The Theory of Evolution

The Theory of Evolution Chapter 14 and 15 Early History of Earth • The earth is undergoing constant changes • Plate tectonics is constantly changing the face of the earth. • The earliest proven age of the earth is around 4.6 billion years. • Around 4.4 billion years ago, the earth would have cooled enough to condense water, this appearance of water allowed life to form. • Early life forms appeared around 3.5 billion years ago. History In Rocks • The oldest rocks found have been dated at around 3.9 million years ago. • The rock cycle explains how the earth constantly builds up and breaks down rocks. • Trapped in this rock are fossils. • Fossils are any evidence of previous life. – Bones, habitats, coprolites etc. Types of Fossils 14.1 Table • Trace Fossils – any indirect evidence left by an animal and may include a footprint or track. • Casts – When minerals in rocks fill the space left by a decayed organism, they form casts. • Molds – A mold forms when an organism is buried in sediment and then decays, leaving an empty space. Types of Fossils 14.1 Table • Amber – entire organisms preserved in ice or tree sap (Jurassic Park) • Petrified/per mineralized – petrified – minerals sometimes penetrate and replace the hard parts of an organism – Per mineralized – void spaces in original organism in filled by minerals. Dating Techniques • Radiometric Dating – The use of radioactive decay to date materials. • Relative Dating – Dating of fossils based on their surrounding rocks. – Theory of superposition – the fossils found nearest to the surface are the youngest. (pile of magazines) Superposition and relation Formation of Fossils • For fossils to form, organisms need to be buried shortly after death. • Most fossils are found in sedimentary rocks. • Sedimentary rocks form at relatively low temperatures and pressures and allow great preservation of fossils. Fossilization Process The Geologic Time Scale • When we speak about the geologic time scale it is important to realize the length of time we are talking about. • The earth began 4.6 billion years ago……humans appeared around 200,000 years ago. • We know this because of the fossil record. The Geologic Time Scale • Imagine the time scale were a roll of toilet paper. • The time that humans have been here is equal to 1 square of the paper. • The total length of the roll would circle the entire school about 2 times. • As you can see, humans have been here for a relatively short time in the geologic time scale Important Eras • Precambrian – about 3.4 billion years ago. – Mostly cyanobacteria • Paleozoic – 543 million years ago – Much more diversity than precambrian • Mesozoic – 248 million years ago – Divided into three periods Triassic,Jurassic, Cretatious • Cenozoic – Began about 65 million years ago The Origin of Life • Spontaneous Generation – long ago, people believed that life began from innate objects….thus the term spontaneous generation. • In 1668 Redi disproved this idea with his experiments. – Redi studied decaying meat to prove that the meat did not produce the maggots. – The microscope was instrumental in his discovery Origins: The Modern Ideas • Biogenesis – The idea that life ‘just appeared’ on the planet. • Science has yet to come up with concrete proof of how life began on the planet. • It is believed in science that life has evolved from much more primitive life forms, and diversified over time. • Protocells were the first types of cells First True Cells • The first true cells were prokaryotic in nature. • The lacked organelles and were very simple autotrophic organisms. • These prokaryotes eventually exploited niches and evolved into more complex organisms, and began to feed on other autotrophs. • Archaebacteria – prokaryotic and live in harsh environments. (sulfur plumes in ocean vents) Section 15.1 Objectives • Summarize Darwin’s theory of natural selection. • Explain how the structural and physiological adaptations of organisms relate to natural selection • Distinguish among the types of evidence for evolution. Charles Darwin and Natural Selection • The modern theory of evolution is the fundamental concept in biology. • Recall that evolution is the change in populations over time • Evolution merely states that individuals that are more successful will breed more then increase the frequency of their genes in the gene pool. Chapter 15 Fossils shape ideas about evolution • When geologists provided evidence indicating that Earth was much older than many people had originally thought, biologists began to suspect that species change over time, or evolve. • Many explanations about how species evolve have been proposed, but the ideas first published by Charles Darwin are the basis of modern evolutionary theory Lamark (Before Darwin) • In 1809 (the year of Charles Darwin's birth), John Baptist Lamark proposed a hypothesis to account for evolution, which he called the Theory of Aquired Trait. • He used this theory to describe how Giraffe's gained their