Descent with Modification Lecture 1 Winter 2014
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
Species Diversity & Unity 2 Organisms suited to their environment Fig. 22.12
Species Diversity & Unity 3 Hierarchy of classification What are some of the characteristics shared by all life? Need a theory (model) that can explain these patterns See Fig. 26.3
Themes in Biology 4 Evolution is the theme that unifies all biology Nothing in biology makes sense except in the light of evolution - Theodosius Dobzhansky See Fig. 1.22
Darwin s Journey 5 Charles Darwin (1809-1882) 1831-1836 Voyage of the HMS Beagle Fig. 22.5
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 (Judeo- Christian) 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 7 Georges Cuvier (1769-1832) - Paleontologist Documented succession of fossils Catastrophism 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
Historical Context of Darwin s Work 8 Charles Lyell (1797-1875) - Geologist Uniformitarianism Mechanisms of change are constant over time Earth older than proposed
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
Historical Context of Darwin s Work 10 Thomas Malthus (1766-1834) Economist 1798 An Essay on the Principle of Population as it affects the Future Improvement of Society Human population has the potential to grow faster than food supply
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
Darwin s Work 1844 Darwin writes essay on evolution of species and natural selection 1859 Darwin publishes On the Origin of Species by Means of Natural Selection 12 1858 Alfred Russel Wallace sends Darwin an essay outlining the process of evolution by natural selection
The Theory of Evolution by Natural Selection 13 Evolution: Decent with modification A genetically based change in the characteristics of a population over time Explains the diversity and similarity of organisms Explains how organisms have come to be adapted to a wide range of environments Process = Natural selection
The Process: Natural Selection 14 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 Individuals with certain heritable traits survive and produce more offspring - they have been naturally selected Outcome of process: A Population s characteristics will change over time = Evolution will occur
Populations 15 Population a group of individuals of the same species living in the same area at the same time Typically breed within the population
Evolution by Natural Selection 16 Evolution: a genetically based change in the characteristics of a population over time
The Theory of Evolution by Natural Selection 17 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
Evolution by Natural Selection 18 What would happen to this population if the predator was a mammal that could see dark beetles more easily than light beetles?
Artificial Selection 19 See Fig. 22.9
Evidence of Evolution 20 Evolution is observable within our lifetime Antibiotic resistant bacteria Insects resistant to pesticides Plants resistant to herbicides Galapagos finches Evolution can be tested experimentally
Evolution in Action: Galapagos Finches 21 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
Evolution in Action: Galapagos Finches 22 Is there variation in this population? What is the average beak size? Beak Depth of Medium Ground Finch. Year = 1976 Population = 751
Evolution in Action: Galapagos Finches 23 Medium ground finches eat seeds Average rainfall year Wide variety of seeds Drought year Shrubs with large, hard seeds Wet Year Shrubs overgrown by vines that produce small seeds
Evolution in Action: Galapagos Finches 24 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? 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
Evolution in Action: Galapagos Finches 25 Were your predictions correct? Did evolution occur? Beak Depth of Medium Ground Finch. Year = 1978 Population = 90
Evolution in Action: Galapagos Finches 26 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 27 Genetic diversity is key! Ray Troll