Evidence of Evolution

Introduction to Evolution • Evolution is a change in the traits of a population over time. – If alleles change, so do traits. • microevolution When evolution happens in a single species, it is called (evolution on a small scale). – particularly over short period of time – ex. bacteria becoming antibiotic resistant • When evolution happens over a long period of time, new species can appear. These large changes are called macroevolution. – ex. horses evolved over millions of years from a much smaller animal. How can evolution happen? • Can look at changes in genes of population over time – If some alleles become more common over time, evolution has occurred – this is a change in allele frequency – genotype’s expression indirectly selected for because the phenotype is a result of the If a particular phenotype is selected for, its underlying genotype is also • where: Antibiotic resistance evolves in bacteria through natural selection, – random mutations create variation, – and bacteria with the antibiotic resistance genes survive antibiotic exposure. – They thrive and pass on those genes, – leading to a population dominated by those resistant strains Darwin’s Epic Journey • • were revolutionizing scientific understanding of the natural world. Sailed aboard the H.M.S. Beagle, at a time when scientists in several fields Geologists were suggesting that Earth was ancient and had changed over time. • they called evolution. Biologists were suggesting that life had also changed, through a process • organisms evolved through descent from common ancestors. explanation for the unity and diversity of life, by proposing how modern Darwin developed a theory of biological evolution that offered a scientific Observations at but differ in altitude: •Islands occupy similar latitude, of S.America mainland) at the Galápagos Islands (west • Darwin observed great diversity the Galápagos • hot, dry, and nearly barren The smallest, lowest islands were • plants and animals rainfall and a different assortment of The higher islands had greater • predictable ways Tortoises, finches, etc. varied in Evolutionary Thought Early Contributions to Contributors to the development of Darwin’s ideas include: • • Lamarck their lifetime. Believed that organisms could pass on traits acquired during • “Use and Disuse” of various body features • “Inheritance of Acquired Characteristics” • Discredited: when the mechanisms of heredity became known. • Important: because he was the first to propose that change intervention. over time was the result of natural phenomena and not divine Evolutionary Thought Early Contributions to • • Malthus Believed that populations increased in size until checked by the environment (‘struggle for existence’) • • Hutton and Lyell slow geological processes the physical features of the earth were the result of Developed the geological theory of uniformitarianism: that still occur today. • • Cuvier Proposed idea of extinction through catastrophes. Cuvier Hutton and Lyell Malthus The Development of Darwin’s Ideas • Darwin’s theory was supported by data collected from: • Observing adaptations of animals (different from European animals) on mainland South America • but Galápagos species were unique, Observing that most of the resembled species on the South American mainland. • Fossil finds of extinct species. • Evidence from artificial selection. Artificial Selection • • Plant and Animal Breeding and plants for centuries. breeding of domesticated animals Humans have controlled the • animals to have useful traits People can breed plants and • over several generations can change an organism’s traits allowed to reproduce, humans By selecting which individuals are • Ex: pigeons, dogs selective breeding Yorkshire terrier: From gray wolf to can result in phenotypic change Artificial Selection • Artificial selection (or selective breeding) involves: • desirable phenotypes. breeding (selecting) from individuals with the most • variation over relatively short time periods. It can result in an astounding range of phenotypic • intense than that occurring in nature. Selection imposed by humans is often more rapid and Domestic dogs (pug) and doves Domestic pigeons broccoli, etc. Cauliflower, Wheat and other crops of Darwin’s Ideas The Development • The first convincing case for evolution, The Origin of Species, was published by Charles Darwin in 1859. • ones by natural selection. argued that new species developed from ancestral • Darwin developed his theory of “survival of the fittest” voyaging extensively on the ship the ‘ with a large body of evidence he collected while by building on earlier ideas and supporting his views HMS Beagle’. • Alfred Russel Wallace, a young specimen collector, extensively and receives most of the credit for it. of Darwin. However, Darwin supported the theory more developed a theory of natural selection independently The Concepts of Darwinism • environments over a long period of time descendants of ancestral forms adapted to different Darwin’s view of life was of ‘descent with modification’: . • The mechanism for adaptation is called ‘natural selection’, and is based on a number of principles: • Overproduction • Variation • Competition • Survival of the