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1: Introduction. An overview of molecular evolution, or what is molecular evolution?

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Presentation on theme: "1: Introduction. An overview of molecular evolution, or what is molecular evolution?"— Presentation transcript:

1 1: Introduction

2 An overview of molecular evolution, or what is molecular evolution?

3 Molecular Evolution: theory and examples Theory: e.g., the equilibrium between mutations, selection, and drift Examples: e.g., chimpanzees and humans share a common ancestor that lived approximately 4 million years ago Exercises: e.g., compute the score of a given maximum parsimony tree

4 1.The evolution of molecular entities, e.g., genes, proteins, introns, inteins, chromosomal arrangements 2. The evolution of organisms and biological complexes, e.g., species, higher taxa, coevolutionary systems, ecological niches, and migratory patterns, by using molecular data. “Molecular Evolution” deals with two subjects:

5 Molecular Evolution deals only with events occurring after the emergence of biological systems that possess replicable genetic material.

6 1.Systematics (Linnaeus). 2.Evolutionary Mechanisms (Darwin, Lamarck) 3.Genetics (Mendel) 4.Populations Genetics (Malthus) 5.Nucleic Acid Research (Miescher) Molecular Evolution: the foundations:

7 1: Introduction

8 Classification Systematics is the science of naming and classifying organisms in regard to their natural relationships.

9 Macrolepiota procera : tasty Lepiota cristata : highly poisonous

10 Classification Systematics is the science of naming and classifying organisms in regard to their natural relationships.

11 4,400 species of animals and 7,700 species of plants

12 Linnaeus's scientific thought God has created the world, it is possible to understand God's wisdom by studying His creation. As he wrote in the preface to a late edition of Systema Naturae: Creationis telluris est gloria Dei ex opere Naturae per Hominem solum -- The Earth's creation is the glory of God, as seen from the works of Nature by Man alone.

13 Animal and plant classifications The “modern” system of classifying all living plants and animals, and fossils, is called the binomial system, and was founded by Carl Linnaeus (1707-1778). A genus and species is identified for each organism, Homo sapiens being one such example. Similar species may be grouped in a single genus (pl. genera).

14 ממלכה מערכה מחלקה סדרה משפחה סוג מין

15 Modern classification

16 Principle of subordination of characters Antoine Laurent de Jussieu developed a natural system as early as 1774, incorporating a natural classification system along with Linnaeus’ binomial nomenclature

17 Fabaceae plant family

18 Darwinian revolution (Origin of species 1859) –If organisms have similar organs it is because they have a common ancestor. –Finding similar organs is finding evolutionary relationships. –Classification became evolutionary classification.

19 From classification to tree of life Dasypus novemcinctus Elephas maximus Homo sapiens Mus musculus Ursus arctos Canis familiaris Hyaena hyaena Felis catus Panthera leo Pantera pardus

20 Phylogenetic tree Elephas maximus Homo sapiens Mus musculus Ursus arctos Canis familiaris Hyaena hyaena Felis catus Panthera leo Pantera pardus Dasypus novemcinctus

21 Phylogenetic tree Elephas maximus Homo sapiens Mus musculus Ursus arctos Canis familiaris Hyaena hyaena Felis catus Panthera leo Pantera pardus Dasypus novemcinctus

22 How are done classification Organisms are classified based on the presence of shared characters that present morphological innovations. Such characters are called: synapomorphies

23 Example of synapomorphies Mammal characteristics: Hairs. Milk.

24 Example of synapomorphies Bird characteristic: Feathers

25 Example of synapomorphies Fabaceae plant family Characteristic: Flower

26 Father of modern taxonomy Emil Hans Willi Hennig (1913 –1976): German biologist who is considered the founder of phylogenetic systematics, also known as cladistics. As a taxonomist, he specialised in dipterans (ordinary flies and mosquitoes).

27

28 Inferences of putative ancestor Putative ancestor of placental mammal

29 In some cases it is difficult to find synapomorphies anthrax bacteria (Bacillus anthracis) Escherichia coli

30 Animal with unknown relationships Myxozoa (fish parasites) Placozoa (simplest known animal)

31 Intermediate conclusion Classical classifications are based on morphological characters However, morphological characters are not enough to solve all the morphological classification

32 1.The evolution of organisms and biological complexes by using molecular data. (e.g., species, higher taxa, coevolutionary systems, and migratory patterns) 2.The evolution of molecular entities (e.g., genes, proteins, chromosomal arrangements) “Molecular Evolution” deals with two subjects:

33 How molecular characters are obtained Species Tissue sample DNA extraction Amplification of a chosen gene Sequencing the gene

34 How evolutionary relationships are inferred SpeciesSequenceInferred evolutionary relationships

35 Example of surprising findings Classical taxonomy: five kingdom ( bacteria )

36 Example of surprising findings Bacteria are form of two different groups the Archea and the Eubacteria Animal Fungi Plant Protista Archae Eubacteria [Woese C, Fox G (1977). Proc Natl Acad Sci USA 74 (11): 5088–90]

37 Intermediate conclusion Molecular characters have changed our vision of evolutionary relationships.

38 Example of surprising findings Moles and hedgehog [Springer MS, Burk A, Kavanagh JR, et al. PNAS 94 (25): 13754-13759 (1997)]

39 Old hypothesis Mole Hedgehog Horse Elephant

40 Molecular results Horse Mole Hedgehog Elephant African Mole African Hedgehog

41 African continent 65 Mya


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