28. What form of nitrogen can most plants absorb and use directly?
(A) nitrite and nitrate
(B) nitrate only
(C) ammonium and nitrogen gas
(D) nitrate and ammonium

24. How do scientists calibrate a molecular clock for a group of organisms with known nucleotide sequences? (A) They use radioactive isotopes to measure the age of DNA material directly. (B) They graph the number of nucleotide differences against the dates of evolutionary branch points known from the fossil record. (C) They analyze fossilized DNA of known age and compare its nucleotide sequences to modern DNA sequences.

25. Which phylum is most closely related to echinoderms? (A) Annelida (B) Mollusca (C) Arthropoda (D) Chordata

26. Some crocodiles and turtles have an exceptional ability to divert blood flow through the heart when they are diving and no longer breathing and exchanging gases. What most likely occurs when these animals dive? (A)Instead of flowing to the lungs, blood travels to the rest of the body to support bodi (B) Instead of flowing to the body, blood travels to the lungs to exchange gases. (C)Instead of flowing to the capillaries, blood travels to alveoli to exchar (D) Blood flow ceases altogether since gases cannot be exchanged while diving.

27. The hormone prolactin, found in distantly related vertebrates, exerts different effect es. From an evolutionary standpoint, this is an indication that p (A) can only have functions related to childbirth. (B) is an ancient hormone whose function diversified through evolution. (C) was a recent evolutionary adaptation. (D) was not required in fish and amphibians.

29. Where does the majority of the net primary production go? (A) Being stored in plants after being photosynthesized (B) Being grazed by herbivores (C) Being processed by decomposers and detritivores (D) Being stored in the soil

30. If a turtle and a night heron both eat the same species of fish, what is the relationship between a turtle and a night heron? (A) predation (B) mutualism (C)parasitism (D) competition

31. Wood frogs freeze solid during the winter and then thaw in the spring. As the freezing progresses, blood circulation stops, which means that cells are not being served by the circulatory system. How would you expect these cells to produce ATP during this time, and what by-product would you expect to build up in these cells? (A) aerobic respiration and CO2 (B) fermentation and lactate (C) fermentation and alcohol (D) photosynthesis and O2

32. Which statement regarding the flow of genetic information is FALSE? (A) Polypeptides form proteins that determine the appearance and function of the cell and organism. (B) Eukaryotic mRNA is processed in several ways before export out of the nucleus. (C) Transcription occurs in the cytoplasm of eukaryotic cells. (D) Ribosomes function as factories that coordinate the functioning of mRNA and tRNA.

33. Uplift and formation of a mountain range divide a freshwater snail species into two isolated populations. Erosion eventually lowers the mountain range and brings the two populations together again, but when they mate, the resulting hybrids all produce sterile young, This scenario is an example of (A) sympatric speciation. (B) allopatric speciation. (C) incomplete speciation. (D) diversifying speciation.

34. Cyanobacteria (A) are photosynthetic archaea. (B) are eukaryotes and the earliest type of algae. (C) are chemoautotrophs. (D) are the only prokaryotes with plantlike, oxygen-generating photosynthesis.