Evolution: Lesson 4.1 (Part 1) PDF

Evolution How animals evolved their iconic features? Giraffes' necks can be up to 10 feet (3 Giraffe’s long necks meters) long, allowing the animals to reach leaves high up in trees. Discokeryx xiezhi, relat...

Evolution How animals evolved their iconic features? Giraffes' necks can be up to 10 feet (3 Giraffe’s long necks meters) long, allowing the animals to reach leaves high up in trees. Discokeryx xiezhi, relative of giraffe had a bony, disk-like shield on the top of its skull bashed their "helmets" together during fights over mates ( "necks-for-sex" hypothesis. ) How animals evolved their iconic features? evolved from a dog-sized ancestor one of the main reasons for this Blue whales' gigantic size accelerated growth is the filter- feeding behavior of baleen whales, which use bristle-like teeth to sieve plankton from the ocean "passive" feeding strategy How animals evolved their iconic features? Tigers’ stripes the markings play an important role in helping a tiger remain hidden while hunting prey the stripes help break up the shape of the animal's body, allowing it to blend in with tall grass.  Is the present generation of humans evolving? 7 To answer the question… (Let’s do a simple group activity. ) Each group is going to discuss their ideas and some pieces of evidence (if any) during the breakout sessions. There should be 1 to 2 representatives who will discuss the group's collective ideas with the whole class after 15minutes of brainstorming. 8 Questions to answer: -Why are we here? -What is human nature really like? -How do we deal with our mortality? 6 Evolution: History and Evidence History and Evidence of Evolution ▪ Organic Evolution ▪ according to Charles Darwin, is “descent with modification” ▪ Populations change over time. ▪ Populations consist of individuals of the same species that occupy a given area at the same time. 8 PRE-DARWINIAN THEORIES OF CHANGE ▪ Empedocles (495–435 BCE) & Aristotle (384–322 BCE) ▪ described concepts of change in living organisms over time 9 ▪ Georges-Louis Buffon (1707– 1788) ▪ attributed change in organisms to the action of the environment ▪ believed in a special creation of species and considered change as being degenerate PRE-DARWINIAN THEORIES OF CHANGE ▪ Erasmus Darwin (1731–1802) ▪ a physician and the grandfather of Charles Darwin ▪ intensely interested in questions of origin and change and believed in the common ancestry of all organisms 15 PRE-DARWINIAN THEORIES OF CHANGE ▪ Jean Baptiste Lamarck (1744–1829) ▪ His theory was based on a widely accepted theory of inheritance that organisms develop new organs, or modify existing organs, as needs arise. ▪ believed that “need” was dictated by environmental change and that change involved movement toward perfection 16 DARWIN’S EARLY YEARS AND HIS JOURNEY ▪ Charles Robert Darwin (1809–1882) ▪ born on February 12, 1809 ▪ entered medical school in Edinburgh, Scotland at the age of 16 ▪ was not interested in a career in medicine because he could not bear the sight of people experiencing pain ▪ enrolled at Christ’s College in Cambridge and graduated with honors in 1831 17 DARWIN’S EARLY YEARS AND HIS JOURNEY ▪ Charles Robert Darwin (1809–1882) ▪ Nominated by Henslow to serve as naturalist on HMS Beagle (1831) Voyage ▪ The voyage gave him ample opportunity to explore tropical rain forests, fossil beds, the volcanic peaks of South America, and the coral atolls of the South Pacific. ▪ On the Origin of Species by Means of Natural Selection was published in 1859 and revolutionized biology 18 19 EARLY DEVELOPMENT OF DARWIN’S IDEAS OF EVOLUTION ▪ Geology ▪ During his voyage, Darwin read Charles Lyell’s (1779–1875) Principles of Geology ▪ Lyell developed the ideas of another geologist, James Hutton, into the theory of uniformitarianism ▪ Geological change occurs over hundreds of millions of years. ▪ This book planted two important ideas in Darwin’s mind: (1) the earth could be much older than 6,000 years and (2) if the face of the earth changed gradually over long periods, could not living forms also change during that time? 15 EARLY DEVELOPMENT OF DARWIN’S IDEAS OF EVOLUTION ▪ Fossil Evidence ▪ Darwin’s spent time digging in the dry riverbeds of the pampas of Argentina, South America ▪ found the fossil remains of an extinct hippopotamus-like animal (Toxodon) and fossils of a horselike animal (Thoatherium) ▪ These fossils were from animals that were clearly different from any other animal living in the region. ▪ also found fossils of giant armadillos and giant sloths 21 The Giant Sloth Modern-day sloths 22 EARLY DEVELOPMENT OF DARWIN’S IDEAS OF EVOLUTION ▪ Galapagos Islands ▪ On its trip up the western shore of South Africa, the HMS Beagle stopped at the Galapagos Islands (named ad the large tortoises that inhabit them) ▪ Tortoises from the drier regions had longer necks than tortoises from wetter habitats. ▪ In spite of their differences, the tortoises were quite similar to each other and to the tortoises on the mainland of South America. 