Transcript Evolution
Evolution 1800’s The Evolution of Evolution Fossil discovery confounded scholars who held notion of a single time of creation; species were perfect and unchanging. Jean Baptiste Lamarck’s ideas: • organisms evolve by the use and disuse of body parts • Inheritance of acquired characteristics Alfred Wallace and Charles Darwin introduced the idea of Natural Selection which has been supported by evidence since the 1850’s. Darwin’s Voyage on the Beagle • 1831 • Collected organisms, became the ship’s naturalist Influences on Darwin…. • Lyell’s • Malthus • Wallace Evolution explains the unity and diversity of life • The history of life, as documented by fossils, is a saga of a changing Earth – billions of years old – inhabited by an evolving cast of life forms. • Evolution accounts for life’s similarities and differences! What similarities??? A theory of evolution by natural selection is an explanation of life’s diversity. Darwin observed the following: Populations produce more offspring than survive. Population size remains relatively stable. Resources are limited. Individuals compete for resources and survival. Individuals of a species have different traits. The variation of traits was passed from parent to offspring. The most fit organisms survive. (“survival of the fittest”) Evolution occurs as favorable traits accumulate in the population. Darwin studied examples of artificial selection A theory of evolution by natural selection is an explanation of life’s diversity. The cornerstone of biology….the theory that helps us understand how life began and continues to succeed….. Evolution by means of natural selection. 1) Members of a species (population) vary in traits & pass those traits onto offspring. (VARIATION) 2) Certain forms of traits are better adapted to the environment than others. (FAVORABLE TRAITS) 3) Individuals with the better adapted traits are more likely to survive & reproduce than those without such traits (FITNESS & REPRODUCTION) 4) Therefore, the trait better adapted to the environment become more common in future generations. The traits not well adapted become less common. The population has evolved. (FAVORABLE GENES PAST ON TO NEXT GENERATION) NATURAL SELECTION Darwin's basic idea of natural selection. The concept is simple; individuals in populations vary slightly from one another. Some of those variations help the individuals that possess them to produce more offspring than others. Those offspring, in turn, inherit the successful variations and produce more offspring themselves. As generations pass, the population evolves towards the variation that is the more successful . There are IMPORTANT points about evolution by natural selection 1. Individuals do not evolve: populations evolve. 2. Natural selection can amplify or diminish only heritable traits. Acquired characteristics cannot be passed on to offspring. 3. Evolution is not goal directed and does not lead to perfection. Favorable traits vary as environments change. 4. Organisms do not evolve structures because of want or need. Instead, evolution is a passive process in which the environment favors certain traits that exist within a population. Adaptations evolve in populations. Organisms do not actively or willingly evolve. Peppered Moths… http://www.biologycorner.com/worksheets/pepperedmoth.html Types of Evidence • Fossil Record (Paleontology) fossil remains indicate different organisms than today • Biogeography unrelated species, in similar environments look alike • Comparative Anatomy structures are similar among different organisms (homologous) structures with no function (vestigial) • Embryology patterns of development similar • Molecular Biology same or similar proteins, all organisms have DNA Fossils • Mostly found in sedimentary rock • Unique conditions result in a fossil molds, casts, • Fossil record helps to reconstruct patterns and trend in the history of life Comparative Morphology: Homologous Structures Comparative Morphology: Vestigial Structures • In humans – Wisdom teeth – Appendix – Tail bone • In Snake – Pelvic girdle • In Whales – Pelvis and femur Comparative Embryology All vertebrate embryos go through the same early phases. Comparative Biochemistry • DNA • Protein comparisons – Cytochrome c Biochemical similarity is greatest among closely related species. • Human & Chimp the same • 104 amino acids • 56 different between humans & yeast – Hemoglobin Homologies indicate patterns of descent that can be shown on an evolutionary tree Darwin was the first to represent the history of life as a tree, – with multiple branchings from a common ancestral trunk – to the descendant species at the tips of the twigs. Today, biologists – represent these patterns of descent with an evolutionary tree, but – often turn the trees sideways. Lungfishes Amniotes Mammals 2 Tetrapod limbs Amnion Lizards and snakes 3 4 Crocodiles Ostriches 6 Feathers Hawks and other birds Birds 5 Tetrapods Amphibians 1 The phylogenetic tree of reptiles shows that crocodilians are the closest living relatives of birds. Lizards and snakes Crocodilians Pterosaurs* Common ancestor of crocodilians, dinosaurs, and birds They share numerous features, including four-chambered hearts, “singing” to defend territories, and parental care of eggs within nests. Ornithischian dinosaurs* Saurischian dinosaurs* Birds A cladogram showing the emergence of new traits Frog Iguana Duck-billed platypus Amnion Kangaroo Hair, mammary glands Gestation Beaver Long gestation Phylogenetic Tree