of three domains, Bacteria, Archaea, and Eukarya. There are other subdivisions that describe these types of arrangements. Exactly how to describe the relationships between life forms involves a discussion of phylogenetic trees. As you will see, newer findings in biology and microbiology have changed the way these phylogenetic trees are arranged. Chapter four discusses genetics and genetic variation. Genetics works on a small scale in the inheritance of certain traits by a descendant from a direct ancestor. It also works on a large scale because it is through a series of genetic mutations that new species are ultimately created. We will talk about Mendelian genetics, the science of mutations, and the advantages and disadvantages that come with certain genetic situations. Chapter five in the course introduces topics related to the origin of life on earth. Life on earth in the beginning of time was very different than it is now. This is partly due to the fact that the early conditions of earth as a planet were vastly different from that of present-day time. The chapter talks about the evolution of viruses and of prokaryotes, which were the first cells to represent life on this planet. There is more to be said about evolution than the evolution of single-celled organisms so this is the topic of chapter six. Eukaryotes are infinitely more complex than prokaryotes—even those that are unicellular. Many eukaryotic organisms are multicellular; for this reason, the evolution of multicellularity is discussed in this chapter. Because evolution happens to populations rather than to individuals, it is important to also talk about the evolution of individuality. There are advantages to evolving in a social environment, which is also covered in this chapter. The major topics of chapter seven in the course are species and speciation. Earlier chapters talk about evolution and its role in the diversity of species on earth. In this chapter, we talk about how species are defined and the different methods in which speciation or the formation of a different species occurs. Historically, species were defined by their similar characteristics but, in this chapter, we talk also about how the knowledge of genetics has changed the definition of what exactly is meant when referring to an organism being of a certain species in today s scientific terms.
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