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Download Organisms throughout time
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Organisms throughout time Adaptation, heredity, natural selection and evolution Adaptation An adaptation is an inherited or set of traits that makes an organism better suited to its environment. Adaptations occur over long periods of time. An organisms body shape and location of its brain are adaptations. Body symmetry Symmetry gives a clue as to the evolutionary development and complexity of the organism. Higher animals, like humans, have bilateral symmetry, meaning the right and left halves of the organism are mirror images of each other. Other organisms, such as starfish, have radial symmetry, meaning they are symmetric about a central axis. These organisms are usually not well adapted for movement. Plant adaptations Plants cannot move so they must grow in such a way to maximize the amount of light and water they absorb. Some may have shallow roots that spread out a long way or have long roots that get water from very deep under ground. The Venus Fly Trap has adapted itself to eating meat in order to get the nutrients it needs. Heredity Heredity is the passing of traits from one offspring to another. Traits are an aspect of an organism that can be described or measured, such as eye color, hair color, etc. Traits are transmitted from parents to offspring in DNA. The inheritance of certain traits is what helps to determine survival in the environment. Eventually only those organisms with the “better” traits will exist. Natural selection Natural selection is the differences in survival and reproduction among members of a population. “survival of the fittest.” – Only the organisms best suited to the environment survive and reproduce. Factors are obtaining food, shelter, light, water. Organisms constantly compete for these resources Factors involved in natural selection 1. 2. 3. 4. 5. Variation among individuals in a population. Heredity of variable characteristics, such as fur color or size Tendency of population size to increase. “struggle for survival.” Difference in inherited characteristics that are passed from generation to generation. Evolution Natural selection is the main reason for evolution. Evolution is the gradual change in an organisms appearance over time. Charles Darwin is the scientist that developed the theory of evolution. Did his research on the Galapagos Islands. Wanted to explain differences in organisms he saw there. Darwin’s analysis 1. 2. 3. 4. There is a lot of variation among species of an organism. No two organisms are exactly alike. Population size tends to increase because of reproduction. Population size can’t go unchecked or it would outgrow food supply and living space. Huge increases in population seldom occur, most populations stay around the same size for long periods of time. Homework Knowing what you have learned about natural selection and adaptation, how and why do you think that giraffes have such long necks? Explain using examples.