Chapter 9 Evolution (PDF)

CHAPTER IX Evolution Diversity of Life  Evolution “Nothing in biology makes sense EXCEPT in the light of evolution.” Theodosius Dobzhansky History of Evolutionary Thought  Early Ideas On Earth’s Organisms Aristotle believed species were fixed creations...

CHAPTER IX Evolution Diversity of Life  Evolution “Nothing in biology makes sense EXCEPT in the light of evolution.” Theodosius Dobzhansky History of Evolutionary Thought  Early Ideas On Earth’s Organisms Aristotle believed species were fixed creations arranged by their complexity Idea lasted 2000 years  Naming of Organisms Linnaeus – 1st to group similar organisms and assign them Latin names Two word name (Genus species) Known as Binomial nomenclature  19th Century Ideas on Evolution Jean-Baptiste Lamarck, 1809 One Of First Scientists To Understand That Change Occurs Over Time Stated that Changes Are Adaptations To Environment acquired in an organism’s lifetime and passed to their offspring.  Lamarck’s Theory of Evolution Idea called Law of Use and Disuse If a body part were used, it got stronger If body part NOT used, it deteriorated  Lamarck’s Mistakes Lamarck Did NOT Know how traits were inherited (Traits are passed through genes) Acquired characteristics are not transmitted to oncoming generations Change Through Mutation Occurs Before An Organism Is Born (they are pre-adaptive changes)  Contributor’s to Darwin’s theory : James Hutton – Gradualism (J) Thomas Malthus – struggle for existence (resources) (Econ) John Baptiste Lamarck – Inheritance of acquired Characteristics and Law of Use and Disuse (Bot.) Charles Lyell –uniformatarianism (J) Georges Cuvier – species extinction (Catastrophism) (J) Alfred Russel Wallace – organisms evolved from common ancestors (Biol.) Charles Darwin the Naturalist  Voyage of the Beagle Charles Darwin Born Feb. 12, 1809 Joined Crew of HMS Beagle, 1831 Naturalist 5 Year Voyage around world Avid Collector of Flora & Fauna Astounded By Variety of Life  Darwin’s Voyage of Discovery A reconstruction of the HMS Beagle sailing off Patagonia.  HMS Beagle’s Voyage 1831-1836 Jan. 1831 Oct. 1836 Sept. 1835 Jan. 1836 Apr. 1832  Voyage of the Beagle During His Travels, Darwin Made Numerous Observations And Collected Evidence That Led Him To Propose A Revolutionary Hypothesis About The Way Life Changes Over Time  The Galapagos Islands Small Group of Volcanic Islands 1000 km West of South America Very Different Climates Animals On Islands Unique » Tortoises » Iguanas » Finches Island species varied from mainland species & from island-to- island species For example, each island had long or short neck tortoises  The Galapagos Islands Finches on the islands resembled a mainland finch More types of finches evolved on the islands where the available food was different (seeds, nuts, berries, insects…) Finches had different types of beaks adapted to their type of food gathering Darwin’s Observations & Conclusions  Darwin’s Observations Patterns of Diversity were shown Unique Adaptations in organisms Species Not Evenly Distributed » Australia, Kangaroos, but No Rabbits » S. America, Llamas  Darwin’s Observations Both Living Organisms & Fossils collected Fossils included: »Trilobites »Giant Ground Sloth of South America This species NO longer existed. What had happened to them? Evidence for Evolution – The Fossil Record  Darwin’s Observations Left unchecked, the number of organisms of each species will increase exponentially, generation to generation In nature, populations tend to remain stable in size Environmental resources are limited  Darwin’s Observations Individuals of a population vary extensively in their characteristics with no two individuals being exactly alike. Much of this variation between individuals is inheritable.  Darwin’s Conclusions Production of more individuals than can be supported by the environment leads to a struggle for existence among individuals Only a fraction of offspring survive each generation Survival of the Fittest  Darwin’s Conclusions Individuals who inherit characteristics most fit for their environment are likely to leave more offspring than less fit individuals Called Natural Selection  Common Descent with Modification Darwin proposed that organisms descended from common ancestors Idea that organisms change with time, diverging from a common form Caused evolution of new species or SPECIATION  EVOLUTION Therefore, Evolution is the slow , gradual change in a population of organisms over time. The Book: Origin of Species  “On The Origin of Species” Upon His Return To England, Darwin Developed His Observations Into The Theory of Evolution But He Did Not Publish For 25 Years – Why?  “On The Origin of Species” Darwin Knew That His Theory Would Be Extremely Controversial And Would Be Attacked His Theory Challenged Established Religious & Scientific Beliefs, Particularly About The Creation Of Man  “On The Origin of Species” He Refused To Publish Until He Received An Essay From Alfred Wallace – Fellow Naturalist – Independently Developed The Same Theory – After 25 Years, Someone Else Had Come To The Same Conclusions From Their Observations Of Nature Publication of “On The Origin of Species” Darwin Presented Wallace’s Essay & Some Of His Work At A Scientific Conference of the Linnaean Society in July of 1858 Then He Started On his book “Origin of Species” It Took Darwin 18 Months To Complete The Book Origin of Species Concepts and Controversy Evolution By Natural Selection Concepts The Struggle for Existence (species compete for food, mates, space, water, etc.) Survival of the Fittest (strongest able to survive and reproduce) Descent with Modification (new species arise from common ancestor replacing less fit species)  Survival of the Fittest Fitness – Ability of an Individual To Survive & Reproduce Adaptation – Inherited Characteristic That Increases an Organisms Chance for Survival  Survival of the Fittest Fitness Is Central To The Process Of Evolution Individuals With Low Fitness – Die – Produce Few Offspring Survival of the Fittest AKA Natural Selection  Survival of the Fittest Key Concept Over Time, Natural Selection Results In Changes In The Inherited Characteristics Of A Population. These Changes Increase A Species Fitness In Its Environment  Descent With Modification Takes Place Over Long Periods of Time Natural Selection Can Be Observed As Changes In – Body Structures – Ecological Niches – Habitats  Descent With Modification Species Today Look Different From Their Ancestors Each Living Species Has – Descended with changes from other species over time Please watch the Evolution of Whales video for the next slide Descent With Modification  Descent With Modification Implies – All Living Organisms Are Related – Single Tree of Life » DNA, Body Structures, Energy Sources Common Descent – All Species, Living & Extinct, Were Derived From Common Ancestors  Major Problem in Darwin’s Theory No mechanism to explain natural selection How could favorable variations be transmitted to later generations? With the rediscovery of Mendel’s work in the first half of the 20th century, the missing link in evolutionary theory was found.  Opposition to Evolution The upheaval surrounding evolution began with Darwin’s publication of On the Origin of Species By Means of Natural Selection The debate continues nearly 150 years later  Theory of Evolution Today Supporting Evidence  1 Homologous Body Structures Scientists Noticed Animals With Backbones (Vertebrates) Had Similar Bone Structure May Differ In Form or Function but Limb Bones Develop In Similar Patterns » Arms, Wings, Legs, Flippers Homologous Structures  2 Similarities In Early Development Embryonic Structures Of Different Species Show Significant Similarities Embryo – early stages of vertebrate development Similarities In Embryonic Evidence for Evolution Development - Comparative Embryology 3 Similarities in Protein and DNA Sequence Evolutionary Time Scales Macroevolution: Long time scale events that create and destroy species.  Evolutionary Time Scales Microevolution: Short time scale events (generation-to-generation) that change the genotypes and phenotypes of populations