Darwin Chapter 22 Charles Darwin 0 Lived in England 0 1809-1882 0 1831-1836: Beagles five-year voyage mapping the coastline of South America 0 1859: On the Origin of Species by Means of Natural Selection
0 EVOLUTION explains how modern organisms evolved over long periods of time through descent from common ancestors On the Origin of Species by means of Natural Selection 0 Published by Darwin in 1859 (158 years ago)
0 Two major claims: 0 The species present on Earth today descended from ancestral species 0 Natural selection is the mechanism for evolution 0 Natural Selection leads to evolutionary adaptation. 0 Individuals with beneficial heritable traits leave
more offspring, therefore, the frequency of those traits increases in the population over generation 0 Evolution changes in a populations genetic composition over time. Darwin challenged traditional views 0 Prevailing view = Earth was only a few thousand years
old, species of organisms were unchanging, created by God Historical context 0 Aristotle (384-322 B.C.) all living forms could be arranged on a scale of increasing complexity = scala naturae 0 species are permanent and perfect and do not
evolve 0 Natural Theology 1700s 0 Based on Old Testament creation story 0 Species were individually designed by God and do not evolve 0 Taxonomy = science of classification 0 Sought to classify the species that God had created 0 Linnaeus (1707-1778) taxonomy showed Gods organization Historical context (continued) 0 Georges Cuvier (1769-1832):
paleontologist; felt changes in fossils at different strata due to catastrophism. 0 Some catastrophe (flood or drought) destroyed large numbers of species at a time 0 Hutton: (1726-1797): gradualism; profound change can take place through the cumulative effect of slow
but continuous processes. 0 Earths geologic features explained by mechanisms currently operating in the world. Historical context (continued) 0 Charles Lyell (1797-1875): uniformitarianism; basic geological processes (wind, rain, erosion, etc.) have not changed throughout Earths history. 0 Darwin reasoned that Earth must be older than 6000 years
Other scientists suggest that evolution occurs 0 Lamarcks theory of evolution: theory of evolution based on the idea that modification acquired during life of an organism passed to offspring. 0 Wallace: also developed
theory of evolution based on natural selection in1858; this pushed Darwin to publish his findings Inherited Characteristics Acquired Characteristics List the characteristics that you
believe you have always had. List your acquired characteristics. For example, you may have brown eyes or curly hair. For example, you may have learned how to play a musical instrument.
Lamarcks Evolutionary Hypothesis 0 Jean Baptiste Lamarck proposed theory of evolution based on growing fossil record 0 Suggested that organisms could change during their lifetimes by selectively using or not using various parts of their bodies. 0 Suggested that individuals could pass these acquired traits onto offspring,
enabling species to change over time 0 Published ideas in 1809 year Darwin was born Evaluating Lamarcks Hypothesis Lamarck was INCORRECT because: 1. Organisms do not have an inborn drive to be perfect 2. Evolution does not mean that over time species
becomes better somehow 3. Evolution does not progress in predetermined direction 4. Traits acquired by organisms during lifetime cannot be passed on to offspring Lamarck gave us some good stuff too! 0 Lamarck was one of 1st to try to explain evolution scientifically using natural processes 0 Recognized link b/w orgs environment and body structures
Darwins research 0 Charles Darwin (1809-1882) 0 Voyage of the HMS Beagle 1831 0 mission to chart the South American coastline 0 Observations: 0 Adaptations of plants and animals were similar in similar environments 0 Geologic change (for example due to earthquake) indicated
that Earth was much older than 6000 years. 0 Geographic distribution of unusual species on Galapagos indicated descent with modification Blue Footed Boobies Artificial Selection Artificial Selection: selective breeding of domesticated plants and animals to produce offspring with genetic traits that humans value
nature provides variation, humans select variations that are useful. Example: a farmer breeds only his best livestock Artificial Selection 0 Humans have been modifying species for thousands of years 0 Darwin saw this being done with dogs 0 He observed that a species could be changed a lot in a
short period of time 0 Thought that the same thing could be happening in nature at a slower pace Differences Natural Selection Artificial Selection 0 Traits that are more
0 Humans choose the beneficial in the organisms environment become more common in the population traits that become more common in the population
What Darwin Knew 0 What did Darwin (and science) know? 0 The Earth is REALLY old 0 4.6 Billion Years 0 The Earth has changed over time 0 Mountains and valleys formed 0 Rivers change course 0 Water erodes land 0 Humans can change organisms
through breeding 0 Organisms have rapid Population Growth 0 Darwin realized most organisms dont survive and reproduce 0 ???Which individuals survive and why??? What Darwin didnt know 0DNA and Genetics 0Knew that traits were passed from parent to offspring
0Didnt know HOW POGIL Struggle for Existence 0 If more individuals are produced than can survive members of a population must compete to obtain food, living space, and other limited necessities of life
0 Called: Struggle for Existence 0 Which individuals come out on top of struggle? Variation and Adaptation 0 Individuals have natural variations among heritable traits 0 Some variants are better suited to life in their
environment than others 0 Predatory species that are faster, longer claws, sharper teeth catch more prey 0 Prey species that are faster, better camouflaged avoid being caught
Some Variations are Favorable 0 Adaptation - any heritable characteristic that increases an organisms ability to survive and reproduce 0 Body parts or structures 0bears claws 0body color camouflage or mimicry 0 Physiological functions 0a plant carrying out photosynthesis 0 Behaviors
0avoidance strategies prey use 0crane flapping wings Darwins Theory of Natural Selection Animals on different islands are in different populations Galapagos Islands were most likely colonized by a single finch species from South America Single species adapted to the varied habitats on the islands Today we have 13 different
species of finch Differ by Beak Shape WHY? Darwins Observations Overproduction 0 Based on Malthus Idea, Darwin realized that species tend to produce
excess offspring 0 limit resources + excess offspring = competition 0 Not Everyone Survives! Variation Differences among members of the same species Most variation is
heritable Siblings look more like each other than they do other people Darwins Observations Natural Selection and Species Fitness 0 Overtime, natural selection results in changes in the
inherited characteristics of a population. 0 These changes increase a species fitness 0 survival rate Summary of Darwins Theory The Process 1. Organisms differ; variation is inherited 2. Organisms produce more offspring than survive
3. Organisms compete for resources 4. Organisms with advantages survive to pass those advantages to their children 5. Species alive today are descended with modifications from common ancestors Summary of Darwins ideas 0 Natural selection refers to the differential success in reproduction which results in adaptations of populations of organisms to their environment
0 Natural selection occurs from the interaction between the environment and the inherent variability in a population 0 Variations in a population arise by chance 0 Natural selection is not a chance phenomenon, since environmental factors set definite criteria for reproductive success
