BIO 105 1st Edition Lecture 8Outline of Previous LectureI. How do we know that something is alive?II. How did Lamarck, Darwin, and Wallace contribute to our understanding of evolution?III. How does evolution by natural selection occur?IV. What is the relationship between genetics and evolution?V. How do artificial and sexual selection, mimicry and coevolution relate to the central concept of natural selection?Outline of Current LectureI. How do we know that new species have evolved?II. What are species?III. How are new species formed?IV. What factors influence how fast new species form?Current LectureBiology 105 Evidence of Evolution; Speciation Essential Questions 1. How do we know that new species have evolved?2. What are species? 3. How are new species formed?4. What factors influence how fast new species form? Interactive Class NotesHow do we know that new species have evolved?I. Macroevolution A. In microevolution, changes in the gene pool of a population generation after generation fine-tune a species for success in its environment. Under certain conditions and a long period of time,These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is bestused as a supplement to your own notes, not as a substitute.the same evolutionary changes can lead to the formation of new species. 1. Evolutionary change of one species into another is macroevolution or descent with modification as Darwin called it. B. Microevolution is easy to demonstrate, but macroevolution is not. There are 5 types of evidence in support of macroevolution: fossils, homology, vestigial structures, biogeography, and convergent evolution. C. Fossils the remains, impressions, or traces of life preserved in rock, provide direct evidence of previous forms of life on Earth. 1. fossils are very valuable for understanding the history of life on Earth, but fossilization is a rare event and the fossil record is incomplete and unsystematic. There are many fossils of some organisms, very few of others, and none for the majority of creatures that have lived on Earth. 2. hard parts like bones, teeth, and shells are most likely to be preserved; only rarely are conditions right for preserving soft parts like worms, flowers, or leaves. a. fossilization most often occurred when an organism was covered with mud, water, or volcanic ash soon after death. Anaerobic conditions are the best because they slow bacterial decay. b. some microscopic structures, such as diatoms with hard shells, and tough pollen grains fossilize well. 3. Fossils show that many organisms previously found on Earth are now extinct. a. they illustrate relationships between extinct and living organisms. i. comparing fossils with their descendants shows how evolutionary changes have occurred over time. b. Understanding environmental changes occurring at the same time can help us understand why the evolutionary changes occurred. c. for example, fossils show that as horses evolved they became larger, paws evolved into hooves, and teeth grew larger and harder. The original small horses lived in forest habitat, but over time it dried out and became grassland. Successful animals were larger, with larger teeth and harder feet which eventually evolved into hooves. i. They grew larger since there are fewer hiding places in grasslands. ii. Hooves allowed faster running on the harder ground iii. Larger, harder teeth were adapted to chewing tough leaves of grasses. D. Homologies: characteristics that are similar between species due to common ancestry; traits inherited from a common ancestor by different species. 1. Often these traits undergo significant evolutionary modification as species adapt to different habitats and life styles. They may end up looking different but they have underlying structural similarity (built the same way) 2. Comparative anatomy shows homologies in structure between species a. example: vertebrate forelimbs all show the same pattern of bones, but sizes and shapes evolved as individual species adapted to running, swimming, flying, climbing, etc. b. example: leaves can be modified into many different shapes carrying out different functions, for example trapping insects, attracting pollinators, and defense 3. Comparative embryology shows similarities in developmental patterns between species2a. example: vertebrate embryos (even human) go through similar stages in which they have gill slits and a tail. This developmental pathway has been inherited from ancient vertebrate ancestors. In fish the slits form the gills; in humans they become parts of the neck and face. b. example: most plants have similar looking seedlings with 2 seed leaves 4. Comparing their anatomy and embryology, it is obvious that vertebrates are related . a. The reason for their similarity is genetic relationship between the organisms. Their genes are similar, so their proteins are similar, and they end up with similar body structures. 5. Comparative biochemistry shows similarities in cell chemistry between all species, from themost primitive bacteria to humans. a. all organisms use DNA to store genetic information. The DNA has the same structure and is used in the same way -- because it evolved once, and all organisms on Earth use it. This is whybacteria can take in human genes and use them to produce human proteins. b. relatedness of species can be studied by determining the degree of similarity of shared genes or proteins. DNA sequences of species can be compared to determine their similarity. Human DNA is only about 1% different from chimp DNA. To put this in perspective, very few other pairs of related species have such similar DNA. E. Vestigial structures are parts of the body no longer used, but which were important to the survival of an ancestral species, and have been inherited from it. 1. Example: whales have tiny leg bones hidden inside their bodies. They don't need legs but they do need a smooth surface to swim efficiently. 2. Many snakes also have bone vestiges from lost limbs. In this case the vestigial leg bones aretucked out of the way up underneath the ribs 3. Other examples of vestigial structures include the wings of flightless