Darwin and Evolution :Darwin and Evolution Biology


Biological Evolution :Biological Evolution Definition: All the changes that have transformed life on earth. Evolutionary change is based mainly on the interactions between populations of organisms and their environment.


Introduction :On November 24, 1859, Charles Darwin published On the Origin of Species by Means of Natural Selection. Darwin made two points in The Origin of Species: Today’s organisms descended from ancestral species. Natural selection provided a mechanism for evolutionary change in populations. The Origin of Species challenged a worldview that had been accepted for centuries. Introduction


Western Culture Resisted Evolutionary Views of Life :In the 1700’s, the dominant philosophy, natural theology, was dedicated to studying the adaptations of organisms as evidence that the Creator had designed each species for a purpose. The key classical Greek philosophers opposed any concept of evolution. Plato (427-347 B.C.) believed in two worlds: one real perfect world and an imperfect illusory world that we perceive through senses. Aristotle (384-322 B.C.) believed that all living forms could be arranged on a ladder (scala naturae) of increasing complexity with every rung taken with perfect, permanent species. Western Culture Resisted Evolutionary Views of Life


Carolus Linnaeus :Carolus Linnaeus Carolus Linnaeus (1707-1778), a Swedish botanist, developed taxonomy, a system for naming species and grouping species into a hierarchy of increasingly complex categories. Linnaeus believed in special creation and the fixity of species. “God creates, Linnaeus arranges.”


Slide 6:French anatomist Georges Cuvier (1769-1832), largely developed Paleontology, the study of fossils. Studied the succession of fossils in the Paris Basin and said: extinction was common in history. he advocated catastrophism, instead of evolution boundaries between strata were due to local flood or drought that destroyed species this area would be repopulated by species immigrating from other unaffected areas. Some followers believed catastrophes were global and God created life anew.


Theories of Geological Gradualism Cleared the Way :James Hutton, a Scottish geologist, in 1795, proposed that the diversity of land forms (e.g., canyons) could be explained by mechanisms currently operating. Hutton proposed a theory of gradualism, that profound change results from slow, continuous processes. Charles Lyell (1797-1875), proposed a theory of uniformitarianism, that geological processes had not changed throughout Earth’s history. For example, processes that build mountains are eventually balanced by the erosion of mountains. Theories of Geological Gradualism Cleared the Way


Slide 8:In 1809, Jean Baptiste de Lamarck (1744-1829) published a theory of evolution based on his observations of fossil invertebrates in the Natural History Museum of Paris. Lamarck thought that he saw what appeared to be several lines of descent in the collected fossils and current species. Each was a chronological series of older to younger fossils leading to a modern species. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings


Slide 9:Lamarck’s mechanism of evolution: use and disuse of parts proposed that body parts used to cope with the environment became larger and stronger, while those not used deteriorated, for example a snake’s legs. inheritance of acquired characteristics. proposed that modifications acquired during the life of an organism could be passed to offspring. A blacksmith could pass his muscles to his offspring. EX. the giraffe individuals could acquire longer necks by reaching for leaves on higher branches and pass this characteristic to their offspring.


Lamarck deserves credit for: :Lamarck deserves credit for: Claiming evolution is the best explanation for the fossil record. Emphasizing the great age of the earth. Stressing adaptations to the environment as primary products of evolution. However, there is no evidence that acquired characteristics can be inherited. Acquired traits (e.g., bigger biceps or the ability to play an instrument) do not change the genes transmitted by gametes to offspring.


Figure 22.1 The historical context of Darwin’s life and ideas :Figure 22.1 The historical context of Darwin’s life and ideas


Charles Darwin (1809-1882) :Charles Darwin (1809-1882) 1825—sent to the University of Edinburgh to study medicine and left without a degree. Enrolled in Christ College, Cambridge University intending to become a clergyman. At that time most naturalists and scientists belong to the clergy. Received a B.A. in 1831. Reverend John Henslow, professor of botany, recommended him to Captain Robert FitzRoy to be the naturalist on the HMS Beagle as it went on a voyage around the world.


Figure 1.17b Diversification of finches on the Galápagos Islands :Figure 1.17b Diversification of finches on the Galápagos Islands


Figure 24.0 A Galápagos Islands tortoise :Figure 24.0 A Galápagos Islands tortoise


Influences on Darwin: :Influences on Darwin: Lyell’s book Principles of Geology—geological changes are the result of slow processes so the earth must be very old. Firsthand observations of massive geological changes—marine shells in the Andes mountains, after an earthquake. Galapagos Island species—especially finches and tortoises Fossils Darwin saw on coast of South America—living forms must be descendants of extinct forms in the fossil record. Biogeography—Related species could be modified by the environment; species on the Galapagos Islands were different from those on the mainland & from island to island. “Essay on the Principle of Population” in which Thomas Malthus said that human suffering was the due to the population increasing faster than resources. Artificial selection - vegetables derived from wild mustard; breeding of pigeons, dogs, cats


Biogeography :Biogeography


Artificial Selection :Artificial Selection


The Origin of Species Developed Two Main Points: :Darwinism has a dual meaning. It refers to evolution as the explanation for life’s unity and diversity. It also refers to the Darwinian concept of natural selection as the cause of adaptive evolution. The Origin of Species Developed Two Main Points: Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings


Slide 19:Central to Darwin’s view of the evolution of life is descent with modification. In descent with modification, all present day organisms are related through descent from ancestors in the past. Descendents of these ancestors accumulated diverse modifications or adaptations that fit them to specific ways of life and habitats. The history of life is like a tree with multiple branches from a common trunk. Closely related species, the twigs of the tree, shared the same line of descent until their recent divergence from a common ancestor.


Slide 21:Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Darwin’s main ideas can be summarized in three points: 1. Natural selection is differential success in reproduction (unequal ability of individuals to survive and reproduce). 2. Natural selection occurs through an interaction between the environment and the variability inherent among the individual organisms making up a population. 3. The product of natural selection is the adaptation of populations of organisms to their environment.


Slide 22:For example, these related species of insects called mantids have diverse shapes and colors that evolved in different environments. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 22.10


Slide 23:Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Darwin envisioned the diversity of life as evolving by a gradual accumulation of minute changes through the actions of natural selection operating over vast spans of time (gradualism). While natural selection involves interactions between individual organisms and their environment, it is not individuals, but populations that evolve. Populations are defined as a group of interbreeding individuals of a single species that share a common geographic area.


Natural Selection in Action: the Evolution of Insecticide-resistance :Natural Selection in Action: the Evolution of Insecticide-resistance Insecticides are poisons that kill insects. The results of application of new insecticide are typically kills 99% of the insects. The insecticide becomes less effective in subsequent applications. The few survivors of the insecticide are those with genes that enable them to resist the chemical attack. Only these resistant individuals reproduce, passing on their resistance to their offspring. In each generation the percentage of insecticide-resistant individuals increases.


Slide 25:Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 22.12


Lines of Evidence Supporting Evolution: :Lines of Evidence Supporting Evolution: Fossils Biogeography Comparative embryology Comparative anatomy a. homologous structures b. vestigial organs Comparative biochemistry a. Amino acid sequences b. DNA sequences


Last Sentence of On The Origin of Species :Last Sentence of On The Origin of Species “There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved.”