Evolutionary Science EVOLUTION. Sir Charles Lyell ( ) Reverend Thomas Robert Malthus ( ) Chevalier de Lamarck ( )

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1 Evolutionary Science EVOLUTION Scientists have discovered millions of different species of organisms, past and present, on earth and millions more species have yet to be discovered! Even though these life forms are diverse, they are fundamentally similar at the cellular and molecular level How has this happened? Biology 12 Sir Charles Lyell ( ) Geologist Suggested that Earth (geological change) had undergone and continues to undergo slow, steady, and very gradual change eg. Erosion. Lyell visited Joggins, Nova Scotia in 1851 where he found many fossils including the remains of large plant trunks, some tiny bones and shells. Reverend Thomas Robert Malthus ( ) Malthus has become widely known for his theories about population and its increase or decrease in response to various factors. He wrote An Essay on the Principle of Population, published from 1798 to 1826, and observed that sooner or later a population gets checked by famine and disease. Chevalier de Lamarck ( ) Alfred Russel Wallace ( ) Believed that the environment was the key factor in evolutionary change 1. Theory of need organisms change because of an inner need to change Eg a fish grows a longer tail because it needs to swim faster to catch prey 2. Theory of use and disuse if structures are not used, they will weaken and disappear 3. Theory that acquired traits can be passed onto the offspring Eg. A giraffe stretches its neck to make it longer then passes the trait to its young. British Naturalist "Every species has come into existence coincident both in space and time with a closely allied species" Wallace wrote a letter to Darwin in 1958 outlining a theory similar to Natural Selection which lead Darwin to publish the conclusions on Natural Selection that he had been working on for 15 years.

2 Charles Darwin ( ) Charles Darwin published The Origin of Species in This describes the theory of Natural Selection. Wallace Vs. Darwin Darwin always put the emphasis on selection acting on individuals whereas Wallace apparently thought selection acted on groups or species. That selection acts on the individual, due to competition between individuals of the same species, is one of the key points in Darwin s theory. Another apparent difference is that Darwin emphasised competition within populations as the driving force for evolution, whereas Wallace put more emphasis on the species meeting the demands of a change in their environment. Galapagos Finches A group of 14 or 15 species of passerine birds found on the Galapagos islands The most important differences between species are in the size and shape of their beaks, and the beaks are highly adapted to different food sources.

3 Evolution defined Geological evolution: change in the earth over time rising of mountains, drifting of tectonic plates etc... Biological Evolution: the cumulative change in the heritable characteristics of a population Cultural Evolution: evolution of our society, cultural norms, values, knowledge etc... Evolution works at the level of a population, Individual organisms cannot evolve There must be variability between individuals in a population There must be a change in the frequency of the alleles in the gene pool of a population Gene Pool Gradualism Vs. Punctuated Equilibrium Gradualism new species arise through gradual changes in their characteristics and evolution occurs slowly over millions of years. Charles Darwin Gradualism vs. Punctuated Equilibrium Evidence for Evolution Punctuated Equilibrium - Species remain the same for long periods of time and then evolve rapidly during a very short interval - Stephen Gould 1. Fossil Record and radioactive dating 2. Comparative anatomy 3. Comparative embryology 4. Comparative biochemistry 5. DNA Sequencing 6. Direct Observation

4 Fossils Fossil Record: Fossils offer evidence that evolution occurred. The sequence in which fossils appear matches the sequence they would have evolved, with bacteria and algae appearing first, fungi and worms later followed by land vertebrates etc... Also many sequences of fossils are known, which link together existing organisms with their likely ancestors Types of Fossils Preserved in amber Preserved in ice Hard parts bones and teeth that don t decay Petrification- organisms submerged in water high in mineral content. Organism takes on minerals and turns to stone. Molds and cast imprints left in mud that hardens Radioactive Dating Radioactive elements decay at a fixed rate The amount of time it takes for half of the atoms to decay is called the half life The age of the rock or fossil can be determined by the percentage of the elements present. Comparative Anatomy Homologous Structures Structures that look superficially different and perform a different function but have unity of type. For example, the forelimbs of a human, mole, horse, porpoise and bat have the same bones in the same relative positions. This indicates they have the same origin and they have become different because they perform different functions. This is called Adaptive Radiation.

