B2~Biology3

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  • B2~ Biology3
    • Evolution
      • Charles Darwin came up with the theory of natural selection.
        • As organisms in a species show variation, he thought that the more successful competitors were more likely to survive, Survival of the fittest.
        • He believed: The successful organisms that survived would reproduce and pass on the adaptations that made them successful.
      • Speciation: When organisms have so much, over a period of time, because of natural selection, a completely new species is formed.
      • Speciation happens when members of a species change enough to become re-productively isolated. (when they can't interbreed to produce fertile offspring.
      • Reproductive isolation is caused by geographic isolation.
      • Geographic isolation: Physical barriers (rivers) divides population of species. Different mutations create new features for each group. Since conditions are different for each side of barrier the features will be beneficial differently.Eventually each group will have developed new features so they won't be able to interbreed, they've become seperate species.
    • Theories of evolution
      • The evolution theory went against religions about how earth developed. The religious authorities ridicules his ideas.
      • There wasn't enough evidence to support his theory and scientists already had other theories.
      • Lamarck's theory: The characteristics that were used a lot would become more developed. He thought these would be passed on to the offspring further developing.
      • Now, the Darwin theory is widely accepted because: the theory has been debated and tested independently by scientists, and the theory has plausible explanation.
    • The Carbon cycle
      • The only arrow going down is Photosynthesis.
        • Plants convert the carbon from the air into sugars. Plants then incorporate this carbon into other carbs, fats, or proteins.
          • Eating the plants passes the carbon along to the animals in a food chain.
            • Both plant and animals respiration returns CO2 to the air.
              • When these plans and animals decay they're broken down by bacteria and fungi releasing CO2 as well.
                • Over millions of years the dead animals and plants can form fossil fuels like coal and oil. When these are burned CO2 is released.
                  • Recycling carbon takes longer in waterlogged soils and acidic soils. This is because they don't have much oxygen so the decomposers work slower. The pH f acid slows their reproduction or kills them.
                • Millions of species of marine organisms make shells made of carbonates. When they die the shells fall to the ocean floor to eventually form limestone. The carbon in these rocks returns to the atmosphere during volcanic eruptions. The ocean absorbs most of the CO2 acting as carbon sinks.
    • The Nitrogen Cycle
      • The 78% of nitrogen in the air is very un-reactive. Protein is needed fro growth so organisms have t obtain it somehow.
      • Nitrogen Fixation: The process of turning N2 from the air into nitrogen compounds in the soil so plants can use them.
        • This can happen by either: Lighting has enough energy to make N2 react O2 to give nitrates; or Nitrogen fixing bacteria in the soil and roots turn N2 into nitrogen compounds.
          • The types of bacteria: Decomposer ( decompose protein and urea to make ammonia), Nitrifying (Turns ammonia in decaying matter into nitrates), Denitrifying (turns nitrates back into N2) and Nitrogen-Fixing,
            • Some Nitrogen-fixing bacteria live in soil. Others in the nodules of roots of legume plants. This is why legume plants are so good at putting nitrogen back into soil.
              • The plants have a mutualistic relationship because the bacteria get food and the food get nitrogen compounds to make into proteins.

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