fittest phenotype • Favorable combinations increase How Natural Selection Happens • Overproduction: • More are born than will survive to reproductive age. • Variation: • to the current conditions Some variations are better suited than others • environment is an organism’s ability to survive and reproduce in its Any heritable characteristic that increases an adaptation. • Competition: • (food, habitat etc.) Offspring compete for limited resources • Survival of the fittest phenotype: • Differences in adaptations affect an individual’s fitness (how well an organism can survive and reproduce in its environment). • some call it, there is differential reproductive success, or, as and others have lower fitness (fewer offspring), When some have higher fitness (more offspring) survival of the fittest. • Favorable combinations increase: • those with unfavorable ones. from individuals with favorable characters than Each new generation will contain more offspring How Natural Selection Happens Natural Selection Inheritance Variations are inherited. The best suited variants leave more offspring. Natural selection favors Natural Selection the best suited at the time Variation Individuals show variation: some variations are more favorable than others Overproduction Populations produce too many young: many must die many sources: • Evidence for evolution comes from observations and experiments. supported by a wealth of • Evolutionary theory is now Evidence for Evolution • Biogeography • Age of Earth and Fossils • Development Comparative Anatomy and • Molecular Biology • Testing Natural Selection anatomy Comparative Paleontology • Biogeographical Evidence called The study of plant and animal distribution is biogeography. • plant and animal species The basic principle of biogeography is that each originated only once. • have of the world for a long time (e.g. Australia), often Regions that have been separated from the rest distinctive species Lemurs are endemic to Madagascar the island of Wallace Line Biogeographical Evidence of the Galápagos. among the most well known The giant tortoises are • environments spread out (radiated) into new evolved from ancestral populations and world suggests that modern forms The distribution of species around the • mainland. similar to, but distinct from, the The Galápagos have species very • past. the islands from the mainland in the Ancestral forms probably migrated to Fossil fish Types of Fossils Bird bones preserved in a tar pit this stone interior of still covers the A layer of shell ammonite Trilobites preserved in sedimentary rock • The term fossil refers to any parts or • its death. that may survive after impressions of an organism slow the process of quickly in conditions that organisms are buried Fossils form best when decay. • sedimentary rock Fossils are most commonly found in . • the organic matter of the organism. seep into tissues and replace or minerals dissolved in water, may teeth, shells) may remain as fossils, Mineral-rich hard parts (bones, Interpretation of Fossils This perfectly preserved skeleton of Archaeopteryx includes impressions of feathers on the forelimbs and tail • The fossil record is an orderly the layers, or array in which fossils appear in strata, of sedimentary rocks. • • moment in time. sediments, they record that When organisms are trapped in determine relative age. ones. Comparing strata helps (stratum, s.) are older than higher The fossils in lower strata A reconstruction of Archaeopteryx. • Transitional Fossils Transitional fossils are fossils with features common to both an ancestral group (ancestral features) and its descendant group (derived features). • how lineages evolved. They are important links in the fossil record, and provide evidence for • record of horses, whales, and birds. Important examples of transitional fossils occur in the fossil • Archaeopteryx is a transitional form between birds and non-avian dinosaurs. Non-avian features Long, bony tail. dinosaurs, although modified. The hind-limb girdle is typical of sockets in the jaws. True teeth set in and lacks a keel. Breastbone is small fusions seen in modern birds. Lacks the bone reductions and fingers with grasping claws. Forelimb has three functional attached to the tail. Impressions of feathers lower leg bones. Incomplete fusion of the Belly ribs. attached to forelimb. Impressions of feathers flat-faced. Vertebrae are almost Avian features • and Common Ancestry The Carnegie Stages Developmental biology studies the and develop. process by which organisms grow • their development–strong evidence of regardless of the total time period of stages, in the same sequence, embryos pass through the same During development, vertebrate shared ancestry. buds Limb Stage 14 Digits form Stage 17 separate Digits Stage 23 12.5 days Mouse Comparative Anatomy • homology The similarity of structure is called . • • Homologous Structures ancestry. Homologies are indicative of common ‣ In divergent evolution, a lineage environments. pressures in different due to different selection splits and evolves independently ‣ this is species to occupy different niches, the formation of a large number of When divergent evolution involves adaptive radiation Evidence of Divergent