Evolution and Natural Selection

Darwin's theory of evolution explains how species of living things have changed over geological time. The theory is supported by evidence from fossils, and by the rapid changes that can be seen to occur in microorganisms such as antibiotic-resistant bacteria. Many species have become extinct in the past and the extinction of species continues to happen.Charles Darwin was an English naturalist. He studied variation (differences) in plants and animals during a five-year voyage around the world in the 19th century. He explained his ideas about evolution in a book called On the Origin of Species, which was published in 1859.Darwin studied the wildlife on the Galápagos Islands - a group of islands on the equator almost 1,000 kilometers west of Ecuador. He noticed that the finches - songbirds - on the different islands there were fundamentally similar to each other, but showed wide variations in their size, beaks and claws from island to island. For example, their beaks were different depending on the local food source. Darwin concluded that, because the islands are so distant from the mainland, the finches that had arrived there in the past had changed over time.Natural selectionThe theory of evolution states that evolution happens by natural selection. Here are the key points:Individuals in a species show a wide range of variation (changes).This variation is because of differences in genes.Individuals with characteristics most suited to the environment are more likely to survive and reproduce. Survival of the fittest!The genes that allowed the individuals to be successful are passed to the offspring in the next generation.Individuals that are poorly adapted to their environment are less likely to survive and reproduce. This means that their genes are less likely to be passed to the next generation. Given enough time, a species will gradually evolve.These processes can be observed in nature. In fact, some of the most important studies showing natural selection in action involve descendants of the finches (a type of bird) that Darwin observed in the Galapagos Islands.Those finch species looked so different from one another that when Darwin first saw them, he did not realize they were all finches. He thought they were blackbirds, warblers, and other kinds of birds. The species he examined differed greatly in the sizes and shapes of their beaks and in their feeding habits, as shown in the table below. Some species fed on small seeds, while others ate large seeds with thick shells. One species used cactus spines to pry insects from dead wood. One species even picked at the tails of large sea birds and drank their blood!Once Darwin discovered that these birds were all finches, he hypothesized that they had descended from a common ancestor. Over time, he proposed, natural selection shaped the beaks of different bird populations as they adapted to eat different foods. How would you explain natural selection in your own words? What happens to traits that do not support survival and reproduction? Match the following terms with their definitions. theory of evolution explains how species of living things have changed over time natural selection traits of an individual that allow it to survive and produce more offspring will eventually appear in every individual of the species, simply because those who have the traits passed down will have more offspring evolution gradual change in a species over time genetic variation Differences in phenotypes among a species, usually caused by random mutations and environmental changes. adaptation A structure, physiological process, or behavior that makes organisms better able to survive and reproduce. The graph below shows average beak sizes of a group of finches on one island over several years. Use the graph to answer the 3 questions that follow.In which of the years studied was average beak size the largest? 1976 1979 1982 1984 Which of the following statements best summarizes this data? Average beak size stayed about the same except during wet years. Average beak size decreased during dry years and increased during wet years. Average beak size increased during dry years and decreased during wet years. Average beak size changed randomly. Sort the statements based on whether they describe selective breeding or natural selection. Each group will have 3 answers. Natural Selection Organisms best adapted to their environment survive and reproduce more successfully than those that are less adapted Bacteria that develop a mutation that allows them to survive an antibiotic will live long enough to reproduce and so spread the 'survival' gene to subsequent generations The angler fish lives in the deep, dark ocean and produces a light that attracts prey Selective Breeding The intentional breeding of organisms by humans to produce organisms with desired characteristics Alaskan Sled dogs have been bred to be healthy and have endurance to run long distances Use the data chart below to answer the following 2 questions. The table above shows average beak measurements for birds living on three islands. If narrow beaks (small width) are best for eating insects, on which island would you expect to find the most birds that eat insects? Verde Azul Rosa Using the table from the question above:On which island does the bird with the smallest beaklengthlive? Verde Azul Rosa Sort each statement based on whether it is an example of sexual or asexual reproduction. Each group will have 4 answers. Sexual Reproduction Two parents contribute genetic information Each offspring is unique and genetically different from others Important source of genetic variation. Meiosis and fertilization are an important part of this process. Asexual Reproduction Involves only one parent Offspring are genetically identical to parent Examples are budding, vegetative propagation, and regeneration Which of the following factors is necessary in order for natural selection to occur in a species? genetic variation within a population an abundance of food resources a strong family structure none of the above The diagram above shows four different species of finches which were discovered by Darwin on his voyage to the Galapagos Islands. Based on this image and the lab that you completed, explain the variations of each bird and how those variations may be helpful or harmful in different types of environments. Answer each of the following questions:1. What variation exists between the finch species?2. What caused this variation as first?3. Why does this variation exist?4. How does this variation help with survival?