5 Analogous Structures Structures that are very different in appearance but serve the same functions. Like the tail fins of a whale and a fish. This implies that they had different origins and have become similar because they perform similar functions. This is called Convergent Evolution. Vestigial Structures These are structures that are reduced and serve no function. Examples are the beginnings of teeth found in embryo baleen whales, despite the adults being toothless, the small pelvis and thigh bone found in the body wall of whales and some snakes, and the appendix in humans. These structures have evolved and lost their function Comparative Embryology Similar patterns of development in embryos of different organisms. This suggests a common evolutionary origin Comparative Biochemistry There is greater similarity between the DNA and proteins of more closely related organisms. Eg. The hemoglobin molecule of a gorilla and a human differ by only one amino acid. Human and Chimpanzee DNA are 98% identical Nuttall test the antibodies against human blood proteins are used to determine how close other organisms blood proteins are to humans.

6 DNA and the Evolutionary Clock Direct Observation Genes are ancestral units of heredity. Maps of gene sequences provide mathematical key to ancestral history. Humans and other advanced organisms have retained many of the same DNA found in the simplest bacteria and blue-green algae even though many of them serve no useful purpose in humans. All living things are related by the immortal thread of DNA By observing organisms such as bacteria, which can reproduce in as little as 20 minutes, evolution can be observed. Bacteria have evolved from forms that were once readily destroyed by penicillin to forms that are now completely resistant. Pathologists are constantly developing new antibiotics to try to keep ahead of the evolution of new pathogenic bacteria Antibiotic Resistance Viruses Resistance to antibiotics is increased though the survival of individuals which are immune to the effects of the antibiotic, whose offspring then inherit the resistance, creating a new population of resistant bacteria. Viruses mutate and evolve even faster than bacteria. New flu viruses crop up every year. A person never gets the same strain of the flu a second time. Evolution of the Horse Mechanisms of Evolution The early ancestors of the modern horse walked on several spread-out toes, an accommodation to life spent walking on the soft, moist grounds of primeval forests. As grass species began to appear and flourish, the horse diets shifted from foliage to grasses, leading to larger and more durable teeth. As predators evolved, the horse's predecessors needed to be capable of greater speeds to outrun predators. This was attained through the lengthening of limbs and the lifting of some toes from the ground in such a way that the weight of the body was gradually placed on one of the longest toes, the third 1. Natural Selection 2. Overproduction 3. Genetic Variation 4. Genetic Drift 5. Artificial Selection 6. Biotechnology

7 Natural Selection Organisms that possess variations that allow them to best adapt to their environment survive to produce offspring thus passing on these favourable traits and increasing the frequency of favourable alleles in the population nature selects which organisms will be successful. Spoon-hand, Knife-hand, Straw-hand demo... Overproduction of Offspring Most species produce more offspring than the environment can support This leads to a struggle for survival Peppered Moths See p. of your Biology 12 Textbook Genetic Variation Variation exists between members of the same species Sexual reproduction promotes variation

8 Genetic Drift Allele frequency is how often alleles occur in a population not all alleles occur with the same frequency and recessive alleles may be more frequent than their dominant counterparts. Genetic Drift is an increase or a decrease in the allele frequency over successive generations Artificial Selection Domesticated animals Domesticated breeds have not always existed in their current form. This change has been achieved by repeatedly selecting for breeding the individuals most suited to human uses. This shows that selection can cause evolution Speciation Speciation by Isolation The formation of a new species Species a population of structurally similar organisms which can interbreed and produce fertile offspring There are 3 causes of speciation: 1. Isolation 2. Migration 3. Natural Selection Geographic Isolation barriers such as mountains deserts or bodies of water prevent the mixing of gene pools which allows differences to accumulate in the isolated organisms. If enough differences accumulate, a new species is formed Speciation by Isolation Cont d... Migration Reproductive Isolation differing mating rituals and courtship behaviours prevent breeding and thus variations accumulate differently in isolated populations. Organisms from one environment move to a new environment. This works two ways: New gene combinations new organisms breed with resident organisms which yields offspring with a new gene combination Migration followed by isolation results in speciation

9 Natural Selection After mutations occur, the environment acts as a selector for the more advantageous traits. The organisms with the advantageous traits survive to produce more offspring and they pass along these traits to their offspring overtime, this leads to differentiation and speciation. Evolution Video /e_s_4.html Evolution Simulations! Yay! n/index.html