Place the following steps in the origin of life in the order that they are hypothesized

Place these events in the history of life on Earth in the order that they occurred. a. accumulation of O2 in Earths atmosphere b. colonization of land by plants and fungi c. diversification of animals (Cambrian explosion) d. origin of eukaryotes e. origin of humans f. origin of multicellular organisms g. origin of prokaryotes

Place the following steps in the origin of life in the order that they are hypothesized to have occurred. a. integration of abiotically produced molecules into membraneenclosed pre-cells b. origin of the first molecules capable of self-replication c. abiotic joining of organic monomers into polymers d. abiotic synthesis of organic monomers e. natural selection among pre-cells

DNA replication relies on the enzyme DNA polymerase. Why does this suggest that the earliest genes were made from RNA?

Contrast exotoxins with endotoxins.

Some species of cyanobacteria form symbiotic relationships with other organisms. What benefit might a protist or fungus receive from a cyanobacterial symbiont? What benefit might a plant receive from a cyanobacterial symbiont?

The bacteria that cause tetanus can be killed only by prolonged heating at temperatures considerably above boiling. What does this suggest about tetanus bacteria?

How is the process used in sewage treatment similar to the decomposition of leaf litter in a forest?

What do all protists have in common?

Which of the following protists is not a human pathogen? a. Toxoplasma b. Trichomonas c. Paramecium d. Giardia

Which algal group is most closely related to plants? a. diatoms b. green algae c. dinoflagellates d. seaweeds

Imagine you are on a team designing a moon base that will be selfcontained and self-sustaining. Once supplied with building materials, equipment, and organisms from Earth, the base will be expected to function indefinitely. One of the members of your team has suggested that everything sent to the base be chemically treated or irradiated so that no bacteria of any kind are present. Do you think this is a good idea? Predict some of the consequences of eliminating all bacteria from an environment.

Interpreting Data Because bacteria divide by binary fission, the population size doubles every generation. Suppose the generation time for bacteria that cause food poisoning (for example, Staphylococcus aureus or Salmonella) is 30 minutes at room temperature. The number of cells in a population can be calculated using this formula. Initial number of cells 2(Number of generations) = Population size For example, if a dish of potato salad is contaminated with 10 bacteria, the bacterial population after 1 hour (2 generations) is 10 22 = 40. Fill in the table below to show how the bacterial population increases when a dish of potato salad is left on the kitchen counter after dinner instead of being refrigerated overnight. Why does the rate of increase change over time? Describe how a graph of the data would look.

State or local public health departments regularly inspect restaurants to ensure that safe food-handling procedures are used. In most states, detailed reports are available online. Locate such a report for a restaurant in your area. Mark the items on the checklist that cover hygiene and food handling, and explain how each item prevents potential contamination by pathogenic prokaryotes. Use the same checklist to inspect your own kitchen and evaluate whether corrective measures are needed.

Probiotics, foods and supplements that contain living microorganisms, are thought to cure problems of the digestive tract by restoring the natural balance of its microbial community. Sales of these products total billions of dollars a year. Explore the topic of probiotics and evaluate the scientific evidence for their beneficial effects. A good starting point is the website of the U.S. Food and Drug Administration, the agency that regulates advertising claims of health benefits of dietary supplements (www.fda.gov/Food/DietarySupplements/default.htm).