long necks. by stretching their necks to reach high leaves, they gained an advantage and passed it on down to their offspring. Short necked giraffes would die out when food was scarce, and long necked giraffes would survive. Lamark (Before Darwin) Theory of need- organisms changed because they needed to in order to survive. Theory of use and disuse – if an organism uses something it stays with them, if they don’t use it, it goes away. Theory of inheritance of acquired characteristics – acquired traits are passed on in reproduction Before Darwin and Wallace • Thomas Malthus (1766-1834) • Essay on the Principle of Population (1798) • Malthus's observation that in nature plants and animals produce far more offspring than can survive, and that Man too is capable of overproducing if left unchecked. • Malthus concluded that unless family size was regulated, man's misery of famine would become globally epidemic and eventually consume Man. Alfred Russel Wallace • Alfred Russel Wallace (1823 - 1913) was a British naturalist, and co-discoverer of the principle of evolution by natural selection. • Wallace travelled to South America with Henry Bates and then to the Malay archipelago. • Like Darwin, he was struck by the variation of species on different islands, and in 1858 he read • Malthus's Essay on the Principle of Population . Together, Wallace and Darwin presented their ideas to the public, although the theory soon became known as Darwinism. Darwin on HMS Beagle • It took Darwin years to develop his theory of evolution. • He began in 1831 at age 22 when he took a job as a naturalist on the English ship HMS Beagle, which sailed around the world on a fiveyear scientific journey. Darwin on HMS Beagle Galapagos Archipelago Darwin on HMS Beagle • As the ship’s naturalist, Darwin studied and collected biological and fossil specimens at every port along the route. • His studies provided the foundation for his theory of evolution by natural selection. Darwin in the Galápagos • On the Galápagos Islands, Darwin studied many species of animals and plants that are unique to the islands but similar to species elsewhere. • These observations led Darwin to consider the possibility that species can change over time. Darwin continues his studies • For the next two decades, Darwin worked to refine his explanation for how species change over time. • English economist Thomas Malthus had proposed an idea that Darwin modified and used in his explanation. • Malthus’s idea was that the human population grows faster than Earth’s food supply. Darwin continues his studies • How did this help Darwin? – He knew that many species produce large numbers of offspring – He also knew that such species had not overrun Earth. Darwin continues his studies • He realized that individuals struggle to compete in changing environmental conditions. • Only some individuals survive the competition and produce offspring • Darwin observed that the traits of individuals vary in populations. Variations are then inherited Darwin continues his studies • Breeding organisms with specific traits in order to produce offspring with identical traits is called artificial selection. • Darwin hypothesized that there was a force in nature that worked like artificial selection. Darwin explains natural selection • Natural selection is a mechanism for change in populations. • It occurs when organisms with favorable variations survive, reproduce, and pass their variations to the next generation. • Organisms without these variations are less likely to survive and reproduce Darwin explains natural selection • As a result, each generation consists largely of offspring from parents with these variations that aid survival • Alfred Russell Wallace, another British naturalist, reached a similar conclusion Darwin explains natural selection • Darwin proposed the idea of natural selection to explain how species change over time • In nature, organisms produce more offspring than can survive. Darwin explains natural selection • In any population, individuals have variations. Fishes, for example, may differ in color, size, and speed Darwin explains natural selection • Individuals with certain useful variations, such as speed, survive in their environment, passing those variations to the next generation. Darwin explains natural selection • Over time, offspring with certain variations make up most of the population and may look entirely different from their ancestors Interpreting evidence after Darwin • Volumes of scientific data have been gathered as evidence for evolution since Darwin’s time. • Much of this evidence is subject to interpretation by different scientists. • One of the issues is that evolutionary processes are difficult for humans to observe directly. Interpreting evidence after Darwin • The short scale of human life spans makes it difficult to comprehend evolutionary processes that occur over millions of years. • Almost all of today’s biologists accept the theory of evolution by natural