23 Galapagos Island 24  Longer-necked Shorter-necked 25 EARLY DEVELOPMENT OF DARWIN’S IDEAS OF EVOLUTION ▪ Galapagos Islands ▪ Darwin made similar observations of a group of dark, sparrow-like birds. ▪ He noticed that the Galapagos finches bore similarities suggestive of common ancestry. ▪ Each species is adapted to a specific habitat on the islands. ▪ Adaptive radiation – the formation of new forms from an ancestral species, usually in response to the opening of new habitats. 26 Open habitats and few predators promoted the radiation of finches into 14 different species. 21 THE THEORY OF EVOLUTION BY NATURAL SELECTION ▪ Darwin worked diligently on the notes and specimens he had collected and made new observations. ▪ He was familiar with the obvious success of breeders in developing desired variations in plant and animal stocks. ▪ He wondered if this artificial selection of traits could have a parallel in the natural world. 22 THE THEORY OF EVOLUTION BY NATURAL SELECTION ▪ Ideas of how change occurred began to develop on his voyage. ▪ They took on their final form after 1838 when he read an essay by Thomas Malthus (1766–1834) entitled Essay on the Principle of Population. ▪ Malthus believed that the human population has the potential to increase geometrically (Geometric growth involves increasing by doubling or by some other multiple rather than by adding a fixed number of individuals with each new generation.) 23 Natural Selection 1. High reproductive potential 2. Inherited variation exists. 3. Constant struggle for limited resources, many individuals die. 4. Adaptive traits become more common in subsequent generations. 30 Adaptation ▪ Occurs when a heritable change in a phenotype increases an animal’s chances of successful reproduction in a specified environment. ▪ Arise as a result of chance mutations ▪ Perpetuated by natural selection 31 Lepus arcticus lives in the arctic of Canada and Greenland on rocky slopes of higher-elevation tundra, where it feeds on leaves, shoots, grasses, flowers, roots, and bark. Arctic hares show a variety of evolutionary adaptations for living in the arctic, including a snowy-white winter coat, relatively small ears to prevent excessive heat loss, and large feet that allow them to “snow-shoe” across the winter landscape. 26 Alfred Russel Wallace ▪ Theory of evolution similar to Darwin’s ▪ Published ideas jointly with Darwin ▪ Impetus for Darwin’s publication of On the Origin of Species by Means of Natural Selection ▪ Darwin given credit ▪ Years of work ▪ Massive accumulations of evidence 33 MICROEVOLUTION, MACROEVOLUTION, AND EVIDENCE OF MACROEVOLUTIONARY CHANGE ▪ Microevolution ▪ Change in the frequency of alleles in a population over time ▪ Macroevolution ▪ Large-scale changes that result in the extinction and formation of new species 34 MICROEVOLUTION, MACROEVOLUTION, AND EVIDENCE OF MACROEVOLUTIONARY CHANGE ▪ Biogeography ▪ Study of the geographic distribution of plants and animals ▪ Life-forms in different parts of the world have distinctive evolutionary histories. ▪ Biogeographers attempt to explain distribution patterns. 35  Biogeography as Evidence of Evolutionary Change. (a) The leopard (Panthera pardus) of Africa and Asia has a similar ecological role to that of the (b) jaguar (Panthera onca) of Central and South America. Their similar form suggests common ancestry, even though they are separated by apparently insurmountable oceanic barriers (c). Spotted varieties of these species are distinguished by the presence (jaguar) or absence (leopard) of small spots within dark rosette markings of their coats. Biogeographers have provided probable explanations for these observations. 