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The concept of Evolution was first suggested by Charles Darwin.

The concept of Evolution was first suggested by Charles Darwin. He called it descent with modification. Since then… massive amounts of evidence has been collected by thousands of scientists. The concept has been tested and confirmed in many different ways making the idea into a:. Theory.

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The concept of Evolution was first suggested by Charles Darwin.

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  1. The concept of Evolution was first suggested by Charles Darwin. He called it descent with modification.

  2. Since then… massive amounts of evidence has been collected by thousands of scientists. The concept has been tested and confirmed in many different ways making the idea into a: Theory

  3. Evolution occurs over time because of the process of: Natural selection Darwin thought that the process of evolution is controlled by nature. Natural selection suggests that traits that help an organism survive in a changing environment are passed on to the next generation. “Favorable Traits” Over many generations, species change. According to Charles Darwin, Natural Selection can influence evolution by:

  4. 1. Overproduction of Offspring Species can produce more offspring than can possibly survive. In a stable environment, populations remain the same from year to the next because not all of the offspring that are born or hatched survive.

  5. So…. Overproduction, leads to a struggle. Organisms compete for food, water and shelter. Those well suited to their surroundings, survive and reproduce. The rest die.

  6. 2. The struggle to survive Organisms within the same niche, compete for limited (finite) resources; food, water, shelter. Battle environmental conditions; temperature, disease, predators.

  7. 3. Variations Organisms within a species are never exactly alike. Members of a population differ so that only some survive if the environment changes. “survival of the fittest”. They can differ in structure, size and color. Variations among individuals can lead to changes in an entire species.

  8. In sexually reproducing organisms, only changes in the genes of sex cells can become the basis for evolutionary change.

  9. selective breeding Man breeds organisms with specific traits that we have selected. This is opposite to Natural Selection.

  10. The differences among offspring are due togenetic variation. The unique combination of traits each organism inherits from its parents.Variability is the raw material for natural selection to work upon. • Genetic Variabilitycomes from: • Mutations:A change in the base sequence of a DNA molecule. When it happens in sperm or eggs, the mutation is passed on to the offspring. • Radiation (X-rays) Chemicals ( Drugs)

  11. 2. Independent Assortment.During Meiosis the genes (on the chromosomes) get “shuffled” randomly into the egg and sperm. This creates different “kinds”of sperm and eggs. a. fertilization The genesrecombine during Note that two of the four offspring in the punnett square at the right have a completely different genetic makeup than that of either parent.

  12. 3. Crossing-over of portions of chromatids

  13. Remember….. Only changes in sex cells can be passed on to offspring. Example: If a father builds huge muscles from working out, will not pass large muscles on to his offspring. A mom gets a nice tan, the baby will not be tan.

  14. Certain variations (appearances or behavior)arebeneficial or an advantage,those best adapted to their environment by having certain traits, survive, and reproduce passing those traits on to their offspring. Atrait that helps an organism survive in itsenvironment is said to haveadaptive value. So…. The number of organisms with this useful trait increase.

  15. Offspring of survivors make up a larger portion of the population Beneficial traits become more common in a population. (gene pool) Harmful traits become less common in a population. As this happens over time it is said the species is evolving.

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