional selection, which favors phenotypes at on extreme, stabilizing selection, which favors the intermediate phenotype, and disruptive selection, which favors both extreme phenotypes, are different ways distribution of traits can change. Some other types of change besides natural selection is genetic drift, a random event that drastically changes a population and results in change in allele frequency, gene flow, movement from one population to another, mutations, and sexual selection, traits that improve mating success.
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| https://commons.wikimedia.org/wiki/File:Genetic_Distribution.svg |
Lastly, we learned about the origin of life. One possible flow of events is simple monomers of marcomolecules to polymers/macromolecules to molecules bound by lipids to molecules begin catalyzing reactions to simple "cell" or protcell to peplication of cells and molecules to endosymbiosis to eukaryotes to sexual reproduction to multiceullar organisms. There are four eras of Earth, Precambrain, Palezoic, Mesozoic, and Cenzoic.
I want to learn more about different forms of life during each era. An unanswered question I have is how many more extinct species we have yet to discover. I wonder about how life began on Earth.
To be more assertive, I tried to take listen to everyone's opinions and then we all decided on one idea that we were all happy with. I still have to work on trying not to let others' over power mine.
Hunger Games Lab
This is a lab we did to study different types of selection.