30  Biogeographic Regions of the World Barriers, such as oceans, mountain ranges, and deserts, separate biogeographic regions of the world. (a) The Sahara and Arabian Deserts separate the Ethiopian and Palearctic regions, (b) the Himalayan Mountains separate the Palearctic and Oriental regions, (c) deep ocean channels separate the Oriental and Australian regions, and (d) the mountains of southern Mexico and Mexico’s tropical lowlands 31 separate the Nearctic and Neotropical regions. MICROEVOLUTION, MACROEVOLUTION, AND EVIDENCE OF MACROEVOLUTIONARY CHANGE ▪ Paleontology ▪ Fossils - Evidence of plants and animals that existed in the past and have become incorporated into the earth’s crust ▪ Direct evidence of sequences of appearance and disappearance of organisms ▪ Paleontologists use this information to provide an understanding of many evolutionary lineages. 32  Paleontological Evidence of Evolutionary Change Fossils, such as these trilobites (Paradoxides), are direct evidence of evolutionary change. Trilobites existed about 500 million years ago and became extinct about 250 million years ago. Fossils may form when an animal dies and is covered with sediments. 33 Reconstruction of an Evolutionary Lineage from Evidence in the Fossil Record The fossil record allows horse evolution to be traced back about 55 million years. The horse ancestors illustrated were not direct ancestor/descendant sequences. The illustrations depict anatomical changes that occurred during horse evolution. Horse ancestors were small, primarily browsing animals that walked on the tips of 3 or 4 toes. Evolution resulted in larger animals adapted to a grazing lifestyle and that walked or ran on the tips of their middle toe digits. 40 MICROEVOLUTION, MACROEVOLUTION, AND EVIDENCE OF MACROEVOLUTIONARY CHANGE ▪ Analogy and Homology ▪ Convergent evolution - evolution of superficially similar structures in unrelated organisms. Similar structures are analogous. ▪ Homology - Resemblance that occurs because of common ancestry 41 MICROEVOLUTION, MACROEVOLUTION, AND EVIDENCE OF MACROEVOLUTIONARY CHANGE ▪ Homology—Comparative Anatomy ▪ Study of the structure of living and fossilized animals and homologies that indicate close relationships 42  The Concept of Homology The forelimbs of vertebrates evolved from an ancestral pattern. Even vertebrates as dissimilar as whales and bats have the same basic arrangement of bones. The digits (fingers) are numbered 1 (thumb) to 5 (little finger). Color coding indicates homologous bones. 43  Vestigial Structures The pelvic bones of baleen whales evolved from functional pelvic bones of the whales’ terrestrial mammalian ancestor. These bones have no apparent function in whales and are an example of a vestigial structure. 38 MICROEVOLUTION, MACROEVOLUTION, AND EVIDENCE OF MACROEVOLUTIONARY CHANGE ▪ Homology—Developmental Patterns ▪ Developmental stages of related animals often retain common features. ▪ Changes in genes controlling development are usually harmful and eliminated by natural selection. ▪ Example is the embryonic stages of vertebrates 45  Developmental Patterns (a) The early embryonic stages of various vertebrates are remarkably similar. These similarities result in the preservation of developmental sequences that evolved in early common ancestors of vertebrates. (b) Organ systems, like the nervous system, also show similar developmental patterns. Later developmental differences may result from evolutionary changes in the timing of developmental events. 46 MICROEVOLUTION, MACROEVOLUTION, AND EVIDENCE OF MACROEVOLUTIONARY CHANGE ▪ Homology—Molecular Biology ▪ Study of nuclear DNA, mitochondrial DNA, ribosomal RNA, and proteins ▪ Molecules provide direct evidence of change in genes. ▪ Genetic similarity (degree of relatedness) is reflected in variation in amino acid sequences in proteins and base sequences in DNA. 41 MICROEVOLUTION, MACROEVOLUTION, AND EVIDENCE OF MACROEVOLUTIONARY CHANGE ▪ Interpreting the Evidence: Phylogeny and Common Descent ▪ Phylogeny - evolutionary relationships among species ▪ It includes the depiction of ancestral species and the relationships of modern descendants of a common ancestor. 42 MICROEVOLUTION, MACROEVOLUTION, AND EVIDENCE OF MACROEVOLUTIONARY CHANGE ▪ Phylogenetic Trees ▪ Show lines of descent ▪ Branches - evolutionary connections ▪ Nodes - branch points -Genes, populations, or species where a 43 change occurs MICROEVOLUTION, MACROEVOLUTION, AND EVIDENCE OF MACROEVOLUTIONARY CHANGE ▪ Modern Synthesis ▪ Principles of modern genetics combined with Darwinian evolutionary theory ▪ This will be further discussed in the next lesson 50 End of Discussion Any questions? 51