Bio 110 HW #1 Tutorials 1-3

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question
Which of these individuals is likely to be most successful in an evolutionary sense?
answer
an organism that dies after five days of life but leaves 10 offspring, all of whom survive to reproduce
question
Each water molecule is joined to _____ other water molecules by ____ bonds.
answer
four other water molecules by hydrogen bonds
question
The unequal sharing of electrons within a water molecule makes the water molecule _____.
answer
polar - The electrons spend more time with the oxygen of the water molecule than with the hydrogens of water. Thus, the oxygen has a net negative charge and the hydrogens have a net positive charge.
question
The tendency of an atom to pull electrons toward itself is referred to as its _____.
answer
electronegativity
question
In this molecule, what type of bond is found between the oxygen and hydrogens?
answer
polar covalent - While oxygen shares electrons with hydrogen, the electrons spend more time with the oxygen than with the hydrogens.
question
Why isn't this insect drowning? But instead is standing on top of the water
answer
surface tension - The high surface tension of water allows the insect to remain on the surface.
question
Which property of water allows dogs to cool themselves by panting?
answer
water's high heat of vaporization - Evaporative cooling takes place when molecules with the greatest kinetic energy leave a fluid as gas molecules. Because of water's high heat of vaporization, a large amount of heat must be absorbed for 1 gram of water to be converted from liquid to gas. The dog loses this heat as the water on its tongue evaporates, allowing him to cool down by panting. To understand why this answer is correct, read about evaporative cooling.
question
Which property of water allows a paper towel to pick up a puddle of water?
answer
adhesion of water molecules to other kinds of molecules - Water adheres to the cellulose molecules in a paper towel, allowing the towel to pick up a puddle of water. This is similar to the adhesion between water molecules and cellulose in cell walls responsible for water transport in plants.
question
Which property of water allows a water strider to walk on water?
answer
water's high surface tension - Water's high surface tension, related to its cohesion, makes water behave as though coated with an invisible film.
question
The large diversity of shapes of biological molecules is possible because of the extensive presence of _____ in the molecules.
answer
Carbon - With four electrons to share, carbon-based molecules can be multibranching and three-dimensionally variable.
question
Which polymers are composed of amino acids?
answer
proteins - Proteins are composed of amino acids joined together.
question
Which of the following is not attached to the central carbon atom in an amino acid?
answer
an oxygen The central carbon atom in an amino acid is bonded to: - an amino functional group - a carboxyl functional group - a side chain (R group) - hydrogen
question
Which part of an amino acid is always acidic?
answer
carboxyl functional group - The carboxyl group (COOH) contains two oxygen atoms that tend to pull electrons away from the hydrogen atom, so this group tends to lose a proton and is acidic.
question
Which monomers make up RNA?
answer
nucleotides - Nucleotide monomers make up nucleic acids.
question
Which of the following statements about the formation of polypeptides from amino acids is true?
answer
A bond forms between the carboxyl functional group of one amino acid and the amino functional group of the other amino acid. A hydroxyl group is removed from the carboxyl group of one amino acid and hydrogen is removed from the amino group of the other amino acid, allowing a bond to form between the two groups.
question
True or false? Enzymes in the digestive tract catalyze hydrolysis reactions.
answer
True - Enzymes in the digestive tract break down food molecules, which is a process that occurs by hydrolysis.
question
Which of the following hydrocarbons has a double bond in its carbon skeleton?
answer
C2H4
question
Information about Fossil Record
answer
The fossil record presents an incomplete picture of the history of life because all species are not equally likely to leave fossils. Hard-shelled species that die where sediment is actively being deposited are most likely to fossilize, whereas soft-bodied species that die where they cannot be buried are rarely fossilized. Moreover, if a species is not abundant or does not exist for a long time, its fossils will likely be rare. Species that die in an environment with a low oxygen content are more likely to leave fossils because a low oxygen content inhibits decomposition.
question
If the half-life of carbon-14 is about 5,730 years, then a fossil that has one-sixteenth the normal proportion of carbon-14 to carbon-12 should be about how many years old?
answer
22,900 years old
question
How many half-lives should have elapsed if 6.25% of the parent isotope remains in a fossil at the time of analysis?
answer
4
question
Approximately how far back in time does the fossil record extend?
answer
3.5 billion years ago
question
The researchers cite evidence that modern humans (H. sapiens) became established in the same region as the last Neanderthals approximately 39,000-42,000 years ago. What does this suggest about the possible overlap of Neanderthals and modern humans in the region?
answer
Neanderthals and modern humans may have lived in the same region for up to approximately 2,000 years, or they may not have overlapped at all.
question
Carbon-14 dating works for fossils up to about 75,000 years old. Most dinosaurs went extinct 65.5 million years ago. Can 14C be used to date dinosaur bones?
answer
No, the 14C present in the dinosaur when it died would decay too much to be measured after 65.5 million years.
question
Radioactive uranium-235 has a half-life of 704 million years. If it was incorporated into dinosaur bones, could it be used to date the dinosaur fossils?
answer
Yes, after 65.5 million years only about one tenth of the 235U would have decayed, leaving plenty to measure in the fossils.
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