selection. Adaptations: Evidence for Evolution • Recall that an adaptation is any variation that aids an organism’s chances of survival in its environment. • Darwin’s theory of evolution explains how adaptations may develop in species. Structural adaptations arise over time • According to Darwin’s theory, adaptations in species develop over many generations • Learning about adaptations in molerats can help you understand how natural selection has affected them. Structural adaptations arise over time • Mimicry is a structural adaptation that enables one species to resemble another species. • In one form of mimicry, a harmless species has adaptations that result in a physical resemblance to a harmful species • Predators that avoid the harmful looking species also avoid the similar-looking harmless species. • In another form of mimicry, two or more harmful species resemble each other • For example, yellow jacket hornets, honeybees, and many other species of wasps all have harmful stings and similar coloration and behavior • Another subtle adaptation is camouflage, an adaptation that enables species to blend with their surroundings. •Because wellcamouflaged organisms are not easily found by predators, they survive to reproduce. Physiological adaptations can develop rapidly • In general, most structural adaptations develop over millions of years. • However, there are some adaptations that evolve much more rapidly • For example, do you know that some of the medicines developed during the twentieth century to fight bacterial diseases are no longer effective? Physiological adaptations can develop rapidly • Physiological adaptations are changes in an organism’s metabolic processes • In addition to species of bacteria, scientists have observed these adaptations in species of insects and weeds that are pests. Other Evidence for Evolution • Physiological resistance in species of bacteria, insects, and plants is direct evidence of evolution • However, most of the evidence for evolution is indirect, coming from sources such as fossils and studies of anatomy, embryology, and biochemistry. Anatomy • As the fossil record becomes more complete, the sequences of evolution become clearer • Structural features with a common evolutionary origin are called homologous structures Anatomy • The body parts of organisms that do not have a common evolutionary origin but are similar in function are called analogous structures. • Although analogous structures don’t shed light on evolutionary relationships, they do provide evidence of evolution. Anatomy • Another type of body feature that suggests an evolutionary relationship is a vestigial structure—a body structure in a present-day organism that no longer serves its original purpose, but was probably useful to an ancestor Anatomy • A structure becomes vestigial when the species no longer needs the feature for its original function, yet it is still inherited as part of the body plan for the species. Four Steps To Evolution (Memorize this) • in nature there is a tendency towards over reproduction. • In any population individuals will exhibit slight variations • Individuals with favorable variations are more likely to survive, reproduce, and pass those variations to the next generations. Four Steps To Evolution (Memorize this) • Over time, the offspring of survivors will make up a larger proportion of the population; depending on environmental factors, after many generations, a population may come to look entirely different MECHANISMS OF EVOLUTION (4) • Mutation – a change in the DNA of an organism this adds to the gene pool providing greater variation. • Genetic drift - change in gene frequency by chance processes • Migration – emigration (out) immigration (in) • Natural Selection-3 types Natural Selection-3 types •Stabilizing - favors average individuals •Directional - when one or more extreme forms of a trait are favored •Disruptive - individuals with either extreme forms of a trait are selected; the average is selected against EVOLUTION OF A SPECIES • Species-a group of organism that can interbreed and produce fertile offspring; horse and a donkey produces a mule • Subspecies- a group of organisms of the same species that are different from one another in several ways yet or of the same species ASSORTED VOCABULARY • Speciation- formation of a new species • Gradualism-the idea that evolution occurs slowly over a long period of time • Punctuated equilibrium-ideas that evolution occurred rapidly for a while with times of no evolution • Geographic isolation- when a population is isolated, interbreeding is prevented ASSORTED VOCABULARY • Adaptation- anything about an organism that allows it to survive in its environment • Mimicry- 1 organism mimics (pretends to be) another organism for the protection of the first organism (coral snake and Louisiana Milk Snake) • Camouflage-blending • Mutation-change in genetic code that usually has a bad effect on an organism (sometimes it has a good effect) The End!!! The End!!!!!!!