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Andrew Friedland • Rick Relyea Environmental Science FIRST EDITION CHAPTER 5 Evolution of Biodiversity © 2012 W. H. Freeman and Company F. assafoetida – Dung of the Devil Nature’s Pharmacy Rosy periwinkle Species Diversity …in a healthy forest Ecosystem Diversity Species Diversity Genetic Diversity Species: •A population of organisms •With shared characteristics •Capable of interbreeding, and •Producing fertile offspring •In nature How diverse are insect populations in the rainforest? What group of insects is most abundant? Where do most insects reside within the rainforest? Species Richness -v- Evenness Derived Trait Environmental pressures affect phenotype Artificial Selection Principles of Natural Selection A mechanism to explain how evolution works Over-reproduction Producing more offspring than can possibly survive in nature Why would an organism waste all of this energy? Because many will not survive, (life’s hard!!), having many offspring ensures that at least some will survive Variation Organisms have differences in the their phenotypes, their characteristics. We’re not all identical!! Sources of variation: 1.mutation 2.meiosis: a. Crossing over b. Independent assortment 3.Sexual reproduction Struggle for Survival Organisms must compete for limited resources What do they compete for? 1.Food 2.Water 3.Mates 4.Territory 5.Shelter Survival of the Fittest Only those organisms best adapted to their environment can survive (and pass on their DNA!) What will happens to populations of organisms over time? A population becomes better suited to its environment. What makes an organism/population/species fit? Adaptation: – A structure, behavior or internal process that makes an organism better suited to its environment Evolution: – Occurs to a population (species), not an individual Hardy Weinberg Equation p2 + 2pq + q2 = 1 What does this mean? A population is comprised of the sum of its various genotypes, and this should remain constant. But it doesn’t remain constant. Ever. It does give us a baseline from which to evaluate change. What factors cause the frequencies of genotypes to change? Allopatric Speciation LAURASIA 120° 80° 40° 80° 120° 120° 80° 80° 120° GONDWANALAND 135 million years ago 225 million years ago NORTH AMERICA EURASIA AFRICA 120° 80° INDIA SOUTH AMERICA 120° 120° 0° 40° AUSTRALIA ANTARCTICA 65 million years ago Present 120° Sympatric speciation through polyploidy Ability of a Species to Adapt to Change Ability of a Species to Adapt to Change Ability of a Species to Adapt to Change Ability of a Species to Adapt to Change ……R and K strategists, coming soon Range of Tolerance for a Species Just one of many factors Is it better to be a generalist? …or a specialist? The Fossil Record Mass Extinctions & Explosions of Life An FRQ, to ponder.