In class this week, we will be discussing Darwin and his theory of descent with
ID: 261176 • Letter: I
Question
In class this week, we will be discussing Darwin and his theory of descent with modification. Darwin viewed life on this planet as descending from an ancestor that lived in the remote past. As this ancestor and its descendants explored new environments, they developed adaptations that better fit them to that environment. Hence, descent with modification can account for the great diversity of organisms that we see today. Darwin envisioned that the best way to represent the relationship among species (both extant and extinct) was in the form of a tree. This week’s forum question will explore the concept of the phylogenetic tree and the reasoning behind its construction. Read the following article: Trait Evolution on a Phylogenetic Tree: Relatedness, Similarity, and the Myth of Evolutionary Advancement and answer the questions that follow.
1) When will natural selection favor the fixation of a mutant allele in a population?
2) If I told you that the lizard under study in the lab had a crest, based on the evolutionary history depicted in Fig.3, you would assume that it also has _____________.
3) What is wrong with the following statement? “Tetrapods evolved from fish.” How would you correct it?
4) From an evolutionary perspective, which is more advanced, a human or a fish? Explain your reasoning.
Explanation / Answer
Natur selection will favor a mutant allele in a population, if the mutant allele confers adaptive advantage to the population and increases the viability of population.
Ans3:
Tetrapods did not evolve from fish. Instead, both fish and tetrapods had the same ancestor.
Ans4:
Humans can be considered more advanced than fishes in evolutionary terms. Humans evolved cell intercalation, which during embryonic development, helps to position the ectodermal and mesodermal axis in the center. However, in fishes , the axis is still at edges.
(No image available for second question).
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