Developing the Theory of Evolution

Transcription

1 Developing the Theory of Evolution Chapter 19 Begin by reading Pg s

2 Evolution is the core theme of biology Nothing in biology makes sense except in the light of evolution Theodosius Dobzhansky

3 Key Terms: Evolution The relative changes in the characteristics of populations that occurs over time (several generations). Adaptation Any trait that helps an organism survive and reproduce in a particular environment. Variation a different form of any particular trait. Discuss the familiar example of the Peppered Moth (pg. 644)

4 Natural vs. Artificial Selection Natural change that occurs because organisms with particular traits help them survive and reproduce under certain environmental conditions. Must have natural diversity within the population. Artificial occurs where a trait is selected for by humans regardless of the health of the organism.

5 Pre-Darwinian lead up to the THEORY of Evolution Plato ( BC); Aristotle ( BC) - Plato s Idealism - Stated that variations in plant and animal populations as being imperfect representations of ideal forms species are fixed, permanent, and do not evolve (Stability of Species)

6 Natural Theology: Pre-Darwin This is today s - Intelligent design theory based on Judeo-Christian culture (old testament) Argued that adaptations in organisms were planned by the creator. each and every species designed for a particular purpose

7 Pre-Darwin Naturalists of the 1700s were pre-occupied with naming new species accepted a limited time scale assumed the fixity of species used newly invented microscopes and telescope to look at embryos and stars recognized that fossils existed of animals unknown in their explorations

8 The Changing Minds of the of the 19 th Century European colonialism leads to the discovery that the number of species is very large. Maybe species can change after all? Although this was discussed in numerous circles, it was contrary to religious teachings and dismissed as heresy.

9 Georges Cuvier ( ): Founder of Paleontology (the study of fossils) Opposed evolution Thought that boundaries between fossil layers corresponded to catastrophic events in the Bible (Noah s flood or droughts) Developed the theory of catastrophism

10 The oldest fossils are in the oldest strata

11 Charles Lyell ( ): Uniformitarianism An embellishment on Hutton s gradualism theory geological processes are so uniform that their rates and effects must balance out through time Suggested the Earth was hundreds of millions of years old. Darwin took only three books with him on the Beagle. One was Lyell s book Principles of Geology

12 Jean Baptiste Lamarck ( ) - The Inheritance of Acquired Characteristics - environmental pressures require animals to strive (unconsciously) toward higher branching pathways of perfection. - Believed that evolution responded to organisms felt needs i.e. use and disuse : examples: biceps of blacksmith, giraffes neck - inheritance of acquired characteristics: modifications acquired during a lifetime can be passed on to offspring - Although wrong, his thinking was visionary. (Environment)

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14 Thomas Malthus published an essay on the Principles of Population - survival of the fittest Malthus explained population growth to Darwin: Populations need to reproduce and will breed rapidly. This will cause competition between members of the population for resources (Limiting Factors). Those who have the ability to get resources will survive. This idea helped Darwin explain & understand how variations could arise within species.

15 Alfred Wallace a British naturalist and explorer. Independently conceived the theory of evolution through natural selection. He was considered the 19th century's leading expert on the geographical distribution of animal species and is sometimes called the "father of biogeography. Wallace became a spiritualist and could not extend the ideas of evolution on to humans.

16 Charles Darwin - ( ) originally intended to study medicine at Edinburgh; later went to Cambridge left to go as a naturalist on the voyage of the Beagle in 1831 to South America Darwin Video

17 In 1831 he left on a 5 year voyage on board the Beagle to survey the coast of South America. He stopped off at the Galapagos Islands for five weeks where the diversity of the plants and animals amazed him.

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19 Darwin saw variation within species on the different Islands. But didn t fully understand what he saw till he returned to England

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21 Darwin s Finches

22 Who would: Crack open hard nuts? pick insects out of cracks in trees? Etc..

23 Darwin s Published Works Darwin reached England in 1836 met Charles Lyell talked with stock breeders and dabbled in breeding himself read Malthus in October 1838 was a friend of Alfred Russel Wallace ( ) who arrived at the theory of natural selection at the same time presented his views with Wallace before publication of On the Origin of Species

24 Darwin cont Charles Darwin published: On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. on November 24, 1859 It was an overnight bestseller Note: Darwin never used the word evolution in his book, and the word evolved only occurred once (the last word of the book). Darwin referred to: Descent with modification

25 Comparison of Lamarck s Theory with that of Darwin

26 Darwin s Theory of Natural Selection (Main Points) All organisms exhibit variability All organisms reproduce more offspring than can survive so competition exists. Therefore, it must be that: Those individuals best suited to their environments survive and reproduce. Any changes in a population are slow and gradual

27 The End

28 Evidence Supporting the Modern Theory of Evolution - Chapter 19.3 Evidence Available to Darwin Fossils Taxonomy Comparative Anatomy Comparative Embryology Biogeography Modern Technologies Molecular Biology

29 Fossil Record Fossils: Are remains or imprints of past life Are preserved in sediments occur in layers (strata) Indicate the presence of species that many no longer occur, or resemble forms of modern species.

30 Strata layers in Rocks

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32 Fossilized remains of a bird like dinosaur Archeopteryx

33 Fossil trilobite

34 Fossils in Amber

35 Fossil Jellyfish

36 Relative aging of Fossils Fossils distributed consistently throughout strata of same age. The order of fossil appearance shows that more complex forms of life appear in higher strata s after simpler forms below. Recent fossils (new/top strata layers) more closely resemble modern day organisms.

37 Absolute Age - Fossils Calculate the Half Lives

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40 Evidence for Evolution Evidence Available to Darwin Fossils Taxonomy Comparative Anatomy Comparative Embryology Biogeography

41 Taxonomy The hierarchical classification system developed by Linnaeus. This system implies species can be grouped together based on their relatedness. Bears with bears, bees with other bees, etc A family tree can be made implying descent

42 Family Tree of Bears

43 Evidence for Evolution Evidence Available to Darwin Fossils Taxonomy Comparative Anatomy Comparative Embryology Biogeography

44 Comparative Anatomy Compares the anatomical structures from different organisms. Similar structures in two or more species are called homologous structures. Homologous structures may perform different tasks in different organisms.

45 Homologous forelimbs

46 Family Tree of the Horse (Equus)

47 Evidence for Evolution Evidence Available to Darwin Fossils Taxonomy Comparative Anatomy Comparative Embryology Biogeography

48 Comparative Embryology Embryos (young stage of organisms are compared) Show similar features due to shared ancestry All vertebrates have tails gill-like branchial arches

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50 Where are we????

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52 Evidence for Evolution Evidence Available to Darwin Fossils Taxonomy Comparative Anatomy Comparative Embryology Biogeography

53 Biogeography Helps to explain the distribution of species. Many related species occur across the earth. Isolated areas (islands, Australia) often have unique species. Biogeography explained by continental drift of plates and speciation.

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55 Map of Oceanic Crust Ages in the Atlantic

56 Map of Earthquake Epicenters,

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59 Molecular Biology Not available to Darwin in 1800 s Includes comparisons of protein sequences DNA sequences cytochrome c (from mitochondria) chloroplast genomes (plants only) Used to developed phylogenetic trees (hypothesized relationships)

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