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Natural Selection and Survival of the “FITTEST” WHO DOES WIN AND WHY? What is Natural Selection? Natural selection is the process by which biological (living) organisms with favorable traits survive and reproduce more successfully than organisms that do not possess such traits. At the same time you will find some organisms with deleterious (not so good) traits survive and reproduce BUT the organisms are not as successful. This selection process is in response to forces in the natural world, as opposed to artificial selection, whereby selection is made by a human being, such as a farmer selecting his breeding stock to get exactly what he wants. Plants may also be selected to grow with certain characteristics. In nature---all animals generally live where they can survive……right? It is like when we talked about a polar bear being brought from Antacrtica and left to live up in our Mountain Green area. How long would the polar bear survive? Or….. we take a squirrel from our West Haven area and we ship him off to Antacrtica, how long will the squirrel survive? Afterall, everything is frozen and he cannot even dig a snow cave in which to live—let alone find food! Let’s look a few examples: Remember--Animals are suited for their environment or they will not survive. So---what makes a fish suitable for the water so he survives so well in that environment? Gills Fins Streamlined body Fish scales Good muscles to swim What allows a deer to be successful in it’s environment? Lightweight Fast runner Big ears Strong muscles Can jump and leap high Able to camouflage well What about survival of a rabbit? A fast get-away is possible Strong muscles in back legs Good hearing Claws and teeth to try to defend Meet Charles Darwin HMS Beagle HMS Beagle was the British ship that Charles Darwin was on board to take a five-year trip around the world. Darwin was only 22 years old. He became the ship’s naturalist—a person who studies the natural world. His job? To learn as much as he could about the living things he saw on the voyage. Darwin saw plants and animals he had never seen before and he wondered why they were so different from those in England. Darwin’s observations led him to develop on of the most important scientific theories of all time; THE THEORY OF EVOLUTION BY NATURAL SELECTION The importance of Natural Selection: The Beagle made many stops along the coast of South America and also traveled to the Galapagos Islands. Darwin’s important observations included the diversity (variety or not the same) of living things, ancient organism remains and the different characteristics of the organisms on the Galapagos Islands. He found many species (a group of similar organisms that can mate with each other and produce FERTILE offspring). He found several types of turtles, iguanas, and finches. They all had different characteristics which allowed each type to survive. Each of the different characteristics were why the animals were surviving. Why was Darwin’s observations about different characteristics important? Darwin could tell just by looking at the characteristics, where the animals lived on the islands. The characteristics were adaptations (a trait that helps an organism survive and reproduce) that helped keep the animals and plants living. One example is the beak shape of a finch. The finches’ beaks were shaped to be able to obtain food in the area of the islands were the finches lived. Other examples were plants that were poisonous or had a bad taste—insects and animals would not eat them so they could reproduce. Some plants had very bright flowers to attract insects to help with the spreading of pollen for reproduction of the plant. See the next page Galapagos Island Tortise Types Finches and different beaks Darwin’s reasoning: He reasoned that plants or animals that arrived on the Galapagos Islands faced conditions that were different from those on the mainland. Perhaps, Darwin hypothesized, the species gradually changed over many generations and became better adapted to the new conditions. The gradual change in a species over time is called---you guessed it--EVOLUTION. Please remember—this is a theory only. Natural Selection: This is the process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species. The same characteristics that helped them survive would be passed on to their offspring. There are some factors that affect natural selection. Those factors are: Overproduction—this occurs when not many offspring are usually successful in surviving from birth—example is for insects. Can you imagine if all the eggs from all insects survived? The whole world would be crowded out by bugs!!! YUCKY!!! Variations: Some food is acceptable to some species but not to others. Some organisms have bright colors and others are not as bright. It can be a protection some times. Selection: Some variations enable individuals better adapted to their environment and so they survive and can reproduce more successfully. The offspring inherit the characteristics that are helpful. Because the environment has “selected” organisms with helpful traits, Darwin proposed that over a long period of time, “natural selection” could/can lead to change. This would aid I the helpful variations accumulating in a species while the unfavorable ones may disappear. Environmental Change If the environment changes that could affect an organism’s ability to survive. This could also lead to a “selection” process. If the organisms in the environment could adapt and survive then the traits that helped them would be passed on. If the animals could not survive then of course all would die and fail to reproduce so the unhelpful characteristics would be eliminated. Humans and other predators literally ate the dodo birds until They were extinct. Their nests were also easy for predators to take The eggs and any babies so preproduction was a problem. They were Extinct about 1755. Sad fact. Genes and Natural Selection: Without variations, all members of a species would have the same traits. Natural selection would not occur because all individuals would have an equal change of surviving and reproducing. Darwin could not explain what caused variations or how they were passed on. Scientists later learned that variations can result from mutation and the shuffling of alleles during meiosis. Genes are passed from parents to their offspring. Because of this, only traits that are inherited, or controlled by genes, can be acted upon by natural selection. Now you know. . . . .