23. Which of the following is a density-independent factor in a population
(A) Food

(B) Habitat
(C) Carrying capacity
(D) Weather

19. Homeotic genes (A) Encode transcription factors that control the expression of genes responsible for specific anatomical structures (B) Are found only in Drosophila and other arthropods (C) Are the only genes that contaln the homeobox domain (D) Encode proteins that form anatomical structures in the fly

20. The upper forelimbs of humans and bats have fairly similar skeletal structures, very different sl shapes and proport s, whereas the corr responding bones in whales have tions. However, genetic data su data suggest that all three kinds of o forganisms div verged from a common ancestor at about the same time. Which of the following is the most likely explanation for these data? (A) Forelimb evolution was adaptive in people and bats, but not in whales (B) Natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy (C)Genes mutate faster in whales than in humans or bats (D) Whales are not properly classified as mammals

21. Chemoautotrophs (A) Use light as energy sou urce and CO2 as a carbon source (B) Use organie con ompound as energy source and organic compound as a carbon source (C) Use light as energy source and organic compound as a carbon source (D) Use inorganic compound (such as methane) as energy source and CO2 as a carbon source

22. Which of the following is the correct description of the tropical (A) Low temperature, rain uniform during the year(B) Long summers, mild winters(C) Warm temperatures and continual rains allow plant growth year-round (D) Low rainfall and dry weather

24. Gymnos sperms (A) Bear seeds on e exposed surfaces of spore-bearing structures (B) Undergo double fertilization (C) Do not have vascular tissues (D)After fertillization, ovary becomes the fruit

25. Which of the following is an example of commensalism (A)Lynx(山貓)andhare(兔) (B) Clown fish lives In anemones (C) Scavengers fight over carcasses(動物屍體) (D) Orchids live attached to a tree trunk

26. In a natural community, the primary consumers are(A) Herbivores(B) Carnivores(C) Detritivores(D) Decomposers

27. Which of the following is NOT the major evolution trend in terrestrial plants (A) Production of microsp pores and megaspores for fertilization (B) Development of vascular tissue (C) Adaptation n to dry environm mental conditions (D) Increasing dominance of the gametophyte phase

28. Which of the following Is an example of post-transcriptional control of gene expression? (A) The addition of methyI groups to cytosine bases of DNA (B) The binding of transcription factors to a pror omoter (C) The removal of introns and alternative splicing of exons (D) Gene amplification contributing to cancer 

29. Which of the following characteristics, structures, or processes is common to both bacteria and viruses? (A) Metabolism(B) Ribosomes(C) Genetic material composed of nucleic acid(D) Cell division