What types of canine do we have in Mississippi? Did you ever wonder why we have such a variety of different kinds of the same type animal? Evolution & Natural Selection Charles Darwin Was an English Naturalist who Developed the theory of evolution by natural selection. Darwin collected most of his data during a voyage of the H.M.S. Beagle when it stopped at the Galapagos Islands. The theory of evolution states that species change over time in response to changes in their environment. Evidences which support the theory of evolution by natural selection . Fossils- which show a change in species structures over time. Speciation The evolution of new species by divergent evolution. Evidences which support the theory of evolution by natural selection . Homologous structures- Indicate that organisms share a common ancestor. Analogous structures have the same function, but do not have a common evolutionary origin. Embryo The earliest stage of growth and development of both plants and animals. Evidences which support the theory of evolution by natural selection . Embryonic similarities– Shows developmental similarities among organisms. Evidences which support the theory of evolution by natural selection . Vestigial structures —indicate evolutionary changes in an organism’s behavior or environment. Evidences which support the theory of evolution by natural selection . Genetic comparisons – indicates evolution from a common ancestor. Evidences which support the theory of evolution by natural selection . Anatomical studies – indicate evolutionary relationships. Do we have evidence that supports the theory of evolution today? Yes Drug resistance of bacteria. Pesticide resistance by insects. Herbicide resistance by weeds. Changes in peppered moth populations in their allele frequencies. Gradualism The theory in evolution that states that changes in species gradually occur over time. Punctuated Equilibrium The theory in evolution that states speciation occurs relatively quickly, in rapid bursts, with long periods of genetic equilibrium in between On the Galapagos Islands, Darwin observed somewhat similar species, with traits suited to their particular environment. One of the adaptations that Darwin observed was of differences in the beak shape of finches (birds). Based on the adaptations that Darwin observed on finches and tortoises on the Galapagos Islands, he wondered if each had originated from an ancestral species. Darwin did not base all of his research on the Galapagos Islands. He observed many species and their geographical location during his voyage. James Hutton’s and Charles Lyell’s work indicated that the Earth is very old (4.5 billion years old). This suggested that the Earth was old enough for evolution to occur. Twenty years after his findings, Darwin published his ideas in a book titled On the Origin of Species. He waited so long because he was disturbed by his findings, which challenged fundamental scientific beliefs. Darwin Decided to go ahead and publish his finding because a scientist named Alfred Wallace sent him an essay which was very similar to Darwin own ideas. Darwin’s Book On the Origin of Species Published in 1859 Natural selection Natural selection could not occur with out inherited variation in species. Natural selection can best be defined as survival and reproduction of the organisms that are genetically best adapted (suited) to the environment. There are two types of selection. One is natural selection which produces the best suited animals for the environment. The other is called artificial selection, this process is often influenced, if not directly chosen by man. Is this animal’s mutation going to be selected for?” Why do mutations occur? Because they are the introduction of new variation through mistakes in DNA. Darwin called the ability of an organism to survive and reproduce in its environment fitness. An adaptation is an inherited trait that makes an organism more suitable to its environment. It gives the organism an advantage in its environment. Examples of vestigial structures (seemingly functionless organs or structures) in humans are the: 1. Coccyx 2. Wisdom teeth 3. Appendix In whales, and in some snakes there are vestigial structures as well, the femur and the pelvis Do whales have legs? The tenets of Natural selection as presented by Darwin are: 1. Individuals organisms in nature differ from one another. Some of this variation is inherited. 2. Organisms in nature produce more offspring than can survive, and many of those that survive do not reproduce. 3. Members of each species must compete for limited resources. 4. Because each organism is unique, each has different advantages and disadvantages in the struggle for existence. 5. Individuals best suited to their environment survive and reproduce most successfully. The animals with characteristics that are not as well suited to their environment die or leave fewer offspring. 6. Species change over time. Over long periods, natural selection causes changes in the characteristics of a species, such as in size and form. New species form and other species disappear. 7.Species alive today have descended with modifications from species that lived in the past. One example of animals being adapted to their environment is camouflage. Leaf frog Another adaptation is mimicry. Syrphid fly Yellow jacket wasp There are two types of mimicry. In Batesian mimicry, the mimic shares signals similar to the model, but does not have the attribute that makes it undesirable to predators. Müllerian mimicry describes a situation where two or more species have very similar warning and both share genuine anti-predation attributes. When lions prey on a herd of antelopes, some antelopes are killed and some escape. Which part of Darwin's concept of natural selection might be used to describe this situation? Survival of the Fittest Movement of genes into and out of a gene pool is called migration. Genetic drift Random change in allele frequencies that occurs in small populations. Genetic Equilibrium Refers to the alleles remaining the same over time within a population. Polyploid Organisms with multiple sets of chromosomes. What is extinction? Extinction is when a species has disappeared permanently. The theory of continental drift hypothesizes that Africa and South America slowly drifted apart after once being a single land mass. The monkeys on the two continents, although similar, show numerous genetic differences. The biggest factor in maintaining these differences is geographic isolation. Scientists have estimated that earth’s early atmosphere consisted of : Ammonia, Methane, Water Vapor, and Hydrogen. The Miller and Urey Experiment The existence of autotrophic bacteria changed Earth’s atmosphere by adding oxygen to it through the process of photosynthesis. This release of oxygen created the ozone layer (ozone is O3) which blocks out deadly ultraviolet radiation from the sun. until the formation of the ozone layer, all life had to remain in the water. What is an adaptation? An inherited characteristic that gives an organism an advantage in its environment. An adaptation can be physical or behavioral. The process by which a population becomes better suited to its environment is know as natural selection by adaptation. The process by which two species evolve in response to changes in each other over time is called coevolution. Examples would be a plant evolving to attract its pollinator, predators and prey, parasite and host. Convergent Evolution: occurs when unrelated species occupy similar niches. Divergent Evolution: The pattern of evolution in which species that once were similar to an ancestral species diverge, or become increasingly distinct. Why are people so interested in Bigfoot?