21. Which feature is typical of an ATP-driven active transport mechanism?
(A) The transport protein must cross to the correct side of the membrane before the solute can bind to it.
(B) The transport protein is irreversibly phosphorylated as transport takes place.
(C) The transport protein catalyzes the conversion of ADP to ATP.
(D) The solute moves against the concentration gradient. 

17. In saltwater fish (A) the concentration of solutes in the internal fluids of saltwater fish is lower than that in the surrounding water. (B)the concentration of solutes in the internal fluids of saltwater fish is higher than that in th environment. (C) large amounts of diluted urine are produced. (D) body fluids have a solute concentration equal to their surroundings.

18. Suppose that the circular muscles in an earthworm have become selectively paralyzed such that they are not able to contract. How will this affect the earthworm's locomotion? (A) The earthworm will be able to elongate, but not get thicker. (B) The earthworm will be able to get thicker, but not elongate. (C) The earthworm will not be able to elongate or get thicker. (D) The earthworm will be able to crawl as normal.

19. In Utah of the USA, there is a clone of aspen trees that covers over 100 acres. Such clones can be considered as a single plant with many stems. It appears that the first stem of this clone originated over 80,000 years ago, even before there were humans in North America. What likely contributes most to the long-term survival (long life span) of aspens? (A) If parts of the organism (clone) are damaged, there are still other parts that can continue growing. (B) All parts of the clone carry the same genes. (C) A shared root system means that all stems receive the same nourishment. (D) Sexual reproduction can occur more frequently in clones.

20. A beetle that feeds exclusively on dead wood is an example of a(n) _______and is part of the________ trophic level. (A) herbivore； first (B) herbivore； second (C) ominvore； second (D) detritivore； first (E) detritivore； second

22. The alleles of a gene are found at______ chromosomes.(A) the same locus on nonhomologous (B) different loci on homologous (C) different loci on nonhomologous (D) the same locus on homologous

23. Which statement about evolutionary adaptation is TRUE? (A) An individual who has learned how to survive cold winters has become adapted to the cold. (B) A population that has an increase in frequency of alleles for thicker fur has become adapted to the cold. (C) Adaptation results when cold temperatures cause mutations for longer fur. (D) Adaptation is possible when all the alleles in a gene pool are the same. 

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.