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Thinking Scientifically
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  1. Viruses are small, infectious particles. They have a genome of either DNA or RNA, but no organelles characteristic of cells. They do not divide by mitosis but are duplicated by having their constituent parts produced and assembled by the infected cell. Viruses can evolve in the same way as living things, by changes in their genome due to random mutation and selection. Would a virus be considered alive? What are the criteria on which you base your answer?
  2. Natural antifreeze molecules allow many animals to exist in conditions cold enough to freeze the blood (or equivalent fluid) of animals without these additives. The usual explanation about how these molecules work is that they bind to tiny ice crystals in the blood and prevent them from getting larger. However, the exact mechanism is still not completely understood. Knowing the role of hydrogen bonding in the transition from liquid water to ice, how might these "natural antifreeze" molecules interact with ice/water to prevent crystal growth?
  3. DNA is a large molecule that is made of two long, thin strands. All of the atoms within each strand are held together by covalent bonds, but the two strands are held together by hydrogen bonds only. Knowing that individual hydrogen bonds are weaker than covalent bonds, but that many hydrogen bonds together make a strong connection, what would you predict about the stability of the DNA molecule?

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