Evolution Species C Species D Species A Species B Wings Flippers Analogous Structures • from a common ancestor. Not all similarities between species are inherited • called → organisms may have different origins, and are Structures with the same function in different • Analogous structures do not imply an evolutionary relationship, but may indicate convergence. • Examples: butterflies, Fins in fish and flippers in mammals Eye structure in octopus and mammals, Wings in birds and Fins ‣ convergent evolution- distantly related species in similar environments dolphin evolve streamline bodies) and similar selection pressures evolve similar features, (ex: shark and Species F Species J Species G Species I Species E Species H Evolution Evidence of Convergent Fish: shark Mammal: dolphin Reptile: icthyosaur (extinct) Bird: penguin Species C Species A Species B Species F Species J Species G Species I Species E Species H Species D Vestigial Organs • Many organisms have degenerate structures that no longer perform the same function as in other organisms. • but became redundant in later species. These organs must have been important in some ancestral form, • the organism’s ability to survive and reproduce. The presence of the vestigial organ may not affect • elimination of the organ. Natural selection would not cause • Examples: • The wings of kiwi are tiny vestiges and useless. • no longer used for vision. The vestigial eyes of burrowing animals are Vestigial Organs in Whales • large, Whales are the descendants of four-legged land mammals that took up an million years ago. aquatic existence some 60 • function. no longer fulfill a locomotory have become very small and the pelvis and femur of whales Over many millions of years, Pelvis Hindlimb Femur Forelimb Whale Ancestors Basilosaurus (Late Eocene) Protocetus (Eocene) Pakicetus (Middle Eocene) Cladogram of Whale Ancestors • skeletons that show much of their anatomy. is extensive and well represented by The fossil record exhibiting whale evolution fossil record Red lines represents probable relatedness Black lines represent Relationships DNA Shows Evolutionary • The DNA of mammals is very groups. mammals look different to other genes because different groups of clearly some difference in these kinds of genes. However, there is similar. They all share the same • DNA sequences in genes can diverged from each other. are and how long ago they show how closely related groups Human: G C G A C G G G C T G C G G C T T A T C G C G C T G T T G G A Chimp: G C G A C G G G C T G C G G C T C A T C G C G C T G T T G G A Rhino: G C G A C G G G C T G C G G C T C A T C G C G C T G C T C G A Horse: G C G A C G G G C T G C G G C T C A T T G C G C T G C T C G A Horse Chimpanzee White rhino Human • Hemoglobin Homology The proteins that the DNA codes for can also be used to determine relationships between species. • Researchers look for similarities (homologies) between the proteins in different species. • represent Differences between these highly conserved proteins are likely to major divergences between groups during the course of evolution. • Hemoglobin is the oxygen-transporting blood protein found in relationships. different organisms can be compared to determine evolutionary most vertebrates. The chain hemoglobin sequences from Increasing difference in amino acid sequence Primates Placental mammals Marsupial Non-mammalian vertebrates chimpanzee 0 Human − Gorilla 1 Gibbon 2 Rhesus monkey 8 Dog 15 Horse 25 Mouse 27 Kangaroo 38 Frog 67 Chicken 45 ATP All known living organisms use . It is the universal energy carrying molecule in cells. ‣ All Life Is Related DNA encodes the genetic instructions of all life. ‣ genetic code The form of these genetic instructions, the , is universal ‣ Traditionally, the phylogeny of organisms was (morphology established by comparing physical structure ). ‣ involving the analysis of In recent decades, molecular techniques DNA, RNA, and proteins have provided more information about how all life on Earth is related. ‣ The Tree of Life evidence for a in the molecular machinery of all cells provide powerful The universality of the genetic code and the similarities common ancestor to all life on Earth. Last Universal Common Ancestor (LUCA) Domain Bacteria Domain Archaea Domain Eukarya Animals Fungi Plants Algae Bacteria that gave rise to mitochondria Bacteria that gave rise to chloroplasts (many pathogens) Protobacteria Cyanobacteria bacteria Other bacteria Hyperthermophillic Ciliates proteins. of which is translated into transcribed into RNA, some molecules. Some DNA is self-replicating DNA machinery consists of In all living systems, genetic same molecular machinery Living systems share the Testing Natural Selection • Back to the Galapagos • • A Testable Hypothesis finches and their offspring) Heritable variation (the Grants measured •Differential survival and reproduction • a severe drought hit the islands • plants produced fewer seeds • birds ate the smaller seeds first • only the largest, hardest seeds remained • birds on the island fell many birds starved, and the total number of • higher evolutionary fitness) likely to survive to reproduce (they had those with the largest beaks were more How Does Resistance Become Common?