Life or not?
A sunflower bends toward light and grows taller over several days. Which two characteristics of life are demonstrated?
Response to the environment and growth and development.
Match each description with the correct term:
Match each group with its building blocks: carbohydrates, proteins, nucleic acids, and lipids.
Carbohydrates: monosaccharides. Proteins: amino acids. Nucleic acids: nucleotides. Many lipids contain glycerol and fatty acids, although lipids are not true polymers.
Correct all three statements:
A student gives plants 2, 6, or 10 hours of light each day and measures their average height after 14 days. Identify the independent variable, dependent variable, and one variable that should remain constant.
Independent variable: hours of light per day.
Dependent variable: average plant height after 14 days.
Possible constant: plant species, water, soil, temperature, or starting size.
Three-part challenge: Why does evaporating sweat cool the body? How much greater is hydrogen-ion concentration at pH 3 than pH 6? What does a buffer do?
Evaporation requires substantial heat, so escaping water carries heat away. A pH of 3 has 1,000 times more hydrogen ions than pH 6. A buffer resists sudden pH changes by accepting or releasing hydrogen ions.
During digestion, water helps break starch into smaller sugar units. Identify the macromolecule group, its building block, and the reaction involved.
Macromolecule: carbohydrate
Building block: monosaccharide, specifically glucose
Reaction: hydrolysis
A researcher tests whether pH affects bacterial reproduction. After 24 hours, the cultures contain:
pH 4: 12 colonies
pH 7: 78 colonies
pH 10: 15 colonies
Write:
Under these experimental conditions, the bacteria grew best at pH 7.