Transcript Station 11
Reporting Category 3 Biological Evolution and Classification Station 11 Natural Selection and Adaptation Essential Question – Bell Ringer • How can natural selection affect the frequency of the occurrence of certain traits in a population over many generations? Through the process of natural selection, certain traits of organisms that are able to adapt to changing conditions in an ecosystem or biome become more prevalent and are more likely to be passed on to the organisms’ offspring. Traits that are not beneficial to an organism are less likely to be passed on to successive generations, and organisms that are not as fit are less likely to pass on their traits to successive generations. Pre-Preview Question During his visit to the Galapagos Islands, Charles Darwin discovered 14 distinct species of finches. These groups had been geographically isolated from one another. Many of them lived on different islands. The species of finches differed mainly in feeding behavior, beak structure, and body size. Yet, all of the species shared some characteristics. • Which of the following statements best explains differences between the finches? A. The beaks of the finches changed so the finches could better access different sources of food. B. The beaks of the finches changed so all of the finches could eat the same types of food. C. The beaks of the finches changed as the species of finches migrated to the same island. D. The beaks of the finches changed as the finches' body sizes changed. Pre-Review Question • The forelimbs of a frog and a horse are examples of structures that are A. Heterotrophic B. Homozygous C. Hermaphroditic D. Homologous Pre-Review Question • In an area of Indonesia where the ocean floor is littered with empty coconut shells, a species of octopus has been filmed "walking" on two of its eight tentacles. The remaining six tentacles are wrapped around its body. Scientists suspect that, with its tentacles arranged this way, the octopus resembles a rolling coconut. Local predators, including sharks, seem not to notice the octopus as often when it behaves in this manner. This unique method of locomotion has been utilized by successive generations of octopi through — A. Selective breeding of the octopus species B. Competition between octopi and their predators C. The process of natural selection D. Ecological succession in marine habitats Use this information to answer the question on the next slide. Using the chart on the previous slide, write and answer this question in your journal. • Which cottontail rabbit—A, B, or C—in the table above is considered the most fit of the three rabbits? Support you answer with data from the table. Copy this chart into your journal and fill in the example information using the pictures on the next slide. The Springbok antelope and the Pronghorn antelope are examples of convergent evolution. The seal’s flipper and the bird’s wing are examples of divergent evolution. The Yucca plant and the Yucca moth are examples of coevolution. Discuss with your partner…. Read and discuss the definitions of biological influences and physical influences in the glossary. Explain the role that biological and physical influences play in natural selection and the effect these influences can have on an ecosystem’s populations and species. Biological influences such as diseases may cause weaker organisms to die out and prevent the passage of their traits to other generations of organisms. Physical influences such as a tsunami may remove food sources for organisms or destroy entire ecosystems. Different organisms may repopulate the emerging, ecosystem changing the direction of evolution or type of evolution from the previous one. Discuss with your partner…. What is the difference between the cactus on the left and the cactus on the right? The cactus on the left is covered with spines or needles; the one on the right does not have them. Discuss with your partner…. What effect does the deer’s feeding behavior have on the ability of each type of cactus to survive and reproduce? The deer feeds only on the spineless cactus. Over time, if the deer reproduces successfully, the spineless cactus will no longer be part of the desert biome, leaving only the cactus with spines to reproduce. If the deer cannot find another food source or does not have traits that enable it to adapt, it must leave the biome or possibly become extinct. Discuss with your partner…. How does the deer’s feeding behavior with respect to the cacti in this desert biome illustrate natural selection or the survival of the fittest? In order for natural selection to occur, it must meet three conditions: variations in characteristics, differences in fitness, and heritable traits The two cacti met these conditions: They had variations in their characteristics—one with spines, one without. They had variations in their abilities to survive and reproduce—the deer ate both the spineless cactus pad and its flowers, meaning it couldn’t reproduce. The trait of spinelessness therefore cannot be passed down to successive generations and is therefore no longer heritable. I need to remember…….. • • • • • • • • • No organism or population of organisms is perfectly adapted to its ecosystem. Natural selection does not produce perfection in the organisms that are adapted to an ecosystem. Adaptations are due to genes that are heritable. Natural selection occurs as the result of three conditions: variations in characteristics in a population, heritable traits, and differences in fitness among organisms within a species. Survival of the fittest does not refer to how physically fit or strong an organism is; rather, it refers to an organism’s ability to reproduce and pass on its traits to the next generation. Natural selection does not act on an individual to make it better adapted to its environment. There are biological and physical influences that determine the survival and success of organisms. There are three types of evolution that occur as a result of natural selection— divergent evolution, convergent evolution, and coevolution. Post Review Question • A population of mosquitos is sprayed with a new insecticide. Most of the mosquitos are killed but a few survive. In the next generation, the spraying continues, but still more are immune to the insecticide. How could these results be explained according to the present concept of evolution? • A. The insecticide caused a mutation in the mosquitos. • B. The mosquitos learned to fight the insecticide. • C. A few mosquitos in the first population were resistant and transmitted this resistance to their offspring. • D. The insecticide caused the mosquitos to develop an immune response which was inherited. Post Review Question • According to the theory of natural selection, why are some individuals more likely than others to survive and reproduce? A. Some individuals are better adapted to their environment than others. B. Some individuals pass on to their offspring new characteristics they have acquired during their lifetimes. C. Some individuals do not pass on to their offspring new characteristics they have acquired during their lifetimes. D. Some individuals tend to produce fewer offspring than others in the same environment.