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Evolution

Evolution. Topic 5.4. Assessment Statements. 5.4.1 Define evolution . 5.4.2 Outline the evidence for evolution provided by the fossil record, selective breeding of domesticated animals and homologous structures.

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Evolution

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  1. Evolution Topic 5.4

  2. Assessment Statements 5.4.1 Define evolution. 5.4.2 Outline the evidence for evolution provided by the fossil record, selective breeding of domesticated animals and homologous structures. 5.4.3 State that populations tend to produce more offspring than the environment can support. 5.4.4 Explain that the consequence of the potential overproduction of offspring is a struggle for survival. 5.4.5 State that the members of a species show variation. 5.4.6 Explain how sexual reproduction promotes variation in a species. 5.4.7 Explain how natural selection leads to evolution. 5.4.8 Explain two examples of evolution in response to environmental change; one must be antibiotic resistance in bacteria.

  3. Define evolution. The process of cumulative change in the heritable characteristics of a population

  4. Fossil record • Life which existed more than 500 mya was very different from life today • Although oceans have been around for nearly 5 billion years, fish fossils have only been found in rocks 500 million years old or younger • None of our present top predators existed at the time of the dinosaurs or before • Many living organisms today have no identical form in the fossil record (exceptions: sharks, cockroaches, ferns) • Conclusion: Life on Earth is constantly changing

  5. Selective breeding (artificial selection) • Breeders learned to choose the males and females with the most desirable genetic characteristics and breed them together • After many generations, breeders realized that certain varieties had unique combinations of characteristics which did not exist before (accumulation of small changes over time) • Artificial and not a driving force of evolution in natural ecosystems

  6. Homologous anatomical structures • Structures similar in form and function but which are found in seemingly dissimilar species • Ex. Humans, bats, and whales all have pentadactyl limbs. This suggests that all five-fingered organisms have a common ancestor

  7. Populations tend to produce more offspring than the environment can support • Why are energy and nutrients vital to the parents’ survival used to produce so many excess seeds, eggs, and spores that are never going to give rise to viable offspring? • Limited resources • Consequences of overproduction: a struggle for survival • Competition for resources can lead to adaptive behavior

  8. Members of a species show variation • Bacteria – very little variation; Why? • Sexually reproductive organisms show great variation; Why? • Variation is closely related to how successful an organism is

  9. Causes of variety • Mutation • May produce genes which lead to diseases • May produce an advantage, such as faster growing rate or better camouflage • Sexualreproduction • Thousands of genes are mixed and combined by meiosis and fertilization

  10. Natural selection • Overproduction of offspring with natural variations • Individuals with poorly suited characteristics tend to be less successful at getting resources and have less a change of surviving to maturity • Individuals with well suited characteristics tend to be more successful at getting resources and have a better chance of surviving to maturity

  11. The successful organisms have a better chance to reproduce and to pass on their successful genetic characteristics to the next generation • Over many generations, the accumulation of changes in the heritable characteristics of a population results in evolution

  12. Examples of natural selection • Antibiotic resistance in bacteria • Medications which kill or inhibit the growth of bacteria • Often give to people who are not suffering from a bacterial infection who may be at risk for an infection • Few bacteria survive one antibiotic so another is given • Bacterium can continue to change genetic makeup through mutations or plasmid transfer and becomes resistant

  13. Pesticide resistance in rats • Pesticides kills most rats • Due to natural variation, a few rats are not affected by the poison • Resistant rats survive and reproduce • To kill the resistant rats, a new pesticide must be used

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