BI 150 Lecture Notes - Lecture 7: Cell Potency, Osculum, Amebocyte
6 Sep 2019
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Document Summary
Life has been evolving on earth for 3. 6 billion years. As new species appear, they share an ancestor with another species (sister species). The relative order of speciation events can be depicted by a phylogenetic tree. Homology: a trait that is similar between species because it existed in their common ancestor and was simply passed to the new species. Convergent trait: a trait that is similar between species because they independently evolved as adaptations to the same type of environment. Traditionally, researchers used morphology to understand evolutionary relationships. Dna sequences: what are the advantages of using dna: no need to understand the morphologies, no assumptions about which morphologies are homologies, each nucleotide is a trait, so we can get thousands of traits easily. Kingdom, phylum, class, order, family, gen us, species. Simplest animals: multicellular but lack true tissues or organs. Cells aggregate into an asymmetrical body full of pores and channels. Lots of variation in shape and size.
