Principles of Paleobiology II - Paleontology - Lecture Notes, Study notes of Geology

Download Principles of Paleobiology II - Paleontology - Lecture Notes and more Study notes Geology in PDF only on Docsity! 1 Principles of Paleobiology Evolutionary Rates and Patterns Introduction A main objective of evolutionary paleobiology is to understand how natural selection works by reconstructing the evolutionary history of different groups of organisms. In this activity you will work with evolutionary rates and patterns that occurred over millions of years. The traditional idea about how fast evolution happens is that species usually change very slowly and gradually through geologic time. This model of evolutionary rates is called phyletic evolution, which may or may not lead to an increase in the number of species.“Gradualists” reason that if more organisms were not destroyed and were instead preserved as fossils, the fossil record of the history of life would be more complete and we could detect the gradual changes more often than we do (which is not very often!). Opposing the phyletic model is the model of punctuated equilibrium (“punk eek”). With punk eek, species do not change morphologically over long period of stasis, and the equilibrium phase is punctuated by rapid speciation events. The new species splits from the main lineage, which may or may not persist. If speciation happens primarily in small, isolated populations, it may happen too quickly to be observed in the fossil record, which supports the punk eek model. Activity 1. Changes in sedimentation rates over time and differences in the preservation of fossils from place to place often make interpreting the evolutionary histories of groups and testing models of evolutionary mode and tempo difficult. Each data point plotted below represents the average of many measurements made on some morphologic variable (e.g., width of a snail shell) in different, closely related populations that have different geologic ages. To show the evolutionary history of the fossil taxa shown, the data points will be connected by lines that represent missing evolutionary steps. a. Connect the data points in Figure A to show one speciation event, and label it. Which model is represented by this evolutionary history? __phyletic evolution____________________________________ b. Connect the data points in Figure B to show one speciation event, and label it. Which model is represented by this evolutionary history? ___punctuated equilibrium (Note that original species shows overall stasis, which is part of the definition of punk eek)_________________________________ c. The evolutionary history in which figure shows more rapid evolution? ____B______ Docsity.com 2 2. Anagenesis occurs when all populations of a species are transformed as a whole into populations of a new species, so the old species becomes extinct as the new one arises. Cladogenesis occurs when some populations of a species split off and become a new species that exists alongside the old species, which results in more species (increased diversity). This exercise teaches the concepts of anagenesis and cladogenesis using evolutionary lineages (which are clades) of radiolaria. The figure below shows the evolution of nine species of the radiolarian Thyrsocyrtis. Evolution from one species to another is shown by an arrow. There are both anagenetic and cladogenetic originations of species. Use the pictures and geologic ranges of the species to answer the following questions. (Note that ‘a’ and ‘b’ refer to different forms of the same species.) C C C C A C A A Docsity.com