Transcript Evolution
PowerPoint® Lecture Slide Presentation by Robert J. Sullivan, Marist College Human Biology Concepts and Current Issues Second Edition MICHAEL D. JOHNSON CHAPTER 22 EVOLUTION AND THE ORIGINS OF LIFE Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Evidence for Evolution: From Many Sources • Fossil record: incomplete but valuable, preserves only hard tissues • Comparative anatomy and embryology: analogous and vestigial structures • Comparative biochemistry: examines similarities between molecules, estimates divergence • Biogeography: impact of geographic barriers and continental drift Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Natural Selection: A Mechanism of Evolution • Random mutations: underlie evolution, introduces allelic variations • Natural selection: encourages “survival of the fittest” • Genetic drift: random changes in allele frequency due to chance events • Bottleneck effect • Founder effect Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Natural Selection: A Mechanism of Evolution (cont.) • Gene flow: differences in gene pool of particular populations due to immigration or emigration • Mass extinctions: eliminate many species, 50% or more Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Evolutionary Tree Figure 22.9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Evolutionary Tree/Phylogenetic Tree • Purpose: to trace evolutionary change and relationships between species • Adaptive radiation: short bursts of evolutionary activity Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. The Young Earth • Inhospitable to life: hot and steamy • Early atmosphere • Consisted of: carbon dioxide, water vapor, hydrogen, nitrogen, methane, ammonia • Did not have: liquid water, oxygen, ozone Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. First Cellular Life: Single-Celled Creatures Resembling Bacteria • Simple organic molecules: formed from atmospheric gases • Amino acids, simple sugars, fatty acids • Self-Replicating RNA and DNA formed on clay templates • First-living cells: anaerobic • Obtained needed chemicals from environmental soup Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Photosynthetic Organisms: Altered Course of Evolution • Photosynthesis • Increase in atmospheric oxygen • Oxygen produced as waste product of carbon dioxide • Evolution of aerobic organisms • Oxygen toxic to anaerobic organisms • Oxygen assisted in breaking down organic compounds, especially in environment • Survivors had to possess chemical pathways to make needed organic compounds Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Evolutionary Time Line Figure 22.11 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Rise of Animals and Human Ancestors • Evolutionary highlights • Nucleus formed, eukaryotes develop, 1.7 billion years ago • First multicellular organisms (seaweed), 1.3 billion years ago • Animals appear, 600 million years ago • Dinosaurs extinct, 65 million years ago • Distinctly human ancestors, 5 million years ago Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Proposed Homo sapien Evolution Figure 22.14 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Human Evolutionary Beginning: Hominids • Taxonomic classification • Kingdom Animalia, Phylum Chordata, Class Mammalia, Order Primata, Family Hominidae, Genus Homo, Species Sapiens • Mammals: vertebrates with hair and mammary glands that produce milk • Primates: hands with five digits, fairly flat fingernails and toenails, forward facing eyes Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Evolution of Homo sapiens • Australopithecus afarensis: upright primate, vegetarian, sexual dimorphism, 4-5 million years ago • Homo habilis: first tool maker, enlarged brain, omnivore, decline in sexual dimorphism, 2.6 million years ago • Homo erectus: more brain enlargement, longer infancy, continued decline in sexual dimorphism, continued tool development, continued social development, spread out of Africa to Europe and Asia, 2 million years ago Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Evolution of Homo sapiens (cont.) • Homo neanderthalensis: may be an extinct branch • Homo sapien: only surviving Homo species, 100,000 to 140,000 years ago Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings. Differences in Race • Racial differences are slight differences in phenotypes between subgroups of a common species • Advantages • Dark skin: protection from ultraviolet (UV) damage in intensive sunlight • Light skin: allows adequate UV radiation for Vitamin D production in less intense sunlight Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings.