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Notes on the Web - Unit Six - Part 6
Other Evidences that Support Evolution and Other Processes of Evolution Including Speciation
Bruce G. Stewart
General Objectives and Study Guide
Your objectives for these Notes on the Web and associated readings and exercises are:
Related Textbook Readings:
Other Evidences that Support Evolution
Life's Origins and Evolution: Geologic Time and The Fossil Record
To get a perspective on the concept of "life" We need at least a brief introduction to the geologic history of the Earth. The Earth was formed some 4.6 billion years ago according to modern geologists who use a variety of scientific evidence to support this date. If you would like to see details on how this estimate is determined and how the other estimates in this section are determined, please visit the following link: http://www.talkorigins.org/faqs/faq-age-of-earth.html We will discuss this in more detail later in the semester, but for now know the following major subdivisions of geologic time: Precambrian time [4.6 billion to 570 million years before present (BP)], Paleozoic Era (570 to 245 million years BP), Mesozoic Era (245-66 million years BP), and Cenozoic Era (66 million years BP to present). Table 6.6-1 presents additional information on geologic time and major events in the evolution of life. Study this table and know the major animal groups that appeared or characterized each era. For another view of geologic time you can visit the following link: http://www.talkorigins.org/faqs/timescale.html. Please note that different summary tables of the geologic time table sometimes use different levels of subdivision (such as the Precambrian is subdivided into different eras, and sometimes periods are merged or split). Do not worry! For our class, I will follow the Table 6.6-1 in these Notes on the Web so that there will be no confusion on what you should learn for testing purposes.
| Required Activity |
| Explore The University of California Museum of Paleontology |
Assignment: Write a summary of at least one geologic period based on your "virtual field trip" to the California Museum of Paleontology. This must be 300 words or more. Go to the Assignments link in your Blackboard class site where you will find the link to submit your assignment to Turnitin.com.
First Organisms. The first living organisms found in the fossil record were prokaryotic cells whose remains have been discovered in rocks dating back to about 3.5 billion years. Prokaryotic cells are the simplest living organisms. Their cells have DNA, but it is not found in a membrane-bound nucleus as in complex eukaryotic cells. Thus, life originated in ancient times in the Precambrian Era of Earth’s history. Is life old or what!
| TABLE 6-6-1. Geologic Time Scale, Major Time Divisions, and Key Evolutionary Events [after Mader’s (1998) Table 20.1] | |||||
| Era | Period | Epoch | Millions of Years BP | Plant Life | Animal Life |
| Cenozoic | Quaternary | Holocene | 0-0.01 | Major losses of native plant communities due to humans accelerates extinction | Development of Human Civilizations; animal extinction rates skyrocket |
| Pleistocene | 0.01-2 | Diversification and spread of herbaceous species | Modern humans appear | ||
| Tertiary | Pliocene | 2-6 | Herbaceous angiosperms appear | First hominids (species of the human family) appear | |
| Miocene | 6-24 | Grasslands spread and forest contract | Apelike mammals and grazing mammals flourish; insect flourish | ||
| Oligocene | 24-37 | Many modern families of flowering plants evolve | Browsing mammals and monkeylike primates appear | ||
| Eocene | 37-58 | Wet subtropical forests thrive | All modern mammal orders are represented | ||
| Paleocene | 58-66 | Angiosperms diversity | Primitive primates, herbivores, carnivores and insectivores appear | ||
| Mesozoic | Cretaceous |
Mass Extinction: Dinosaurs and Most Reptiles |
|||
| 66-144 | Flowering plants spread; coniferous trees decline | Placental mammals appear; modern insect groups appear | |||
| Jurassic | 144-208 | Cycads and other gymnosperms flourish | Dinosours flourish; birds appear | ||
| Triassic | 208-245 | Cycads and ginkgoes appear; forests of gymnosperms and ferns dominate | First mammals appear; first dinosaurs appear; corals and mollusks dominate seas | ||
| Paleozoic | Permian | 245-286 | Conifers appear | Reptiles diversity; amphibians decline | |
| Carboniferous | 286-360 | Age of great coal-forming forests; club mosses, horsetails, and ferns flourish | Amphibians diversify; first reptiles appear; first great radiation of insects | ||
| Devonian | 360-408 | First seed ferns appear | Jawed fishes diversify and dominate seas; first insects and first amphibians appear | ||
| Silurian | 408-438 | Low-lying vascular plants appear on land | First jawed fishes appear | ||
| Ordovician | 438-505 | Marine algae flourish | Invertebrates spread and diversify; jawless fishes (first vertebrates) appear | ||
| Cambrian | 505-570 | Marine algae flourish | Invertebrates with exoskeletons dominate | ||
| Precambrian Eon (from 4,600 million years ago to about 570 mya) | 700-570 | Soft-bodied ulticellular organisms appear | |||
| 2,100-700 | First complex (eukaryotic) cells appear | ||||
| 3,100-3,500 | First prokaryotic cells in stromatolites appear | ||||
| 4,600 | Earth formed | ||||
Some Questions to Promote Learning on Geological Processes and the Age of the Earth
Other Processes of Evolution
Agents of Evolutionary Change
Population Genetics Including the Hardy-Weinberg Equilibrium Principle
This has been previously presented in Unit Five of your Notes on the Web. It is mentioned again here to point out its relationship in understanding aspects of evolution, namely, the structure and patterns of change in population gene pools.
Mutations
This has been studied previously in Unit Four of you Notes on the Web primarily from the perspective of molecular patterns of mutation. You should study your textbook readings where you will find mention of the role of mutations in producing the raw material for evolutionary change.
Genetic Drift
Also previously discussed in your notes, but mentioned here for its relationship to evolution, namely, its role in affecting allele frequencies in populations..
Founder Effect
Also previously mentioned in your notes, but mentioned here for perspective in evolution, namely, its role in affecting allele frequencies in populations.
Non-random Mating Due to Natural Selection
This has been covered in detail in previous parts of this unit of your Notes on the Web. It is mentioned here to emphasize its importance and relationship to the following processs of speciation.
Speciation Processes
Study the following topics thoroughly in your textbook readings and/or previous notes.
Human Evolution
Modern humans (Homo sapiens) are one of the millions of species on earth. Our origins in scientific terms followed the same natural processes as for any other species, and we study and understand our origins through the same tried and true scientific methods. Our biology textbook has a nice section on human evolution, and you should read that material. Here are some supplemental resources for the interested student.
Textbook Study Reminder
Study your related textbook readings thoroughly. The brief notes above are only meant as an introduction and do not cover the objectives comprehensively, but your textbooks do an excellent job of this... with beautiful illustrations! Check the general objectives above to make sure that you have covered all of the topics in the textbook readings.
The "Self Test" and other questions will be helpful for general biology students, although many more detailed questions will be included in the lecture exam. Similarly, study questions in the zoology textbook will be helpful review for general zoology students, but again, they are not comprehensive.
As with all materials throughout the semester, you will have opportunities to ask questions or ask that any relevant material from your assignments be discussed in class and/or in threaded discussions on Internet.
© 2005, 2007 Bruce G. Stewart