Biology Homework Chapter 15: Evolution - Phylogeny and Cladistics
Textbook assignment:Chapter 15: Phylogeny, sections 13-19.
- 15.14 A phylogeny or evolutionary history of a species is constructed by comparing structures in similar species. Homologous structures have similar structures reflecting possible common ancestry. Analogous structures do not show common ancestry, although they may be used similarly across different species. Convergent evolution occurs when analogous structures develop in similar ways, even though the species exhibiting these structures do not share a close common ancestry. [This is an example of the same answer solving a similar problem.]
- 15.15 Systematics is the process of creating classification systems for all organic forms, whether currently extant or evidenced only in the fossil record. Some confusion may result from the common names of organisms, so the modern binomial naming conventions specify genus and species to allow for correct identification. The classification groupings are domains, kingdoms, phyla, classes, orders, families, genii, and species. All members of the higher group share similar characteristics.
- 15.16 Attempts to draw trees of inheritance and relationships between fossilized species is called phylogeny. Phylogenetic systematics (cladistic analysis) determines when branching occurs in a phylogentic tree by identifying primitive (shared) and derived (unique) characteristics in each line. Note that the derived characters of a branch are primitive characteristics to any further branches down the line!
- 15.17 Molecular biology using DNA sequencing (molecular systematics) has become a common tool used to determine relationships between species. Those species with more sequences in common are considered more closely related than those with fewer shared sequences.
DNA comparisons have yielded more commonality in sequencing than we might have expected from the wide differences between some species. For example, 50% of the DNA sequencies in humans appear in identical format in yeasts. The common descent principle of evolution is used to explain these similarities.
- 15.18 The rate of mutations (assumed by counting differences from the most common set of DNA between two species) is determined by matching the appearance of a mutation to the fossil records. The average rate of change provides a scale, called the molecular clock, that can be used to estimate other dates or validate conclusions reached by other means.
- 15.19 The modern classification system is under constant revision. Until recently, the 5-kingdom (bacteria, protists, fungi, plants, animals) classification proposed by Whitaker in 1969 was dominant. More recent genetic studies have led to the use of a three-domain system (bacteria, archaea, eukarya).
Read the following weblecture before chat: MacroEvolution and Phylogeny
Take notes on any questions you have, and be prepared to discuss the lecture in chat.
Perform the study activity below:
Use the Lizard Evoluion Virtual Lab to explore applications of the theory of eovlution to the anole lizard species of the Caribbean. This time, focus on Module 2 to develop a phylogentic tree for lizard species.
Chat Preparation Activities
- Essay question: The Moodle forum for the session will assign a specific study question for you to prepare for chat. You need to read this question and post your answer before chat starts for this session.
- Mastery Exercise: The Moodle Mastery exercise for the chapter will contain sections related to our chat topic. Try to complete these before the chat starts, so that you can ask questions.
- Required: Complete the Mastery Exercise with a score of 85% or better.
- Optional: Test yourself with the textbook multiple choice questions and note any that you miss that still don't make sense. Bring questions to chat!
- Go to the Moodle and take the quiz for this chapter.
Read through the lab for this week; bring questions to chat on any aspect of the lab, whether you intend not perform it or not. If you decide to perform the lab, be sure to submit your report by the posted due date.
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