15. ________ are toxic proteins secreted by pathogenic bacteria, and ________ are toxic components of the outer membrane of gram-negative bacteria.
(A) Endotoxins； parasites
(B) Endotoxins； botulinum toxins
(C) Exotoxins； enterotoxins
(D) Exotoxins； endotoxins
(E) Endotoxins； enterotoxins

11.The process through which species not closely related may come to resemble one another if they live in a similar environment is known as (A) coevolution. (B) homology. (C) convergent evolution. (D) paedomorphosis. (E) diversified

12.What is an example of exaptation? (A) Some insects do not develop wings when resources are plentiful. (B) Human middle ear bones are derived from ancestral gill arch tissue. (C) Wings of bats and wings of birds are homologous. (D) Mutation rates can increase at higher temperatures. (E) Mutation rates can change at various times.

13. The largest group of prokaryotes is the ________, which obtain both energy and carbon from ________. (A) autotrophs； inorganic molecules (B) chemoautotrophs； decaying organic material (C) chemoheterotrophs； organic molecules (D) photoautotrophs； light (E) chemoautotrophs； organic material

14. Evidence for similarities between Archaea and Eukarya includes the (A) absence of introns from genes in both groups. (B) fact that both contain circular DNA without histones. (C) presence of peptidoglycan in the cell walls of both groups. (D) fact that both have several kinds of relatively complex RNA polymerases. (E) absence of cell wall in both groups.

16. Plasmodium, the organism that causes malaria, is a(n) (A) amoeba. (B) stramenopile. (C) ciliate. (D) alveolate. (E) excavate.

17. Which option correctly represents the most likely sequence of the evolution of plants, from earliest to most recent? (A) bryophytes, seedless vascular plants, gymnosperms, angiosperms (B) seedless vascular plants, bryophytes, angiosperms, gymnosperms (C) bryophytes, seedless vascular plants, angiosperms, gymnosperms (D) bryophytes, gymnosperms, seedless vascular plants, angiosperms (E) bryophytes, angiosperms, seedless vascular plants, gymnosperms

18. Which structure is found in angiosperms but not gymnosperms? (A) root (B) spores (C) seeds (D) ovule (E) fruit

19. Most familiar types of fungi including mushrooms, puffballs, and shelf fungi are examples of (A) chytrids. (B) ascomycetes. (C) zygomycetes. (D) basidiomycetes. (E) streptomyces.

20. The function of the sphincter between the stomach and small intestine is to (A) retain chyme in the stomach until pepsin digestion is complete. (B) periodically release chyme into the small intestine in squirts. (C) release bile into the duodenum when chyme is present. (D) release pancreatic secretions into the duodenum when chyme is present. (E) pancreatic secretions transiently into the duodenum when chyme is present.

21. Which hormone is produced by adipose cells and helps to control appetite? (A) insulin (B) bile (C) gastrin (D) leptin (E) interferon