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Biodiversity 1 Globally - ~1.8 million species ~10,000 birds ~ 4629 mammals ~ 8240 reptiles ~ 900,000 insects (named) ~ 300,000 vascular plants ~ 20,000 fish Descent with Modification Lecture 1 Winter 2014 2 Species Diversity & Unity Species Diversity & Unity 3 • Hierarchy of classification • What are some of the characteristics shared by all life? • Organisms suited to their environment Fig. 22.12 • Need a theory (model) that can explain these patterns See Fig. 26.3 Themes in Biology 4 5 • Charles Darwin (1809-1882) • 1831-1836 – Voyage of the HMS Beagle Evolution is the theme that unifies all biology “Nothing in biology makes sense except in the light of evolution” - Theodosius Dobzhansky Darwin’s Journey See Fig. 1.22 Fig. 22.5 1 Historical Context of Darwin’s Work 6 Plato & Aristotle (384-322 B.C.) • Species are fixed • Ladder of life (scale of nature) Special Creation/Natural Theology (JudeoChristian) • The world is ~ 6000 years old • Species represent independent/separate entities • Species are fixed Carolus Linnaeus (1707-1778) • Taxonomic system based on similarities Historical Context of Darwin’s Work – Events in the past happened suddenly – Mechanisms of change in the past are different than those operating today James Hutton (1726-1797) - Geologist • Gradualism (1795) – Change occurs through slow, continuous process – Mechanisms of change still occurring today 8 – Human population has the potential to grow faster than food supply Historical Context of Darwin’s Work 9 Jean-Baptiste de Lamarck (1744-1820) Naturalist • Proposed that species have changed through time and are related by common ancestry (1809) • Mechanism - Inheritance of acquired characteristics – Mechanisms of change are constant over time – Earth older than proposed • Thomas Malthus (1766-1834) Economist • 1798 – “An Essay on the Principle of Population as it affects the Future Improvement of Society” 7 Georges Cuvier (1769-1832) - Paleontologist • Documented succession of fossils • Catastrophism Charles Lyell (17971875) - Geologist • Uniformitarianism Historical Context of Darwin’s Work Historical Context of Darwin’s Work 10 Darwin’s Work 11 Darwin observed patterns • Descent with Modification – Species are related by common ancestry – Species change through time Darwin proposed a process • Natural Selection 2 Darwin’s Work 12 • 1844 – Darwin writes essay on evolution of species and natural selection • 1859 – Darwin publishes On the Origin of Species by Means of Natural Selection • Explains the diversity and similarity of organisms • Explains how organisms have come to be adapted to a wide range of environments Process = Natural selection 14 Populations Darwin’s Four postulates (criteria) 1. Individuals within a population vary in traits 2. Variation must be heritable (genes/DNA) 3. In every generation, more offspring are produced than can survive. Only some individuals survive to reproduce. 4. Survival and reproduction of individuals is not random • Outcome of process: A Population’s characteristics will change over time = Evolution will occur 16 Evolution: a genetically based change in the characteristics of a population over time 15 Population • a group of individuals of the same species living in the same area at the same time • Typically breed within the population Individuals with certain heritable traits survive and produce more offspring - they have been “naturally selected” Evolution by Natural Selection 13 Evolution: • Decent with modification • A genetically based change in the characteristics of a population over time • 1858 –Alfred Russel Wallace sends Darwin an essay outlining the process of evolution by natural selection The Process: Natural Selection The Theory of Evolution by Natural Selection 17 The Theory of Evolution by Natural Selection • What is “survival of the fittest”? • Darwinian fitness (relative fitness) – Ability of an individual to produce offspring, relative to the ability in other individuals in the population – Measurable quantity • Adaptation – Any heritable trait that increases fitness of an individual under prevailing environmental conditions relative to individuals lacking this trait 3 18 Artificial Selection Evolution by Natural Selection 19 What would happen to this population if the predator was a mammal that could see dark beetles more easily than light beetles? See Fig. 22.9 20 Evidence of Evolution 21 Evolution in Action: Galapagos Finches • Evolution is observable within our lifetime – Antibiotic resistant bacteria – Insects resistant to pesticides – Plants resistant to herbicides – Galapagos finches • Evolution can be tested experimentally • Finches on some of the Galapagos Islands studied since early 1970’s – Peter & Rosemary Grant • Finch population had variation in many heritable traits, including beak size The Beak of the Finch. Jonathan Weiner. 1995 How and Why Species Multiply: The Radiation of Darwin's Finches. Peter & Rosemary Grant. 2007 22 Evolution in Action: Galapagos Finches • Is there variation in this population? • What is the average beak size? 23 Evolution in Action: Galapagos Finches Medium ground finches eat seeds • Average rainfall year – Wide variety of seeds Beak Depth of Medium Ground Finch. • Drought year Year = 1976 • Wet Year Population = 751 – Shrubs with large, hard seeds – Shrubs overgrown by vines that produce small seeds 4 24 Evolution in Action: Galapagos Finches 25 Evolution in Action: Galapagos Finches 1977 was a drought year. • Make a prediction - what would happen to the population size of the medium ground finch from 1976 to the end of 1977? • Were your predictions correct? • Did evolution occur? Beak Depth of Medium Ground Finch. Year = 1978 Population = 90 – Draw a graph illustrating your prediction • Make a prediction – what would happen to the beak depth of the medium ground finch, if measured in 1978? – Draw a graph illustrating your prediction 26 27 Evolution in Action: Galapagos Finches 1983 was an extremely wet year What types of medium ground finishes had the greatest reproductive success? (e.g., what characteristics did they have?) Evolution by Natural Selection • Genetic diversity is key! Ray Troll 5